Endangered and Threatened Wildlife and Plants; Threatened Species Status for Dakota Skipper and Endangered Species Status for Poweshiek Skipperling, 63671-63748 [2014-25190]
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Vol. 79
Friday,
No. 206
October 24, 2014
Part II
Department of the Interior
asabaliauskas on DSK5VPTVN1PROD with RULES
Fish and Wildlife Service
50 CFR Part 17
Endangered and Threatened Wildlife and Plants; Threatened Species
Status for Dakota Skipper and Endangered Species Status for Poweshiek
Skipperling; Final Rule
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Federal Register / Vol. 79, No. 206 / Friday, October 24, 2014 / Rules and Regulations
DEPARTMENT OF THE INTERIOR
Executive Summary
Previous Federal Action
Fish and Wildlife Service
Why we need to publish a rule. Under
the Endangered Species Act, a species
may warrant protection through listing
if it is endangered or threatened
throughout all or a significant portion of
its range. Listing a species as an
endangered or threatened species can
only be completed by issuing a rule.
This rule will finalize the listing of the
Dakota skipper (Hesperia dacotae) as a
threatened species and the Poweshiek
skipperling (Oarisma poweshiek) as an
endangered species.
The basis for our action. Under the
Endangered Species Act, we can
determine that a species is an
endangered or threatened species based
on any of five factors: (A) The present
or threatened destruction, modification,
or curtailment of its habitat or range; (B)
Overutilization for commercial,
recreational, scientific, or educational
purposes; (C) Disease or predation; (D)
The inadequacy of existing regulatory
mechanisms; or (E) Other natural or
manmade factors affecting its continued
existence. We have determined the
threats to both species include:
• Habitat loss and degradation of
native prairies and prairie fens,
resulting from conversion to agriculture
or other development; ecological
succession and encroachment of
invasive species and woody vegetation
primarily due to lack of management;
past and present fire, haying, or grazing
management that degrades or eliminates
native prairie grasses and flowering
forbs; flooding; and groundwater
depletion, alteration, and
contamination.
• Other natural or manmade factors,
including loss of genetic diversity, small
size and isolation of sites,
indiscriminate use of herbicides such
that it reduces or eliminates nectar
sources, climate conditions such as
drought, direct mortality from fire and
other management activities or natural
occurrences, direct or indirect mortality
from indiscriminate use of pesticides,
and other unknown stressors.
• Existing regulatory mechanisms are
inadequate to mitigate these threats to
both species.
Peer review and public comment. We
sought comments from independent
specialists to ensure that our
designation is based on scientifically
sound data, assumptions, and analyses.
We invited these peer reviewers to
comment on our listing proposal. We
also considered all other comments and
information received during the
comment period.
Please refer to the proposed listing
rule for the Dakota skipper and
Poweshiek skipperling (78 FR 63574;
October 24, 2013) for a detailed
description of previous Federal actions
concerning this species.
50 CFR Part 17
[Docket No. FWS–R3–ES–2013–0043;
4500030113: 4500030113]
RIN 1018–AY01
Endangered and Threatened Wildlife
and Plants; Threatened Species Status
for Dakota Skipper and Endangered
Species Status for Poweshiek
Skipperling
AGENCY:
Fish and Wildlife Service,
Interior.
Final rule.
ACTION:
We, the U.S. Fish and
Wildlife Service (Service), determine
threatened species status under the
Endangered Species Act of 1973 (Act),
as amended, for the Dakota skipper
(Hesperia dacotae), a butterfly currently
found in Minnesota, North Dakota,
South Dakota, Manitoba, and
Saskatchewan and endangered species
status for the Poweshiek skipperling
(Oarisma poweshiek), a butterfly
currently found in Michigan,
Minnesota, Wisconsin, and Manitoba.
The effect of this regulation will be to
add these species to the List of
Endangered and Threatened Wildlife.
DATES: This rule becomes effective
November 24, 2014.
ADDRESSES: This final rule is available
on the internet at https://
www.regulations.gov and https://
www.fws.gov/midwest/Endangered/.
Comments and materials we received, as
well as supporting documentation we
used in preparing this rule, are available
for public inspection at https://
www.regulations.gov. All of the
comments, materials, and
documentation that we considered in
this rulemaking are available by
appointment, during normal business
hours at: U.S. Fish and Wildlife Service,
Twin Cities Field Office, 4101 American
Boulevard East, Bloomington,
Minnesota 55425; (612) 725–3548; (612)
725–3609 (facsimile).
FOR FURTHER INFORMATION CONTACT:
Peter Fasbender, Field Supervisor, Twin
Cities Field Office, 4101 American
Boulevard East, Bloomington,
Minnesota 55425; (612) 725–3548; (612)
725–3609 (facsimile). Persons who use a
telecommunications device for the deaf
(TDD) may call the Federal Information
Relay Service (FIRS) at 800–877–8339.
SUPPLEMENTARY INFORMATION:
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SUMMARY:
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Background
Please refer to the proposed listing
rule for the Dakota skipper and the
Poweshiek skipperling (78 FR 63574;
October 24, 2013) for a summary of
species information.
Status Assessments for Dakota Skipper
and Poweshiek Skipperling Dakota
Skipper
Species Description
The Dakota skipper (Hesperia
dacotae) is a member of the skipper
family Hesperiidae and was first
described in 1911 from collections taken
at Volga, South Dakota, and Grinnell,
Iowa (Skinner 1911 in Royer and
Marrone 1992a, p. 1). The family
Hesperiidae comprises seven
subfamilies worldwide, four of which
occur in North America, north of
Mexico (Brower and Warren at https://
tolweb.org/Hesperiidae). There are 21
recognized species in the genus
Hesperia (ibid). Dakota skipper is the
accepted common name for H. dacotae.
The Dakota skipper is a small to
medium-sized butterfly with a wingspan
of 2.4–3.2 centimeters (cm) (0.9–1.3
inches (in)) and hooked antennae (Royer
and Marrone 1992a, p. 3). Like other
Hesperiidae species, Dakota skippers
have a faster and more powerful flight
than most butterflies because of a thick,
well-muscled thorax (Scott 1986, p.
415).
Adult Dakota skippers have variable
markings. The dorsal surface of adult
male wings ranges in color from tawnyorange to brown and has a prominent
mark on the forewing; the ventral
surface is dusty yellow-orange (Royer
and Marrone 1992a, p. 3). The dorsal
surface of adult females is darker brown
with diffused tawny orange spots and a
few diffused white spots restricted to
the margin of the forewing; the ventral
surfaces are dusty gray-brown with a
faint white spotband across the middle
of the wing (Royer and Marrone 1992a,
p. 3). Adult Dakota skippers may be
confused with the Ottoe skipper (H.
ottoe), which is somewhat larger with
slightly longer wings (Royer and
Marrone 1992a, p. 3). Dakota skipper
pupae are reddish-brown, and the larvae
are light brown with a black collar and
dark brown head (McCabe 1981, p. 181).
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General Life History
Dakota skippers are univoltine
(having a single flight per year), with an
adult flight period that may occur from
the middle of June through the end of
July (McCabe 1979, p. 6; McCabe 1981,
p. 180; Dana 1991, p. 1; Royer and
Marrone 1992a, p. 26; Skadsen 1997, p.
3; Swengel and Swengel 1999, p. 282).
The actual flight period varies
somewhat across the range of each
species and can also vary significantly
from year to year (e.g., Rigney 2013a, p.
138), depending on temperature
patterns (Bink and Bik 2009, Koda and
Nakamura 2012). Females emerge
slightly later than males (Dana 1991, p.
15, Rigney 2013a, p. 138), and the
observed sex ratio of Dakota skippers
was roughly equal during peak flight
periods (Dana 1991, p. 15; Swengel and
Swengel 1999, pp. 274, 283).
The Dakota skipper flight period in a
locality lasts 2 to 4 weeks, and mating
occurs throughout this period (Braker
1985, p. 46; McCabe and Post 1977, pp.
36–38; McCabe 1979, p. 6; McCabe
1981, p. 180; Dana 1991, p. 15; Swengel
and Swengel 1999, p. 282; Rigney
2013a, p. 138). Adult male Dakota
skippers exhibit perching behavior
(perch on tall plants to search for
females), but occasionally appear to
patrol in search of mating opportunities
(Royer and Marrone 1992a, p. 25).
Dakota skippers lay eggs on broadleaf
plants (McCabe 1981, p. 180) and
grasses (Dana 1991, p. 17), although
larvae feed only on grasses. Potential
lifetime fecundity is between 180 and
250 eggs per female Dakota skipper;
realized fecundity depends upon
longevity (Dana 1991, p. 26). Female
Dakota skippers lay eggs daily in
diminishing numbers as they age (Dana
1991, pp. 25–26). Dana (1991, p. 32)
estimated the potential adult life span of
Dakota skipper to be 3 weeks and the
average life span (or residence on site
before death or emigration) to be 3 to 10
days on one Minnesota prairie.
Dakota skippers overwinter as larvae
and complete one generation per year.
Dakota skipper eggs hatch after
incubating for 7–20 days; therefore,
hatching is likely completed before the
end of July. Recent research at the
Minnesota Zoo demonstrated that,
under controlled conditions in the
laboratory, Dakota skippers eggs
hatched after 11 to 16 days, and the
majority of the caterpillars hatched on
the 13th and 14th days (Runquist 2014,
pers. comm.). After hatching, Dakota
skipper larvae crawl to the bases of grass
plants where they form shelters at or
below the ground surface with silk,
fastened together with plant tissue
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(Dana 1991, p. 16). They construct 2–3
successively larger shelters as they grow
(Dana 1991, p. 16). The larvae emerge
from their shelters at night to forage
(McCabe 1979, p. 6; McCabe 1981, p.
181; Royer and Marrone 1992a, p. 25)
and appear to clip blades of grass and
bring them back to their shelters to
consume (Dana 2012a, pers. comm.).
Dakota skippers have six or seven
larval stages (instars) (Dana 1991, pp.
14–15) and overwinter (diapause) in
ground-level or subsurface shelters
during either the fourth or fifth instar
(McCabe 1979, p. 6; McCabe 1981, pp.
180, 189; Dana 1991, p. 15; Royer and
Marrone 1992a, pp. 25–26). In the
spring, larvae resume feeding and
undergo two additional molts before
they pupate. During the last two instars,
larvae shift from buried shelters to
horizontal shelters at the soil surface
(Dana 1991, p. 16).
Food and Water
Nectar and water sources for adult
Dakota skippers vary regionally and
include purple coneflower (Echinacea
angustifolia), blanketflower (Gaillardia
aristata), black-eyed Susan (Rudbeckia
hirta), purple locoweed (Oxytropis
lambertii), bluebell bellflower
(Campanula rotundifolia), prairie
milkvetch (Astragalus adsurgens) (syn.
A. laxmannii), and yellow sundrops
(Calylophus serrulatus) (Dana 1991;
McCabe and Post 1977, pp. 36–38;
Royer and Marrone 1992a, p. 21; Rigney
2013a, p. 142). Plant species likely vary
in their value as nectar sources due to
the amount of nectar available during
the adult flight period (Dana 1991, p.
48). Nectar source preferences are
typically indicated as the relative
proportion of plants selected for
nectaring among all the available
species in a particular area. Swengel
and Swengel (1999, pp. 280–281)
observed nectaring at 25 plant species,
however, most of the nectaring was at
purple coneflower and blanketflower.
Dana (1991, p. 21) reported the use of
25 nectar species in Minnesota with
purple coneflower most frequented;
McCabe (1979, p. 42; McCabe 1981, p.
187) observed Dakota skippers using
eight nectar plants. Dakota skippers in
Manitoba were recently observed
nectaring on 12 species of plants,
primarily black-eyed Susan, but also
including 6 species that were previously
unrecorded as nectar flowers: White
sweetclover (Melilotus alba), purple
prairie clover (Petalostemon purpureus),
yellow evening-primrose (Oenothera
biennis), palespike lobelia (Lobelia
spicata), fiddleleaf hawksbeard (Crepis
runcinata), and upland white aster
(Solidago ptarmicoides) (Rigney 2013a,
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pp. 4, 57). In addition to nutrition, the
nectar of flowering forbs provides water
for Dakota skipper, which is necessary
to avoid desiccation during flight
activity (Dana 1991, p. 47; Dana 2013,
pers. comm.). Some plant species listed
in some studies as nectar flowers are
likely used for perching and patrolling
rather than as nectar sources.
The flight of the adult female
typically extends beyond that of males
(Dana 2014, pers. comm.; Dana 1991,
pp. 1,15; Rigney 2013a, p. 138);
therefore the two sexes can visit the
same nectar plant species at different
rates (e.g., if the flowering period is
more coincident with either the male or
the female flight period). For example,
Dana (1991, p. 21) observed a greater
number of males than females visiting
purple locoweed—this plant is already
past its flowering peak at the beginning
of the male flight and nearly finished
flowering by the peak female flight
(Dana 2014, pers. comm.).
Dakota skipper larvae feed on several
native grass species; little bluestem
(Schizachyrium scoparium) is a frequent
food source of the larvae (Dana 1991, p.
17; Royer and Marrone 1992a, p. 25),
although they have been found on
Dichanthelium spp., and other native
grasses (Royer and Marrone 1992a, p.
25). When presented with no other
choice, Dakota skipper larvae may feed
on a variety of native and nonnative
grasses (e.g., Kentucky bluegrass (Poa
pratensis)) at least until diapause (Dana
1991, p. 17). The timing of growth and
development of grasses relative to the
larval period of Dakota skippers are
likely important in determining the
suitability of grass species as larval host
plants. Large leaf blades, leaf hairs, and
the distance from larval ground shelters
to palatable leaf parts preclude the value
of big bluestem and Indian grass as
larval food plants, particularly at
younger larval stages (Dana 1991, p. 46).
In captivity, Dakota skipper larvae ate
big bluestem (Andropogon gerardii), at
older larval stages, and prairie dropseed
(Sporobolus heterolepis) (Runquist
2014, pers. comm.). Captive larvae also
fed on smooth brome (Bromus inermis)
(Dana 1991, p 17), but this was not
tested in a natural setting and the
structural features of this grass would
hinder or prevent larval survival (Dana
2013, pers. comm.). The tight empirical
correlation between occurrence of
Dakota skippers and the dominance of
native grasses in the habitat, indicates
that population persistence requires
native grasses for survival (Dana 2013,
pers. comm.).
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Dispersal
Dakota skipper are not known to
disperse widely; the species was
evaluated among 291 butterfly species
in Canada as having relatively low
mobility. Experts estimated Dakota
skipper to have a mean mobility of 3.5
(standard deviation = 0.7) on a scale of
0 (sedentary) to 10 (highly mobile)
(Burke et al. 2011, p. 2279; Fitzsimmons
2012, pers. comm.). Dakota skippers
may be incapable of moving greater than
1 kilometer (km) (0.6 miles (mi))
between patches of prairie habitat
separated by structurally similar
habitats (e.g., crop fields, grassdominated fields or pasture, but not
necessarily native prairie) (Cochrane
and Delphey 2002, p. 6). Royer and
Marrone (1992a, p. 25) concluded that
Dakota skippers are not inclined to
disperse, although they did not describe
individual ranges or dispersal distances.
McCabe (1979, p. 9; 1981, p. 186) found
that concentrated activity areas for
Dakota skippers shift annually in
response to local nectar sources and
disturbance.
In a mark–recapture study, average
adult movements of Dakota skipper
were less than 300 meters (m) (984 feet
(ft)) over 3–7 days; marked adults
crossed less than 200 m (656 ft) of
unsuitable habitat between two prairie
patches and moved along ridges more
frequently than across valleys (Dana
1991, pp. 38–40). Dana (1997, p. 5) later
observed reduced movement rates
across a small valley dominated by
exotic grasses compared with
movements in adjacent widespread
prairie habitat. Roads and crop fields
were suspected as impediments for
movement among prairie patches along
two sites of the main valley (Dana 1997,
p. 5), although movements beyond the
study area were beyond the scope of the
1997 mark–recapture study (Dana 2013,
pers. comm.). Skadsen (1999, p. 2)
reported possible movement of Dakota
skippers in 1998 from a known
population at least 800 m (2625 ft) away
to a site with an unusually heavy
growth of purple coneflower; he had not
found Dakota skippers in three previous
years when coneflower production was
sparse. The two sites were connected by
native vegetation of varying quality,
interspersed by a few asphalt and gravel
roads (Skadsen 2001, pers. comm.).
In summary, the best information we
have suggests that dispersal of Dakota
skipper is very limited due in part to its
short adult life span and single annual
flight. Therefore, the species’ extirpation
from a site is likely permanent unless it
is within about 1 km (0.6 mi) of a site
that generates a sufficient number of
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emigrants or is artificially reintroduced
to a site; however, the capability to
propagate the Dakota skipper is
currently lacking.
Habitat
Dakota skippers are obligate residents
of undisturbed (remnant, untilled) highquality prairie, ranging from wet-mesic
tallgrass prairie to dry-mesic mixedgrass prairie (Royer and Marrone 1992a,
pp. 8, 21). High-quality prairie contains
a high diversity of native plant species,
including flowering herbaceous plants
(forbs). Royer and Marrone (1992a, p.
21) categorized Dakota skipper habitat
into two main types that were once
intermixed on a landscape scale, but are
now mostly segregated. The first,
referred to as ‘‘Type A’’ by Royer et al.
(2008, pp. 14–16), is low wet-mesic
prairie that occurs on near-shore glacial
lake deposits. Type A Dakota skipper
habitat is dominated by bluestem
grasses, with three other plant species
almost always present and blooming
during Dakota skipper’s flight period:
Wood lily (Lilium philadelphicum),
bluebell bellflower, and mountain
deathcamas (smooth camas; Zigadenus
elegans) (McCabe 1981, p. 190). This
habitat type has a high water table and
is subject to intermittent flooding in the
spring, but provides ‘‘sufficient relief to
provide segments of non-inundated
habitat during the spring larval growth
period within any single season’’ (Royer
et al. 2008, p. 15). Common forbs in
bloom during the late season in Type A
habitat include Rocky Mountain blazing
star (Liatris ligulistylis), Canada
goldenrod (Solidago canadensis), strict
blue-eyed grass (Sisyrinchium
montanum), common goldstar (Hypoxis
hirsuta), and black-eyed Susan (Lenz
1999, p. 6). Type A habitats also contain
small patches of dry-mesic prairie
inhabited by Dakota skippers. Common
forb species in these dry-mesic areas
include stiff sunflower (Helianthus
pauciflorus Nutt. ssp. pauciflorus) and
candle anenome (Anemone cylindrica),
although purple coneflower was rare in
these habitats (Lenz 1999, pp. 6–11).
Dakota skipper inhabits Type A habitat
in north-central North Dakota, southeast
North Dakota, and Manitoba.
The second Dakota skipper habitat
type, referred to as ‘‘Type B’’ by Royer
et al. (2008, p. 14), occurs on rolling
terrain over gravelly glacial moraine
deposits and is dominated by bluestems
and needle grasses (Heterostipa spp.).
As with Type A habitat, bluebell
bellflower and wood lily are also
present in Type B habitats, but Type B
habitats also support more extensive
stands of purple coneflower, upright
prairie coneflower, and common
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gaillardia (Royer and Marrone 1992a, p.
22). Both Type A and Type B prairies
may contain slightly depressional (low
topographical areas that allow for the
collection of surface water) wetlands
with extensive flat areas and slightly
convex hummocks, which are dryer
than the wet areas (Lenz 1999, pp. 4, 8).
In northeastern South Dakota, Dakota
skippers inhabit primarily Type B
habitats with abundant purple
coneflower, but they also occur in
nearby Type A habitats in some areas
(Skadsen 1997, p. 4). All Type A
habitats occupied by Dakota skipper in
South Dakota are near hill-prairie (Type
B) habitats that are managed with fall
haying (Skadsen 2006b, p. 2).
Little bluestem and porcupine grass
(Hesperostipa spartea) are the
predominant grass species in Dakota
skipper habitat in South Dakota
(Skadsen 2006b, p. 2). Dry-mesic
prairies suitable for Dakota skippers in
South Dakota typically include little
bluestem, side oats grama, porcupine
grass, needle-and-thread grass
(Hesperostipa comata), and prairie
dropseed, and a high diversity and
abundance of forbs, including purple
coneflower, purple prairie clover, white
prairie clover, yellow sundrops, prairie
groundsel (Packera plattensis), prairie
milkvetch, eastern pasqueflower
(Pulsatilla patens), old man’s whiskers
(prairie smoke, Geum triflorum),
western silver aster (Symphyotrichum
sericeum), dotted blazing star (Liatris
punctata), tall blazing star (L. asper),
meadow zizia (Zizia aptera), blanket
flower, prairie sagewort (Artemisia
frigida), and leadplant (Amorpha
canescens) (Skadsen 2006b, pp. 1–2).
Purple coneflower occurs at all sites
where the Dakota skipper has been
recorded in South Dakota, although it is
absent at some sites where Dakota
skipper is abundant in other States
(Skadsen 2006b, p. 2).
In Minnesota, Dakota skippers often
inhabit Type B habitats, however, the
species has been documented in Type A
habitats, particularly in Kittson and
Stearns counties. Dana (1997, p. 8)
described typical habitat in Minnesota
as dry-mesic prairie dominated by midheight grasses with an abundance of
nectar sources including purple
coneflower and prairie milkvetch
(Astragalus laxmannii Jacq. var.
robustior). Southern dry prairies in
Minnesota are described as having
sparse shrub cover (less than 5 percent)
composed primarily of leadplant, with
prairie rose (Rosa arkansana),
wormwood sage, or smooth sumac
(Rhus glabra) present and few, if any,
trees (Minnesota DNR 2012a). Dana
(1991, p. 21) never encountered Dakota
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skippers in wet or wet-mesic prairies in
Minnesota, despite abundance of
suitable plants and the frequent use of
these habitats by similar skipper
species. In systematic surveys at 12
Minnesota sites, Swengel and Swengel
(1999, pp. 278–279) found that Dakota
skippers were significantly more
abundant on dry prairie than on either
wet-mesic prairie.
In Manitoba, Dakota skipper habitat
has been described as Type A prairies,
where the species tends to occupy the
slightly higher, drier areas of wet-mesic
prairie where nectar sources are more
abundant (Webster 2003, p. 7). Recent
studies classify Dakota Skipper sites in
Manitoba as tallgrass or medium to
tallgrass prairies that have been subject
to minimal disturbance, generally
consisting of higher, dryer prairies
adjacent to lower areas with sedges
(Rigney 2013a, p. 155). Inhabited areas
are dominated by native grasses and
sites are generally characterized as
having the following plant species: Big
bluestem, little bluestem
(Schizachyrium scoparius), tufted hair
grass (Deschampsia caespitosa),
switchgrass (Panicum virgatum),
Cusick’s bluegrass (Poa cusickii),
porcupine grass, common spikerush
(Eleocharis palustris), wood lily (Lilim
philadelphicum), wild onion (Allium
stellatum), mountain death camas
(Zygadenus elegans), death camas
(Zygadenus gramineus), common gold
star (Hypoxis hirsute), wild prairie rose,
American licorice (Glycyrrhiza
lepidota), white prairie clover
(Petalostemon candidum), purple
prairie clover, Seneca snake root
(Polygala senega), meadow zizia,
northern bedstraw (Galium boreale),
harebell, palespike lobelia, common
yarrow (Achillea millefolium), pale
agoseris (Agoseris glauca), heath aster
(Aster ericodes) or white prairie aster
(A. falcatus), smooth aster (Aster laevis),
Flodman’s thistle (Cirsium flodmanii),
fiddle leaf hawksbeard, eastern daisy
fleabane (Erigeron annuus), Maximilian
sunflower (Helianthus maximilianii),
Nuttall’s sunflower (Helianthus
nuttallii), meadow blazing star, blackeyed Susan, upland white aster, and
stiff goldenrod (Solidago rigida) (Rigney
2013a, pp. 155–156).
Occupied habitats in Saskatchewan
are similar to the drier upland dry-mesic
mixed-grass prairie hillside habitats in
Manitoba, which is dominated by
bluestems and needlegrass. The Dakota
skipper was most common on ridgetops
and hillsides near purple coneflower
(Webster 2003, p. 8).
In North Dakota, an association of
bluestems (Schizachyrium scoparium,
Andropogon gerardii) and
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needlegrasses, typically invaded by
Kentucky bluegrass, typifies dry-mesic
Dakota skipper habitat in the rolling
terrain of river valleys and the Missouri
Coteau (Royer and Marrone 1992a, p.
22). These prairies, located on the
western edge of the species’ known
range, typically contain wood lily,
bluebell bellflower, coneflowers, and
other asters as nectar sources; in some
areas, mountain deathcamas also occurs
(Royer and Marrone 1992a, p. 22). The
location of larval food plants rarely
seems to affect Dakota skipper
distribution within habitats because
these warm-season grasses are usually
dominant and evenly dispersed
(Swengel 1994, p. 6), although invasion
by smooth brome grass and other
invasive species may displace or
extirpate native larval food plants
(Culliney 2005, p. 134; Bahm et al.
2011, p. 240; LaBar and Schultz 2012,
p. 177).
Two key factors, soils unsuitable for
agriculture and steep topography, have
allowed remnant native-prairie habitats
inhabited by Dakota skippers to persist
(Royer and Marrone 1992a, p. 22).
McCabe (1979, pp. 17–18; 1981, p. 192)
and Royer et al. (2008, p. 16) have
linked the historical distribution of
Dakota skippers to surface geological
features and soils that are glacial in
origin and, possibly, regional
precipitation-evaporation ratios (ratio of
evaporation occurring naturally in one
location over a given area compared to
the amount of precipitation, such as rain
and snow, falling over the same area).
Soil types typical of Dakota skipper sites
were described as sandy loams, loamy
sand, or loams (Lord 1988 in Royer et
al. 2008, pp. 3, 10). Additional edaphic
(soil) features, such as soil moisture,
compaction, surface temperature, pH,
and humidity, may be contributing
factors in larval survival and, thus,
important limiting factors for Dakota
skipper populations (Royer et al. 2008,
p. 2). For example, edaphic parameters
measured in sites throughout the range
of Dakota skipper and occupied by the
species included a bulk density (an
indicator of soil compaction) that
ranged from 0.9g/cm3 to 1.3 g/cm3 and
mean soil pH that ranged from 6.3 to 6.7
with high micro-scale variation
(variation on a small scale) (Royer et al.
2008, p. 10). Soil texture ranged from 4
to 12 percent clay, 53 to 74 percent
sand, and 14 to 39 percent silt (Royer et
al. 2008, p. 12). Seasonal soil
temperatures, measured at three depths
(20, 40, and 60 cm (8, 16, and 24 in))
were the same at all depths within a
site; occupied Minnesota sites generally
had higher soil temperatures at all
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depths than occupied sites in North
Dakota or South Dakota (Royer et al.
2008, p. 11). Royer did not measure
these parameters in unoccupied sites.
Rigney (2013a, pp. 108–109)
measured edaphic features at 8 sites in
Manitoba occupied by the species and
broadly characterized the soil
compaction (at 10 cm) as 570 to 990
kPA, bulk density ranging from 0.75 to
1.30 kg/L, mean soil surface air
temperature at 18 °C during Julian
weeks 28–39 (continuous count of
weeks since the beginning of the
calendar year), and mean relative
humidity at 85 percent during the same
time period. Soils were classified as clay
loams and sandy loams, with generally
low to moderate compaction (<1375
kPA) and bulk densities, which is
indicative of little or no compacting
forces from cattle grazing, tilling, or
agricultural vehicles (Rigney 2013a, pp.
104, 119).
Royer (2008, pp. 2, 16) hypothesized
that Dakota skipper larvae are
particularly vulnerable to desiccation
(drying out) during dry summer months
and require ‘‘vertical water distribution’’
(movement of shallow groundwater to
the soil surface) in the soils or wet low
areas to provide relief from high
summer temperatures. Humidity may
also be essential for larval survival
during winter months since the larvae
cannot take in water during that time
and depend on humid air to minimize
water loss through respiration (Dana
2013, pers. comm.). Royer (2008, pp.
14–15) measured microclimalogical
levels (climate in a small space, such as
at or near the soil surface) within
‘‘primary larval nesting zones’’ (0 to 2
cm (0 to 0.8 inches) above the soil
surface) throughout the range of Dakota
skippers, and found an acceptable
rangewide seasonal (summer) mean
temperature range of 18 to 21 °C (64 to
70 °F), rangewide seasonal mean dew
point ranging from 14 to 17 °C (57 to 63
°F), and rangewide seasonal mean
relative humidity between 73 and 85
percent. Royer (2008) only examined
occupied areas for these parameters;
therefore, the statistical and biological
significance of these edaphic variables
cannot be determined from his study.
Species Occupancy
We generally consider the Dakota
skipper or Poweshiek skipperling to be
‘‘present’’ at sites where the species was
detected during the most recent survey,
if the survey was conducted in 2002 or
more recently and there is no evidence
to suggest the species is now extirpated
from the site (e.g., no destruction or
obvious and significant degradation of
the species’ habitat), with the exception
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of the following four sites. We consider
the species to be present at one
Poweshiek skipperling site in Michigan
where the species was observed at the
site in 1996, and no further surveys
have been conducted. This site,
however, still has suitable habitat for
the species according to species experts
in the State and at least one other
species of prairie-fen-dependent
butterfly is present (Hosler 2013, pers.
comm.). Therefore, the Poweshiek
skipperling is most likely still present at
this site. We also consider the Dakota
skipper to be present at one site
(Chanarambie Creek in Minnesota)
where the most recent survey was from
1994. At this site, no evidence suggests
the species is not still present because,
based on a species-expert review of the
site, the habitat and management is still
conducive to the species (Dana 2013,
pers. comm.). Additional sites where we
consider Dakota skipper to be present
include two sites in Minnesota with
1996 records (Bluestem Prairie and
Buffalo River State Park). Although no
survey for the species has taken place at
Bluestem Prairie since 1996, a 2012
assessment of the habitat at the site
indicates that this site is a high-quality
prairie that contains the native prairie
flora conducive to the Dakota skipper
(Selby 2012, p. 9). The site at Buffalo
River State park, which adjoins
Bluestem Prairie, has not been surveyed
since 1996, but recent habitat
assessments show that it still contains
prairie habitats with the native prairie
flora conducive to the species (MN DNR
2013, unpubl.). Furthermore, the species
expert in Minnesota supports that the
species is most likely still present at
these sites.
We assigned a status of ‘‘unknown’’ if
the species was found in 1993 or more
recently, but not in the most recent one
to two sequential survey year(s) since
1993 and there is no evidence to suggest
the species is now extirpated from the
site (e.g., no destruction or obvious and
significant degradation of the species’
habitat). We considered a species to be
‘‘possibly extirpated’’ at sites where it
was detected at least once prior to 1993,
but not in the most recent one to two
sequential survey years(s). A species is
also considered ‘‘possibly extirpated’’ at
sites where it was found prior to 1993
and no surveys have been conducted in
1993 or more recently. At least three
sequential years of negative surveys, no
matter what years they were conducted,
were necessary for us to consider the
species ‘‘extirpated’’ from a site, because
of the difficulty of detecting these
species, as explained further in this
section. A species is also considered
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‘‘extirpated’’ at sites where habitat for
the species is no longer present. If the
species is considered to be extirpated
from a site, the occupancy status would
not change unless the species is
detected at that location during future
surveys.
When determining whether the
species occupancy is unknown, possibly
extirpated, or extirpated at a particular
site, we used the survey year 1993 as a
cut-off date, because most known sites
(more than 81 percent of known
Poweshiek skipperling sites and more
than 86 percent of known Dakota
skipper sites) have been surveyed at
least once since 1993, and survey data
more than 20 years old may not reflect
the current status of a species or its
habitat at a site (for example, due to
habitat loss from secondary succession
of woody vegetation or a change in plant
communities due to invasive species).
Although it cannot be presumed that the
species is absent at sites not surveyed
since 1993, the likelihood of occupancy
of these sites should be considered
differently than sites with more recent
survey data (e.g., due to woody
vegetation succession over time). When
analyzing survey results, we disregarded
negative surveys conducted outside of
the species’ flight period (outside of
June or July) or under unsuitable
conditions (e.g., high wind speeds over
approximately 16 miles-per-hour). We
accepted survey data from those
surveyors with whom we were
confident in their ability to identify the
species in the field.
After we applied these standards to
initially ascertain the status of the
species, we asked species experts and
Service personnel to help verify,
modify, or correct species’ occupancy at
each site (particularly for sites with
questionable habitat quality or those
that have not been surveyed recently).
In most cases, we used the status
confirmed during expert review, unless
we received additional information (e.g.,
additional survey or habitat data
provided after the expert reviews) that
suggests a different status at a particular
site.
Timing of surveys is based on initial
field checks of nectar plant blooms and
sightings of butterfly species with
synchronous emergence (sightings of
butterfly species that emerge at the same
time as Dakota skipper and Poweshiek
skipperling), and, more recently,
emergence estimated by a degree-day
emergence model using high and low
daily temperature data from weather
stations near the survey sites (Selby,
undated, unpublished dissertation).
Surveys are conducted during flight
periods when the species’ abundance is
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expected to be at levels at which the
species can be detected. However, as
with many rare species, detection
probabilities are imperfect and some
uncertainty remains between nondetection and true absence (Gross et al.
2007, pp. 192, 197–198; Pellet 2008, pp.
155–156). Three sequential years of
negative surveys is sufficient to capture
variable detection probabilities, since
each survey year typically encompasses
more than one visit (e.g., the average
number of visits per Dakota skipper site
per year ranges from 1 to 11), and the
probability of false absence after 5–6
visits drops below 5 percent for studied
butterfly species with varying average
detection probabilities (Pellet 2008, p.
159). Therefore, the site is considered
‘‘extirpated’’ if there are three sequential
years of negative surveys (preferably,
each year has more than one survey
date).
It cannot be presumed that the species
is not persisting at a site only because
there have not been recent surveys. At
several sites, the species has persisted
for longer than 20 years; for example,
Dakota skipper was first recorded at
Scarlet Fawn Prairie in South Dakota in
1985 and has had positive detections
(the species was detected during a
survey) every survey since that date.
The most recent detection was in 2013.
The year 1993 was chosen based on
habitat-related inferences, specifically,
the estimated time for prairie habitat to
degrade to non-habitat due to woody
encroachment and invasive species. For
example, native prairies with previous
light-grazing management that were
subsequently left idle transitioned from
mixed grass to a mix of woody
vegetation and mixed grass in 13 years
and it was predicted that these idle
prairies would be completely lost due to
woody succession in a 30-year
timeframe (Penfound 1964, pp. 260–
261). The time for succession of idle
prairie depends on numerous factors,
such as the size of the site, edge effects
(the changes that occur on the boundary
of two habitat types), and the plant
composition of adjacent areas.
This approach is the most objective
way to evaluate the data range-wide.
Most sites have been surveyed over
multiple years, although the frequency
and type of surveys varied among sites
and years. Surveys were conducted
using various protocols (e.g., Pollard
walks (Pollard 1975), modified Pollard
walks, wandering transects, timed
transects) depending on the objective of
the survey, funding or available
resources, and staff. In several cases,
species experts provided input on
occupancy based on their familiarity
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with the habitat quality and stressors to
populations at particular sites.
To summarize, there are few sites
with relatively older data where we
consider the species to still be present.
In general, most Poweshiek skipperling
sites with a present status have had a
positive detection in 2008, or more
recently with a few exceptions. At one
Poweshiek skipperling site, the species
was observed at the site in 1996, and no
further surveys have been conducted.
The remaining Poweshiek skipperling
sites where the species is considered
present have had detections in 2013,
except four sites where the species was
detected in 2008, 2010, 2011, or 2012,
and no further surveys have occurred.
Likewise, in general, most Dakota
skipper sites with a present status have
had a positive detection in 2002, or
more recently, with a few exceptions. At
four Dakota skipper sites we consider
the species to be present with the most
recent record from 2001 or earlier
including one site where the most
recent survey was from 1994, and two
sites with 1996 records. No evidence
suggests that the species is not still
present at these sites because the best
information indicates that the site’s
habitat is still conducive to the
butterfly, and, therefore, the species
may still be present there. We also
consider Dakota skipper to be present at
the following sites: 17 sites in Canada
that were surveyed most recently in
2002; 1 additional site with a 2002
detection of the species and a favorable
habitat assessment in 2012; 1 site with
a 2003 detection; 1 site with a 2005
detection; 1 site with a 2006 detection;
19 sites in Canada that were surveyed
most recently in 2007; 2 additional sites
with a 2007 detection; 1 site with a
positive detection in 2008; 3 sites with
a positive detection in 2009; 23 sites
with positive detections in 2012; and 10
sites with positive detections in 2013.
asabaliauskas on DSK5VPTVN1PROD with RULES
Population Distribution and Occupancy
Status
Once found in native prairies in five
States and two Canadian provinces, the
Dakota skipper and its habitat have
undergone dramatic declines; the
species is now limited to native prairie
remnants in three States and two
Canadian provinces. The Dakota skipper
is presumed extirpated from Illinois and
Iowa and no longer found in eastern
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Minnesota. Populations persist in a few
locations in western Minnesota,
northeastern South Dakota, North
Dakota, southern Manitoba, and
southeastern Saskatchewan. Royer and
Marrone (1992a, p. 5) speculated that
Dakota skippers may also occur in far
eastern Montana and southeastern
Saskatchewan, in habitats similar to
those occupied by the species in
northwestern North Dakota. The Dakota
skipper was subsequently found in
Saskatchewan in 2001 after 40 years of
searching (Hooper 2002, pers. comm.),
but no actual records have been found
in Montana and Royer (2002, pers.
comm.) no longer thinks that the species
ever occured in Montana.
From its earliest identification, the
Dakota skipper was considered rare
(Royer and Marrone 1992a, p. 1),
although considerable destruction of its
habitat likely occurred even before the
species was first described in 1911.
Habitat destruction and degradation has
greatly fragmented Dakota skipper’s
range from its core through its northern
and western fringes (McCabe 1981, p.
179; Royer and Marrone 1992a, p. 28;
Schlicht and Saunders 1994, p. 1; Royer
1997, p. 2; Schlicht 1997a, p. 2; Schlicht
1997b, p. 2; Skadsen 1997, pp. 25–26;
Skadsen 1999c, p. 15; Swengel and
Swengel 1999, p. 267). The historical
distribution of Dakota skippers may
never be precisely known because
‘‘much of tallgrass prairie was
extirpated prior to extensive ecological
study’’ (Steinauer and Collins 1994, p.
42), such as butterfly surveys.
Destruction of tallgrass and mixed-grass
prairie began in 1830 (Samson and
Knopf 1994, p. 418), but significant
documentation of the ecosystem’s
butterfly fauna did not begin until about
1960. Therefore, most of the species’
decline probably went unrecorded.
Based on records of vouchered
specimens, however, we know that
Dakota skipper range has contracted
northward out of Illinois and Iowa. The
species was last recorded in Illinois in
1888 (McCabe 1981, p. 191) and in Iowa
in 1992 (Orwig and Schlicht 1999, p. 6).
Britten and Glasford’s (2002, pp. 363,
372) genetic analyses support the
presumption that this species formerly
had a relatively continuous distribution;
the small genetic divergence (genetic
distance) among seven sites in
Minnesota and South Dakota indicate
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63677
that populations there were once
connected. Dakota skipper dispersal is
very limited due in part to its short
adult life span and single annual flight.
Therefore, the species’ extirpation from
a site is likely permanent unless it is
within about 1 km (0.62 mi) of a site
that generates a sufficient number of
emigrants or is artificially reintroduced
to a site.
The Dakota skipper’s range once
comprised native prairie in five States
and Canada, extending from Illinois to
Saskatchewan; it now occurs only in
native prairie remnants in portions of
three States and two Canadian
provinces. Of the 264 historically
documented sites, there are 83 sites
where we consider the Dakota skipper
to be present, 88 sites with unknown
status, 41 possibly extirpated sites, and
52 that are considered extirpated (Table
1). Approximately 47 percent (39 of 83)
of the sites where the species is
considered to be present are located in
Canada, mostly within three isolated
complexes, and were observed in 2002,
or in 2007 with no subsequent surveys.
Four additional locations where we
consider the species to be present in
Manitoba had positive detections of the
species as recently as 2012 (Rigney
2013a, p. 117). The remaining 42 sites
where the species is considered to be
present are about equally distributed
among Minnesota (11 sites), North
Dakota (16 sites), and South Dakota (14
sites). Researchers made positive
detections of the species in 10 of these
sites in 2013. The species was observed
at 19 of these sites in 2012. Other U.S.
sites with a present status with
relatively older positive detections and
no subsequent surveys for the species
include one site with a positive
detection in 1994, two sites with
positive detections in 1996, one site
with a positive detection in 2002, one
site with a positive detection in 2005,
one site with a positive detection in
2006, two sites with a positive detection
in 2007, one site with a positive
detection in 2008, and three sites with
a positive detection in 2009. At several
of these sites, the habitat has been
assessed more recently than they were
surveyed for the species. The
distribution and status of Dakota
skipper in each State of known
historical or extant occurrence are
described in detail below.
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TABLE 1—NUMBER OF HISTORICALLY DOCUMENTED DAKOTA SKIPPER SITES WITHIN EACH STATE AND THE NUMBER OF
SITES WHERE THE SPECIES IS THOUGHT TO BE PRESENT, UNKNOWN, POSSIBLY EXTIRPATED, OR EXTIRPATED
State’s
percentage
of the total
number of
historical
sites
State
Present
Unknown
Possibly
extirpated
Illinois ...............................................................................
Iowa ..................................................................................
Minnesota .........................................................................
North Dakota ....................................................................
South Dakota ...................................................................
Manitoba ..........................................................................
Saskatchewan ..................................................................
0.4
1.1
26.1
20.5
32.6
14.0
5.3
....................
....................
....................
11
16
14
28
14
28
14
45
1
0
Total Number of Historically Documented Sites ..............
Percent of the Total Number of Historical Sites by
Occupancy ............................................................
....................
83
....................
32
Illinois
Dakota skippers are considered to be
extirpated from Illinois. The species was
last recorded near Chicago in 1888
(McCabe 1981, p. 191).
Iowa
There are three historical records of
Dakota skippers in three counties in
Iowa (Dickinson, Poweshiek, and
Woodbury), but the species is presumed
extirpated from the State (Schlicht and
Orwig 1998, pp. 84–85; Selby 2004a, pp.
1, 5; Selby 2012, pers. comm.; Nekola
and Schlicht 2007, p. 9). The species
was last seen at Cayler Prairie
(Dickinson County) in 1992, but surveys
of this site in 2000, 2004, 2005, and
2007 were negative, so we presume it to
be extirpated from that site (Schlicht
and Orwig 1998, p. 85; Selby 2004a, p.
5; Selby 2006a, p. 5; Selby 2008, p. 6).
The species was not observed at eight
sites surveyed in the period 1988–1997
(Swengel and Swengel 1999, pp. 288–
289), at eight sites surveyed in 2004
(Selby 2004a, p. 5), nor during extensive
surveys at 32 sites in 2007 (Selby 2008,
p. 6).
asabaliauskas on DSK5VPTVN1PROD with RULES
Minnesota
Minnesota historically contained
about 26 percent of the sites where the
Dakota skipper has been recorded (Table
1) (Service 2014, unpubl. geodatabase).
Since the earliest known record (1965)
of the species in Minnesota, 66 sites
have been recorded in the State, but
recent surveys indicate that the species
is declining in the State (Service 2014,
unpubl. geodatabase). Of the 69 known
locations of Dakota skipper in
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Minnesota; the species is extirpated or
possibly extirpated from 30 of those
sites, and the status is unknown at 28
others (Service 2014, unpubl.
geodatabase). The Dakota skipper is
considered to be present at 11 sites in
Minnesota in 3 counties: Clay, Lincoln,
and Murray, although 2 of those sites
have not been surveyed since 1996, and
1 site has not been surveyed since 1994.
McCabe (1981, p. 187) observed very
stable population numbers in Minnesota
prairies that he visited repeatedly 1968–
1979. On dry-mesic prairie in Lincoln
County, Minnesota, Dana (Dana 1997,
pp. 3–5) also observed stable numbers
into the thousands during his intensive
studies from 1978 to 1983. Schlicht
(1997a, p. 13) and Reiser (1997, p. 16)
reported more variable numbers on the
same sites in 1995–1996, and based on
these more recent observations, Dana
(1997, pp. 3–5) suggested that
populations could experience
significant size fluctuations between
years. At Hole-in-the-Mountain
preserve, Minnesota, Dana (1991, pp.
36–37) found peak abundance of
approximately 1,000 Dakota skippers
over about 40 ha (98 ac); he estimated
that 2,000–3,000 individuals may have
been alive at various times during the
flight period and that only one-third to
one-half of adults were alive
simultaneously. Where they occur, these
high adult densities persist for only
about a week to 10 days during the
single annual flight period (Selby and
Glenn-Lewin 1989, pp. 24–28).
The percentage of sites surveyed each
year in Minnesota with positive
detections remained relatively stable
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Extirpated
Total
18
11
10
2
0
1
3
12
13
17
6
0
1
3
69
54
86
37
14
88
41
52
264
33
15
20
....................
from 1985 to 2005, with an average
detection rate of 67 percent for all
survey years with more than one site
surveyed (excluding sites newly
discovered in the first year it was
discovered), an average of 70 percent
detection rate for survey years with 5 or
more sites surveyed and an average of
66 percent detection rate for survey
years with 10 or more sites surveyed.
One exception to the high detection
rates was 1994; only 26 percent (5 of 19
sites) of sites surveyed in 1994 resulted
in positive detections. Recent surveys of
the species resulted in significantly
lower than average positive detections.
The percent of sites surveyed each year
with positive detections has recently
decreased from 70 percent (7 of 10 sites)
in 2005, to 47 percent (8 of 17 sites) in
2007, 56 percent (10 of 18 sites) in 2008,
6 percent (1 of 16 sites) in 2012, and to
7 percent (1 of 15 sites) in 2013 (for
years with greater than 10 sites
surveyed, see Figure 1). Only one
individual was detected in Minnesota
during 2012 surveys, which included 18
sites with previous records and 23
prairie remnants without previous
records for the species (Dana 2012c,
pers. comm.; Runquist 2012a, pers.
comm.; Olsen 2012, pers. comm.).
Dakota skippers were detected at 1 site
in Minnesota during 2013 surveys,
which included 15 sites with previous
records and 12 prairie remnants without
previous records for the species
(Runquist 2014, pp. 3–6; Selby 2014, pp.
2–5; Rigney 2013b, p. Appendix B;
Service 2014, unpubl. geodatabase.).
The cause for this sharp decline is
unknown.
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The Dakota skipper is presumed
extirpated at 12 sites in Minnesota; at 7
of these sites the species has not been
observed since 1984 or earlier. Four
sites at which the species is now
presumed to be extirpated have had
fairly recent positive observations. The
species was last observed at Prairie
Waterfowl Production Area (WPA) in
Big Stone County in 2000 (Skadsen
2000, p. 1), for example, but was not
found in 2008 (Selby 2009a, p. i), 2010,
and 2012 (Service 2014, unpubl.
geodatabase). Dakota skippers were
observed at the Glacial Lakes WPA in
2001 (Schlicht 2001b, p. 18), but the
species was not observed in 2003, 2004,
and 2005 (Selby 2006b, p. Appendix A
xii); the species is now considered to be
extirpated at that site (Service 2014,
unpubl. geodatabase). The last
observation of Dakota skipper at the Big
Stone National Wildlife Refuge (NWR)
in Lac Qui Parle County was in 2000,
and it was not observed during surveys
in 2009, 2011, or 2012 (Skadsen 2012a,
p. 5). Dakota skippers were observed at
Chippewa Prairie in 1995, but not in
1996, 2005, and 2012 (Service 2014,
unpubl. geodatabase). Of the 18 sites
where the species is possibly extirpated,
4 have not been surveyed since the
species was last seen in 1989 or earlier.
Dakota skippers at two of the sites
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where the species is possibly extirpated
have not been observed since 1991
(Service 2014, unpubl. geodatabase).
One site, with a positive detection in
1998, was ranked as ‘‘possibly
extirpated’’ based on expert opinion.
The remaining 11 sites had positive
observations prior to 1993, were
surveyed once more recently, and had a
negative observation (Service 2014,
unpubl. geodatabase).
The status of the Dakota skipper is
unknown at 28 sites; Dakota skipper
have not been observed at 14 of these
sites since the mid- to late 1990s,
despite one or two years of survey effort
at several sites. The remaining 14 sites
with unknown status have had positive
observations in 2007 or more recently,
but are given this designation due to one
or two subsequent negative surveys. For
example, Dakota skipper was
documented at the Gens Prairie in
Murray County and Woodstock Prairie
in Pipestone County in 2007, but the
species was not observed during surveys
in 2008 or 2013 (Selby 2009a, p.
Appendix 5 li, xxxiii and Appendix 4
xlix; Selby 2014, p. 5).
In 2007 and 2008, the Minnesota DNR
carried out a broad survey effort to
assess the status of Dakota skipper and
other prairie butterflies in the State after
experts noted significant declines in
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these species in west-central Minnesota
beginning in 2003 (Selby 2006b, p. 30).
Researchers surveyed 17 and 19 sites
with previous Dakota skipper records in
2007 and 2008, respectively; Dakota
skipper was found at 8 sites each year
and at 1 site where it had not previously
been recorded (Selby 2009a, p. 6). The
surveys confirmed Dakota skipper’s
extirpation from one site in Cottonwood
County, where it was last recorded in
1970.
A parallel study in 2007 (Dana 2008)
consisted of more intensive work at a
few sites thought to contain some of the
State’s most viable populations of
Dakota skipper. Among these sites was
The Nature Conservancy’s Hole-in-theMountain preserve in Lincoln County,
which was the only Minnesota
population rated as secure in 2002
(Cochrane and Delphey 2002, p. 16).
The 2007 surveys indicated that the site
still supported a substantial population,
but that it may have decreased in size
since earlier studies were conducted
(Dana 1991, p. 36; Dana 2008, p. 18).
Dakota skippers were not detected
during the 2012 or 2013 flight periods
(Runquist 2012, pp. 13–14, 18–20;
Runquist 2012a, pers. comm., Selby
2014, p. 5); therefore, we consider the
status of the species at the Hole-in-theMountain preserve to be unknown.
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Relatively important populations of
Dakota skipper in Minnesota may still
occur at the Prairie Coteau, Felton
Prairie, and Glacial Lakes complexes,
but the 2012 and 2013 survey results
raised concern for the species’ status at
Prairie Coteau. The number of Dakota
skippers encountered per 100 m (328 ft)
of transect at Prairie Coteau State
Natural Area (SNA) were 1.7 in 1990
and 1.1 in 2007 (Dana 2008, p. 19). No
Dakota skippers were observed at Prairie
Coteau SNA during the 2012 or 2013
flight periods (Runquist 2012, pp. 9–10);
therefore, we consider the status of the
species to be unknown at that site. Selby
(2009b, Appendix 4, p. iv) recorded 14
Dakota skippers during a 5-hour survey
in 2007 at the Felton Prairie SNA.
During a 1-hour survey in 2008, nine
Dakota skippers were recorded and with
little indication of any substantial
change since the previous year (Selby
2009b, Appendix 5, p. iv); Felton Prairie
was resurveyed in 2013, and no Dakota
skippers were observed (Service 2014,
unpubl. geodatabase). The number of
Dakota skippers recorded during recent
surveys at Glacial Lakes State Park has
been low despite good habitat
conditions. An apparently widespread
population was present as recently as
2001 when Skadsen (2001, p. 24) found
Dakota skippers along almost all of 40
km (25 mi) of transect in and around the
park—he recorded as many as 31 Dakota
skippers along one transect (Skadsen
2001, p. 24). Selby (2009a, p. 1 and 1iv)
surveyed the same areas in 2007 and
2008, describing habitat at survey sites
as good to excellent, but recorded only
eight Dakota skippers during about 7
hours of surveys in and around the park
(Selby 2009a, p. 1 and 1iv). Glacial
Lakes State Park surveys conducted in
2012 were outside of the Dakota skipper
flight period (Runquist 2012a, pers.
comm.), and the species was not
detected in 2013 (Selby 2014, p. 5).
In summary, the Dakota skipper is
now considered to be extirpated or
possibly extirpated from at least 30 of
the 69 sites in Minnesota, which
historically contained approximately 26
percent of all known historical Dakota
skipper locations rangewide (Table 1).
The species is considered to be present
and unknown at 12 and 27 sites,
respectively. However, only one
individual male was detected in the
State during 2012 surveys, which
included 18 sites with previous records;
2012 surveys for undiscovered
populations were also carried out on 23
prairie remnants without previous
records for the species. Only 6
individual Dakota skipper were
observed in 2013 surveys in Minnesota,
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which included 15 sites with previous
records; 2013 surveys for undiscovered
populations were also carried out on 12
prairie remnants without previous
records for the species (Service 2014,
unpubl. geodatabase). Similar surveys of
prairie remnants with no previous
documentation of Dakota skipper were
completed in Minnesota in 2007 and
2008. Based on these surveys, the
likelihood that significant undiscovered
Dakota skipper populations occur in
Minnesota is low.
North Dakota
North Dakota historically contained
approximately 21 percent of all known
historical locations of Dakota skippers
rangewide (Table 1); the State contained
54 historical sites distributed among 18
counties (Service 2014, unpubl.
geodatabase). The Dakota skipper is
currently present at 16 sites in 5 North
Dakota counties, of these, 11 occur
within the Towner-Karlsruhe complex
in McHenry County, 1 is within the
Sheyenne National Grasslands complex
in Ransom County, 2 are in northern
McKenzie County, and 1 site is in Wells
County. Of the 16 sites where we
consider the Dakota skipper to be
present, 15 sites had positive
observations of the species in 2012. The
remaining site had positive observations
in 2002. The status of the species is
unknown at 14 sites; 10 of these sites
have not had positive records since the
mid- to late 1990s, and the other 4 sites
had positive records between 2001 and
2003. The Dakota skipper is presumed
extirpated from 13 sites and 4 counties,
primarily due to heavy grazing, weed
control, and other disturbances (e.g.,
bulldozing at Killdeer Mountain to
reduce aspen growth, Royer 1997). The
species is possibly extirpated from 11
additional sites and 3 additional
counties.
Researchers surveyed 25 sites,
believed to possibly have Dakota
skipper populations, in 2012; of these
sites, 23 had previous records of the
species (Royer and Royer 2012a, entire).
Thirteen of the 25 surveyed sites had
Dakota skipper present (Royer and
Royer 2012a, pp. 3–4; Royer and Royer
2012b, pp. 2–3). One new site was
found in 2012 (Royer and Royer 2012a,
p. 33), adjacent to a site with previous
records but with different landownership, so the researcher considered
it a new site. Another new site was
found in North Dakota in 2012, in Wells
County, where two observations were
made—possibly the same individual
(HDR, Inc. 2012, pp. 21–23). At sites
with Dakota skipper, lower average
encounter frequencies were observed
across the State in 2012 (State average
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= 9.4 encounters per hour) than during
the 1996–1997 statewide surveys (State
average = 17.4 encounters per hour)
(Royer and Royer 2012b, p. 5; Royer and
Royer 2012a. pp. 7–8). Three sites with
previous Dakota skipper records in
North Dakota were surveyed during the
2013 flight period; the species was not
detected in any of those surveys (Fauske
2013 data (in ND National Guard 2013,
in litt.; HDR Engineering 2013, pp. 10–
11).
Of the Dakota skipper populations in
North Dakota, none may be secure,
although the Towner-Karlsruhe complex
was considered to be the stronghold for
the species in the State in 2002
(Cochrane and Delphey 2002, p. 17),
and most of the sites where the species
is currently present are still occupied by
‘‘viable populations’’ (Royer 2012a,
pers. comm.). All of the habitat where
the species is present in the TownerKarlsruhe complex is Type A (wetmesic) habitat (Royer and Marrone
1992a, pp. 21–22; Royer et al. 2008, pp.
14–16). Three sites within the TownerKarlsruhe complex are owned by the
North Dakota State Land Department,
and the remaining nine sites with extant
populations are privately owned. Some
Towner-Karlsruhe sites are linked by
highway rights-of-way that contain
native prairie vegetation and by other
prairie remnants (Royer and Royer
2012a, p. 18). In 2002, none of these
sites were described as secure (Cochrane
and Delphey 2002, pp. 66–67) since
each is subject to private or State
management options that could
extirpate Dakota skipper from the site.
In 1999, it was estimated that about 30
percent of the Towner-Karlsruhe area
still contained native prairie (Lenz 1999,
p. 2); more recent observations indicate
that several native prairie sites have
been invaded to varying extents by
nonnative species, such as leafy spurge,
Kentucky bluegrass, and alfalfa
(Medicago sativa), and several are
subject to intense grazing or early
haying (Royer and Royer 2012b, pp. 5–
6, 7–10, 13–16, 18–19, 22–23; Royer
2012, in litt.).
Dakota skipper populations in the
Sheyenne National Grasslands complex
have experienced intensive grazing,
leafy spurge (Euphorbia esula) invasion,
and the effects of herbicides used to
control leafy spurge and grasshoppers
(Royer 1997, pp. 15 and 27). For
example, McCabe (1979, p. 36) cited the
McLeod Prairie in the Sheyenne
Grasslands in southeastern North
Dakota as the best site for Dakota
skippers in North Dakota. Since then,
however, leafy spurge invasion has
significantly modified the habitat, and
the Dakota skipper is now extirpated
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from the site (Royer 1997, p. 14).
Swengel and Swengel (1999, p. 286) did
not find Dakota skippers at eight survey
sites in the Sheyenne grasslands during
1988–1997, although Royer did observe
a few isolated Dakota skippers in the
Sheyenne National Grasslands during
this period (e.g., Royer 1997, pp. 14–15).
Dakota skippers were recorded at one
new site (Gregor) in the Sheyenne
National Grasslands in 2001 (Spomer
2004, pp. 14–15). The status of Dakota
skipper at the Gregor site is currently
unknown, since the species was not
observed during the 2002 survey (Royer
and Royer 2012a, pp. 3–4).
Orwig (1996, p. 3) suggested that
Brown’s Ranch in Ransom County,
owned by The Nature Conservancy, had
potential to support a metapopulation
(groups of local populations
interconnected by dispersal habitat) in
the Sheyenne River watershed. More
recently, however, Spomer (2004, p. 36)
found that the population there was not
doing well, and Royer failed to find the
species in 2012 (Royer and Royer 2012a,
p. 3). Therefore, the status of the species
at the Brown Ranch site is unknown.
Royer (1997, pp. 15 and 27) claimed
that, throughout the Sheyenne
Grasslands, both public and private
lands have been so heavily grazed and
altered by grasshopper and leafy spurge
control that extirpation of Dakota
skippers from the area is almost certain
to occur. The population at Venlo
Prairie, for example, deteriorated from
good/fair in 2001 to poor in 2003 due
to intense grazing and disappearance of
flowers (Spomer 2004, pp. 9, 12); the
species is now considered to be
extirpated at that site. The population at
Garrison Training Area in McLean
County is now considered unknown due
to negative surveys in 2004 and 2013
(Fauske 2004, p. 1; Fauske 2013 in ND
National Guard 2013, in litt.).
In 2002, experts ranked all sites
outside of the two complexes discussed
above as threatened or vulnerable; most
were small and isolated populations
threatened by conversion and invasive
species (Cochrane and Delphey 2002,
pp. 66–67). Most of these sites are now
considered extirpated or possibly
extirpated. Today, only 3 sites outside
of the Towner-Karsruhe Complex and
Sheyenne National Grasslands
complexes are thought to have extant
(present) Dakota skipper populations. In
addition to the Towner-Karsruhe
Habitat Complex sites in McHenry
County, only 2 of the 25 sites surveyed
by Royer in 2012, both in northern
McKenzie County, may have ‘‘viable
populations’’ (Royer 2012b, pers.
comm.), although only one individual
was observed at each site in 2012 (Royer
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and Royer 2012b, pp. 16–17). Only three
sites with previous records were
surveyed in North Dakota during the
2013 flight period, and the Dakota
skipper was not observed (Fauske 2013
in ND National Guard 2013, in litt.; HDR
Engineering 2013, pp. 10–11).
In summary, North Dakota contains
approximately 21 percent (N = 54) of all
known historical locations of the
species rangewide; however, the current
occupancy status of the Dakota skipper
is unknown at 14 sites, and it is
considered to be extirpated or possibly
extirpated from at least 24 of the 54
known sites in the State (Table 1). The
species is considered to be present at 16
sites in the State. North-central North
Dakota may hold hope for the species’
long-term conservation. Dakota skipper
was detected at 13 of the 25 sites
surveyed during 2012 (23 of the sites
had previous Dakota skipper records);
average encounter frequencies observed
across the State in 2012 (9.4 encounters
per hour), however, were lower than
during the 1996–1997 State-wide
surveys (ND State average = 17.4
encounters per hour) using the same
methodology. The species was not
detected at the three sites surveyed in
2013.
Although only a small fraction of all
grassland in North Dakota has been
surveyed for Dakota skippers, a
significant proportion of the unsurveyed area is likely not suitable for
Dakota skipper. The species was never
detected at approximately 108
additional locations in North Dakota
that were surveyed for the species in the
period 1991–2013 (USFWS 2014,
unpubl. geodatabase). Many of these
sites have been surveyed multiple times
over multiple years (USFWS 2014,
unpubl. geodatabase). Surveys for the
Dakota skipper are typically conducted
only in areas where floristic
characteristics are indicative of their
presence. New potential sites surveyed
are generally focused on prairie habitat
that appears suitable for the species and
has a good potential of hosting the
species, in other words, sites are not
randomly selected across the landscape.
Therefore, researchers have a higher
likelihood of detecting the species at
these sites than at sites randomly
selected across the landscape. Based on
these surveys, the likelihood that
significant numbers of undiscovered
Dakota skipper populations occur in
North Dakota is low. Moreover, data
available from the numerous sites that
have been surveyed are likely to be
representative of areas that have not
been surveyed—that is, population
trends and the nature and extent of
stressors that may impact the
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populations in un-surveyed areas can
reasonably be inferred by analyzing data
collected from the sites that have been
surveyed.
South Dakota
South Dakota historically contained
approximately 33 percent of all known
locations of Dakota skippers rangewide
(Table 1). Since the earliest known
record of Dakota skipper (1905) in South
Dakota, 86 sites have been documented
across 11 counties in the State, but
recent surveys indicate that the species
is declining in the State (Service 2014,
unpubl. geodatabase). Of the 86
historical sites, Dakota skipper is
presumed extirpated from 17 sites and
2 counties (Brown and Moody), and is
possibly extirpated from 10 additional
sites. Dakota skipper is considered
present at 14 sites, and the status of the
species is unknown at 45 sites. Twentyseven sites in South Dakota with
previous Dakota skipper records were
surveyed in 2012; the species was
detected at 9 of those sites (Service
2014, unpubl. geodatabase). Eight
additional sites within the species’
historical range were surveyed during
the 2012 flight period, which resulted in
the discovery of two new nearby Dakota
skipper sites (Service 2014, unpubl.
geodatabase; Skadsen 2012a, pers.
comm.). Twenty-eight sites in South
Dakota with previous Dakota skipper
records were surveyed in 2013; the
species was detected at 9 of those sites
(Service 2014, unpubl. geodatabase).
Ten additional sites within the species’
historical range were surveyed during
the 2013 flight period, which resulted in
no new Dakota skipper sites discovered
(Service 2014, unpubl. geodatabase).
The proportion of positive surveys at
known sites has fluctuated over time;
however, the 2012 and 2013 surveys
had the lowest positive detection rate
(35 percent and 32 percent,
respectively) for the last 16 years (since
1996), much less than comparable
survey years (years with 10 or more sites
surveyed) in South Dakota.
While there are some sites with earlier
records, most South Dakota sites were
initially documented during extensive
surveys conducted during 1996 to 1998.
Forty-eight locations without previous
records were surveyed during 2002–
2004, which resulted in the discovery of
20 new Dakota skipper sites in
northeastern South Dakota (Skadsen
2003, p. 8; Skadsen 2004, pp. 3–6), but
due to more recent negative surveys, the
occupancy of the species is currently
unknown or extirpated at many of these
sites (Skadsen 2011, p. 5; Skadsen
2012b, pp. 4–5; Skadsen, 2012, pers.
comm.; Skadsen 2003, p. 10; Skadsen
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2004, p. 2; Skadsen 2006a, p. 2, 10;
Skadsen 2006b, p. 5; Skadsen 2007, p.
3; Skadsen 2008, p. 3, 12; Skadsen 2009,
p. 3). Additional survey effort resulted
in the discovery of nine new sites
between 2005 and 2012, with a
maximum of three new sites discovered
in 2006 (Skadsen 2010a, p. 6; Skadsen
2012b, pp. 4–5; Skadsen 2012, pers.
comm.; Skadsen 2005, pp. 5–6, Skadsen
2006a, p. 12; Skadsen 2006b, p. 5;
Skadsen 2007, p. 3; Skadsen 2008, p. 9;
Skadsen 2009, p. 2). Eight additional
sites without previous documentation of
the species were surveyed in 2012,
which resulted in the discovery of two
nearby sites (Service 2014, unpubl.
geodatabase). To summarize, new sites
have been discovered in South Dakota
during most survey years since 2002,
however, the number of new sites
discovered each year has been low
recently; two or three new sites have
been discovered each survey year since
2005 (three sites in 2005, two sites in
2006, two sites in 2007, zero sites in
2010, two sites in 2012, and zero sites
in 2013). The rate that known sites are
becoming extirpated is higher than the
rate of new discovery—the occupancy of
the species at many sites is now
unknown or extirpated due to more
recent negative surveys.
The species has never been
documented in Clark County, but
because few surveys have been
conducted there, the county may
contain undiscovered populations
(Skadsen 2006b, p. 1). Skadsen (2012b,
pers. comm.) doubts the existence of
public lands with suitable Dakota
skipper habitat in Clark County and has
not received permission to survey a few
possible suitable locations that are
privately owned.
Although only a small fraction of all
grassland in eastern South Dakota has
been surveyed for Dakota skippers (e.g.,
Dakota skipper surveys have been
conducted on less than approximately
30,000 acres (12,140 ha) in South
Dakota within the species range (Service
2014, unpubl. geodatabase)), a
significant proportion of the unsurveyed area may not be suitable for
the Dakota skipper, based on surveys in
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additional areas of possible habitat
where the species was not detected . For
example, there is an estimated 1,620,549
acres (ac) (655,813 hectares (ha)) of
unbroken (untilled) grasslands that may
provide habitat for the Dakota skipper in
the nine counties where the Dakota
skipper is considered be present or to
have unknown occupancy in South
Dakota (HAPET 2012, unpubl. data).
Additional areas of unbroken prairie
were estimated in three other counties
where the species may have occurred
historically (HAPET 2012, unpubl.
data). While these lands represent
unbroken grassland in South Dakota, the
models used to identify unbroken
grassland are not able to identify plant
species, plant species composition,
floristic quality, or presence of invasive
species (Loesch 2013, pers. comm.).
Therefore, it is not known if these
unbroken grasslands contain the
specific native prairie plants that the
Dakota skipper requires (as discussed in
detail in the Background section of this
proposed rule) and, therefore, may not
equate to suitable habitat for the species.
The species was never detected at
approximately 79 additional locations
in South Dakota that were surveyed
from 1991 through 2013 (USFWS 2014,
unpubl. geodatabase). Several of these
sites have been surveyed multiple times
in one year or during multiple years
(USFWS 2014, unpubl. geodatabase).
Surveys for Dakota skipper are typically
conducted only in areas where floristic
characteristics are indicative of their
presence. For example, in South Dakota,
Skadsen (1997, p. 2) selected for surveys
dry-mesic prairie that supported purple
coneflower and wet-mesic prairie that
supported wood lily and mountain
deathcamas based on searches for these
sites by car and reports from resource
managers. Only sites with landowner
permission are accessed for surveys,
however, new potential sites surveyed
are generally focused on prairie habitat
that appears suitable for the species and
has a good potential of hosting the
species, in other words, sites are not
randomly selected across the landscape.
Therefore, researchers have a higher
likelihood of detecting the species at
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these sites than at sites randomly
selected across the landscape. Based on
these surveys, the likelihood that
significant undiscovered Dakota skipper
populations occur in South Dakota is
low. Moreover, data available from the
numerous sites that have been surveyed
are likely to be representative of areas
that have not been surveyed—that is,
population trends and the nature and
extent of stressors that may impact the
populations in un-surveyed areas can
reasonably be inferred by analyzing data
collected from the sites that have been
surveyed.
Since there is little long-term
quantitative data for sites in South
Dakota, we examined presence–absence
(non-detection) data over time. The
percent of sites surveyed each year with
positive detections of the species
remained relatively stable from 1985 to
2010, with an average positive detection
rate of 63 percent for all survey years
with more than one site surveyed
(excluding new sites for the first year of
discovery), an average positive detection
rate of 60 percent for survey years with
at least 5 sites surveyed, and an average
positive detection rate of 71 percent for
survey years with at least 10 sites
surveyed. One exception to the high
detection rates was during the 1991
survey year when none (0 of 7 sites) of
the sites surveyed in 1991 resulted in
positive detections of the species,
excluding 3 new sites that were
discovered that year. Another exception
was in 1996, when 2 of the 8 sites with
previous records surveyed had a
positive detection; however, 6 new sites
were discovered that year. The detection
rate remained relatively stable until
2010, when the percent of sites with
positive detections fell from 89 percent
(8 of 9 sites) in 2010, to 46 percent (5
of 11 sites) in 2011, 35 percent (9 of 26
sites) in 2012, and 32 percent (9 of 28
sites) in 2013 (Figure 2). These types of
fluctuations had been observed in prior
years; therefore, it is difficult to
determine a clear trend in the data using
positive detections—the last two survey
years may fall within the normal range
of variation.
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The Outer Coteau des Prairies
subsection of the North Central
Glaciated Plains section of Bailey’s Ecoregions is thought to be a stronghold for
Dakota skipper, since nearly 34 percent
of the total documented Dakota skipper
sites are within that subsection (89 of
the 264 documented sites—Service
2014, unpubl. geodatabase). Most of
these Outer Coteau des Prairie sites are
in South Dakota; 73 of the 86 Dakota
skipper sites in South Dakota are within
the Outer Coteau des Prairies subsection
(Service 2014, unpubl. geodatabase).
Dakota skipper is considered to be
present at only 9 of those 73 sites—the
species status is unknown at 40 of those
sites, possibly extirpated at 8 sites, and
extirpated at the remaining 16 sites
within that ecoregion subsection in
South Dakota (Service 2014, unpubl.
geodatabase).
In summary, South Dakota
historically contained approximately 33
percent of all known locations of the
species rangewide. The current
occupancy status of the Dakota skipper
is unknown at 45 sites, and it is
considered to be extirpated or possibly
extirpated from at least 27 of the 86
known sites in the State, although large
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areas of grasslands remain in South
Dakota we don’t expect significant
additional populations to be found if
more surveys were conducted.
Furthermore, downward trends and
threats impacting populations at known
sites are also likely occurring at
potentially undiscovered sites. The
species is considered to be present at 14
of the 86 documented sites in the State.
Twenty-six sites in South Dakota with
previous Dakota skipper records were
surveyed in 2012; the species was
detected at nine of those sites; eight
sites with no previous records for the
species were surveyed during the 2012
flight period, which resulted in the
discovery of two nearby sites. Twentyeight sites in South Dakota with
previous Dakota skipper records were
surveyed in 2013; the species was
detected at 9 of those sites (Service
2014, unpubl. geodatabase). Ten
additional sites within the species’
historical range were surveyed during
the 2013 flight period, which resulted in
no new Dakota skipper sites discovered
(Service 2014, unpubl. geodatabase).
The proportion of positive surveys at
known sites has fluctuated over time;
however, the 2012 and 2013 surveys
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63683
had the lowest positive detection rate
(35 percent and 32 percent,
respectively) for the last 16 years (since
1996)—much less than comparable
survey years in South Dakota.
Manitoba
Manitoba historically contained
approximately 14 percent (N = 37) of the
known locations of the Dakota skipper
rangewide. The Dakota skipper is
considered present at 1 isolated site and
28 sites split between 2 distinct
complexes, 12 sites near Griswold and
16 sites along Lake Manitoba. The 12
sites near Griswold are located
approximately 200 km (124 mi)
southwest of the populations along Lake
Manitoba (at 16 sites) and about 125 km
(78 mi) northeast of the nearest
population in Saskatchewan (Webster
2003, pp. 5–6; Webster 2007, p. 4). The
species is considered to be unknown at
one site near Griswold where the
species was detected in 2007 and 2011,
but not during the most recent survey
year (2012) (Rigney 2013a, p.117). The
species is presumed extirpated or
possibly extirpated from eight sites in
Manitoba, including from the Tallgrass
Prairie Preserve, where it has not been
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found in the seven most recent survey
years (Webster 2003, p. 5; Westwood et
al. 2012, p. 1; Westwood 2007, pers.
comm.; Hamel et al. 2013, pp. 8–16)—
(the later surveys were focused on
Poweshiek skipperlings, but other
species were recorded), and one site that
was converted to a flaxseed field
(Webster 2003, p. 7).
In 2007, researchers surveyed 16 sites
for the Dakota skipper near Griswold,
Manitoba (Webster 2007, p. 4), and
found Dakota skippers at 14 of the 16
sites; 12 of these represent new sites for
the species in Manitoba (Webster 2007,
p. 4). Four of these sites were
resurveyed in subsequent years (2010,
2011, and 2012)—the species is
considered to be present at two sites, is
unknown at one site due to a recent
negative survey, and extirpated at the
fourth site due to 3 consecutive negative
survey years (Rigney 2013a, p. 117;
Service 2014 unpublished database).
The species is considered to be present
at the remaining 10 sites that have not
been surveyed since 2007.
Until recently, population estimates
and trends at the sites near Griswold in
south west Manitoba have not been
examined quantitatively; however, the
population appears to be relatively
stable at one site, may be declining at a
second site, and is considered
extirpated from two sites with repeated
survey years. Numbers observed during
searches at a site near Griswold in 2007
did not appear to change appreciably
since 2002 surveys, when the
population was estimated (nonquantitatively) to be approximately 750
individuals (Webster 2003, p. 5; Webster
2007, p. 4). A total of 273 adults were
observed during a 3.3-hour survey at the
second site, where the population was
estimated non-quantitatively to be about
2,000 individuals (Webster 2007, p. 4).
Survey methodology changes in the
years since 2007 (two to five surveys per
site per flight period in the timeframe
2009–2013 compared to single site visits
per year prior to 2008) have provided
more rigorous population estimates at
four Manitoba sites near Griswold and
have shown a marked reduction in
densities since 2002 or 2007 at three of
the four sites (Rigney 2013a, p. 117).
The Dakota skipper is present at two of
the four sites near Griswold with
repeated survey years. The estimated
densities (mean number of individuals
observed per hour) at one site remained
at 1/hour in 2011 and 2012 and was
approximately 30/hour in 2011 and 33/
hour in 2012 at a second site. The
species is considered extirpated at one
of these sites, because it was not
detected during 2010, 2011, and 2012
surveys. The status of the species is
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unknown at another site where the
estimated numbers fell from 2/hour to
zero detected in 2012 (Rigney 2013a, p.
117).
The Dakota skipper was first recorded
near Winnipeg in 1933 and near Miniota
in 1944 and then at two additional sites
in the early 1990s. The species is
considered to be extirpated or possibly
extirpated at all of these sites (Service
2014 unpubl. geodatabase).
In 2002, the species was observed at
19 sites near Lundar, within about 25
km (16 mi) east of Lake Manitoba
(Interlake region) (Webster 2003, p. 4);
however, most of these sites have not
been surveyed since. Similar to the
Griswold sites, the survey methodology
changes in years since 2007 (two to five
surveys per site per flight period during
2009–2013 compared to single site visits
per year prior to 2008) have provided
more rigorous population estimates at
four Manitoba sites near Lake Manitoba
(Interlake region) and have shown a
marked reduction in densities since
2002 or 2007 at two of the four sites
(Rigney 2013a, p. 117). The species is
considered present at two of four sites
that have been surveyed since 2002 in
this area; the species is considered
extirpated from the other two sites due
to three consecutive negative survey
years (2010, 2011, and 2012) (Rigney
2013a, p. 117). The mean number of
individuals observed per hour at one
site has declined from 2/hour in 2011 to
1/hour in 2012 (Rigney 2013a, p. 117).
The mean number per hour increased
from approximately 1/hour to 6/hour at
another site (Rigney 2013a, p. 117). The
species is considered to be present at
the remaining 14 Interlake sites that
have not been resurveyed since 2002
(Service 2014, unpublished database).
Several additional areas were
examined for potential Dakota skipper
habitat in 2007, including areas east of
Hwy 21, within the Lauder Sandhills
Wildlife Management Area, north of
Oak Lake and near Tilston, Sinclair,
Cromer, and Brandon, as well as other
locations. Most of the areas examined
were under row crop agriculture, were
heavily grazed, were dry scrub prairies,
or were otherwise habitats unsuitable
for Dakota skipper (Webster 2007, p. 6).
In 2007, the areas near Brandon and the
high ground within the wetland
complexes near Oak Lake still contained
potentially suitable habitat (Webster
2007, p. 6).
The nearest known extant (present)
population of Dakota skippers in
Manitoba is approximately 120 km (75
mi) from the closest extant (present)
population in North Dakota and about
111 km (69 mi) from the closest
Saskatchewan population. Britten and
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Glasford (2002, pp. 367, 372) suggested
that Manitoba populations are
genetically distinct from a group of
populations in Minnesota and South
Dakota, although populations in
additional intervening locations should
be sampled to confirm this hypothesis
(Runquist 2012b, pers. comm.).
Saskatchewan
Saskatchewan historically contained
approximately 5 percent (N=14) of all
known records of Dakota skippers
rangewide. In Saskatchewan, the Dakota
skipper is restricted to undisturbed or
lightly grazed, steep, south-facing hills
near the Souris River (Webster 2007, p.
ii). The Dakota skipper was first
recorded south of Oxbow,
Saskatchewan, in 2001 where three
males were collected (Hooper 2003, p.
124) on an ungrazed knoll within a
patch of mixed-grass prairie that was
approximately 1 ha (2 ac) in extent.
Dakota skippers were found at three
additional sites during 2002 surveys
(Webster 2003, pp. 6–7). In 2007,
researchers surveyed 16 sites in
southeastern Saskatchewan and found
Dakota skippers at 10 of these sites
(including Oxbow); 8 of these represent
new sites for the species in
Saskatchewan (Webster 2007, p. i).
During 2007 surveys, which were
conducted late in the flight period, only
a few individuals were observed at each
site where the species was present
(Webster 2007, p. ii). Nine of these sites
where the species was found in 2007
were surveyed along an approximate 50km (31-mi) stretch of steep hillsides
along the ridgeline north of Souris
River; distances between sites range
from 1 to 28 km (0.8 mi to 17 mi). We
consider Dakota skipper to be present at
all 14 sites in Saskatchewan, although 3
of those sites have not been surveyed
since 2002. The nearest known extant
population of Dakota skippers in
Saskatchewan is approximately 111 km
(69 mi) from the closest extant (present)
population in North Dakota and 200 km
(125 mi) from the closest Manitoba
population.
Poweshiek Skipperling
Species Description
The Poweshiek skipperling (Oarisma
poweshiek) is a member of the skipper
family, Hesperiidae, and was first
described by Parker (1870, pp. 271–
272). Parker (1870, pp. 271–272)
provided the original description of this
species from his type series collected
near Grinnell, Iowa. It was named for
the county in which it was found
(Poweshiek County), but it was
misspelled, Powesheik, in the original
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description. This spelling was retained
by most early authorities (Lindsey 1922,
p. 61; Holland 1931, p. 360). Miller and
Brown (1981, p. 31) used the corrected
spelling, Poweshiek, but then Miller and
Ferris (1989, p. 31) changed it back in
their supplement. Current usage is
mixed, with many authorities retaining
the original spelling (e.g., Miller 1992,
p. 20), while others have opted for the
corrected spelling (Layberry et al. 1998,
p. 48; Opler et al. 1998, p. 363;
Glassberg 1999, p. 167; Brock and
Kaufman 2003, p. 306). Layberry et al.
(1998, p. 48) state ‘‘. . . since it is a
clear case of an original incorrect
spelling it can be corrected [rule 32(c)ii
of the International Code of Zoological
Nomenclature].’’
Poweshiek skipperlings are small and
slender-bodied, with a wingspan
generally ranging from 2.3 to 3.0 cm (0.9
to 1.2 in). The size of Poweshiek
skipperlings appears to vary somewhat
across their range (Royer and Marrone
1992b, p. 3). North Dakota and South
Dakota specimens tend to be slightly
smaller than the 2.9 to 3.2 cm (1.1 to 1.3
in) range given by Parker (1870) for the
type specimens from Grinnell, Iowa
(Royer and Marrone 1992b, p. 3). A
sample of Richland County, North
Dakota, specimens from Royer’s
collection had an average wingspan of
2.8 cm (1.1 in) for males and 3.0 cm (1.2
in) for females. South Dakota specimens
in Marrone’s collection had an average
wingspan of 2.6 cm (1.0 in) for males
and 2.7 cm (1.1 in) for females. The
upper wing surface is dark brown with
a band of orange along the leading edge
of the forewing. Ground color of the
lower surface is also dark brown, but the
veins of all but the anal third of the
hindwing are outlined in hoary white,
giving an overall white appearance to
the undersurface.
The Poweshiek skipperling is most
easily confused with the Garita
skipperling (Oarisma garita), which can
be distinguished from Poweshiek
skipperling by their smaller size,
quicker flight, and overall goldenbronze color (Royer and Marrone 1992b,
p. 3). Another distinguishing feature is
the color of the anal area of the ventral
hindwing (orange in Garita; dark brown
in Poweshiek). The Garita skipperling
generally occurs west of Poweshiek
skipperling range, although there are
records of both species from two
counties in southeastern North Dakota
and two counties in northwestern
Minnesota (Montana State University—
Big Sky Institute 2012, Butterflies of
North America https://
www.butterfliesandmoths.org, Accessed
5/14/12; Minnesota Department of
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Natural Resources (DNR) 2012, Rare
features database. Accessed 5/14/12).
McAlpine (1972, pp. 85–92) described
Poweshiek skipperling eggs as pale
yellowish green, mushroom shaped
with a flattened bottom, a slightly
depressed micropyle (pore in the egg’s
membrane through which the sperm
enter) and smooth surfaced. They were
0.8 millimeters (mm) (0.01 in) long, 0.7
mm (0.03 in) wide and 0.5 mm (0.02 in)
high. The overall color of the head and
body of the larvae is pale grass-green,
with a distinctive darker green middorsal stripe and seven cream-colored
stripes on each side. First instars were
1.8 mm (0.07 in) at hatching, and the
lone 7th instar survivor was 23.6 mm
(1.0 in) near the end of that stage.
McAlpine did not have any observations
past the 7th instar (the stage between
successive molts, the first instar being
between hatching and the first molt)
(McAlpine 1972, pp. 85–93).
General Life History
Poweshiek skipperlings lay their eggs
near the tips of leaf blades and
overwinter as larvae on the host plants
(Bureau of Endangered Resources in
Swengel and Swengel 1999, p. 285,
Borkin 2000, p. 7). Poweshiek
skipperlings have also been documented
laying eggs on the entire length of grass
leaf blades and on low-growing
deciduous foliage (Dupont 2013, p. 133).
McAlpine (1972, pp. 85–92) described
the various life-history stages of
Poweshiek skipperling, and recent
studies of captive Poweshiek
skipperlings at the Minnesota Zoo
provide additional information
(Runquist 2013, pers. comm.). McAlpine
(1972, pp. 85–93) observed hatching of
larval Poweshiek skipperling after about
9 days. McAlpine’s records were
incomplete, and he did not have any
observations past the 7th instar, but he
believed that there should have been
one or two additional instars, followed
by the chrysalis (pupa) and then the
imago (adult) stages (McAlpine 1972,
pp. 85–93). Captive Poweshiek
skipperling eggs hatched 8 to 9 days
after oviposition (Runquist 2013, pers.
comm.). After hatching, Poweshiek
skipperling larvae crawl out near the tip
of grasses and may remain stationary,
with their head usually pointing
downward (McAlpine 1972, pp. 88–92).
Unlike Dakota skippers, Poweshiek
skipperling do not form shelters
underground (McAlpine 1972, pp. 88–
92; Borkin 1995, p. 9; Borkin 2008, pers.
comm.), instead the larvae overwinter
up on the blades of grasses and on the
stem near the base of the plant (Borkin
2008, pers. comm.; Dana 2008, pers.
comm.). Borkin (2008, pers. comm.)
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observed larvae moving to the tips of
grass blades to feed on the outer and
thinner edges of the blades, with later
movement down and among blades.
Mature Poweshiek skipperling
caterpillars reared in captivity ranged in
size from approximately 22 to 25 mm
(0.9 to 1 inch) in length just prior to
pupation (Runquist 2013, pers. comm.).
Food and Water
For the Poweshiek skipperling, nectar
plants vary across its geographic range.
Smooth ox-eye (Heliopsis helianthoides)
and purple coneflower were noted as
the frequently visited nectar plants in
Iowa, Minnesota, and North Dakota
(Swengel and Swengel 1999, p. 280).
Other nectar species used were stiff
tickseed (Coreopsis palmata), blackeyed Susan, and palespike lobelia
(Swengel and Swengel 1999, p. 280). On
drier prairie habitats in Iowa and
Minnesota, purple coneflower is used
almost exclusively, and the emergence
of the adults corresponds closely to the
early maturity of this species’ disk
florets (Selby 2005, p. 5). On the wetter
prairie habitats of Canada and the fen
habitats of Michigan, favored nectar
plants are black-eyed Susan, palespike
lobelia, sticky tofieldia (Triantha
glutinosa), and shrubby cinquefoil
(Dasiphora fruticosa ssp. floribunda)
(Nielsen 1970, p. 46; Holzman 1972, p.
111; Catling and Lafontaine 1986, p. 65;
Bess 1988, p. 13; Summerville and
Clampitt 1999, p. 231). Recent studies in
Manitoba indicate that the most
frequently used nectar plants are blackeyed Susan, upland white aster, and
self-heal (Prunella vulgaris) (Dupont
2013, pp. 70–71). In addition to
nutrition, the nectar of flowering forbs
provides water for Poweshiek
skipperling, which is necessary to avoid
desiccation during flight activity (Dana
2013, pers. comm.).
Until recently, the larval food plant
was presumed to be elliptic spikerush
(Eleocharis elliptica) or sedges, but this
was based on limited observations,
primarily from the Michigan
populations (e.g., Holzman 1972, p.
113). More recent observations show
that the preferred larval food plant for
some populations of Poweshiek
skipperling is prairie dropseed (Borkin
1995, p. 6); larvae have also been
observed feeding on little bluestem
(Schizachyrium scoparium) (Borkin
1995, pp. 5–6) and sideoats grama
(Bouteloua curtipendula) (Dana 2005a,
pers. comm.). Poweshiek skipperling
larvae have been observed feeding on
Carex sp. (Borkin 1994, p. 6; Borkin
1996, p. 2), although not through the
entire larval development (Borkin 2014,
pers. comm.). Poweshiek skipperling
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have been observed laying eggs
(ovipositing) on mat muhly
(Muhlenbergia richardsonis) (Cuthrell
2012a, pers. comm.), a grass in
Michigan’s prairie fens (Penskar and
Higman 1999, p. 1). Captive-reared
caterpillars fed most successfully on
prairie dropseed, and older caterpillars
(late 2-day instar and older) successfully
fed on little bluestem, big bluestem, and
side-oats gramma (Runquist 2013, pers.
comm.). One post-diapause Poweshiek
skipperling was successfully reared to
adulthood on Pennsylvania sedge
(Carex pensylvanica) (Runquist 2013,
pers. comm.).
In southwestern Minnesota dry hill
prairies, Poweshiek skipperling
oviposition was observed on prairie
dropseed, little bluestem, big bluestem,
porcupine grass, and a couple
unidentified species; a larva was
observed feeding on sideoats grama
(Dana 2005a, pers. comm.). Poweshiek
skipperlings were observed to oviposit
on big bluestem in Wisconsin (Borkin
2012a, pers. comm.), although
indiscriminate oviposition on
unsuitable larval plants has been
observed during high summer
temperatures (Borkin 1995, p. 6). Borkin
(1995, p. 4) also observed oviposition on
an unidentified sedge (Eleocharis sp.),
but only 2 eggs were found on the sedge
in comparison to more than 100 eggs
found on prairie dropseed. In Manitoba,
Poweshiek skipperlings were observed
ovipositing on big bluestem, white
sweet clover, an unidentified goldenrod
(Solidago spp.), and juvenile bur oak
(Quercus macrocarpa) leaves (Dupont
2013, p. 73). Poweshiek skipperlings
have also been documented laying eggs
on the entire length of grass leaf blades,
including the tips, and on low-growing
deciduous foliage (Dupont 2013, p. 133).
Dana (2013, pers. comm.) noted that
larvae seem to begin feeding at a very
fine, threadlike blade tip and females
placed eggs on fine blade tips of grasses
during some observed ovipositions.
Consistent with field observations of
female oviposition on fine blades of
grass, captive-reared caterpillars (early
instars) preferred feeding on finer leaf
blades (Runquist 2013, pers. comm.).
Dispersal
Poweshiek skipperlings are also not
known to disperse widely; the species
was evaluated among 291 butterfly
species in Canada as having relatively
low mobility; experts estimated
Poweshiek skipperling to have a mean
mobility of 2 (standard deviation = 1.4)
on a scale of 0 (sedentary) to 10 (highly
mobile) (Burke et al. 2011, p. 2279;
Fitzsimmons 2012, pers. comm.). A
mark–recapture study was conducted in
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Manitoba in 2008 and 2009; however,
only 2 of the 56 marked individuals in
2008 were recaptured and none of the
16 marked individuals in 2009 were
recaptured, so available data are
insufficient to examine within and
between site dispersal (Dupont 2013,
pp. 68–70). After 2 days, the two
recaptured individuals were within 50
m (165 ft) of their initial capture
location (Dupont 2013, p. 69).
Besides this study in Manitoba, which
had too few recaptures to make any
statistically significant conclusions, we
are unaware of any other studies that
documented the dispersal distance of
the species. Therefore, we used the
Dakota skipper as a surrogate species to
estimate the maximum dispersal
distance of Poweshiek skipperlings and
verified our assumptions with expert
review. In a mark–recapture study,
average adult movements of Dakota
skippers were less than 300 meters (m)
(984 feet (ft)) during a period of 3–7
days; marked adults crossed less than
200 m (656 ft) of unsuitable habitat
between two prairie patches and moved
along ridges more frequently than across
valleys (Dana 1991, pp. 38–40). Dana
(1997, p. 5) later observed reduced
movement rates across a small valley
dominated by exotic grasses with roads
and crop fields compared with
movements in adjacent widespread
prairie habitat. Roads and crop fields
were suspected as impediments for
movement among prairie patches along
two sites of the main valley (Dana 1997,
p. 5), although movements beyond the
study area were beyond the scope of the
1997 mark–recapture study (Dana 2013,
pers. comm.). Skadsen (1999, p. 2)
reported possible movement of Dakota
skippers in 1998 from a known
population at least 800 m (2,625 ft)
away to a site with an unusually heavy
growth of purple coneflower; he had not
found Dakota skippers in three previous
years when coneflower production was
sparse.
Based on expert opinion, a maximum
dispersal distance of 1.6 km (1.0 mi)
was estimated to be a reasonable and
likely distance for male Poweshiek
skipperling to travel between patches of
prairie habitat separated by structurally
similar habitats (e.g., perennial
grasslands but not necessarily native
prairie) (Westwood 2012a and 2012b,
pers. comm.; Dana 2012b, pers. comm.).
The species, however, will not likely
disperse across habitat that is not
structurally similar to native prairies,
such as certain types of row crops or
anywhere not dominated by grasses
(Westwood 2012a and 2012b, pers.
comm.; Dana 2012b, pers. comm.). In
Manitoba, Poweshiek skipperling have
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been observed avoiding dispersal over
short distances, even to suitable habitat,
if a barrier such as a road exists between
suitable prairie habitat and nectar
sources (Westwood et al. 2012, p. 18).
Since experts estimated Dakota
skippers to have a mean mobility of 3.5
(standard deviation = 0.7) on a scale of
0 (sedentary) to 10 (highly mobile),
which is higher than the estimate for the
Poweshiek skipperling (mean mobility
of 2) (Burke et al. 2011, p. 2279;
Fitzsimmons 2012, pers. comm.), we
used the estimated dispersal distance of
the Dakota skipper, approximately 1 km
(0.6 mi) (Cochrane and Delphey 2002, p.
6), which is more conservative than the
1.6 km (1.0 mi) estimated for the
Poweshiek skipperling by expert
opinion (Westwood 2012b, pers. comm.,
Dana 2012b, pers. comm.). One
kilometer is a reasonable maximum
dispersal distance, since no data
documents the species that document a
greater distance travelled.
In summary, using the best
information available, dispersal of
Poweshiek skipperling is very limited
due in part to its short adult life span
and single annual flight. Therefore, the
species’ extirpation from a site is likely
permanent unless it is within about 1
km (0.6 mi) of a site that generates a
sufficient number of emigrants or is
artificially reintroduced to a site;
however, the capability to propagate the
Poweshiek skipperling is currently
lacking.
Habitat
Poweshiek skipperling habitats
include prairie fens, grassy lake and
stream margins, moist meadows, sedge
meadow, and wet-to-dry prairie.
McCabe and Post (McCabe and Post
1977, pp. 36–38) describe the species’
habitat in North Dakota as ‘‘. . . high
dry prairie and low, moist prairie
stretches as well as old fields and
meadows.’’ Royer and Marrone (1992b,
p. 12) describe Poweshiek skipperling
habitat in North Dakota and South
Dakota as moist ground in undisturbed
native tallgrass prairies. Poweshiek
skipperling habitat throughout Iowa and
Minnesota is described as both ‘‘high
dry’’ and ‘‘low wet’’ prairie (McCabe
and Post 1977, pp. 36–38). The only
documented Illinois record was
associated with high rolling prairie
(Dodge 1872, p. 218); the only
documented Indiana record was from
marshy lakeshores and wetlands
(Blatchley 1891, p. 398; Shull 1987, p.
29).
Southern dry prairies in Minnesota
are described as having sparse shrub
cover (less than 5 percent) composed
primarily of leadplant, with prairie rose,
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wormwood sage, or smooth sumac
present and few, if any, trees (Minnesota
DNR 2012a, p. 1). Southern mesic
prairies also have sparse shrubs (5–25
percent cover) consisting of leadplant
and prairie rose with occasional
wolfberry (Symphoricarpos
occidentalis) and few, if any, trees
(Minnesota DNR 2012b, p. 1).
The disjunct populations of
Poweshiek skipperlings in Michigan
have more narrowly defined habitat
preferences, variously described as wet
marshy meadows (Holzman 1972, p.
114), bog fen meadows or carrs (Shuey
1985, p. 181), sedge fens (Bess 1988, p.
13), and prairie fens (Michigan Natural
Features Inventory 2011, unpubl. data;
Michigan Natural Features Inventory
2012, unpubl. data); prairie fen is the
currently accepted name for this habitat
type. Bess (1988, p. 13) found the
species primarily in the drier portions of
Liberty Fen, Jackson County, dominated
by ‘‘low sedges’’ and an abundance of
nectar sources. Summerville and
Clampitt (1999, p. 231) noted that the
population was concentrated in areas
dominated by spikerush and that only
10–15 percent of the fen area was
occupied despite the abundance of
nectar sources throughout. Poweshiek
skipperling have been described as
occupying peat domes within larger
prairie fen complexes in areas either
dominated by mat muhly or prairie
dropseed (Cuthrell 2013a, pers. comm.).
A few prairie fens in Michigan also
contain other rare butterflies, such as
Mitchell’s satyr and swamp metalmark
(Cuthrell 2013a, pers. comm.).
Poweshiek skipperling populations in
Wisconsin are also disjunct from the
population to the west and are
associated with areas that contain
intermixed wet prairie, wet-mesic, and
dry-mesic prairie habitats (Borkin 1995,
p. 6; Swengel 2013, pers. comm.). The
dry-mesic habitats in the Scuppernong
Prairie contain ‘‘extensive patches of
prairie dropseed and little bluestem
grasses’’ (Borkin 1995, p. 7). Survival in
wetter areas, which tend to burn cooler
and less completely, coupled with low
recolonization rates, or the
disproportionate loss of wet versus dry
prairie could give the false impression
that the wet areas were their preferred
habitat (Borkin 1995, p. 7). Puchyan
Prairie consists of wet-mesic prairie that
grades lower into sedge meadow (WI
DNR Web site https://dnr.wi.gov/topic/
Lands/naturalareas/
index.asp?SNA=172; Swengel 2013,
pers. comm.) and adult Poweshiek
Skipperlings have been observed in wet
prairie there, although it is not known
if these areas function as successful
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larval habitat (Swengel 2013, pers.
comm.).
Like the Dakota skipper, it has been
hypothesized that Poweshiek
skipperling larvae may be vulnerable to
desiccation during dry summer months
(Borkin 2012a, pers. comm.) and require
movement of shallow groundwater to
the soil surface or wet low areas to
provide relief from high summer
temperatures or dry conditions (Royer et
al. 2008, pp. 2, 16; Borkin 2012a, pers.
comm.). Humidity may also be an
essential factor to larval survival during
winter months since the larvae cannot
take in water during that time and
depend on humid air to minimize water
loss through respiration (Dana 2013,
pers. comm.).
Royer (2008, pp. 14–15) measured
microclimatological (climate in a small
space, such as at or near the soil surface)
levels within ‘‘larval nesting zones’’ (0
to 2 cm above the soil surface) at six
known Poweshiek skipperling sites, and
found an acceptable rangewide seasonal
(summer) mean temperature range of 18
to 21 °C (64 to 70 °F), rangewide
seasonal mean dew point ranging from
14 to 17 °C (57 to 63 °F), and rangewide
seasonal mean relative humidity
between 73 and 85 percent. Royer
(2008) examined only occupied areas for
these parameters; therefore, the
statistical and biological significance of
these edaphic variables cannot be
determined from his study.
Canadian populations of Poweshiek
skipperlings are restricted to a single
2,300-ha (5,683-ac) area in southeastern
Manitoba (COSEWIC 2003, p. 5). The
wet to mesic tallgrass prairie in this area
is characterized by low relief (1–2 m (3–
7 ft)), with alternating lower, wetter
areas and higher, drier prairie;
Poweshiek skipperlings tend to be
concentrated on or near the edge of the
higher, drier prairie (COSEWIC 2003, p.
8). Spikerush is frequent in the wetter
areas, and prairie dropseed, black-eyed
Susan, and palespike lobelia are
frequent in the drier areas (COSEWIC
2003, pp. 7–8). The wet-mesic tallgrass
prairies in Manitoba vary in size and
occur along bluffs of Bur oak and
trembling aspen (Populus tremuloides
Michx.) (Catling and Lafontaine 1986;
Dupont 2013, p. 17). Little bluestem, big
bluestem, and Indian grass were the
three most common grasses in managed
study plots in Manitoba (Dupont 2013,
p. 85). Plant species generally associated
with upland, drier portions of the mesic
tallgrass prairies in Manitoba include:
Big bluestem, pale-spike lobelia, prairie
dropseed, mountain death camas, stiff
goldenrod, black-eyed Susan, and
meadow blazing-star (Environment
Canada 2012, p. 6). In lower, wetter
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prairies with Poweshiek skipperlings,
the following species are listed as often
seen: Willow (Salix spp.), sedges (Carex
spp.), rushes (Juncus spp.), groundsels
(Pakera spp.), tufted hairgrass, creeping
bentgrass (Agrostis stolonifera), mat
muhly, elliptic spike-rush, fourflowered yellow loosestrife (Lysimachia
quadriflora), and common self-heal
(Environment Canada 2012, p. 6). Most
of these plants were also commonly
observed in study plots surveyed in
2008–2009 (Dupont 2013, p. 86). The
soils where the Poweshiek skipperling
occurs in Manitoba are described as
shallow, rocky, and highly calcareous
(Westwood and Borkowsky 2004 in
Dupont 2013, p. 19).
Prairie fen habitat soils in Michigan
are described as saturated organic soils
(sedge peat and wood peat) and marl, a
calcium carbonate (CaCO3) precipitate
(MINFI Web site accessed August 3,
2012). In other States, soil textures in
Poweshiek skipperling habitats are
classified as loam, sandy loam, or loamy
sand (Royer et al. 2008, pp. 3, 10); soils
in moraine deposits are described as
gravelly, except the deposits associated
with glacial lakes.
Population Distribution and Occupancy
The Poweshiek skipperling is
historically known from eight States,
ranging widely over the native wetmesic to dry tallgrass prairies from
eastern North and South Dakota (Royer
and Marrone 1992b, pp. 4–5) through
Iowa (Nekola and Schlicht 2007, p. 7)
and Minnesota (Minnesota DNR,
Division of Ecological Resources,
unpubl. data), with occurrences also
documented in northern Illinois (Dodge
1872, p. 218), Indiana (Blatchley 1891,
p. 898), Michigan (Holzman 1972, p.
111; McAlpine 1972, p. 83), and
Wisconsin (Borkin 2011, in litt.; Selby
2010, p. 22). The relatively recent
discovery of Poweshiek skipperling
populations in the Canadian province of
Manitoba further extends its known
historical northern distribution
(Westwood 2010, pp. 7–22; Dupont
2010, pers. comm.). Additional
historical accounts of Poweshiek
skipperling from the States of Montana,
Colorado, and Nebraska are likely
misidentifications of its western
congener, the Garita skipperling.
Once common and abundant
throughout native prairies in eight
States and at least one Canadian
province, the Poweshiek skipperling
and its habitat have experienced
significant declines. The species is
considered to be present at a few native
prairie remnants in two States and one
location in Manitoba, Canada. The
species is presumed extirpated from
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Illinois and Indiana, and the status of
the species is uncertain in four of the six
States with relatively recent records
(within the last 20 years). The historical
distribution of Poweshiek skipperling
may never be precisely known because
‘‘much of tallgrass prairie was
extirpated prior to extensive ecological
study’’ (Steinauer and Collins 1994, p.
42), such as butterfly surveys.
Destruction of tallgrass and mixed-grass
prairie began in 1830 (Sampson and
Knopf 1994, p. 418), but significant
documentation of the ecosystem’s
butterfly fauna did not begin until about
1960. Therefore, most of the decline of
the Poweshiek skipperling probably
went unrecorded. Poweshiek
skipperling dispersal is very limited due
in part to its short adult life span and
single annual flight. Therefore, the
species’ extirpation from a site is likely
permanent unless it is within about 1
km (0.6 mi) of a site that generates a
sufficient number of emigrants or is
artificially reintroduced to a site.
Recent survey data indicate that
Poweshiek skipperling has declined to
zero or to undetectable levels at 96
percent of sites where it has ever been
recorded. Until about 2003, Poweshiek
skipperling was regarded as the most
frequently and reliably encountered
prairie-obligate skipper butterfly in
Minnesota, which contains
approximately 48 percent of all known
Poweshiek skipperling locations
rangewide. Numbers and distribution
dropped dramatically in subsequent
years, however, and the species was not
seen in Minnesota from 2007 through
2012. Two individuals were observed at
one site in 2013 (Weber 2014, in litt.;
Dana 2014, pers. comm.). In Iowa, the
Poweshiek skipperling was found at 2 of
33 sites with previous records surveyed
in 2007; the species was last observed
at one site in 2008. Iowa contains about
14 percent of documented sites
rangewide. Unidentified threats to the
species have acted to extirpate or
sharply diminish populations at all or
the vast majority of sites in Iowa and
Minnesota (Dana 2008, p. 16; Selby
2010, p. 7).
South Dakota historically contained
about 23 percent of the rangewide sites
with documented presence of
Poweshiek skipperling, although recent
surveys in that State also suggest an
emergent and mysterious decline. The
species was last observed in South
Dakota in 2008, at three sites. Surveys
conducted in 2009–2013 flight seasons
in South Dakota resulted in zero
detections of the species. North Dakota
historically contained about six percent
of the rangewide sites with documented
presence of Poweshiek skipperling; the
species was last observed in North
Dakota in 2001. Survey efforts in North
Dakota have been minimal between
1998 and 2011, but surveys conducted
in 1997 documented more than 10
Poweshiek skipperlings at 1 site; 6
individuals were counted at 1 site, and
0 were detected at 6 other sites. Surveys
conducted during the 2012 and 2013
flight seasons in North Dakota resulted
in zero detections of the species.
Seven Michigan sites were recently
ranked as having good or better
‘‘viability,’’ a habitat-based element
occurrence rank assigned by the
Michigan Natural Features Inventory
(2011); however, the number of
individuals observed at a few of those
sites has declined in recent years, and
the species is presumed extirpated from
one of those sites. Currently, four of the
ten extant occurrences of Poweshiek
skipperling in Michigan are considered
to have good or better viability
(Michigan Natural Features Inventory
(2011, unpubl. data). Each of those faces
threats of at least low to moderate
magnitude, and the State contains only
about 6 percent of all known historical
Poweshiek skipperling records. One
population of Poweshiek skipperlings in
Wisconsin had fairly consistent
numbers observed over the last 5 years
(17 to 63 individuals counted using
modified Pollard transect covering 15 ac
(6 ha) in approximately 40 minutes), but
the species was not observed in 2013
surveys. One population in Manitoba
has fairly consistent numbers (typically
hundreds of individuals observed each
year). To summarize, of the 298
documented sites, there are 12 sites
where we consider the Poweshiek
skipperling to be present, 111 sites with
unknown status, 96 possibly extirpated
sites, and 79 where we consider the
species to be extirpated (Table 2). The
distribution and status of Poweshiek
skipperling in each State of known
historical or extant occurrence are
described in detail below.
TABLE 2—NUMBER OF HISTORICALLY DOCUMENTED POWESHIEK SKIPPERLING SITES WITHIN EACH STATE AND THE NUMBER OF SITES WHERE THE SPECIES IS THOUGHT TO BE PRESENT, UNKNOWN, POSSIBLY EXTIRPATED, OR EXTIRPATED
State’s
percentage
of the total
number of
historical
sites
State
Present
Unknown
Possibly
extirpated
Extirpated
Total
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Illinois ...............................................................................
Indiana .............................................................................
Iowa ..................................................................................
Michigan ...........................................................................
Minnesota .........................................................................
North Dakota ....................................................................
South Dakota ...................................................................
Wisconsin .........................................................................
Manitoba ..........................................................................
1.3
0.3
13.8
5.7
48.3
5.7
23.2
1.3
0.3
....................
....................
....................
9
1
....................
....................
1
1
....................
....................
4
2
58
8
36
3
....................
....................
....................
24
....................
64
6
2
....................
....................
4
1
13
6
21
3
31
....................
....................
4
1
41
17
144
17
69
4
1
Total Number of Historically Documented Sites ......
Percent of the Total Number of Historical Sites by Occupancy ........................................................................
....................
12
111
96
79
298
....................
4%
37%
32%
27%
....................
Illinois
The Poweshiek skipperling
historically occurred in Illinois,
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although only one historical occurrence
is supported (Table 2). In the early
1870s, Dodge (1872, p. 218) reported
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abundant Poweshiek skipperling
occupying ‘‘the high rolling prairie that
forms the divide between the Illinois
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and Rock rivers’’ in Bureau County,
Illinois. In addition to Bureau County,
the Web site Butterflies and Moths of
North America lists Poweshiek
skipperling historical occurrences for
Lake and Mason Counties, which were
submitted to the Web site before the
date field was required, so a default date
of January 1, 1950, was assigned, which
is outside of the typical flight period
(https://www.butterfliesandmoths.org/
species/Oarisma-poweshiek; accessed
August 16, 2012). The Web site
maintains a verifiable database on
species occurrences, but there is no
accessible supporting data for the Lake
and Mason Counties records (Lundh
2012, pers. comm.). One additional
record, housed at University of
Wisconsin–Oshkosh, was collected in
DuPage County in 1968 and was
recently identified as a Poweshiek
skipperling. The location where the
specimen was collected has since been
converted and is no longer a prairie, and
it is presumed that the species is
extirpated from that location (Borkin
2014, pers. comm.). Poweshiek
skipperling is, therefore, presumed to be
extirpated from Illinois.
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Indiana
There is one supported historical
occurrence of Poweshiek skipperlings in
Indiana (Table 2). Blatchley (1891, p.
898) reported small numbers of
Poweshiek skipperlings near Whiting,
Indiana; Shull (1987, p. 49) expressed
confidence that this record is authentic.
The Poweshiek skipperling is
considered extirpated from Indiana.
Iowa
Iowa historically contained
approximately 14 percent (N=41) of all
known records of Poweshiek
skipperlings rangewide (Table 2). The
Poweshiek skipperling was historically
known to occur at 38 sites in 13
counties in Iowa (Nekola 1995, p. 8;
Saunders 1995, pp. 27–28; Selby 2005,
p. 18; Nekola and Schlicht 2007, p. 7;
Selby 2010, p. 6); however, this number
may vary slightly (up to 41 sites)
depending on how one divides sites
along the Little Sioux River in the
Freda-Cayler area (Selby 2012a, pers.
comm.). Early reports from Parker (1870,
p. 271) described Poweshiek skipperling
as abundant on a prairie slope at
Grinnell, Iowa, while Lindsey (1917, p.
352; 1920, p. 320) noted additional rare
occurrences in Story, Dickinson,
Poweshiek, and Woodbury Counties,
Iowa—among these, habitat has long
since been destroyed in all but
Dickinson County.
In 1993–1994, 65 sites were surveyed
in 17 counties where Dakota skipper or
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Poweshiek skipperling had been
previously recorded or where prairie
and butterfly surveys or infra-red
photography suggested the presence of
Poweshiek skipperling habitat
(Saunders 1995, pp. 7–8). Among the 65
sites surveyed, Poweshiek skipperlings
were found at 29 sites in 10 counties
(Saunders 1995, p. 27). In 2000,
Poweshiek skipperlings were found at
six sites surveyed in and near Cayler
Prairie and Freda Haffner Kettlehole
State preserves in Dickinson County
(Selby 2000, p. 19). Followup surveys of
this complex in 2004, 2005, and 2007,
however, produced no confirmed
sightings (Selby 2010, p. 6). Extensive
surveys were conducted in 2007, and
included 32 of the 38 sites in the State
with post-1990 records (Selby 2008, pp.
4, 6). Poweshiek skipperlings were
found at 2 of the 38 sites surveyed—
Hoffman Prairie State Preserve in Cerro
Gordo County and Highway 60 Railroad
Prairie in Osceola County (Selby 2008,
pp. 6–7). Five of the six sites not
included in the 2007 surveys had very
little quality prairie (Selby 2012a, pers.
comm.). Supplementary surveys
conducted further west along U.S.
Highway 18 in Hancock County also
produced no confirmed sightings (Selby
2010, p. 7). No surveys were conducted
at previously known Poweshiek
skipperling sites in the State during the
2012 flight season. No Poweshiek
skipperlings were observed in surveys
in 2013 at two sites with relatively
recent records of the species (2005 and
2008) (Olsen 2013, p. 2).
The Poweshiek skipperling is
presumed extirpated or possibly
extirpated from all but four of the
known sites in Iowa. The status of the
Poweshiek skipperling is unknown at
four sites: Highway 60 Railroad Prairie,
Floete Prairie in Dickinson County,
Florenceville Prairie, and Hayden
Prairie in Howard County. There have
been no surveys at Highway 60 Railroad
Prairie since the species was observed
there in 2007 (Selby 2012a, pers.
comm.). The last observation of
Poweshiek skipperling at Floete Prairie
was in 1994, and the habitat ‘‘did not
appear to be very good quality’’ in 2007,
although the site was not surveyed for
butterflies that year (Selby 2012a, pers.
comm.) or in subsequent years. The
Poweshiek skipperling was last
observed at the Florenceville Prairie in
1994 (Saunders 1995, p. 27), but not
during the 2007 survey year (Selby
2010, pp. 8–11). The species was last
observed at Hayden Prairie in 2005, but
not during surveys conducted in 2007
(Selby 2010, p. 10) or 2013 (Olsen 2013,
p. 2). Four Poweshiek skipperlings were
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found at Hoffman Prairie in Cerro Gordo
County in 2008 (Selby 2009b, p. 3), but
none were found during surveys in 2009
(Selby 2009b, p. 7) and 2010 (Selby
2010, p. 7). We initially assigned an
unknown status to the Hoffman Prairie
site because the species had not been
seen in the 2009 and 2010 survey years;
however, Selby believes that the species
may be extirpated from this site (Selby
2012a, pers. comm.), so we assigned a
status of extirpated to this site, which
was confirmed with negative surveys in
the 2013 flight season (Olsen 2013, p. 2).
To summarize, the Poweshiek
skipperling was historically
documented in 41 sites in Iowa. The
species occupancy is unknown at 4 of
those sites, and the species is
considered to be extirpated or possibly
extirpated at 13 and 24 sites,
respectively (Table 2). The species is not
considered to be present at any of the
sites in Iowa.
Michigan
Michigan historically contained
approximately 6 percent (N=17) of all
known records of Poweshiek
skipperlings rangewide (Table 2).
Poweshiek skipperling has been
historically documented at 17 sites in 6
counties in Michigan. The species was
first recorded in Michigan in 1893 at
Lamberton Lake near Grand Rapids in
Kent County (Holzman 1972, p. 111)
and then at nearby Button Lake Fen
(also known as Emerald Lake Fen) in
1944 (McAlpine 1972, p. 83). Shrubs
have invaded both sites, however, and
no Poweshiek skipperlings have been
found at either of these two western
Michigan sites since 1944 and 1968,
respectively (Michigan Natural Features
Inventory 2011, unpubl. data). Holzman
(1972, p. 111) documented Poweshiek
skipperling in Oakland County in 1970,
and the species has since been found at
a total of 15 locations in eastern
Michigan.
The Poweshiek skipperling is
currently considered to be present at
nine sites (Table 2) in four counties in
Michigan: Jackson, Lenawee, Oakland,
and Washtenaw. The species has been
observed recently (2008–2013) at most
of those sites, except at the Liberty Bowl
Fen in Jackson County, which has not
been surveyed since one individual was
observed in 1996. The status of the
species is unknown at two sites; Bullard
Lake in Livingston County, where
Poweshiek skipperlings were last seen
in 2007, but not in subsequent surveys
in 2008 and 2009 (Cuthrell 2012a, pers.
comm.), and Liberty Fen (Grand River
Fen) in Jackson County, where
Poweshiek skipperlings were observed
in 2012 but not in 2013 surveys
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(Cuthrell 2013, pers. comm.). The
species is presumed extirpated from six
sites including the only two sites in
Kent County and three sites in Oakland
County: Rattalee Road, Fenton Road,
and Rattalee Lake Fen (Call C Burr
Preserve) fens. The species has not been
observed at the Rattalee Road and
Fenton Road sites since 1970 and 1973,
respectively (Michigan Natural Features
Inventory 2011, unpubl. data). Four
Poweshiek skipperlings were seen in
2009 at the Rattalee Lake Fen (Calla C
Burr Preserve), but none were observed
during surveys conducted in 2010,
2011, and 2012 (Cuthrell 2012a, pers.
comm.; Michigan Natural Features
Inventory 2011, unpubl. data). The
Michigan Natural Features Inventory
(MNFI) also considers the two sites in
Kent County to be extirpated due to
habitat loss and destruction, Lamberton
Lake and Button Lake (also known as
Emerald Lake); the species has not been
observed at either site since 1968 and
1944, respectively. The species is
presumed to be extirpated at Whalen
Lake Fen in Livingston County, where
the species has not been observed since
1998 despite three subsequent years of
surveys (Michigan Natural Features
Inventory 2011, unpubl. data).
Four of Michigan’s nine extant
(present) Poweshiek skipperling
occurrences were recently considered to
have at least good viability (Michigan
Natural Features Inventory 2011,
unpubl. data); however, 2013 survey
results have put the viability in
question. Three of these sites, Buckhorn
Lake also known as Big Valley), Brandt
Road Fen (also known as Holly Fen) and
Long Lake Fen, are within 20 km (12 mi)
of one another in Oakland County; all
with relatively large numbers (61–389)
of the species recorded in 2010–2012
surveys (Michigan Natural Features
Inventory 2011, unpubl. data; Cuthrell
2012a, pers. comm.). In 2013, however,
2 individuals (0.008/hr.) were recorded
at Buckhorn Lake, which was down
from 84 individuals (0.35/hr.) recorded
the previous survey year (2012) with
similar effort, and 53 individuals (0.33/
hr.) were recorded at Brandt Road in
2013, down from 71 individuals (0.59/
hr.) recorded the previous survey year
(2012) with similar effort. The largest
extant (present) Poweshiek skipperling
population in Michigan may be at Long
Lake Fen, where 25 individuals (0.2/hr.)
were counted during 2013 surveys,
down from 389 individuals (2.2/hr.) and
225 individuals (1.3/hr.) observed in the
previous two survey years (2011 and
2012, respectively) with similar
sampling effort. In 2012, Long Lake Fen
was thought to be the largest population
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of Poweshiek skipperling in the United
States. However, it is subjected to
intense development pressure, and
results from 2013 surveys show low
numbers. A fourth site, Grand River Fen
(also known as Liberty Fen) in Jackson
County, is approximately 100 km (62
mi) from the other three sites, and was
also considered to have good viability in
2011, but the viability is questionable
since 2013 surveys for the species were
negative. In 2010, researchers counted
54 (0.3/hr.) Poweshiek skipperling at
Grand River Fen, and 114 (0.6/hr.) in
2011 (Michigan Natural Features
Inventory 2011, unpubl. data; Cuthrell
2012a, pers. comm.). This number fell to
14 (0.1/hr.) in 2012 and zero in 2013
(Cuthrell, 2012a, pers. comm.; 2012b,
pers. comm.; 2013, pers. comm.).
Small populations, immediate threats
that have significant impacts on the
species, or both limit the viability of the
remaining five sites where we consider
Poweshiek skipperling to still be present
in Michigan. In 2010, eight (0.1/hr.)
Poweshiek skipperlings were recorded
at Park Lydon in Washtenaw County; 12
individuals were counted in 2011 (0.1/
hr.), 22 were counted in 2012 (0.2/hr.),
and 1 individual was counted in 2013
(Cuthrell 2012a, pers. comm.; 2013,
pers. comm.). Two individuals (0.02/hr.)
were recorded at Goose Creek
Grasslands (also known as Little Goose
Lake Fen) in Lenawee County in 2010,
and nine (0.07/hr.) were seen in 2011
(Cuthrell 2012a, pers. comm.; 2012b,
pers. comm.). Only one Poweshiek
skipperling was seen during a 15minute 3-person survey in 2007 at the
Snyder Lake site. Fourteen individuals
were observed during 2008 surveys at
Halstead Lake Fen (Michigan Natural
Features Inventory 2011, unpubl. data),
and 18 were observed in 2012 (Cuthrell
2012a, pers. comm.); neither survey year
had units of effort associated with the
counts at this site. One individual was
counted at Bullard Lake fen in 2007, but
the species was not observed in the two
most recent survey years (2008 and
2009); therefore, the status is unknown
at that site. We have only one year of
data from Liberty Bowl Fen, where the
species was recorded in 1996. The Eaton
Road Fen is thought to be fairly viable,
where 15–20 individuals were observed
on multiple occasions in 2005, and a
high of 68 individuals were observed in
2011 (Cuthrell 2012b, pers. comm.). The
Eaton Road site is approximately 0.6 km
(1 mi) from the Long Lake Fen site and
is considered a sub-site within Long
Lake Fen (Cuthrell 2012b, pers. comm.),
but we consider it to be a separate site
for the purposes of this rule.
To summarize, Poweshiek skipperling
was historically documented in 17 sites
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in Michigan (Table 2). The species is
considered to be present at 9 of the sites,
although the numbers observed in 2013
were substantially less than in previous
years with similar survey effort. The
occupancy is unknown at 2 sites, and
the species is considered to be
extirpated at 6 sites.
Minnesota
Minnesota historically contained
approximately 48 percent (N=144) of all
known records of Poweshiek
skipperlings rangewide (Table 2). There
are approximately 189 historical
Poweshiek skipperling occurrence
records in 32 counties in Minnesota
[Minnesota Natural Heritage Inventory
(MN NHI) database accessed June 19,
2013, plus additional surveys]. Clusters
of records occur within five general
areas from the State’s southwest corner
to near the Canadian border in the
north. Based on the proximity of some
occurrences to one another (e.g.,
overlapping or occurrences in close
proximity to one another in one general
location), there appear to be
approximately 144 distinct historical
site records in the State (Dana 2012d,
pers. comm; Service 2014, unpubl.
geodatabase). Poweshiek skipperling are
presumed extirpated or possibly
extirpated from at least 85 of these
known sites. The status of the species is
unknown at 58 sites, although 27 of
those locations have not been surveyed
since 2003, and the species has
undergone a sharp decline in the State
since then.
An extensive survey effort was
completed in 1993 and 1994 (Schlicht
and Saunders 1994, entire; Schlicht and
Saunders 1995, entire). During those
surveys, Poweshiek skipperlings were
found in 11 of 19 sites on which the
species had been previously recorded
and in 13 new sites, for a total of 25 of
63 surveyed prairie sites; the species
was present at 30 and 39 percent of the
sites in 1993 and 1994, respectively
(Schlicht and Saunders 1995, pp. 5–7).
These results contrast sharply with
those from the surveys conducted in
2007 and 2008, when the species was
found at four and zero percent of sites,
respectively. Although the species was
apparently more common in 1993 and
1994, numbers of Poweshiek skipperling
found during surveys were typically
low. Large numbers were observed at
only three sites (Schlicht and Saunders
1995, p. 4). At one of these sites, Glynn
Prairie, 25 Poweshiek skipperling were
recorded during a 50-minute survey in
July 1993 (Schlicht and Saunders 1995,
data sheet); no Poweshiek skipperling
were observed at this site during the
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2007 survey despite good survey
conditions (Selby 2009a, p. xxxv).
Until about 2003, the Poweshiek
skipperling was regarded as ‘‘the most
frequently and reliably encountered
prairie-obligate skipper in Minnesota’’
(Dana 2008, p. 1). Signs of the species’
decline in Minnesota were noted in
2003 when Selby (2005, p. 20) found
sharply lower numbers in and near
Glacial Lakes State Park (Selby 2005, p.
20) compared to those observed in 2001
(Skadsen 2001, pp. 22–24). For example,
numbers recorded along four transects
that were surveyed in both years
decreased from 104 to 2 individuals
(Selby 2006b, Appendix 2, p. ii). In 2004
and 2005, Selby (2006b, Appendix 2,
p. 2) did not record a single Poweshiek
skipperling on any of these transects in
and around the park during 11 separate
surveys.
An extensive survey effort was
conducted in 2007 and 2008 throughout
most of the species’ known range in the
State (Selby 2009a, entire). Sites with
previous Poweshiek skipperling records
that were considered to have the
greatest conservation importance to the
species (large, high-quality prairie
remnants) were surveyed, as well as
sites with no previous records that
appeared likely to support the species
(Selby 2009a, p. 2). In 2007, 70 sites in
15 counties were surveyed, including 26
sites with previous Poweshiek
skipperling records (Selby 2009a, pp. 1,
6). In 2008, 58 sites were surveyed in 13
counties, including 22 sites with prior
records (Selby 2009a, pp. 1, 6). A total
of 34 sites with previous Poweshiek
skipperling records were surveyed in
both years combined. Poweshiek
skipperling presence was recorded on
only three of the 70 surveyed sites in
2007; each of these three sites had just
one confirmed individual (Selby 2009a,
p. 1). No Poweshiek skipperlings were
observed on any of the 58 sites surveyed
during the 2008 flight period (Selby
2009a, p. 1).
In 2007, multiple transect surveys
were conducted in four sites with
previously well-documented Poweshiek
skipperling populations—transects
totaling 52,985 m (33 mi) were surveyed
without observing a single Poweshiek
skipperling (Dana 2008, p. 5). About
half of these transects (totaling 20,959 m
(13 mi)) were in the Prairie Coteau
Scientific and Natural Area (SNA),
where in 1990 Selby recorded 116
Poweshiek skipperlings during the flight
peak (Selby and Glenn-Lewin 1990, pp.
19–20) along a total of about 6,250 m (4
mi) of transects (Dana 2008, p. 16). No
Poweshiek skipperling were observed
during surveys of the Prairie Coteau
SNA in 2012 (Runquist 2012, pp. 9–10).
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Additional surveys were conducted in
2012; however, Poweshiek skipperling
were not observed at any of the 18 sites
with relatively recent records (Runquist
2012, pp. 4–25; Selby 2012, p. 2; Selby
2013, p. 2; Dana 2012c, pers. comm.;
Runquist 2012a, pers. comm.; Olsen
2012a, pers. comm.). Fifteen additional
prairie sites with potential habitat or
records of other skippers were surveyed
in 2012, but no Poweshiek skipperling
were observed (Runquist 2012, pp. 4–
25; Selby 2012, p. 2; Selby 2013, p. 2;
Dana 2012c, pers. comm.; Runquist
2012a, pers. comm.; Olsen 2012a, pers.
comm.). Twenty-one sites with previous
records of the species were resurveyed
in 2013 and 7 additional sites, with no
previous records, were also surveyed for
the species (Runquist 2014, pp. 3–6;
Selby 2014, pp. 2–5; Rigney 2013b, p.
Appendix B). Three individual
Poweshiek skipperlings were observed
at one site in Polk County—this is the
first credible sighting of the species in
the State since 2007 (Webster 2013,
pers. comm.; Dana 2014, pers. comm.;
Service 2014, unpub. database).
Nearly half (approximately 48
percent) of all documented Poweshiek
skipperling sites rangewide are in
Minnesota, thus the apparent collapse of
large numbers of Poweshiek skipperling
populations across the State may pose a
significant challenge for the long-term
existence of this species. Although the
possibility remains that the species is
extant at some sites where recent (2007,
2008, 2012, or 2013) surveys were
negative, it seems unlikely that it is
present at those sites in any significant
numbers. Extensive surveys in 1993 and
1994 documented the species at about
35 percent of all surveyed sites, whereas
the 2007 effort found them at only about
2 percent of all sites surveyed; no
Poweshiek skipperling were detected
despite widespread and robust survey
efforts involving multiple observers in
2008 or 2012 (Dana 2008, p. 8; Selby
2009a, p. 1; Dana 2012c, pers. comm.;
Runquist 2012a, pers. comm.; Olsen
2012, pers. comm.; Runquist 2012, pp.
4–25; Selby 2012, p. 2, 2013, p. 2).
Three individuals were sighted at one
location in 2013 (Webster 2013, pers.
comm.; Dana 2014, pers. comm.).
To summarize, Poweshiek skipperling
was historically documented in
approximately 144 sites in Minnesota
(Table 2). The species is not considered
to be present at any of these sites, except
at one location (Table 2). The occupancy
is unknown at 58 sites, and the species
is considered to be extirpated or
possibly extirpated at 21 and 64 sites,
respectively (Table 2).
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63691
North Dakota
North Dakota historically contained
approximately 6 percent (N=17) of all
known records of Poweshiek
skipperlings rangewide (Table 2).
Poweshiek skipperlings have been
historically documented at 17 sites
(Table 2) in 7 North Dakota counties
(Selby 2010, p. 18; Service 2014,
unpubl. geodatabase): Cass, Dickey,
LaMoure, Ransom, Richland, and
Sargent in the southeastern corner of the
State and Grand Forks County in the
Northeast. Poweshiek skipperling are
now considered extirpated or possibly
extirpated from nine sites and four
counties (Cass, Dickey, LaMoure, and
Grand Forks) in North Dakota. The
status of the species is unknown at 8
sites, where the species was last
observed between 1996 and 2001, but
not during the most recent 1–2 year(s)
surveyed. Four sites with fairly recent
Poweshiek skipperling records were
surveyed in 2012; Poweshiek
skipperling were not found at any of
those sites (Royer and Royer 2012b, pp.
21–24; Royer and Royer 2012a, p. 6).
One additional site was surveyed,
which had the potential for Poweshiek
skipperling presence because of its
proximity to a known site for the
species; however, no Poweshiek
skipperling were found (Royer and
Royer 2012b, pp. 18–19; Royer and
Royer 2012a, p. 6; Royer 2012b, pers.
comm.). The species was not observed
at six sites with previous records of
Poweshiek skipperlings that were
surveyed in 2013. The species
occupancy at two of these sites with
2013 surveys was updated from
unknown to extirpated based on three
consecutive years of negative surveys
(Service 2014, unpubl. geodatabase).
The Poweshiek skipperling was
known from seven North Dakota sites
across six counties in the 1990s;
however, only two of those sites were
considered to have extant populations at
that time; three records were
represented by incomplete or
ambiguous locality data, and the species
was assumed to be extirpated at one site
(Royer and Marrone 1992b, pp. 8–11).
Surveys conducted in the State after
1992 documented additional
populations, but the most recent surveys
at these sites were mostly negative.
Orwig discovered eight new populations
of Poweshiek skipperling (six in
Richland County and two in Sargent
County) during 3 years of survey work
(1995–1997) in southeastern North
Dakota (Orwig 1995, pp. 3–4; Orwig
1996, pp. 4–6, 9–12; Orwig 1997, p. 2).
The species was found at two of the
eight sites surveyed in 1997 (Orwig
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1997, p. 2) and at two additional sites
in 1996 (Spomer 2004, p. 11).
Once abundant at several known sites
in North Dakota, Poweshiek
skipperlings have experienced a
dramatic decline over the last few
decades. In 1977, McCabe and Post
(1977a, p. 38), for example, found
Poweshiek skipperling to be abundant at
McLeod Prairie in Ransom County,
stating that they could ‘‘be collected two
at a time on the blossoms of Longheaded coneflower . . .’’ In 6 years of
subsequent monitoring (1986–1991),
however, Royer failed to find a single
Poweshiek skipperling at the site after it
was converted to a cattle-loading area
(Royer and Marrone 1992b, p. 10). Royer
and Marrone (1992b, pp. 10–11)
assumed the species had been
extirpated at this site. Similarly, the
number of Poweshiek skipperlings
recorded during surveys at the West
Prairie Church site along the boundary
of Cass and Richland counties, fell from
hundreds in 1986, to four in 1990, and
zero in 1991 and 2012 (Royer and
Marrone 1992b, p. 8; Royer and Royer
2012b, p. 21). Poweshiek skipperlings
are unlikely to persist at this small and
isolated site (Royer and Royer 2012b, p.
21; Royer 2012c, pers. comm.).
The last observation of a live
Poweshiek skipperling in North Dakota
was in 2001, at a new site discovered by
Spomer (2001, p. 9) in Ransom County.
Poweshiek skipperlings were not found
in subsequent surveys at this site in
2002, 2003, and 2012 (Spomer 2001, p.
2; Spomer 2002, p. 3; Spomer 2004 p.
36; Selby 2010, p. 18; Royer and Royer
2012b, p. 22), although the 2012 survey
may have been conducted too late in the
year to detect the species at that site
(Royer 2012b, pers. comm; Royer 2012d,
pers. comm.). Therefore, the status of
the species at this site is unknown.
To summarize, Poweshiek skipperling
was historically documented in 17 sites
in North Dakota (Table 2). The species
is not considered to be present at any of
these sites (Table 2). The occupancy is
unknown at eight sites, and the species
is considered to be extirpated or
possibly extirpated at three and six
sites, respectively (Table 2).
South Dakota
South Dakota historically contained
approximately 24 percent (N=69) of all
known records of Poweshiek
skipperlings rangewide (Table 2). The
Poweshiek skipperling has been
historically documented at
approximately 69 sites (Table 2) across
10 counties in South Dakota (Selby
2010, p. 19). Based on expert review and
additional survey and habitat
information, the status of the species
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was determined to be unknown at 36
sites, possibly extirpated at 2 sites, and
presumed extirpated at the remaining 31
sites (Table 2); at least 8 of the
extirpated sites have been destroyed by
conversion, gravel mining, loss of native
vegetation, flooding, or heavy grazing
(Skadsen 2012c, pers. comm.).
The Poweshiek skipperling was not
detected at any site that was surveyed
between 2009 and 2013: 6 sites in 2009,
10 sites in 2010, 1 site in 2011, 10 sites
in 2012, and 25 sites in 2013 (Skadsen
2009, p. 12; Skadsen 2011, p. 5; Skadsen
2010, pers. comm.; Skadsen 2012a, pers.
comm.; Skadsen 2012b, p. 3; Skadsen
2013, pp. 3–4). The 2009 to 2013 results
are in marked contrast to surveys
conducted in 2002 when the species
was recorded at 23 of 24 sites surveyed
(Skadsen 2003, pp. 11–45). Cool and
wet weather may have depressed
butterfly populations, in general, in
eastern South Dakota and west-central
Minnesota in 2009 as it apparently did
in 2004 (Skadsen 2004, p. 2; Skadsen
2009, p. 2). In 2012 and 2013, five and
nine additional sites, respectively, with
potentially suitable native-prairie
habitat but with no previous records of
the species were surveyed, but no
Poweshiek skipperling were observed
(Service 2014, unpubl. geodatabase).
Wisconsin
Wisconsin historically contained
approximately 1 percent (N=4) of all
known records of Poweshiek
skipperlings rangewide (Table 2).
Naturalists reported Poweshiek
skipperling to be common to abundant
on prairies in southeastern Wisconsin in
the late 1800s (e.g., in Milwaukee and
Racine Counties), although exact
localities are unknown (Borkin 2011, in
litt.; Selby 2010, p. 22). By 1989,
however, the species was listed as State
endangered (Borkin 2011, in litt.). The
Poweshiek skipperling is considered to
be present at one site in Wisconsin
(Table 2); Puchyan Prairie State Natural
Area (SNA) is approximately 100 km (62
mi) to the northwest of the Kettle
Moraine State Forest in Green Lake
County. The status of the species is
unknown at three sites within the
Southern Unit of the Kettle Moraine
State Forest in Waukesha County. An
additional 2010 record of a butterfly was
incorrectly identified as a Poweshiek
skipperling at Melendy’s Prairie Unit of
the Scuppernong Prairie SNA (Borkin
2012b, pers. comm.).
The two occurrences of Poweshiek
skipperling in the Kettle Moraine State
Forest inhabit small areas that were
once part of a larger prairie complex,
which was fragmented by conversion to
agriculture, other human development,
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and encroachment of woody vegetation
(Borkin 2011, in litt.). Up until 2013, the
largest population in Wisconsin was
within a 6-ha (15-ac) prairie remnant on
Scuppernong Prairie SNA at Kettle
Moraine State Forest, which had record
counts exceeding 100 individuals in
1994, 1995, 1998, and 1999 (Borkin
1995, p. 10; Borkin 1996, p. 7; Borkin
2000, p. 4; Borkin 2011, in litt.). Four
were found in 2007 (Borkin 2008, in
litt., p. 1), although these data were
collected during a single transect survey
that may have been early in the flight
season and are, therefore, not
comparable to other survey years
(Borkin 2012a, pers. comm.). A
maximum count of 42, 17, 63, and 45
were counted in 2009, 2010, 2011, and
2012, respectively (Borkin 2011a, pers.
comm.; Borkin 2012c, pers. comm.). The
relatively low maximum count in 2010
may be due to the timing of the flight
(early) and the timing of the survey
effort (late); therefore, the peak flight
may have been missed (Borkin 2013,
pers. comm.). A controlled burn in late
March of 2012 may correlate with lower
numbers observed during the 2012 flight
(Borkin 2012a, pers. comm.). While this
difference may be within the range of
variation observed over the previous 4
years (Wisconsin DNR 2012, in litt.), the
range in variation may be skewed due
to the low numbers observed in 2010
due to the timing of the flight and the
survey effort (Borkin 2013, pers.
comm.). No Poweshiek skipperlings
were observed at Scuppernong during
repeated surveys in 2013 (Borkin 2013,
pers. comm.)—this is the first time no
individuals have been observed there
since regular surveys began in the 1990s
(Borkin 2014 pers. comm.). Each year,
surveys were conducted with similar
effort—modified Pollard transect
covering 15 ac (6 ha) in approximately
40 minutes (Borkin 2014, pers. comm.).
After brush was cleared from the area
in 2002, a small number of Poweshiek
skipperlings were discovered the
following year in a small isolated prairie
remnant patch at a second site in the
Kettle Moraine State Forest, (Borkin in
litt 2008). Once the intervening woody
growth was removed, individuals
presumably dispersed from the
Scuppernong SNA remnant prairie to a
small habitat patch about 200 ft (61 m)
away (Borkin 2012a, pers. comm.).
Surveys at each habitat patch have
consistently yielded counts of less than
10 (Borkin 2008, in litt.), with a
combined high count of 11 to 15
individuals in 2011. A total of six
individuals, with a high single day
count of three, were observed in eight
surveys during 2012 (Borkin 2012c,
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pers. comm.; Borkin 2012a, pers.
comm.). No Poweshiek skipperlings
were observed in 2013 (Borkin 2013,
pers. comm).
The status of the Poweshiek
skipperling is unknown at a third and
much larger fragment of Kettle Moraine
State Forest, the Kettle Moraine Low
Prairie SNA, which is adjacent to the
Wilton Road site. The Kettle Moraine
Low Prairie SNA was overgrown by
shrubs including willows (Salix spp.),
quaking aspen (Populus tremuloides),
and glossy buckthorn (Frangula alnus)
and has been managed with a series of
controlled burns, in addition to a 1975
wildfire (Borkin 2011, in litt; Borkin
2012a, pers. comm.; Wisconsin DNR
2012, in litt). The highest number
recorded at the Kettle Moraine Low
Prairie SNA was 28 on July 8, 1995
(Borkin 2012a, pers. comm.).
Preliminary attempts in 2000 to 2003 to
augment the population with adults
from Scuppernong SNA and captivereared larvae were not successful
(Borkin 2012a, pers. comm.). A single
Poweshiek skipperling was sighted
there on July 2, 2004, but none were
found in surveys conducted in 2007–
2009 and 2011–2012 (Borkin 2011b,
pers. comm.; Borkin 2012a and 2012c,
pers. comm.). Two Poweshiek
skipperlings were recorded in 2010 at
this site (Wisconsin DNR2012, in litt.);
however, no photographs or voucher
specimens confirm the sighting. This
site was surveyed less intensively than
Scuppernong Prairie, because of the
species’ relatively low density and
abundance at Kettle Moraine Low
Prairie SNA (Borkin 2012a, pers.
comm.). Extensive brush cutting,
additional burns, and restoration of the
hydrology have been undertaken in
recent years (Borkin 2012a, pers.
comm.).
Poweshiek skipperlings are present at
a third site in Wisconsin, Puchyan
Prairie SNA, in Green Lake County,
although this population is small and
declining (Borkin 2009, pers. comm.).
The Poweshiek skipperling was first
discovered at Puchyan Prairie in 1995,
and 6 to 30 individuals have been
recorded in subsequent surveys (Borkin
2008, in litt.; Swengel 2012, pers.
comm). In 2012, Swengel (2012, pers.
comm.) found a maximum of three
individuals, despite several hours of
searching over 3 days. In 2013, Swengel
(2013, pers. comm.) found a total of
three individuals during 2 days of
searching.
Additional sites in eight counties
(Crawford, Grant, Iowa, Jefferson,
Monroe, Rock, Sauk, and Walworth)
have been surveyed in an attempt to
find undiscovered Poweshiek
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17:13 Oct 23, 2014
Jkt 235001
skipperling populations. Four of the
eight sites surveyed in 1998 and 1999
seemed to have adequate host plants,
nectar resources, and size typical of
Poweshiek skipperling habitat, but
Poweshiek skipperling were not present
at any of the sites (Borkin 2000, pp. 5–
7).
To summarize, Poweshiek skipperling
was historically documented in 4 sites
in Wisconsin (Table 2). The species is
considered to be present at one site and
the occupancy is unknown at three sites
(Table 2).
Manitoba
Manitoba historically contained less
than 1 percent (N=1) of all known
records of Poweshiek skipperlings
rangewide (Table 2); however, multiple
Poweshiek skipperling historical
records occur in one general location—
a complex of several nearby small sites
within the Tallgrass Prairie Preserve—in
far southern Manitoba, near the United
States border. Poweshiek skipperlings
were first recorded in Canada near Vita,
Manitoba, in 1985 at each of seven
prairies surveyed, and populations were
described as abundant but localized
(Catling and Lafontaine 1986, p. 63).
Poweshiek skipperlings were found at
15 of 18 locations surveyed within the
same area in 2002 (COSEWIC 2003, p.
5).
The Poweshiek skipperling is
currently present at one location in
Canada, The Nature Conservancy of
Canada Tall Grass Prairie Preserve near
Vita, Manitoba (Westwood 2010, p. 2;
Westwood et al. 2012, p. 1; Hamel et al.
2013, p. 1). Poweshiek skipperlings
were historically moderately common in
areas of the preserve (Klassen et al.
1989, p. 27). In 2002, Webster (2003, p.
5) counted approximately 150
individuals, and in 2006, approximately
126 individuals were sighted across 10
sites (Westwood 2010, p. 3). Surveys of
10 sites in 2008 and 2009 yielded 281
and 79 Poweshiek skipperlings,
respectively (Dupont 2010, pers.
comm.). Poweshiek skipperling
numbers in the preserve declined
sharply after a 647-ha (1,600-ac) wildfire
in fall 2009 burned much of the species’
habitat, including areas that likely
contained the largest and highest
density populations (Westwood 2010, p.
2); surveys of comparable effort to the
2008 and 2009 surveys yielded only 13
Poweshiek skipperlings on the preserve
in 2010 (Westwood 2010, pp. 7–22).
Surveys of 45 sites within the Tall Grass
Prairie Reserve during 2011 resulted in
13 sites with positive sightings, 9 of
which were new sites (Westwood et al.
2012, p. 11; Dupont 2011, pers. comm.).
The average number of Poweshiek
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63693
skipperlings found at each site ranged
from 10 to 15 per hour. These numbers
are up considerably from 2010, but not
as high as observed in 2008 (Dupont
2011, pers. comm.). In 2012, a total of
50 individuals were observed, which
was ‘‘low when compared to historic
densities’’ (Hamel et al. 2013, p. 17).
Poweshiek skipperling sites in Manitoba
are often surveyed up to 7 times during
the flight period each year (Westwood
2013, pers. comm.). The preserve has
detailed management recommendations
to facilitate recovery of the Poweshiek
skipperling (Westwood 2010, p. 5).
Following an assessment and status
report completed in 2003 under the
Committee on the Status of Endangered
Wildlife in Canada (COSEWIC), the
Poweshiek skipperling was listed under
the Species at Risk Act as Threatened in
Canada in July 2005 (COSEWIC 2003).
A recovery strategy is now in place for
the species in Canada (Environment
Canada 2012), which includes critical
habitat designations within and adjacent
to The Nature Conservancy of Canada
Tall Grass Prairie Preserve
(Environment Canada 2012, p. ii).
Summary of Comments and
Recommendations
In the proposed rule published on
October 24, 2013 (78 FR 63574), we
requested that all interested parties
submit written comments on the
proposal by December 23, 2013, during
which we held public meetings on
November 5, 2013, in Minot, North
Dakota; November 6, 2013, in Milbank,
South Dakota; November 7, 2013, in
Milford, Iowa; November 13, 2013, in
Holly, Michigan; and November 14,
2013, in Berlin, Wisconsin. We also
contacted appropriate Federal and State
agencies, scientific experts and
organizations, and other interested
parties and invited them to comment on
the proposal. Newspaper notices
inviting general public comment were
published in the following papers:
Detroit Free Press, Detroit, MI; The
Detroit News, Detroit, MI; Berlin
Journal, Berlin, WI; The Forum of FargoMoorhead, Fargo, ND; Minneapolis StarTribune, Minneapolis, MN; Mukwonago
Chief, Mukwonago, WI; The Des Moines
Register, Des Moines, IA; Bismark
Tribune, Bismark, ND; The Argus
Leader, Sioux Falls, SD. We did not
receive any requests for a public
hearing. All substantive information
provided during comment periods has
either been incorporated directly into
this final determination or addressed
below. Comments specific to the
proposed designation of critical habitat
for the two species (78 FR 63625) will
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be addressed in the final critical habitat
determination.
Peer Reviewer Comments
In accordance with our peer review
policy published on July 1, 1994 (59 FR
34270), we solicited expert opinion
from ten knowledgeable individuals
with scientific expertise that included
familiarity with the Dakota skipper or
the Poweshiek skipperling and its
habitat, biological needs, and threats.
We received responses from seven of the
peer reviewers.
We reviewed all comments received
from the peer reviewers for substantive
issues and new information regarding
the listing of the Dakota skipper or the
Poweshiek skipperling. The peer
reviewers generally concurred with our
methods and conclusions and provided
additional information, clarifications,
and suggestions to improve the final
rule. Peer reviewer comments are
addressed in the following summary
and incorporated into the final rule as
appropriate.
asabaliauskas on DSK5VPTVN1PROD with RULES
General
(1) Comment: Peer reviewers thought
that the Service’s interpretation of
literature addressing threats to these
species was well researched. However,
some peer reviewers suggested that
further research would strengthen or
refine our understanding of these
butterflies.
Our Response: The Act requires us to
make a determination on the status of
species based on the best available
information. However, we agree that
that further studies of these species
would further our understanding and
help us with the recovery planning and
implementation. We will consider
further research needs in our recovery
planning efforts.
(2) Comment: One peer reviewer
stated that, in the Executive Summary,
the Service did not describe the effects
of habitat management on butterflies,
but rather focused on the impacts to
native vegetation.
Our Response: We have updated the
executive summary to include the direct
mortality that may occur due to
management activities or natural
occurrences. This subject is discussed in
further detail in the Background section
of this final listing rule.
Taxonomy
(3) Comment: One peer reviewer
provided a correction to the number of
subfamilies in the family Hesperiidae
and the number of species in the genus
Hesperia. Specifically, the family
comprises 7 subfamilies world-wide, 4
of which occur in North America, north
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of Mexico. There are 21 recognized
species in the genus Hesperia (ibid), not
18 as cited in the proposal.
Our Response: We corrected the
statements in the Background section of
this final listing rule.
Species Biology
(4) Comment: One peer reviewer
provided details on Dakota skipper and
Poweshiek skipperling biology,
specifically, information pertaining to
early life stages and larval food choices,
which were learned from captiverearing trials at the Minnesota Zoo.
Our Response: We have incorporated
the updated information into the
Background section of this final listing
rule.
(5) Comment: Two peer reviewers
suggested that we incorporate the
findings of two recently published
Master’s theses (Dupont 2013, Rigney
2013a) that have new information on the
Dakota skipper and Poweshiek
skipperling, including data from surveys
at several locations for both species in
Manitoba. These studies also show a
greater decline in both species in
Canada over the last 10 years than is
indicated in the proposed listing rule.
Our Response: We incorporated data
from the referenced Master’s theses in
the Dakota skipper Background section
in this final listing rule. The new
information, although important to our
full understanding of the status of the
species throughout their ranges, does
not change our listing determinations
for the two species.
(6) Comment: A peer reviewer stated
that based on personal observations and
McAlpine’s 1972 report, upon hatching,
Poweshiek skipperling larvae crawl out
near the tip of grasses, and do not crawl
to the base of grasses, as was stated in
the proposal.
Our Response: We corrected the
statement regarding Poweshiek
skipperling larval behavior in the
Background section of this final listing
rule.
(7) Comment: A peer reviewer noted
that a species’ nectar preference is
usually indicated by selection in greater
frequency rather than the proportion of
the species among all available nectar
sources (because random selection
would be expected to result in selection
frequency equal to the species’
proportion of the available choices). All
of the references cited in the rule report
nectar preferences as the relative
proportion among observed choices.
Our Response: We clarified this point
in the Background section of this final
listing rule.
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Food and Water
(8) Comment: Peer reviewers provided
corrections to the lists of flowers used
as nectar sources and the importance of
several plants as nectar sources for the
butterflies.
Our Response: We corrected the
nectar flowers for Dakota skipper
accordingly in the Background section
of this final listing rule. Also, we
removed upright prairie coneflower,
fleabane, and white prairie clover from
our list of important nectar species. We
did not remove black-eyed Susan,
because Rigney (2013a, p. 142) reported
Dakota skippers were frequently
observed nectaring on that species in
Canada.
(9) Comment: One peer reviewer
stated that the assertion that Dakota
skipper larvae feed only on native
grasses has not been established, and
further stated that when confined with
no other choice, Dakota skipper larvae
may feed on a variety of native and
nonnative grasses. Exotic cool-season
grasses, such as Kentucky bluegrass and
smooth brome are available, and
generally of good nutritional quality,
when overwintering larvae emerge from
hibernation and begin feeding. The tight
empirical correlation between
occurrence of this skipper and the
dominance of native plants in the
habitat, however, indicates that the
species requires native grasses.
Our Response: We have incorporated
this information into the final listing
rule, and recognize that Dakota skipper
larvae can use both native and
nonnative plants as food during certain
stages of larval development. Some
exotic cool-season grasses may be
suitable larval food plants during
limited times of larval development;
however, the morphology and growth of
these grasses may determine the
suitability for the species, and if those
grasses dominate a site, the chances for
larvae finding suitable food sources is
decreased.
(10) Comment: One peer reviewer
provided additional information on
observations of Poweshiek skipperling
oviposition and larval food use in
Wisconsin.
Our Response: We have incorporated
the information into the Background
section of this final listing rule.
(11) Comment: One peer reviewer
corrected our interpretation of his
observations on Poweshiek skipperling
oviposition (egg-laying) to state that
larvae need to begin feeding on very
fine, threadlike blade tips, and that
females placed eggs on fine blade tips of
grasses during some observed
ovipositions.
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Our Response: We have incorporated
this information into the Background
section of this final listing rule.
(12) Comment: One peer reviewer
stated that the summary of the best
available information for Dakota skipper
dispersal is adequate and incorporates
all of the information of which the
reviewer is aware. The reviewer did
correct our interpretation of Dana’s 1997
mark-and-recapture study. The reviewer
stated that roads and crop-fields were
suspected to be impediments to Dakota
skipper movement; however, this was
not explicitly tested during the study.
Another reviewer wanted clarification
on our basis for the estimated maximum
dispersal distance of the Poweshiek
skipperling.
Our Response: We corrected the
dispersal section of this final rule to
accurately present Dana’s 1997 markand-recapture study findings, and added
information from an additional study. In
one mark-and-recapture study in
Manitoba, the Poweshiek skipperling
was found within 50 m (165 ft) of its
original capture location (Dupont 2013,
p. 69). Besides this study in Manitoba,
which had too few recaptures to make
any statistically significant conclusions,
we are unaware of any other dispersal
studies for the species. Therefore, we
used Dakota skipper (and dispersal
studies on this species) as a surrogate
species to estimate the maximum
dispersal distance of the Poweshiek
skipperling (e.g., Dana 1991, Dana 1997,
Skadsen 1999a), and verified our
assumptions with expert opinion and
Burke (2011). Experts generally agreed
that 1.6 km (1.0 mi) was a reasonable
estimate for Poweshiek skipperling
dispersal distance (Westwood 2012b,
pers. comm.; Dana 2012b, pers. comm.).
However, according to Burke et al.
(2011), the Poweshiek skipperling was
less mobile than the Dakota skipper.
Since experts generally assumed the
maximum dispersal distance of the
Dakota skipper was 1 km (0.6 mi), we
used 1 km (0.6 mi) as a conservative
maximum dispersal distance for the
Poweshiek skipperling.
(13) Comment: One peer reviewer
questioned the accuracy of the mobility
value assigned to the Dakota skipper
from the Burke et al. (2011) publication.
The reviewer suggested that the
strongest evidence for limited dispersal
capabilities is the absence of
observations outside of native-prairie
habitat. Butterflies that are highly
mobile are occasionally observed in
unsuitable habitat; however, factors
such as the rarity of the species, its
small size and inconspicuous
appearance, and the rarity of observers
that are both interested in skippers and
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capable of identifying them, makes the
absence of observations in unsuitable
habitats weak evidence for the absence
of movement over long distances. The
reviewer further stated that, since we
have little basis for measuring dispersal
in this species, but we have no evidence
that it does much dispersing, we should
assume that dispersal is very limited.
Our Response: The Burke et al. (2011)
paper was published in a peer-reviewed
scientific journal (using expert
interviews); however, we recognize the
limitations of the data therein and,
therefore, have arrived at our conclusion
that the Dakota skipper has low
dispersal capability based on this paper
in conjunction with other reports and
observations.
Habitat
(14) Comment: One peer reviewer
corrected the statement that Type B
habitat (as explained in the Background
section above) was the only habitat type
inhabited by the Dakota skipper in
Minnesota, as the species has been
documented in other habitat types,
particularly in Type A habitat in Kittson
and Stearns Counties.
Our Response: We corrected the
statement regarding Dakota skipper
habitat types in Minnesota in this final
listing rule. It should be noted, however,
that there is only one recent (2009)
record of a Dakota skipper in Kittison
County, Minnesota, and two sites in
Stearns County where the species is
possibly extirpated.
(15) Comment: One peer reviewer
stated that the assertion in our proposed
rule that Dakota skipper larvae are
‘‘particularly vulnerable to desiccation
during dry summer months’’ was a
hypothesis, with no confirming
evidence. The paper cited only surveyed
occupied habitat and did not test
unoccupied areas for the same
parameters.
Our Response: We realize the
limitations of Royer’s 2008 study, and
have corrected our interpretations
accordingly in this final rule;
specifically, the sampling design
(edaphic parameters were measured
only in occupied areas, and no
unoccupied areas were examined to test
the significance of the findings) does not
allow for statistically significant
conclusions.
(16) Comment: One peer reviewer
corrected the definition given for ‘‘larval
nesting zones’’ measured for edaphic
characteristics in Royer (2008). The
‘‘primary larval nest zone’’ in which
they measured temperature and
humidity is described as 0–2 cm above
the soil surface, not between the soil
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surface and 2 cm deep as stated in the
proposed rule.
Our Response: We have corrected the
statement regarding larval nesting zones
in the Background section of this final
rule.
Occupancy
(17) Comment: Ane peer reviewer
commented on the adequacy of the
categorization of population status, and
stated that it was done in an
appropriately conservative way, but did
not think this would affect the ultimate
decision for either species
Our Response: We developed the
occupancy criteria to be as objective as
possible in light of the information we
had, which was complicated by the
variability of the frequency and lack of
error quantification of the survey data.
We applied the occupancy rules
consistently, in the same way
throughout the range of each species,
with discretion given to species experts
who were familiar (e.g., who had
conducted relatively recent site visits or
butterfly surveys) with the sites within
their State. Using the best information
available, we attempted to balance our
determination as to whether the species
was likely present or not at a particular
location. We determined that at sites
where the species was detected during
the most recent survey, if the survey
was conducted in 2002 or more
recently, this was a reasonable
timeframe to assume its presence, if
there was no evidence of habitat
destruction or significant degradation of
the habitat. Some other comments,
however, indicated that the 10-year
timeframe was too long to assume
presence of an annual species, such as
these butterflies, while others thought
we should still be assuming presence at
locations with detections much farther
back (prior to 1993), if we had no
evidence that the habitat hadn’t been
destroyed there. However, we believe
that we have taken the most reasonable
approach to defining occupancy, used
the best available scientific information
appropriately, and have been consistent
in making this determination.
(18) Comment: One peer reviewer
noted that it would be useful to clarify
the importance of unknown sites and to
determine if habitat in ‘‘unknown’’ sites,
and sites where extirpation has
presumed to have occurred, is actually
in a condition to support future
populations, particularly for future
reintroductions.
Our Response: It is important to
distinguish among sites where the
species is likely extirpated, where the
species is still present, and where we
are unsure of the species’ presence, in
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order to determine the current status of
these species. The habitat at individual
sites varies, but where we had evidence
that the habitat was destroyed, we
considered those sites to be extirpated
(and, thus, unsuitable for future
reintroductions). The habitat at other
sites may still be suitable for one or both
species, and its role in future recovery
efforts, such as reintroductions, will be
considered during the recovery
planning and implementation phase for
these species.
(19) Comment: One peer reviewer
requested that we define some terms
used in the proposed rule; in particular,
the terms ‘‘positive detections,’’
‘‘detection rate,’’ and ‘‘liv’’.
Our Response: Positive detections
refers to the number of times the species
was detected during a survey. Detection
rate is calculated as the number of times
the species was detected (at a singular
site or groups of sites), divided by the
number of surveys (at a singular site or
groups of sites). Finally, ‘‘liv’’ refers to
the page number in the preface of a
cited publication (Roman numeral for
page 54).
(20) Comment: Does the definition of
species extirpation from a site apply to
surveys conducted in 1993, or to those
done more recently?
Our Response: We considered the
species to be extirpated from a site if
there were at least three sequential years
of negative surveys, no matter the year
those sites were surveyed, and the
species has not subsequently been
documented at the site. For example, if
a site was only surveyed in 1991, 1995,
and 1999, and there were no positive
detections of the species during all 3
years, we assumed that the species is
extirpated from that site. The species
occupancy at that site would not change
unless the species is detected at that site
in the future. We have clarified this
definition in the Background section of
this final listing rule.
(21) Comment: One peer reviewer
wanted further clarification on our
justification for including four Dakota
skipper sites with older records in the
present occupancy category. The
reviewer suggested we review the
previous densities of the species at the
four sites and the proximity of nearby
sites from which individuals could
recolonize the sites in question.
Our Response: The species occupancy
at one of four South Dakota sites has
been updated to ‘‘unknown’’ after
further review of the information
available for the site, including 2013
survey data that were not available to us
at the time we drafted the proposed
rule. However, there is no evidence to
suggest that the species is not still
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present at the remaining three sites (all
in Minnesota), because the best
information indicates that the sites’
habitats are still suitable for the
butterfly, and, therefore, despite the lack
of recent surveys, the species may still
be present there.
(22) Comment: A peer reviewer noted
that at several points the proposed rule
indicates that survey efforts may vary in
number of visits, but that certain survey
results were not considered, because
they were not conducted at the
appropriate time. The peer reviewer
questioned whether we can presume
that the surveys that were considered
are comparable, regardless of the
number of visits visits, whether those
surveys all meet some minimum
criteria, and whether there was a
standard survey effort measurement.
Our Response: Since the purpose of
site surveys differed by site, the amount
of effort also varied. For example, if the
goal of the survey was to verify if the
species was present at a particular
location, a surveyor may have stopped
the survey effort as soon as the first
individual was detected, which may
have occurred after a short, one-time
visit. On the other hand, if the survey
purpose was to count individuals
during the peak flight of a species, the
site may have been visited every day
throughout the adult flight period, and
more quantitative measurements, such
as number of individuals observed per
hour, may have been recorded. We used
all types of surveys, as long as they were
conducted during the appropriate time
of the year (mid-June through mid- to
late July), and during appropriate
conditions (e.g., generally wind speeds
less than 16 mph, unless the species
was detected at higher speeds).
Furthermore, we only considered
surveys from individual surveyors who
are able to reliably identify the species
in the field.
(23) Comment: A peer reviewer noted
that the proposed rule states that
existing models are unable to identify
specific plant species, invasive species,
and floristic quality, and the Service
concludes that unbroken grasslands
‘‘may not contain the specific native
prairie plants that the Dakota skipper
requires. . . .’’ This statement appears
to be contradicted later in the
document.
Our Response: We clarified the
statements in this final listing rule. The
intent of the first statement is to
acknowledge that existing habitat
models cannot identify specific species
or determine floristic quality necessary
to support Dakota skipper populations.
The models may be useful in narrowing
down areas that may contain the
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necessary nectar plants and larval food
plants, but presence of specific plant
species and suitability for the Dakota
skipper must be verified by other means
(e.g., on the ground plant surveys). The
second statement refers to the
possibility of yet undiscovered areas of
suitable habitat where the Dakota
skipper may exist, because not every
area that is suitable has been surveyed
for the species.
(24) Comment: A peer reviewer noted
that survey site selection may be
influenced by the expert’s knowledge of
potential habitats, land ownership, and
the ability to gain landowner permission
to access areas for surveys.
Our Response: We acknowledge that
survey sites may be selected for a
variety of reasons. A site may be
surveyed because there is known
suitable prairie habitat in an area, but
the exact survey location may depend
on other variables, such as the ability to
gain landowner permission to survey.
Status and Trends
(25) Comment: One peer reviewer
provided additional 2009 data for the
Felton Prairie site in Minnesota.
Our Response: We incorporated this
data into this final listing rule.
(26) Comment: One peer reviewer
requested clarification on the butterfly
survey methodology and how floristic
diversity was rated at some of the
survey locations.
Our Response: The survey
methodology varied among locations,
years, surveyors, and by other factors,
and it is difficult to succinctly describe
the methodology used for more than 20
years of surveys for hundreds of survey
sites. For that reason, we examined the
data in terms of the rate of positive
detections over the years at each survey
location as a way to compare data across
multiple survey methods and years. We
applied certain standards that each
survey must meet (see response to
comment 22, above). In this final listing,
we describe survey methods or floristic
quality determination methods for
specific locations when it is necessary
to understand the results for a particular
survey, and describe typical survey and
floristic methodologies in the
Background section of this final rule.
(27) Comment: A peer reviewer
commented that the number of
historical populations of Dakota skipper
that remain extant is probably
overestimated, given the results of
recent resurvey efforts. In particular,
this peer reviewer questioned whether it
was realistic to assume species presence
at five Minnesota sites, given the
dramatic declines and apparent
extirpation of populations at some of the
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best sites within recent years. The
reviewer suggested assigning those sites
as ‘‘possibly present’’ or ‘‘status
unknown’’ category, and targeting these
sites for future surveys to determine the
species’ presence, particularly because
recent declines do not appear to be due
to habitat degradation or loss.
Our Response: Based on 2013 survey
data, we changed the occupancy for
several sites. When determining species
occupancy at a site, we balanced
information on habitat succession with
the available survey data to avoid falsely
assuming the species is absent from
less-surveyed sites that still have
suitable habitat.
(28) Comment: A peer reviewer
commented that, based on surveys
conducted in 2013, the status of both
the Dakota skipper and the Poweshiek
skipperling in Minnesota is likely more
dire than suggested in the proposal. No
Dakota skippers or Poweshiek
skipperlings were observed during
duplicate surveys conducted at 13 sites.
During single surveys conducted later in
the flight period (the time when adult
butterflies are able to fly) at two
additional sites in Clay County, MN, six
Dakota skippers were seen at one of
those sites and no Poweshiek
skipperling were observed at either site.
Both sites had fairly good numbers
during 2008 surveys. Additionally, one
peer reviewer suggested that we
incorporate results from 2013 surveys of
sites in Kittson County, Minnesota. No
Dakota skippers were observed at Lake
Bronson in 2013; however, there was
one highly likely sighting, and the area
contains moderate-quality habitat. The
Frenchman’s Bluff sites in Minnesota
were surveyed on July 11, 2013, which
was during the period of peak
abundance in the phenologically
(relationship between a periodic
biological phenomenon and climatic
conditions) delayed year, but the Dakota
skipper was not observed. The
estimated probability of the species
presence at the site is 90 percent, based
on the abundance of habitat and purple
coneflower in bloom.
Our Response: We incorporated the
2013 data into this final listing rule. Due
to several negative results from 2013
surveys, particularly in Minnesota, the
occupancy status at several sites has
been updated in this final listing rule.
We still determine that the Dakota
skipper should be listed as threatened,
and provide justification for our
determination in this final listing rule.
(29) Comment: One peer reviewer
suggested that we incorporate
information from a 2013 report of
butterfly surveys in South Dakota.
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Our Response: We incorporated 2013
survey results in this final listing rule.
(30) Comment: A peer reviewer
suggested that the Dakota skipper
population densities as described in
2003 and 2007 status assessments may
no longer accurately describe the
populations and the threats causing
population declines. For example,
reported sightings of Dakota skippers
within the Riding Mountain National
Park in Manitoba (Walleyn 2002) are
likely not valid; there are no voucher
specimens to confirm the report. There
are no known sites that are owned by
the Government in Canada.
Our Response: We incorporated
updated information regarding several
sites in Manitoba and Saskatchewan.
We have no records of any confirmed
Dakota skipper sites within the Riding
Mountain National Park in Manitoba.
(31) Comment: One peer reviewer
noted that there has been a decline in
the number of individual Dakota
skippers observed during the flight
period compared to the populations
observed in 2002 and 2007. The current
population estimates are much lower
than those described in Webster’s 2002
and 2007 reports. Furthermore, the
methods for estimating densities have
changed; survey methodology has
become more rigorous, with 2 to 5 visits
per site per year from 2009–2013
compared to single visits prior to 2008.
Our Response: We incorporated 2013
data into this final listing rule. Due to
largely negative results from 2013
surveys, the occupancy status of the
species at several sites has been updated
in this final listing rule.
(32) Comment: One peer reviewer
stated that there is a DuPage County,
Illinois, record of a Poweshiek
skipperling—the specimen was
collected in 1968 near the DuPage River,
and was only recently identified as a
Poweshiek skipperling.
Our Response: We have added the
DuPage County record to the Illinois
status and distribution section of this
final listing rule.
(33) Comment: One peer reviewer
stated that, because no Poweshiek
skipperlings were observed in 2013 at
Scuppernong Scientific and Natural
Area (SNA) in Wisconsin, nor at the
nearby Wilton Road site, those
populations may be extirpated. The peer
reviewer also stated that the apparent
decline in numbers was also observed in
Michigan.
Our Response: We have updated the
Background section of this final listing
rule to include the 2013 data for those
two locations. Because there are just one
or two years of negative data at the
Scuppernong SNA and Wilton Road
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sites, the occupancy status at both sites
is unknown.
(34) Comment: A peer reviewer
commented that the low numbers of
Poweshiek skipperling observed in 2012
at Scuppernong SNA were at least
partially due to the spring burns of 25–
30 percent of their prime breeding
habitat at that location. The range of
variation of the maximum numbers
observed in 2009–2012 may be skewed
due to the low numbers observed in
2010, when the peak flight may have
been missed due to an early flight and
late survey effort. The anticipated
increase in the population in 2012 due
to a mild winter and early spring
phenology was not observed, which
may indicate that the burn killed a high
number of larvae.
Our Response: We clarified the
statements regarding the uncertainty of
the effect that the 2012 spring burn had
on the Poweshiek skipperling
population at that location. It is difficult
to make cause-and-effect statements
without direct measures of larvae
mortality following a burn.
(35) Comment: A peer reviewer stated
that the same protocol has been used for
Poweshiek skipperling surveys in
Wisconsin since the early 1990s—a
modified Pollard transect count with a
set transect pattern covering 6 ha (15 ac)
of area and 40 minutes to complete.
Our Response: We clarified the
methodology used at the Scuppernong
SNA sites in the Background section of
this final listing rule.
Factors Affecting the Species
(36) Comment: A peer reviewer
suggested that it would be useful to rank
or evaluate risks to the butterfly
populations as they relate to
management recommendations. For
example, would haying carry a lower
risk of causing extirpations? The level of
risk, however, would depend on the
type, duration, and timing of haying
activities versus the type of fire
management applied to sites.
Our Response: Ranking management
methods goes beyond the scope of this
final listing document and is more
appropriate for recovery planning.
Furthermore, management
recommendations may vary for each
location, based on the habitat type and
condition; therefore, it may not be
possible to generalize the level of risk
associated with various management
types.
(37) Comment: One peer reviewer
commented on the level of private
landowner awareness of the species and
its status on their lands. Specifically, in
Canada, most private landowners are
unaware of the presence of the Dakota
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skipper, and this may also be true for
private landowners in the United States.
Even where current management on
lands may be conducive to the species,
it is not typically due to a conscious
effort to conserve the species.
Landowner apathy should be
considered a threat of considerable
concern.
Our Response: We agree that some
landowners may not be aware of the
presence of either butterfly on their
lands and that land may not be
intentionally managed for the
conservation of the species, but rather
used in ways that are inadvertently
favorable to the species. We have
discussed this issue further in Factor E
of this final listing rule. In the United
States, we have notified private
landowners of most of the sites where
we believe the species is still present or
its status is unknown, and many of the
sites where the species is extirpated or
possibly extirpated, but where the
habitat may still be suitable for the
species. We will continue to focus on
public awareness and work
cooperatively with landowners
following listing.
(38) Comment: One peer reviewer
asked for clarification on the reduction
of Dakota skipper range, specifically
what was meant by our statement of ‘‘an
approximately 690-km (430-mi)
reduction of its range’’
Our Response: We have removed this
phrase from this final listing rule,
because it was unclear. The Dakota
skipper is considered to be extirpated
from Illinois and Iowa and no longer
occurs in eastern Minnesota.
Factor A
(39) Comment: One peer reviewer
recommended that the date of first
allowable haying be after July 22,
because some adult flight has been
documented after the date of July 16,
which was our recommendation for the
earliest haying. Another peer reviewer
noted that in Manitoba, August 1 is the
recommended earliest haying date at
Dakota skipper and Poweshiek
skipperling sites, although little haying
is occurring where the Poweshiek
skipperling is present. Sites should not
be hayed within 3 to 4 weeks of the
beginning of the adult flight period to
prevent destruction of nectar plants.
While there may be situations in the
United States where sites undergo
haying ‘‘no more than every other year,’’
most sites in Manitoba are hayed for
several years in a row, but there are no
studies on the impact of repeat annual
haying.
Our Response: Our categorization of
stressors as having high, medium, or
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low impacts on the species, and the
criteria we use to define those
categories, were developed specifically
to guide our analysis of the factors
affecting the species, and are not
intended as guidelines for conservation
efforts. Conservation guidelines for the
Dakota skipper are available (online at
https://www.fws.gov/midwest/
endangered/insects/dask/
DASKconservationguidelines.html), and
we are developing similar guidelines for
the Poweshiek skipperling. In those
guidelines, we recommend that haying
activities occur after the adult flight
period.
(40) Comment: A peer reviewer asked
whether, in the grazing section of the
proposed rule, did the Service mean
that even when grazing is hard enough
to eliminate the skipper, the habitat
potential isn’t completely destroyed, as
it is by mining or plowing, and can be
restored?
Our Response: This is correct, and we
clarified the language in this rule to
more clearly state that, unlike habitat
destroyed by mining or plowing, for
example, intensely grazed habitat has
potential to recover or be restored.
Attempts have been made to restore
prairie remnants that have been plowed
or mined (where significant soil
disturbance has occurred), but such
restorations have not been successful for
the Dakota skipper or Poweshiek
skipperling, at least in observable
timeframes.
(41) Comment: A peer reviewer noted
that the proposal asserts that ‘‘grazing is
one of the primary treatments for
controlling smooth brome and
enhancing native plant diversity in
prairies that have been invaded by this
nonnative grass species.’’ The peer
reviewer stated that the assertion goes
beyond anything in the cited document
(Service 2006). There is no supporting
research for grazing reducing brome,
while at the same time maintaining or
improving the native species
composition. There is, however, support
for the opposite—that grazing can
stimulate brome and reduce native
diversity. Smart et al. (2011) discuss
grazing as a promising possibility, based
on inferential, circumstantial, and
anecdotal information, and the group
agreed that experimental investigation is
a big need. More accurately, the citation
would support this statement: ‘‘grazing
may be a valuable tool for controlling
smooth brome invasion and maintaining
native diversity in prairies, especially
where circumstances make the use of
fire difficult.’’
Our Response: We clarified the
statement regarding grazing as a
potential management tool for invasive
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species control to more accurately
reflect the proceedings of the Service
workshop (Service 2006) and Smart et
al. (2011). Smart et al. (2011) used
repeated clipping methods to simulate
intensive early-season grazing and
discusses the potential for using grazing
as a tool to improve native prairie under
certain conditions.
(42) Comment: One peer reviewer said
that recent statistics related to habitat
conversion show that the statement,
‘‘The economic benefit of grazing to
ranchers may also benefit the species at
some sites by deterring conversion of
remnant prairies to row crop
agriculture’’ is out-of-date, and said this
sentence contributes little to the
argument that remaining habitat is
secure.
Our Response: We clarified the
statement on conversion in this final
rule to reflect the current economic
conditions that row crop agriculture is
generally more economically profitable
than light grazing.
(43) Comment: A peer reviewer noted
that the proposed rule includes little
discussion of soil compaction as a result
of grazing. A field demonstration by
Natural Resources Conservation Service
(NRCS) staff showed that soil
compaction on a heavily grazed pasture
was almost as hard as a brick, and very
little of the water falling on it soaked in.
Soil of this character would be quite
difficult for the larvae of Dakota skipper
to penetrate for shelter construction,
causing them to be more exposed to
predators, parasitoids, and other
environmental stresses. The Poweshiek
skipperling would not be affected by
compaction, as it doesn’t burrow.
Our Response: We agree that soil
compaction due to heavy grazing may
cause the Dakota skipper to be more
exposed to predators, parasites, and
other environmental stresses, such as
fire, than if they were able to build
underground shelters, and we have
taken this into consideration in our
evaluation of the threats to the species.
(44) Comment: A peer reviewer
commented that the effects of grazing in
Manitoba and Saskatchewan, as stated
in Webster (2007), may not be
applicable under current population
scenarios. Even light grazing may be
detrimental on dry short-grass prairie
sites prior to and during the adult flight
period.
Our Response: We incorporated this
information into the Factor A threats
analysis of this final listing rule, below.
(45) Comment: A peer reviewer stated
that potash mining, gravel mining,
flooding, and associated flooding
protection activities may be significant
threats to these species in Canada.
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Our Response: We incorporated this
information into the Factor A threats
analysis of this final listing rule, below.
(46) Comment: One peer reviewer
recommended that we not include the
research from an unpublished paper by
Schlicht (2001a), due to serious flaws in
the methodology.
Our Response: Because of serious
concern over the methods used in this
unpublished paper, we removed the
information from Schlicht (2001a) from
this final listing rule (under Factor A—
Fire), below.
(47) Comment: A peer reviewer stated
that the discussion on threats from fire
in the proposed rule focuses on
controlled burns, but wildfires are a
serious problem in Manitoba and
previously inhabited sites in
northwestern Minnesota. Due to the
highly fragmented nature and
comparatively small size of sites,
wildfire may be a greater threat than
either haying or grazing activities.
Our Response: We considered
wildfires to have moderate to high
impacts to Dakota skipper and
Poweshiek skipperling populations; the
impacts would depend on the timing,
intensity, and extent of the burn. We
discuss wildfires in Manitoba in the
Background (population distribution
and status) section and in Factor E of
this final rule, and considered that
fragmentation due to stochastic events,
such as wildfires, may lead to extinction
at isolated sites (Factor E).
(48) Comment: One peer reviewer
provided a link to the Northern
Tallgrass Prairie Lepidoptera
Conservation Conference Working
Group Reports Synthesis.
Our Response: We added the
reference to the discussion regarding
conservation efforts under Factor A in
this final listing rule, below.
(49) Comment: A peer reviewer noted
that, in the Conservation Efforts To
Reduce Habitat Destruction,
Modification, or Curtailment of Its
Range section of the proposed rule,
there was reference to a 1995 expert
panel and plan. The peer reviewer asked
whether an actual plan was developed.
Our Response: The group outlined a
plan for surveying populations and
characterizing sites and habitats at
priority areas, identifying and
recommending management needs,
monitoring, and outreach and
education; however, this plan was not
drafted or finalized.
(50) Comment: A peer reviewer noted
that, in a number of incidences within
the last decade in Canada, sites have
had general population declines or sites
have been lost to intense agricultural
use.
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Our Response: We are aware of four
sites in Canada where the Dakota
skipper is now extirpated or possibly
extirpated due to habitat destruction.
Only sites where we believed the
species is currently present or possibly
present (unknown) were evaluated in
our threats assessment.
(51) Comment: One peer reviewer
provided details on Poweshiek
skipperling populations following
prescribed burns in Manitoba (based on
Dupont 2013). Specifically, Poweshiek
skipperling populations were most
numerous in sites burned 5 to 8 years
previously. The species was absent in
sites that were burned the previous year,
in small numbers in areas that were
burned 2 to 4 years prior, and absent
from areas that were burned 10 or more
years before the survey.
Our Response: We have incorporated
this information under Factor A of this
final listing rule, below.
Factor C
(52) Comment: One peer reviewer
provided additional information on
Wolbachia, a bacteria affecting many
butterfly species.
Our Response: We incorporated the
new information into our discussion on
Wolbachia under Factor C of this final
listing rule, below.
(53) Comment: A peer reviewer
commented that parasitism, predation,
and disease may be significant stressors
to Poweshiek skipperlings and Dakota
skippers. A hypothesis in the rapid
decline of the Poweshiek skipperling,
and possibly the Dakota skipper, is that
a newly virulent pathogen or a new
parasitoid has increased mortality above
normal levels. The small number of
predation and parasitization events that
were observed is evidence only of the
difficultly in documenting such events.
Dana (1991, pp. 26–27) reported
observing predation on the butterfly by
arthropods and large robber flies
(Asilidae), which are common in upland
prairie habitats. The peer reviewer also
cited and discussed several studies that
pertain to predation on butterflies.
Our Response: We reviewed the
McCabe (1981) and Dana (1991) reports
again and considered additional
information on the normal population
dynamics of insects, how these factors
may explain the rapid decline of the
Poweshiek skipperling, and perhaps the
Dakota skipper, and how these factors
may affect small, isolated populations in
the future. We cannot conclude with
certainty that parasitism and predation
are significant stressors, because these
occurrences are extremely difficult to
observe, and only a few studies
document these events. Therefore, we
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conclude that the level of impact from
disease, parasitism, and predation is
uncertain, but do not dismiss the
possibility that these factors may
become significant in the future.
Factor D
(54) Comment: A peer reviewer
commented that, in North Dakota, the
fundamental purpose of management of
State School lands is economic, not
scientific or environmental.
Consequently, if such land does not
produce income for the State, it may be
subjected to deliberate change in
management strategy, including sale at
auction. The Dakota skipper’s security
at no fewer than two sites in North
Dakota, therefore, depends on the
economic value of hay, because those
sites are on North Dakota Trustlands
and are currently under haying
management.
Our Response: We have incorporated
this information into Factor D of this
final listing rule.
(55) Comment: A peer reviewer stated
that the Poweshiek skipperling was
listed as State-endangered in Minnesota
on August 19, 2013.
Our Response: We have updated the
State status of the Poweshiek
skipperling in Minnesota in this final
rule.
Factor E
(56) Comment: One peer reviewer
stated that, although the Service has not
collected much direct evidence of
threats to populations of the Poweshiek
skipperling in North Dakota compared
to Dakota skippers in the State, it is
reasonable to assume that the same
factors that affect the Dakota skipper
have similarly affected the Poweshiek
skipperling, because the two species
share a preponderance of habitat
characteristics, and often are sympatric
(have overlapping ranges).
Our Response: The Service agrees
with the reviewer’s statement. We also
think that the reverse is true: It is
reasonable to assume that Dakota
skipper may be vulnerable to the factors
that have caused dramatic declines in
the Poweshiek skipperling, but perhaps
with a delay in timing. We consider this
possibility in our analysis.
(57) Comment: One peer reviewer
provided detailed information on the
size and isolation of Dakota skipper
sites in central Manitoba. These sites are
generally greater than 158 ac (64 ha),
and all are separated by 1 km (0.6 mi).
Several sites are separated by many
kilometers (miles). The reviewer also
suggested that the Service consider the
implications of the separation of the
U.S. and Canada sites.
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Our Response: We have incorporated
this information, supplemented by
information in two recently published
Master’s theses (Dupont 2013, Rigney
2013a), to update our threats analysis
for Canadian populations. Although we
were unsure of the size of many sites in
Canada, most sites were separated by
more than 1 km (0.6 mi); therefore,
approximately 25 of the sites evaluated
in Canada were thought to be at least
moderately affected by small size and
isolation. The Canada sites where
Dakota skippers are considered to be
present are approximately 115 km (71
mi) from the nearest U.S. sites, and the
Manitoba site is approximately 166 km
(103 mi) from the nearest Poweshiek
skipperling site in Minnesota.
(58) Comment: A peer reviewer noted
that South Dakota State University
conducted a climate change analysis,
with an emphasis on terrestrial habitats,
in association with the revision of the
South Dakota Wildlife Action Plan.
Our Response: We reviewed that
report and incorporated relevant
information into Factor E of this final
listing rule. We will also consider this
report during recovery planning for the
two species.
(59) Comment: One peer reviewer
queried as to whether either species has
been evaluated using NatureServe’s
Climate Change Vulnerability Index
(https://connect.natureserve.org/
science/climate-change/ccvi)?
Our Response: The Service has not
evaluated either species using
NatureServe’s Climate Change
Vulnerability Index, but will consider
using this tool in the recovery phase.
We used several studies specific to the
Dakota skipper and Poweshiek
skipperling, as well as general studies of
climate-related changes in the Midwest
and throughout North America. See the
Climate Change section of this final rule
for more details on the studies used.
(60) Comment: A peer reviewer
suggested that the Service should
provide more detail on the need for
future planning, potential dispersal
corridors, restoration of existing sites,
and potential reintroduction and
augmentation sites. The high degree of
habitat fragmentation and isolation of
sites combined with the limited
dispersal ability of these species have
potential for long-term implications,
and management actions, even if
effective in short-term conservation of
local populations, may not be enough to
prevent the species from extirpation.
Our Response: We agree with the peer
reviewer that detailed planning will be
needed to recover the Dakota skipper
and Poweshiek skipperling. The Service
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will begin the recovery planning process
once the final listing becomes effective.
(61) Comment: One peer reviewer
wanted to know how the species would
be treated for law enforcement
purposes, in order to ensure that private
landowners and others that may have
these species on their land would
comply with section 9 of the Act. The
reviewer asked specifically about
unauthorized collection, handling, and
possession that could result in a
violation of section 9 of the Act, as
listed in the ‘‘Available Conservation
Measures’’ section of the proposed
listing rule. The reviewer stated that it
may be likely that private citizens have
specimens of these species in their
possession.
Our Response: If private citizens hold
specimens of either species that have
been collected in the past, they should
report these specimens to their local
conservation officer or Service
enforcement official to receive the
appropriate documentation that they
were collected prior to listing.
Collecting either the Dakota skipper or
Poweshiek skipperling after they are
listed would be a violation of section 9
of the Act, unless the collector held an
appropriate permit from the Service.
(62) Comment: One peer reviewer
noted that the list of nonnative species
in the ‘‘Available Conservation
Measures’’ section of the proposed
listing rule are already well-established
species. A more meaningful list would
include species that are not already
established, to prevent future invasive
species issues that negatively impact
these and other native species, and that
would inform land managers of plant
selection for grassland or wildliferelated plantings.
Our Response: We agree that glossy
buckthorn, reed canary grass, and leafy
spurge are well established in many
areas within the range of the species. It
is still important for landowners to
know that these nonnative species are
detrimental to the butterflies and their
habitat, so they may avoid introducing
them to additional areas or conduct
activities that would spread their
growth. We added purple loosestrife to
the list of invasive plants as well.
Purposeful introductions of any of the
above species would be detrimental to
the butterflies and their habitats. This
list is not exhaustive, and other
nonnative species may be destructive to
the butterflies or their habitats.
(63) Comment: A peer reviewer asked
how the habitats in which the
Poweshiek skipperling or Dakota
skipper is known to occur will be
defined, and whether that information
will be available to the public, such that
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landowners can comply with section 9
of the Act.
Our Response: The Service maintains
a list of counties that are within the
current range of the species on publicly
accessible Web sites. We suggest that
project proponents contact their State’s
U.S. Fish and Wildlife Service
Ecological Services Field Office for
specific information on their area. The
species are likely to be present only in
areas with suitable native-prairie
habitat, and may be present in nearby
grass-dominated areas suitable for
dispersal during the adult flight period.
Suitable habitats are further described
in the Background section of this final
listing rule.
4(d) Rule
(64) Comment: A peer reviewer
suggested that the 4(d) rule should
exempt take caused by haying only after
July 22, because the Dakota skipper
flight period extends until after July 15
at some sites in some years.
Our Response: We acknowledge that
extending the earliest date of haying
from July 15 to July 22 may further
minimize the likelihood of adverse
effects to the Dakota skipper, but we
will retain the July 15 date for the
following reasons: First, factors other
than the date in the 4(d) rule will likely
play a greater role in determining actual
haying dates, and those factors are likely
to cause much of the haying conducted
in areas where the Dakota skipper
occurs to be carried out later than the
July 22 date suggested by the
commenter. Second, the July 15 date has
been used for many years in a variety of
conservation agreements as a date to
ensure that the effects of haying on
nesting birds is minimized. It is
typically included, for example, as a
required provision in grassland
conservation easements purchased on
private lands by the Service. By
retaining the July 15 date, we minimize
the likelihood of causing confusion, and
encourage greater cooperation with our
conservation partners. Third, even if
haying is conducted immediately after
July 15, it may be sufficient to minimize
adverse effects to Dakota skippers at
most sites and in most years. Moreover,
in years when the flight period is
ongoing past July 15, the Service can
work voluntarily with landowners and
land managers to delay haying until the
flight period is over.
Comments From Federal Agencies
(65) Comment: The National Guard in
North Dakota (NDARNG) commented on
their concern that training activities on
the Camp Grafton South (CGS) and
Garrison Training Area (GTA) will be
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restricted and that the NDARNG would
be overwhelmed with new permitting
and reporting requirements due to the
listing of the Dakota skipper. The
NDARNG requested that either Stateowned or federally-owned land that is
operated and managed by the NDARNG
be exempt from these proposed rules
per proposed § 17.47(b)(3) for military
training conducted on lands covered
under an Integrated Natural Resources
Management Plan (INRMP).
Our Response: Neither the CGS nor
the GTA was included in the proposed
critical habitat designation. However,
according to section 4(b)(B)(iii) of the
Act, the Department of Defense must
still comply with section 9 of the Act,
including the prohibition preventing
extinction and taking of endangered
species and threatened species.
(66) Comment: The NDARNG
provided additional reports by Fauske
for surveys conducted in the CGS and
GTA in 2003 and 2004. The National
Guard also mentioned surveys that were
conducted by Fauske in 2013 at those
locations. Dakota skipper was not
observed at those sites in those years.
Our Response: We incorporated the
data from the 2003 and 2004 reports
into this final listing rule. We have not
been able to obtain the data from
Fauske’s 2013 surveys, but did
incorporate the National Guard’s claim
of negative surveys in 2013 into this
final listing rule.
(67) Comment: One commenter stated
that two publications (Grant et al. 2009,
DeKeyser et al. 2009) that discuss
management of prairies show that
sometimes prescriptions for long-term
management of habitat are at odds with
short-term management of the species.
For example, no or light grazing or lateseason haying may lead to invasion of
cool-season exotic grasses and loss of
native forb and grasses. Thus no
management could sometimes be
considered a threat, just as prairie
conversion may cause take.
Our Response: We agree that no
management or lack of disturbance may
be a threat to Dakota skipper and
Poweshiek skipperling habitat and that
haying, grazing, and fire may be an
important management tool for these
butterflies, if carried out appropriately.
These topics are discussed further in
Factor A in this final listing rule, below.
Adaptive management may be necessary
at many locations to take into account
the underlying causes of habitat
degradation and the long-term and
short-term consequences of management
to the habitat and the species. We will
be addressing management at specific
locations during recovery planning for
both species.
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(68) Comment: A Federal agency
commented that some native-prairie
plant species decrease without proper
grazing management, and long-term
monitoring is needed to properly
examine plant species declines.
Furthermore, plant species declines may
be due to other factors, such as
landscape position, climatic factors,
historical and current management, and
other ecological site conditions. Several
papers cited in the proposed rule
incorrectly identify forb species that
decrease due to grazing, such as the
purple coneflower.
Our Response: We acknowledge that
long-term monitoring data would be a
valuable indicator of important plant
species declines. Unfortunately, we do
not have long-term monitoring
established at most sites; therefore, we
must rely on the best information
available. Most references to grazing
impacts on prairie butterflies are based
on ancillary observations made during
research focused on other management
impacts. Some of these may be
observational data of changes in site
conditions at a particular site from one
year to the next following changes in
management regimes. We cite a few
studies that show that certain levels of
grazing remove nectar sources and are,
therefore, likely to adversely affect
Dakota skipper populations (e.g., Rigney
2013a, pp. 143, 153). We discuss
grazing, including the effects of grazing
management in different habitat types,
further in Factor A of this final listing
rule, below.
(69) Comment: A Federal agency
noted that the proposed listing rule
states that a large portion of the Dakota
skipper habitat should remain ungrazed
or lightly grazed during the adult flight
period. Management focused on
preserving every life stage of the
butterflies will actually lead to their
demise by inadvertently destroying their
habitat.
Our Response: Britten and Glasford
(2002) recommend minimizing
disturbance of Dakota skipper habitat
during the flight period (late June to
early July) to maximize genetically
effective population sizes (the number
of adults reproducing), to offset the
effects of genetic drift of small
populations (change in gene frequency
over time due to random sampling or
chance, rather than natural selection).
All life stages are essential to the
survival of the species, including the
adult flight stage, which is when
breeding occurs. Removal of important
nectar sources during the short adult
flight period can adversely affect the
Dakota skipper (e.g., Rigney 2013a, pp.
143, 153). Thus, it is equally important
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to minimize disturbance of Poweshiek
skipperling habitat during their adult
flight period for the same reasons.
(70) Comment: A Federal agency
noted that Britten and Glasford (2002, p.
373), cited in the proposed rule, does
not identify grazing as a disturbance, as
the proposed rule indicates.
Our Response: Although Britten and
Glasford (2002) did not specifically
identify grazing as a disturbance, other
information sources indicate that
grazing can disturb adult Dakota
skippers and Poweshiek skipperlings,
because it may remove important nectar
sources (e.g., Rigney 2013a, pp. 143,
153). Both the beneficial and negative
effects of grazing are further discussed
in Factor A of this final listing rule,
below.
Comments From States
(71) Comment: A State commented
that a comprehensive survey effort
throughout the range of the two species
is prudent, if not necessary, before any
listing can occur.
Our Response: Under the Act, we are
obligated to use the best available
scientific and commercial information
in decisions on whether to list a species.
In this case, the best available
information included results from
surveys, reports by scientists and
biological consultants, natural heritage
data, and expert opinion from biologists
with extensive experience studying the
Dakota skippers and Poweshiek
skipperling and their habitats, whether
published or unpublished. We are
required to make a decision based on
that available data. Also, see response to
comment 76.
(72) Comment: The Minnesota
Department of Natural Resources (MN
DNR) agrees with the Service’s
conclusion that these species warrant
protection under the Act and fully
supports the proposed threatened status
for the Dakota skipper and the proposed
endangered status for the Poweshiek
skipperling. The MN DNR has a long
history of commitment to the
conservation of these species and has
been an active participant in recent
efforts to assess their status in
Minnesota. The MN DNR agrees with
the Service’s conclusions regarding
factors affecting the species and their
resulting status. In light of recent
findings, the MN DNR has reclassified
both species as endangered under
Minnesota’s Endangered Species
Statute, effective August 19, 2013.
Our Response: We appreciate our
partnership with MN DNR and their
supporting comments, and have
updated the information regarding the
reclassification of both species under
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Minnesota’s Endangered Species Statute
in Factor D of this final listing rule.
Habitat
(73) Comment: The North Dakota
Game and Fish Department suggests that
the Service use NRCS Ecological Sites of
North Dakota as a means to describe
specific potential habitat, rather than
Type A and Type B habitat as described
in the proposed rule. The ecological site
descriptions and transition models
would help direct the proper grazing
prescription to promote and achieve the
plant species composition appropriate
for the given site and requisites for these
two butterfly species.
Our Response: We are considering
using NRCS ecological site descriptions
as a tool for managers and others to
narrow down potential habitat for one
or both species. However, NRCS
ecological site descriptions have not
been developed for all areas where the
species may be present. For the
purposes of this final listing, we found
that Type A and Type B habitat
descriptions were descriptive of the
habitat and flowering forbs and grasses
necessary for the two butterflies.
(74) Comment: North Dakota
commented that, based on the specific
precipitation and evaporation rates of
Dakota skipper habitat that McCabe
suggests, the western area of North
Dakota should not be considered as part
of the range for the Dakota skipper, as
those areas do not meet those specific
rates.
Our Response: We have determined
that the Dakota skipper is threatened
throughout its range, which includes the
18 counties where the species has been
documented in North Dakota. The
Dakota skipper is historically known
from several counties in western North
Dakota (e.g., McKenzie, Burke, Montrail,
and Dunn counties) and is considered to
be present in at least two locations in
McKenzie County. The Dakota skipper
may still occur in areas of western North
Dakota that may have conditions that
are different from what McCabe (1981)
describes for some of the eastern
counties. See the Background section of
this final listing rule for a list of
counties in each State.
(75) Comment: North Dakota
commented that it appears that any
native grassland in North Dakota that
has not been cultivated is potential
Dakota skipper habitat.
Our Response: To more clearly define
what constitutes Dakota Skipper habitat
and where take of Dakota skippers may
occur, the Service developed tools to
help determine whether the species may
be present in specific areas, which are
available on the Internet at https://
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www.fws.gov/midwest/Endangered/
section7/s7process/s7guid_
cons.html#dask. We will continue to
refine these materials to help reduce
uncertainty as to where Dakota skippers
may occur. Dakota skippers are present
on only a subset of native grassland and
are unlikely to be present in areas where
key habitat features are lacking. Those
features are described in the
Background section of this rule and in
the materials available on the Internet.
As we work to conserve Dakota
skippers, we will provide landowners
and land managers with information
that is as accurate and up-to-date as
possible to describe the areas where the
species is likely to be present. In
addition, we will also work with these
parties to ensure that they understand
what activities are likely to cause take
of the species, whether or not the take
would be exempted under the 4(d) rule,
and what actions may be implemented
to conserve the species.
Population Status and Distribution
(76) Comment: A State commented
that surveys appear to be focused on
repeated visits to sites that were
previously inventoried, and a systematic
search for additional sites has not been
conducted. Furthermore, a few new
sites have been discovered since 1996
without such a systematic search for
new sites, which suggests that many
new sites may be found with a
systematic search. Additionally,
roadside searches for habitat are not a
scientifically valid method for
identifying potential habitat.
Our Response: The search for
additional locations of both species has
been conducted using a variety of
approaches over the years, and potential
sites have been narrowed down on the
landscape using topographic and aerial
maps, State natural heritage habitat
mapping data, aerial surveys, roadside
surveys, and other methods. Other sites
have been surveyed because of a
proposed project and the known
potential for suitable habitat in the area
or proximity to other known locations of
the butterflies. Many sites are repeatedly
surveyed to understand long-term
trends in the presence of the species or
to quantify other population parameters.
Although only a small fraction of all
grassland in North Dakota, South
Dakota, and Minnesota has been
surveyed, a significant proportion of the
un-surveyed area is likely not suitable
for the species. For example, the species
was not detected at approximately 108
additional locations in North Dakota
that were surveyed for the species in the
period 1991–2013 (USFWS 2014,
unpubl. geodatabase). Similarly, in
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South Dakota and Minnesota, 79 and
148 additional locations, respectively,
were surveyed for the species in the
period 1991–2013 (USFWS 2014,
unpubl. geodatabase).
Many of these sites have been
surveyed multiple times over several
years. Surveys for the Dakota skipper
are typically conducted only in areas
that have the particular plant species
the skipper requires. New potential sites
surveyed are generally focused on
prairie habitat that appears suitable for
the species and has a good potential of
hosting the species. Therefore,
researchers have a higher likelihood of
detecting the species at these sites than
at sites randomly selected across the
landscape. Based on these surveys, the
likelihood that significant numbers of
undiscovered Dakota skipper
populations occur in North Dakota,
South Dakota, or Minnesota is low. We
acknowledge that there may be some
undiscovered populations, however,
and are exploring using spatially
explicit modeling to develop probability
occurrence maps of both species, to help
direct future surveys and conservation
efforts.
(77) Comment: Since the Poweshiek
skipperling has not been detected in
South Dakota since 2002, South Dakota
should not be included in the listing
proposal. Further research needs to be
conducted to determine if this species is
present in South Dakota before it is
listed.
Our Response: According to our data
and analysis, the species’ presence is
unknown at 36 of the total 69 sites
where the species has been documented
in South Dakota. The species was
detected at least once at all 36 of these
sites in 1993 or later; 19 of these sites
had positive detections of the species in
2002 or later. The most recent detection
of the species in South Dakota was at
two sites in 2008. Surveys for the
species were not conducted at any of the
36 sites with unknown occupancy
between the years 2007 and 2011, and
we cannot presume that the species is
not persisting at a site only because
there have not been consistent annual
surveys. At several sites, the species has
persisted for longer than 20 years; for
example, the Dakota skipper was first
recorded at Scarlet Fawn Prairie in
South Dakota in 1985 and the species
was detected during every survey since
that date. Similarly, the Poweshiek
skipperling was first recorded at
Waubay National Wildlife Refuge in
1969 and was recorded during every
year the site was surveyed through
2003. South Dakota is in the range of the
Poweshiek skipperling, and the species
is listed throughout its range. See our
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response to comment 76 regarding
additional surveys or research.
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Factor A
(78) Comment: A State commented
that careful implementation of grazing
and prescribed fire can be an effective
management tool in prairie remnants.
The Service should provide clear and
practical HMGs/BMPs (Habitat
Management Guidelines/Best
Management Practices) for acceptable
use of prescribed fire and grazing
implementation.
Our Response: We developed Dakota
skipper conservation guidelines (https://
www.fws.gov/midwest/endangered/
insects/dask/
DASKconservationguidelines.html) that
address grazing, prescribed fire, weed/
invasive species control, and other
topics, and are preparing similar
guidelines for the Poweshiek
skipperling. While some detail is
provided in terms of timing, periods of
rest, and number and size of burn units,
the Service stresses that effective
implementation of the conservation
measures relies on a thorough and
accurate understanding of the
distribution and status of the Dakota
skipper and Poweshiek skipperling and
their habitat within a management area.
These two species are likely to be nonuniformly distributed within habitat
areas (e.g., Rigney 2013a, p. 140).
Therefore, a species expert should
frequently assess and map habitat and
distribution of the species within
management areas to ensure that
managers may act based on correct and
up-to-date information.
(79) Comment: A State asked whether
grazing of potential butterfly habitat
other than low mesic sites will
constitute take.
Our Response: Such decisions will
require site-specific information. If a
project occurring in potential butterfly
habitat may affect one or both species or
its habitat, we suggest contacting the
Service’s Ecological Service Office in
your State.
(80) Comment: A State commented
that habitat modification and
fragmentation may be a large threat to
many grassland species. While other
factors may need to be addressed to
protect the species, conversion of
grasslands is the largest single issue.
Once land conversions have occurred,
the land cannot be restored to match the
specific requirements of these specialist
species. Listing can be viewed by
private landowners as an encumbrance
and a disincentive to conserve
grassland; hence privately owned
grassland could be converted, due to the
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current crop commodity environment
and demand for additional cropland.
Our Response: We agree that
conversion of remnant prairies is a
significant concern. Conversion of land
to agricultural and other uses is
discussed in Factor A of this final listing
rule, below.
Factor E
(81) Comment: South Dakota
commented that, as part of the South
Dakota Wildlife Action Plan Revision,
experts at South Dakota State University
conducted a climate change analysis
with an emphasis on terrestrial habitats.
Our Response: The Service
appreciates this information. We
reviewed the climate report and
included information from it into Factor
E of this final listing rule. This report
will also help inform recovery planning
and implementation.
Economic Concerns
(82) Comment: A State questioned
how a private landowner would be
compensated if, during the course of the
Service’s activities for monitoring the
critical habitat areas, the private
landowner’s land or property is
damaged.
Our Response: Surveys for either
species on private lands would only be
conducted with landowner permission.
Surveys for the species and its habitat
are not destructive in nature and have
little, if any, impact on the land.
(83) Comment: North Dakota
commented that listing these two
species will add a substantial workload
relative to highway improvement
project development, construction, and
maintenance, due to additional section
7 consultations with the Service. This
increased workload could add months
to project timelines and would cause a
major and unnecessary disruption to the
highway and road systems in North
Dakota.
Our Response: Although an increased
workload for section 7 consultations
may be associated with listing these two
species, section 4 of the Act requires
species to be listed as endangered or
threatened solely on the basis of their
biological status and threats to their
existence. Section 7 of the Act requires
Federal agencies to use their legal
authorities to promote the conservation
purposes of the Act and to consult with
the Service to ensure that effects of
actions they authorize, fund, or carry
out are not likely to jeopardize the
continued existence of listed species.
During consultation, the action agency
receives a biological opinion or
concurrence letter addressing the
proposed action. In the relatively few
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cases in which the Service makes a
jeopardy determination, the agency
offers reasonable and prudent
alternatives for how the proposed action
could be modified to avoid jeopardy.
The Service will work with the
consulting agency as expeditiously as
possible to complete the section 7
consulation process in a timely manner.
(84) Comment: A State asked, what
would happen should a private
landowner incidentally take either
species during the course of routine
farming operations on private land.
Our Response: Under the Act, it is
unlawful for a person to take a listed
animal without a permit. Take is
defined as ‘‘harass, harm, pursue, hunt,
shoot, wound, kill, trap, capture, or
collect or attempt to engage in any such
conduct.’’ Through regulations, the term
‘‘harm’’ is defined as ‘‘an act which
actually kills or injures wildlife. Such
an act may include significant habitat
modification or degradation where it
actually kills or injures wildlife by
significantly impairing essential
behavioral patterns, including breeding,
feeding, or sheltering.’’ Section 10 of the
Act may be used by landowners
including private citizens, corporations,
Tribes, States, and counties who want to
develop property inhabited by listed
species. Landowners may receive a
permit to take such species incidentally
to otherwise legal activities, provided
they have developed an approved
habitat conservation plan (HCP). HCPs
include an assessment of the likely
impacts on the species from the
proposed action, the steps that the
permit holder will take to avoid,
minimize, and mitigate the impacts, and
the funding available to carry out the
steps. HCPs may benefit both
landowners and the species by securing
and managing important habitat, and by
addressing economic development with
a focus on species conservation.
We recognize that the Dakota skipper
and Poweshiek skipperling remain only
on lands where management has
allowed them to survive. This is due to
good land-stewardship, and we want to
encourage management practices that
support the butterflies. To minimize
impacts to landowners and promote
continued cooperation with them while
recovering the Dakota skipper, the
Service developed a 4(d) rule under the
Act for that species. This 4(d) rule
exempts incidental take of Dakota
skippers caused by certain routine
livestock operations and mowing
recreational trails. Any ‘‘take’’ that
results from private landowner activities
not exempted under the 4(d) rule would
require a permit from the Service.
Therefore, private landowners with
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Dakota skippers on their property
should become familiar with the
contents of the 4(d) rule and contact the
Service if they have questions. Actions
that may cause ‘‘take’’ and require a
permit from the Service include
prescribed burns, haying before the
adult flight period ends, broadcast
herbicide treatments, some insecticide
treatments, and permanent conversion
of the Dakota skipper’s grassland
habitats. The 4(d) rule does not apply to
take of the Poweshiek skipperling
because it is listed as endangered, and
the Act does not allow 4(d) rules for
endangered species. Any activity that
would result in take of Poweshiek
skipperlings would first require a permit
from the Service.
(85) Comment: A State commented
that where section 7 consultations will
be required is unclear. What areas
would have to be surveyed to determine
whether the species is present? A large
amount of potential habitat may need to
be surveyed during the short adult flight
period, and there are a limited number
of qualified entomologists to conduct
the surveys.
Our Response: The Dakota skipper
and the Poweshiek skipperling are both
closely tied to native-prairie habitats
and are unable to inhabit areas such as
nonnative grasslands, weedy roadsides,
or tame haylands. In addition, these
butterflies are not likely to inhabit
reconstructed prairies (e.g., former
cropland replanted to native-prairie
species). Therefore, the Service
recommends that, to determine whether
a section 7 consultation may be required
or recommended, action agencies
should first coordinate with their local
U.S. Fish and Wildlife Service
Ecological Services field office and
provide a description of the area that
would be affected, directly or indirectly,
by the proposed or ongoing action. If
survey data are unavailable or
inconclusive for the action area, and
features of Dakota skipper or Poweshiek
skipperling habitat are predominant in
at least part of the area, a survey by a
qualified individual may be
recommended. The Service is
developing a list of qualified surveyors,
which will be available through the
field offices in each State.
(86) Comment: North Dakota
expressed concern that any impact to
native grasslands in North Dakota will
be considered take and require an
incidental take permit. Adjusting the
timing of construction activities will not
avoid take because of the species’
biology.
Our Response: The Dakota skipper
and Poweshiek skipperling historically
occurred in 18 and 7 counties in North
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Dakota, respectively, and unless the
species are discovered in additional
counties, section 7 consultation would
be required only in those counties and
on a subset of lands within those
counties where the species may occur or
where critical habitat has been
designated. You may obtain a list of
counties in which the species may occur
from the U.S. Fish and Wildlife Service
Ecological Services field office in your
State. Furthermore, these two species
have specific habitat requirements
(native, unbroken prairies), and it is
likely that many action areas will not
contain those types of prairie habitats.
Therefore, project proponents should
first provide the field office with a
description of the area that would be
affected by the proposed or ongoing
action to determine whether a section 7
consultation may be required or
recommended. See our response to
comment 85 and the Background of this
final listing rule for additional
information regarding the habitats these
two species inhabit.
(87) Comment: A State asked whether
reinitiation under section 7 of the Act
will need to occur, or will any new
restrictions be recommended when new
projects begin or existing projects are
renewed.
Our Response: Section 7(a)(2) of the
Act requires Federal agencies to consult
with the Service to ensure that actions
they fund, authorize, permit, or
otherwise carry out will not jeopardize
the continued existence of any listed
species or adversely modify designated
critical habitat. Therefore, reinitiation of
section 7 consultations may be required
for ongoing, new, or revised actions that
may affect the Dakota skipper or
Poweshiek skipperling or their
designated critical habitat. We
recommend contacting the U.S. Fish
and Wildlife Service Ecological Services
field office in your State to determine
the need for section 7 consultations on
specific projects.
(88) Comment: A State asked what
types of conservation or mitigation
measures would be needed to offset
potential impacts to the species or
designated critical habitat, and how will
the Service ensure timely approval of
mitigation measures.
Our Response: The Service developed
conservation guidelines for the Dakota
skipper that are available online
(https://www.fws.gov/midwest/
endangered/insects/dask/
DASKconservationguidelines.html) and
is developing similar guidelines for the
Poweshiek skipperling. We suggest that
private landowners implement
applicable guidelines to assist species
and habitat conservation efforts and
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contact their local Service Ecological
Services field office if they are planning
an activity that may affect one of these
species. For actions with a Federal
nexus, action agencies should contact
their local field office to discuss the
timeliness of our section 7 consultation
process. For example, from the date that
formal consultation is initiated, the
Service is allowed 90 days to consult
with the agency and applicant (if any)
and 45 days to prepare and submit a
biological opinion. Biological opinions
may include reasonable and prudent
measures and terms and conditions,
both intended to minimize the impact of
incidental take.
(89) Comment: A State asked whether
State natural resource agencies be
expected to restore the species to Stateowned lands where they are considered
to be extirpated.
Our Response: The Service will work
with the State agencies and other
stakeholders through recovery planning
to identify areas that would aid in
recovery of these species, and determine
appropriate actions to take on those
lands.
(90) Comment: A state commented
that incentive-based voluntary programs
work well for other species and may be
a better solution to conserving the
species than listing and critical habitat
designations. The State would like to
provide potential voluntary methods
and programs to assist and incentivize
landowners to implement conservation
measures and practices that enhance
butterfly habitat.
Our Response: We appreciate any
assistance to incentivize landowners to
conserve these species. Voluntary
actions can have a significant
contribution to conservation. If such
measures are in place when we are
evaluating a species for listing, we
consider those measures and how they
affect the status of the species in our
determination. The Service’s policy
regarding voluntary prelisting
conservation actions (79 FR 42525, July
22, 2014), encourages voluntary
conservation actions for non-listed
species. However, a species may still
warrant listing if such voluntary actions
are not in place when we are evaluating
a species for listing, or if those actions
are not sufficient to affect the need to
list a species. We suggest you contact
the Service’s Ecological Services Field
Office in your State to discuss voluntary
conservation programs in detail.
(91) Comment: A State suggested that
the Service should develop habitat
management guidelines and best
management practices (HMGs/BMPs) in
close collaboration with State agencies
and others knowledgeable about
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effective prairie management. Many
State-owned prairies are managed with
the support of Federal funding, and
HMGs/BMPs are needed immediately in
order for the State agencies to comply
with the Act. Such HMGs/BMPs should
include clear guidance on: Prescribed
fire; grazing; appropriate use of
herbicides on occupied sites; pesticide
buffers around occupied sites and notice
to landowners adjacent to occupied
sites; adherence to and enforcement of
pesticide labels; available tools and
incentives, including incentives and
management practices for expanding
prairie restoration to adjacent restorable
lands; distinct measures for occupied
habitat and unoccupied habitat,
including lands targeted for restoration
or enhancement; measures for restored
habitat, and the point at which habitat
is considered restored; and importance
of effectiveness monitoring and adaptive
management practices in ensuring that
HMGs/BMPs produce the desired
benefits to the species and their habitat.
Our Response: We appreciate this
comment and look forward to working
with our State partners in implementing
conservation and providing assistance.
The Service has developed conservation
guidelines for the Dakota skipper that
are available online (https://
www.fws.gov/midwest/endangered/
insects/dask/
DASKconservationguidelines.html) and
is developing similar guidelines for the
Poweshiek skipperling. The Dakota
skipper conservation guidelines
address: Prescribed fire management,
grazing, haying and native seed harvest,
habitat preservation, habitat restoration,
weed/invasive species control,
maintenance of genetic diversity within
populations, and coordinated
management. The Service looks forward
to continued collaboration with State
agencies and other stakeholders to
further develop and refine these
conservation guidelines. These
guidelines will be used as a basis to
begin a discussion of HMGs/BMPs
development.
(92) Comment: A State suggested that,
if HMGs/BMPs cannot be completed
before the effective date of the listing,
the final rule should be delayed until
the necessary guidance is available.
Our Response: Section 4(b)(6)(A) of
the Act establishes that the Service must
make a final determination as to its
proposed action within 1 year of
publishing the proposal, unless there is
substantial disagreement about the
sufficiency or accuracy of the available
data on which that decision is based, for
which the Service may seek up to a 6month extension.
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4(d) Rule
(93) Comment: A state suggested that
the 4(d) rule be expanded to exempt
take caused by prescribed burns, as it is
a valuable habitat management tool.
Our Response: Although we can
establish general guidelines for
managers and landowners who are
planning prescribed burns in Dakota
skipper habitats, we determined that it
would not be advisable to broadly
exempt take caused by burning in the
4(d) rule. The impacts of prescribed
fires on Dakota skipper populations
depend on numerous factors that
warrant site-specific evaluation,
including the number, proximity, and
size of populations in nearby unburned
areas; fuel loads; timing of the fire;
likelihood of escape from fire units; and
post-fire management of unburned
units. If fires are proposed in areas
where they are likely to result in take of
Dakota skippers, individual reviews
should be conducted to determine
potential effects to the species.
(94) Comment: A state suggested that
the 4(d) rule should specifically exempt
mowing and haying of road rights-ofway under all jurisdictions (State,
county, or township). Exemptions
should apply in the area from the road
surface to the right-of-way boundary.
Our Response: We modified the 4(d)
rule to exempt take of Dakota skippers
caused by mowing native grassland for
hay after July 15 within transportation
rights-of-way. Except for mowing of
section line rights-of-way and
recreational trails, the 4(d) rule only
exempts take of Dakota skippers that
occurs as a result of mowing or haying
that is part of routine livestock ranching
activities. Except for the two specific
cases mentioned above—mowing
section line rights-of-way and
recreational trails—the 4(d) rule does
not exempt take of Dakota skippers
caused by mowing that does not
produce hay for livestock consumption.
Regardless, the 4(d) rule exempts take of
Dakota skippers only if the haying is
carried out after July 15. We also further
clarified that Dakota skippers do not
inhabit tame hayland or grassland
(hayland or grassland planted to, and
composed primarily of, nonnative grass
species, such as smooth brome).
(95) Comment: One commenting
agency indicated its support for the 4(d)
rule, but also stated that it does not
support the exemption of the listed
activities for purposes other than
ranching and trail maintenance, and
requested that the Service clarify that
the listed activities would not be
permitted if used for other categories of
actions. These activities include haying
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and spot application of herbicides to
control noxious weeds.
Our Response: In the final 4(d) rule,
the Service clarifies that take would be
exempted for certain activities listed in
the 4(d) rule when carried out in
relation to routine livestock operations.
We did, however, also clarify that take
that occurred as a result of mowing
native grassland for hay would be
exempted if conducted after July 15 in
transportation rights-of-way.
(96) Comment: A State commented
that, in the 4(d) rule, only exempting
spot spraying of weeds is overly
restrictive. Leafy spurge, for example,
cannot be effectively controlled at the
seedling stage by spot spraying.
Our Response: We understand that
there may be cases where spot-spraying
is insufficient to control outbreaks of
noxious weeds. Frequent herbicide
applications, however, have been
associated with reduced diversity of
native flowering plants in native
rangelands (e.g., Smart et al. 2011, p.
184). Therefore, take caused by
broadcast herbicide applications is not
exempted by the 4(d) rule. It many
cases, Dakota skippers may not be
present in areas where broadcast
applications are necessary. The Service
can provide technical assistance to help
determine whether Dakota skipper may
be present. If noxious weed control is
needed where the Dakota skipper is
likely to be present, the Service will
work with landowners or land managers
to identify techniques that avoid take.
(97) Comment: One commenter
requested guidance on whether
prescribed fire and the activities
described under the 4(d) rule could be
implemented ‘‘on sites that might have
historically supported’’ Dakota skipper.
Our Response: Take of Dakota skipper
is prohibited under the Act, unless it is
a specific action that is exempted under
the 4(d) rule, which applies to all State,
private, or tribal lands. If an action is
implemented on a site where the Dakota
skipper is no longer present, then take
is unlikely. An action could result in
take of Dakota skippers at sites where
the species has been extirpated if key
habitat features are still present and an
extant population inhabits a nearby
area. In those cases, Dakota skipper may
have reoccupied the site, and we
recommend coordinating with the
Service to ensure that a proposed
activity is not likely to result in take of
Dakota skippers.
(98) Comment: One commenter stated
that the list of counties in which the
proposed 4(d) rule did not exempt take
caused by grazing (Eddy, McHenry,
Richland, Rolette, Sargent, and
Stutsman) did not directly correspond
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to the list of counties in which critical
habitat was proposed (McHenry,
McKenzie, Ransom, Richland, Rolette,
and Wells).
Our Response: We revised the 4(d)
rule to exempt take caused by grazing
throughout the range of the species, and
not limited to certain counties. Thus,
the final 4(d) rule exempts take of
Dakota skippers caused by livestock
grazing on all private, State, tribal, and
other non-Federal (e.g., county) lands.
Public Comments
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General
(99) Comment: A number of public
comments opposed the listing of the
Dakota skipper and Poweshiek
skipperling as federally threatened or
endangered species, but provided no
substantive scientific or commercial
evidence suggesting that listing is not
warranted.
Our Response: While we appreciate
the opinion of all interested parties, the
Service must base its decision of
whether to list the Dakota skipper and
Poweshiek skipperling solely on the
basis of the best scientific and
commercial data available.
(100) Comment: Several comments
stated that listing these species will
interfere with private property rights
and cause economic impacts, such as
reduction in land values, fines to
citizens, prohibitions to development,
wasteful use of taxpayer money, and
intrusion to grazing and farming
operations.
Our Response: For listing actions, the
Act requires that we make
determinations ‘‘solely on the basis of
the best available scientific and
commercial data available’’ (16 U.S.C.
1533(b)(1)(A)) regarding the status of the
species. Therefore, we do not consider
any information concerning potential
economic or other possible impacts
when making listing determinations. We
will work with entities to conserve the
butterflies and develop workable
solutions. Furthermore, in this rule, we
have included a 4(d) rule for the Dakota
skipper that exempts take from certain
routine grazing activities. The presence
of a listed species does not give
government employees or
representatives any rights to access
private property.
(101) Comment: A commenter stated
that the Service did not use the best
available science in the proposal. There
is a lack of evidence to justify the
proposed actions.
Our Response: The comment did not
provide details on what scientific
information we failed to consider in our
proposal. In preparation of the proposal
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and this final rule, we used the best
available scientific and commercial
information of which we are aware. We
sought comments from independent
peer reviewers to ensure that our
determination is based on scientifically
sound data, assumptions, and analysis.
The peer reviewers stated that our
proposed rule was based on the best
available scientific information.
Additionally, the results of 2013 surveys
conducted throughout the range of both
species in the United States and
information from recently published
research conducted in Saskatchewan
and Manitoba were considered in our
final listing rule.
(102) Comment: A commenter stated
that listing under the Act and critical
habitat designations are intertwined and
cannot be separated, as the Service has
done with these proposals.
Our Response: When a species is
proposed for listing as endangered or
threatened under the Endangered
Species Act (Act), we must consider
whether there are areas of habitat we
believe are essential to the species’
conservation. The listing determination
and critical habitat determination for
the Dakota skipper and Poweshiek
skipperling were conducted at the same
time and in coordination with each
other. The proposed rules for each
action were published on the same date,
but in separate documents. We are
currently working to finalize the critical
habitat determination for these two
species, which will be published
shortly.
(103) Comment: A commenter
requested that we clarify the status that
is proposed for each species, as it is
confusing which is proposed as
threatened and which as endangered.
Our Response: The Dakota skipper is
listed in this rule as a threatened
species, and the Poweshiek skipperling,
as an endangered species.
(104) Comment: A commenter
requested that the listing and critical
habitat designations for these species
will create an adversarial atmosphere
between the Service and the agricultural
community, and punish producers, who
are the best stewards of habitat for a
variety of species.
Our Response: We based our listing
decisions on the basis of biological
information and have determined that
the Dakota skipper is threatened and the
Poweshiek skipperling is endangered
under the Act. The Service is committed
to working with private landowners,
public land managers, conservation
agencies, nongovernmental
organizations, and the scientific
community to conserve the Dakota
skipper and Poweshiek skipperling and
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their habitats. For example, in
recognition of efforts that provide for
conservation and management of the
Dakota skipper and its habitat in a
manner consistent with the purposes of
the Act, we developed a 4(d) rule that
outlines the prohibitions, and
exceptions to those prohibitions,
necessary and advisable for the
conservation of the Dakota skipper. We
believe that exempting incidental take
of Dakota skippers that may result from
grazing in certain geographic areas will
afford us more time to protect the
species’ habitats in these areas and will
facilitate the coordination and
partnerships needed to recover the
species.
(105) Comment: The North Dakota
Stockman’s Association commented that
they have policy supporting the use of
sound science in decisionmaking. Much
of the science used to develop these
proposals was not peer-reviewed or
published, and was largely based on
internal documents. The Service’s own
‘‘Information Standards Under the
Endangered Species Act’’ policy calls
for ‘‘review of all scientific and other
information used by the Services to
prepare biological opinions, incidental
take statements, and biological
assessments to ensure that any
information used by the Services to
implement the Act is reliable, credible,
and represents the best scientific and
commercial data available.’’ Sound,
peer-reviewed science needs to be the
foundation of any proposal, but
particularly of those with such serious
implications for citizens.
Our Response: Under the Act, we are
obligated to use the best available
scientific and commercial information,
which in this cased included results
from surveys, reports by scientists and
biological consultants, natural heritage
data, and expert opinion from biologists
with extensive experience studying the
Dakota skipper and Poweshiek
skipperling and their habitats, whether
published or unpublished. The Service’s
databases were also referenced several
times within the document (e.g., Service
2014, unpublished geodatabase). These
databases were built using hundreds of
sources, including unpublished reports,
published papers, and State heritage
data. We referenced these databases in
the proposed and final listing
document, in places where we
summarized data across many sources.
All of the reports utilized in these
databases are publically available, upon
request.
Additionally, we sought comments
from independent peer reviewers to
ensure that our determinations are
based on scientifically sound data,
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assumptions, and analysis. We solicited
information from the general public,
nongovernmental conservation
organizations, State and Federal
agencies that are familiar with the
species and their habitats, academic
institutions, and groups and individuals
that might have information that would
contribute to an update of our
knowledge of the species, as well as the
activities and natural processes that
might be contributing to the decline of
either species. The existing body of
literature on the Dakota skipper and
Poweshiek skipperling, including
results from surveys, reports by
scientists and biological consultants,
natural heritage data, and expert
opinion from biologists with extensive
experience studying the Dakota skipper
and Poweshiek skipperling and their
habitats, whether published or
unpublished, is the best available
information.
(106) Comment: A commenter noted
that the Dakota skipper listing priority
number indicating threats of moderate
to low magnitude.
Our Response: The Service believes
that the Dakota skipper warrants
protection under the Act, as a
threatened species, as discussed in
detail in this final listing rule. The
listing priority number was changed
from 11 to 8 on December 6, 2007 (72
FR 69034), and the Dakota skipper
remained a candidate species with a
listing priority number of 8 in
subsequent notices through October 26,
2011 (76 FR 66370). The listing priority
numbers range from 1 to 12, indicating
the relative urgency for listing plants or
animals as threatened or endangered.
The criteria used to assign this number
reflect the magnitude and immediacy of
threat to the species, as well as the
relative distinctiveness or isolation of
the genetic material they possess. This
latter criterion is applied by giving a
higher priority number to species that
are the only remaining species in their
genus, and a lower priority number to
subspecies and varieties. The listing
priority number assigned to a species,
however, does not necessarily reflect the
classification the Service ultimately
determines is appropriate for a species
when making a listing determination, as
new information may become available
that affects that decision.
(107) Comment: A commenter
questioned how this listing would
adversely affect other species.
Our Response: We are unaware of any
adverse effects that these listings would
have on other native species of plants or
animals. Nonnative or invasive plant
species and species of woody plants
encroaching into prairie habitats may be
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managed to maintain or increase the
quality of native-prairie habitats.
(108) Comment: Commenters asked
whether those who are enrolled in the
Conservation Reserve Program,
Environmental Quality Incentive
Program, or other U.S. Department of
Agriculture programs would be subject
to special requirements. How will the
listing affect those who have Federal
crop insurance, have received a Federal
loan or Federal disaster assistance, or
own property that has a Federal
easement? If a landowner is required to
seek consultation before requesting
Federal funding or authorization for an
action that may affect a listed species or
critical habitat, what cost will be
involved, both in terms of money and
time? Will this be reflected in the
economic impact analysis the Service is
preparing?
Our Response: Proposed projects in
areas where one or both species may be
present or on designated critical habitat
that has a Federal nexus (in other
words, funded, authorized, or carried
out by a Federal agency) will be
required to undergo consultation with
the Service under section 7 of the Act.
In such cases, it is the responsibility of
the Federal agency involved to complete
the consultation. In those instances, the
action agency should contact the
Service’s Ecological Services Office in
their State if they are planning an
activity that may affect the species or its
critical habitat. For more information
about section 7 consultations, visit the
Service’s Web site (https://www.fws.gov/
endangered/what-we-do/consultationsoverview.html). In accordance with the
Act, we cannot consider possible
economic impacts in making a listing
determination. However, section 4(b)(2)
of the Act states that the Secretary shall
designate and make revisions to critical
habitat on the basis of the best available
scientific data after taking into
consideration the economic impact,
national security impact, and any other
relevant impact of specifying any
particular area as critical habitat.
(109) Comment: One commenter
recommended that better
documentation is needed when
Landowner Incentive Program grants or
other government funding is used.
Our Response: Government-funded
grant accomplishment reports are
typically available online. Information
on our grant programs available to aid
species recovery can be found at
https://www.fws.gov/grants.
(110) Comment: Private landowners
who are participating in the Service’s
recovery program for the Karner blue
butterfly commented that private
landowners are critical to the protection
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of endangered and threatened species.
Private landowners often provide
suitable ‘stepping stone’ habitat
otherwise unavailable to public
agencies. The Federal status of the
Karner blue butterfly facilitated habitat
improvements and public awareness
that may not have occurred but for the
protection of that species. The
commenter believes that listing the
Dakota skipper and Poweshiek
skipperling will similarly benefit these
two species.
Our Response: We thank you for your
comment and participation in species
recovery efforts. The Service
understands the importance of private
landowner participation and support in
recovery of the Dakota skipper and
Poweshiek skipperling and will
continue to work with all stakeholders
to this end.
(111) Comment: One commenter
expressed disappointment with the
Service stating that other Service
projects that are of great benefit to
society, the commenter did not believe
that listing the butterflies was one of
them. The commenter questioned why
these two butterflies are of such
importance that they should be listed.
Our Response: In the preamble to the
Endangered Species Act of 1973,
Congress recognized that endangered
and threatened species of wildlife and
plants ‘‘are of esthetic, ecological,
educational, historical, recreational, and
scientific value to the Nation and its
people.’’ In this statement, Congress
summarized convincing arguments
made by scientists, conservationists,
and others who are concerned by the
disappearance of unique creatures. The
Service is responsible for implementing
the Act, and as such, must determine
whether any species is an endangered or
threatened species, based on the best
scientific and commercial data available
regarding the status of that species, not
based on a certain benefit to society or
importance.
Although the Service does not
consider the value of a particular
species when making a listing
determination, these butterflies are
important and do provide a societal
benefit. Humans depend on the variety
of life for food, clothing and medicines.
When we lose species we lose their
potential for the future and we lose their
effect on other species which, in turn,
have ecosystem roles and future value.
Continued degradation of our lands and
waters that reduces our biological
diversity—the variety of life—is
important. Habitat and water
degradation, and maybe even climate
change, can be reversed, but the loss of
a species and its genes are irreversible.
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Further, the prairie ecosystem is not
completely gone, yet, but it will be if we
do not take measures to save its plants
and animals. Protecting these small
butterflies means protecting their
habitats, so that some of this ecosystem,
with all its variety of life, remains.
Humans depend on the variety of life for
food, clothing and medicines. The
variety of life that we have in this
country, including functioning
ecosystems, is our natural heritage.
(112) Comment: One commenter
stated that change, both desired and
undesired, is a natural part of the
evolutionary cycle.
Our Response: Although extinctions
occur naturally, scientific evidence
strongly indicates that the current rate
of extinction is much higher than the
natural or background rate of the past.
The main force driving this higher rate
of loss is habitat loss. Over-exploitation
of wildlife for commercial purposes, the
introduction of harmful exotic
(nonnative) organisms, environmental
pollution, and the spread of diseases
also pose serious threats to our world’s
biological heritage. None of these
creatures exists in a vacuum. All living
things are part of a complex, often
delicately balanced, network called the
biosphere. The earth’s biosphere, in
turn, is composed of countless
ecosystems, which include plants and
animals and their physical
environments. No one knows the
myriad ways the extinction of organisms
will affect the other members of its
ecosystem, but the removal of a single
species can set off a chain reaction
affecting many others. Furthermore,
many individual species are uniquely
important as indicators of
environmental quality. The rapid
decline of the Poweshiek skipperling
and Dakota skipper may be an indicator
of a greater environmental problem.
Regardless of the reason for the species’
decline, it it meets the definitions of a
threatened or endangered species under
the Act, we are obligated list it under
the Act.
(113) Comment: A commenter noted
that prairie ecosystems are one of the
most endangered ecosystems of the
world. Currently only 4 percent of
remnant tallgrass prairie remains in the
United States, and the loss in habitat
has led to the declines in the Poweshiek
skipperling and Dakota skipper.
Furthermore, these two species play an
important role in the prairie ecosystem,
and by protecting them, we also protect
other prairie plants and animals.
Our Response: Native tallgrass and
mixed-grass prairies have been reduced
by 85 to 99.9 percent of their former
area throughout the historical range of
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both species (Samson and Knopf 1994,
pp. 418–419). Even further destruction
of remnant prairies has occurred since
Samson and Knopf’s study. Conversion
is discussed in Factor A of this final
listing rule, below.
(114) Comment: A commenter stated
that the limits and prohibitions on land
uses like grazing and haying that are a
result of this listing will negatively
affect livestock producers. For example,
the areas in North Dakota within the
range of the butterflies are significant
beef-producing counties. Limiting
grazing or haying on those lands will
have serious economic ramifications for
the cattle-ranching landowners. Because
of the terrain, some of these lands are
suited only for livestock grazing. If those
lands cannot be used for that purpose,
their value will largely be diminished.
Under the Service proposals, six North
Dakota counties are deemed too
sensitive for grazing, and it appears that
grazing will be prohibited there
altogether.
Landowner concerns about
compliance could influence those
impacted to convert their grass and
haylands to other uses before a final rule
is in effect. This would be detrimental
to both the livestock industry and the
butterflies the Service is aiming to
protect.
Our Response: Through public
meetings, meetings with private
landowners, and outreach efforts, the
Service has attempted to reduce the
concerns of private individuals. It is
important for private individuals to
know that only those projects or actions
that occur in areas where the butterflies
may be present or on designated critical
habitat and that have a Federal nexus
(in other words, funded, authorized, or
carried out by a Federal agency) must
undergo consultation with the Service
under section 7 of the Act. In such
cases, it is the responsibility of the
Federal agency involved to complete the
consultation. We suggest that private
landowners contact their local Service
Ecological Services Office if they are
planning an activity with a Federal
nexus that may affect the species or its
critical habitat. For more information
about section 7 consultations, visit the
Service’s Web site (https://www.fws.gov/
endangered/what-we-do/consultationsoverview.html). Under the 4(d) rule for
the Dakota skipper, take of Dakota
skippers caused by certain routine
livestock operations on all non-Federal
lands is exempt from the prohibitions
under section 9 of the Act. For more
information on the 4(d) rule for the
Dakota skipper, refer to the Provisions
of the 4(d) Rule for the Dakota Skipper
section of the preamble to this final rule.
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(115) Comment: A commenter stated
that livestock owners are the original
stewards of this land and other natural
resources, and the general management
practices utilized by these owners are
ecologically sound and enhance the
productive capabilities of the land.
These practices may even be enhancing
the habitat for these two butterflies. As
private landowners and stewards of
livestock, land, and other natural
resources, we look for policies that
allow coexistence and do not threaten
our livelihood.
Our Response: We appreciate your
comment. Landowners deserve great
credit for their land stewardship, and
we want to continue to encourage those
management practices that support the
butterflies. The Service also strives to
find ways to work with people while
protecting imperiled species. To this
end, the Act allows for some flexibility
for species that are listed as threatened;
the Service is able to tailor the
protections of the Act to what it deems
as necessary and advisable to provide
for the conservation of such species. We
have developed a 4(d) rule for the
Dakota skipper that provides for the
conservation of the species while
allowing some flexibilities for
landowners. This 4(d) rule exempts
incidental take of Dakota skippers that
is caused by certain routine livestock
operations and mowing of recreational
trails. For more information on the 4(d)
rule for the Dakota skipper, refer to the
Provisions of the 4(d) Rule for the
Dakota Skipper section of this final rule,
below.
Biology and Habitat
(116) Comment: A commenter stated
that the Service is correct to rely on
Royer et al. (2008) for understanding
and describing Dakota skipper habitat.
Dakota skipper data in Minnesota are
overwhelmingly attributable to Type B
(upland prairie: Dry-mesic or dry).
However, type A and B habitats can
blend into each other. As correctly
described by the Service here, upland
and lowland prairie are often
intermixed in both habitat types (A and
B).
Our Response: We describe prairie
types as Type A or Type B habitat, but
realize that the two habitat types may be
intermixed, there may be smaller
patches that may be better categorized,
or specific microhabitats that the
species uses at various times to fulfill
their biological needs.
Occupancy
(117) Comment: A commenter stated
that the definition of occupancy is
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difficult to understand and should be
clarified.
Our Response: We clarified the
definition of occupancy in this final rule
by adding language that clarifies that the
three sequential years of negative
surveys necessary to consider the
species extirpated from a site could be
from any survey year. We also clarified
that the occupancy status of an
extirpated site would not change unless
the species was detected at that location
during future surveys. We strove to be
as accurate as possible in defining
occupancy for the purposes of the
listing and critical habitat
determinations. If you are unsure
whether either species may occur on
your property, we suggest you contact
the Service’s Ecological Services Field
Office in your state.
(118) Comment: A commenter stated
that the Service’s methodology for
classifying occupancy is well supported.
Given the difficulties of detecting these
small butterflies most observable in the
brief period per year when it is in the
adult life stage, a conservative approach
is justified. The timing of the adult
flight period and the species’ abundance
varies greatly among years, due to
climatic variation. At least 3 years of
surveys are needed before an area
should be considered extirpated.
Furthermore, those 3 years of surveys
need to be detailed efforts per survey,
with multiple dates of surveys per year.
Our Response: We appreciate your
comment in support of our occupancy
rationale. We agree that multiple dates
of surveys per year are desired to verify
non-detection of the species in a given
year. We have added language to clarify
that point in the Background section of
this final listing rule, above.
(119) Comment: A commenter stated
that the determinations to list these two
butterflies are based on historical
declines, although significant
documentation of butterfly fauna did
not occur until 1960, and it is, therefore,
impossible to determine anything about
the historical range or any possible
historical declines. How are past
declines relevant to the species now,
and why is the Service listing these
species now, as opposed to when those
declines were occurring? It is not
possible to characterize the magnitude
of threats to these species without
knowing what has caused the historical
decline and understanding what
constitutes natural levels of inter-annual
population fluctuation.
Our Response: We consider historical
declines, and the ongoing effects of
those historical declines, as well as
current and recent declines, in our
determinations. Significant population
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declines have occurred in both species
very recently and are still ongoing, and
the effects of historical declines
continue to impact both species today.
Populations that were historically
fragmented by habitat destruction
continue to be isolated from one
another, which may have negative
genetic consequences or increased
vulnerability to stochastic events, for
example.
Population Status and Distribution
(120) Comment: A commenter stated
that the survey methods are inadequate
and poorly described. In particular, it
appears that a high percentage of survey
sites are in close proximity to roads.
These sites may be disturbed sites, and
some literature indicates Dakota
skippers do not occupy formerly
disturbed and subsequently restored
sites.
Our Response: As described in the
Background section of this final listing
rule, above, Dakota skippers occupy
native-prairie sites that have never been
plowed. During the adult flight period,
it is possible that Dakota skipper may
use lesser quality grassland dominated
areas to travel (disperse) from one
native-prairie site to another nearby
native-prairie site. Surveys were
conducted using various protocols (for
example, Pollard walks (Pollard 1975),
modified Pollard walks, wandering
transects, and timed transects)
depending on the objective of the
survey, funding, or available resources
and staff. Describing the details of
survey methods for each site is beyond
the scope of this rule, however, those
details are described in the survey
reports that are cited within this final
rule. We added some brief examples of
commonly used survey methodologies
in the Background section of this final
listing rule.
(121) Comment: A few commenters
suggested that there are multiple
approaches to interpreting data and
conducting trend analyses. One such
suggested approach is to use the
concepts of Schlicht et al. (2009, Table
10, p. 439) and Swengel and Swengel
(2012b, Table 2). The observed timing of
population declines may differ
depending on the approach used. As
such, the commenter cautions that the
information included in Figures 1 and 2
of the proposed listing rule should be
interpreted carefully, and provides
specific suggestions for an alternate
approach.
Our Response: We acknowledge that
there are other ways to look at the data
and the approach suggested by the
commenter would be a good way to
determine the apparent disappearance
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(either absence or undetectable levels)
of a species at each particular site.
These types of analyses may be an
appropriate approach for recovery
planning and implementation, and we
will consider their utility at that time.
We believe the way we interpreted the
data in the listing rule is appropriate for
looking at the overall trends in
detections and non-detections of the
species through the years across all of
the known sites, without relying on the
numbers of individuals observed at each
site during each survey year, since we
often do not have those data. Although
many of the skipper sites have been
surveyed over multiple years, the
frequency and type of surveys varied
among, and sometimes within, sites and
years. Surveys may have been
conducted using various protocols and
with varied objectives and, therefore,
had varying results. For instance, some
surveys focused simply on documenting
species presence while others
documented the numbers observed in a
certain area, distance, or period of time.
Whether or not the species was detected
in a given year is the only common
result of all the surveys, so that is the
data we used to evaluate trends through
time.
(122) Comment: One private citizen
commented that he has never observed
the Dakota skipper and the Poweshiek
skipperling on his property or anywhere
else.
Our Response: Dakota skippers and
Poweshiek skipperlings have a single
adult flight period per year that
typically occurs from the middle of June
through the end of July. The actual
flight period varies somewhat across the
range of each species and can also vary
significantly from year-to-year, but
typically lasts 2 to 4 weeks. Both the
Dakota skipper and Poweshiek
skipperling are small and cryptic
species. Therefore, it is unlikely
someone will observe these two species
unless they are actively searching for
the species in suitable habitat within
their ranges during the short adult flight
period. The likelihood of observing
these species recently is low, because
these two species have reached
undetectable levels, even by
experienced observers, at most of their
known locations.
(123) Comment: One commenter
recommended that surveying and
monitoring protocols be developed for
the two species.
Our Response: Because the objectives
of surveys may vary across the range of
these species, we recommend contacting
the Service’s Ecological Services Field
Office in your State to discuss the
appropriate survey protocol to use for
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particular projects, habitat types, and
geographic areas. To facilitate effective
cooperation among agencies,
organizations, and individuals
interested in the distribution of these
species, the Service will maintain a list
of individuals who meet certain
qualifications for conducting reliable
surveys for the target species.
(124) Comment: One commenter
provided results from butterfly surveys
conducted for the past 19 years (1995–
2013) in Clay and Polk counties,
Minnesota. Low numbers of Dakota
skippers were observed in 1996, 2006,
2007, and 2010. The Poweshiek
skipperling was observed in 1997–2002,
2004–2006, and two individual
Poweshiek skipperlings were observed
in 2013.
Our Response: We appreciate
receiving the new information on
Dakota skipper and Poweshiek
skipperling occurrences in Minnesota.
We verified the information with
Minnesota Department of Natural
Resources staff (a qualified surveyor),
who confirmed the validity of the data.
We confirmed that the individual was
capable of identifying the Poweshiek
skipperling and that the 2013
observations were valid. This
information was incorporated into this
final listing rule. The Service has
prioritized the Polk County location for
surveys in future years.
(125) Comment: A commenter noted
that the Service included two graphs
indicating a decline in Dakota skipper
sites in Minnesota and South Dakota,
but did not include a graph for North
Dakota. The 2012 abstract by Royer
indicates that ‘‘essentially the same
proportion of count locations hosted
detectable Dakota skipper populations
. . .’’ in 1996, 1997 and 2012, but that
the encounters per hour had decreased.
The commenter contend that fewer
‘‘encounters per hour’’ could be the
result of many factors, including the
very specific conditions necessary to do
an accurate sampling. The summary
data does not provide the necessary
background to determine other factors
that could have influenced the
‘‘encounters per hour’’ count.
Our Response: The detection versus
non-detection data for Dakota skippers
in North Dakota produced no clear
trend. If we examine years with more
than 10 sites surveyed, for example, we
find that in 1991, the species was
detected at 19 of the 31 sites surveyed
(61 percent); in 1995, the species was
detected at 5 of the 10 sites surveyed (50
percent); in 1996, the species was
detected at 13 of the 18 sites surveyed
(72 percent); in 1997, the species was
detected at 10 of the 25 sites surveyed
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(40 percent); in 1998, the species was
detected at 11 of the 17 sites surveyed
(65 percent); and in 2012, the species
was detected at 15 of the 27 sites (56
percent) surveyed (where the species
had previously been observed). Royer
(2012) was correct that the proportion of
sites with detections versus nondetections of Dakota skippers were
similar (e.g., statewide proportions in
1996 (72 percent), 1997 (40 percent),
and 2012 (56 percent)). Therefore, we
examined the results of sites that Royer
(2012) surveyed using methods that
quantified results such that they could
be compared among years.
Royer used the same survey protocol,
timed transect searches (where the
number of individuals observed per
hour were recorded), for the surveys
conducted in 1996–1997, 1998, and
2012 (Royer 1997, Royer and Royer
2012b). Furthermore, Royer’s 1996,
1997, 1998, and 2012 surveys (Royer
1997, Royer and Royer 2012b) adhered
to our acceptable survey standards (e.g.,
wind speeds, time of day). Therefore,
the variation in numbers observed
attributable to survey error is expected
to be negligible. Average encounter
frequencies observed across the State in
2012 (10.7 encounters per hour) were
lower than during the 1996–1997 and
1998 statewide surveys (North Dakota
State average = 16.94 encounters per
hour and 22.67 encounters per hour,
respectively). At the site level, sites
surveyed in 1996–1997 or 1998
generally had higher numbers of Dakota
skippers encountered per hour than in
2012.
(126) Comment: A commenter stated
that the proposed listing of the Dakota
skipper as a threatened species is
unwarranted at this time. In North
Dakota, surveys show that essentially
the same proportion of locations had
detectable levels of Dakota skipper in
1996–1997 (46 percent) as in 2012 (46
percent). Additionally, new sites have
been discovered in North Dakota, even
though a systematic survey has not been
conducted. A substantially lower
encounter rate in 2012 compared to
historical surveys was reported, but one
year of data does not justify listing.
Our Response: Although the
proportion of sites surveyed with
positive detections of the species is
similar when comparing sites surveyed
in North Dakota in 1996–1997 with
those surveyed in 2012, the numbers of
individuals observed recently were
substantially lower than in previous
surveys; see our response to Comment
125. In addition to the survey data and
population trend information, the
Service also considers listing species
based on an analysis of threats,
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described in detail in this final listing
rule. The results of that threat analysis
indicates that all of the Dakota skipper
sites where the species is considered to
be present or unknown in North Dakota
have one or more documented threat of
moderate to high levels. At least one
moderate- to high-level threat is
documented in all Minnesota, North
Dakota, South Dakota, and Canada
Dakota skipper sites with present or
unknown occupancy.
(127) Comment: A commenter stated
that the Service rightly states that most
Poweshiek skipperling decline likely
went unrecorded because most prairie
destruction occurred prior to 1960, but
most prairie butterfly surveys post-date
those declines. Most decline during
1960–2000 also went largely
undocumented. This is evidenced by
the large number of sites in Minnesota
that fall into an uncertain occupancy
category. Longer term Poweshiek
skipperling decline has been masked by
data paucity and turnover in sites
surveyed.
Our Response: We agree that there is
a paucity of data at many sites in recent
years (1960–1993). However, most
Poweshiek skipperling sites and Dakota
skipper sites have been surveyed at least
once in 1993 or more recently. The lack
of surveys at a given site since 1993
does mean that we are uncertain of the
occupancy at many sites. We used a
cautious approach; by assigning sites
unknown status, we cannot say that the
species is truly absent or extirpated
from a site, while acknowledging that
the species may still be present,
possibly at undetectable levels, if
suitable habitat is still present. More
surveys are needed at these sites to
determine if the species is present.
(128) Comment: A commenter stated
that, at the time of Swengel’s (1992)
review, Poweshiek skipperlings had
fewer known populations, were more
highly concentrated in preserves (a
single kind of ownership and land use
category), were in a narrower range,
were more concentrated in a highly
destroyed ecosystem (tallgrass prairie),
and had a worse immediate response to
typical preserve management (fire) than
Karner blue butterflies, which were
federally listed in 1992. Poweshiek
skipperlings are capable of high local
abundance in a few sites, but these
population numbers are highly volatile,
and so extremely low numbers also
occur during these abundance
fluctuations. Compared to Dakota
skipper incidence within Poweshiek
skipperling range, Poweshiek
skipperlings occurred on relatively more
preserves, but Dakota skippers had a
range further west, including mixed-
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grass prairie, less of which has been
destroyed. Also, the Dakota skipper is
more compatibile with agricultural uses
on ranch land (e.g., Royer 1992;
Marrone 1992). Thus, the Dakota
skipper had relatively more habitat,
even if there were fewer known sites
specifically in Minnesota. Furthermore,
there is a tendency to assume that
habitat protection (making a site a
preserve) means the skippers in the
preserve are secure; thus, if few are
found on a given survey, the assumption
is that this is due to the surveys being
conducted at the wrong time, or due to
fluctuations in abundance resulting
from climatic variation. It is only
through consistent long-term monitoring
with the sites held constant (as in
Swengel and Swengel 2013) that trend
can be distinguished from those issues.
Our Response: Because of the number
of historical sites and the various ways
that data were collected at those sites,
we examined the range-wide data using
detections and non-detections. We agree
that there are few sites with consecutive
years of data, and even fewer that have
data over the long term. We have
examined the data at individual sites
where we had several consecutive years
of data, and found that Poweshiek
skipperling numbers have appeared to
decline, along with the number of sites
with positive detections (vs. nondetections) of the species.
(129) Comment: A commenter stated
that the sudden recent decline in
Poweshiek skipperlings over the last 10
years is likely because there are few new
populations being discovered to replace
the already undetectable, previously
known populations. Furthermore,
conservationists identified the best sites
first; thus, more recently discovered
populations were not as large and robust
as the earlier discovered populations.
Those more fragile populations would
have less favorable prospects for longterm persistence. This also contributes
to the sense that decline is now
occurring everywhere. In addition, in
some places, such as North Dakota, the
dramatic population declines of the
Poweshiek skipperling primarily
occurred prior to 2000 (see Royer and
Marrone 1992a, b; and Orwig 1994;
1995; 1996; and 1997).
Our Response: We acknowledge that
there are documented declines in
Poweshiek skipperling populations
prior to 2000. However, in our
comprehensive review, it appears that
many sites with known populations of
Poweshiek skipperlings have
simultaneously declined to undetectable
levels across much of the species’ range
in the early 2000s.
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Factors Affecting the Species—General
(130) Comment: A commenter stated
that, throughout the proposed listing
rule, the Service attributes perceived
threats to the Dakota skipper as threats
to the Poweshiek skipperling or vice
versa. The Service must independently
evaluate threats to each species and may
not assume that a threat to one species
is necessarily a threat to the other.
Our Response: We have conducted
the analysis of factors affecting the
species separately for the two species.
Since these two species have similar
biology and are often found in the same
locations, they face similar or identical
threats at many locations. Therefore,
when describing the factors, we discuss
their effects to both species together
when they are the same or similar. For
example, if a remnant (untilled) native
tallgrass prairie is being considered for
a housing development, the resulting
habitat conversion would affect both
species by removing suitable habitat
from the landscape.
(131) Comment: A commenter stated
that listing these species will impede
the use of certain grassland management
tools such as grazing, haying, burning,
and chemical spraying that are
necessary to meet the desired habitat for
these butterflies.
Our Response: The listing of these
two butterflies will not necessarily
impede the use of these grassland
management tools. The Service
recognizes that management, including
grazing, haying, prescriptive fire or
targeted herbicide treatments, may be
needed to benefit the species and their
habitats, as discussed in Factor A and
Factor E of this final listing rule, below.
The types, extent, duration, and
intensity of various management
regimes that would benefit the
butterflies may depend on the specific
past, present, or future threats at that
location. The success of management
regimes will need to be monitored and
adjusted accordingly.
(132) Comment: A commenter noted
that suggestions of ‘‘light,’’ ‘‘limited’’
and ‘‘no’’ grazing and ‘‘late-season
haying’’ are mentioned in the proposed
rule to support rebuilding the butterfly
populations. However, such practices
have proven to have long-term
implications that will actually do the
opposite. For instance, limiting or
eliminating grazing and haying is likely
to promote invasion by exotic grasses,
such as smooth brome grass and
Kentucky bluegrass, which will compete
with the very same native species that
the butterflies require for habitat. The
Service should encourage and
incentivize grazing and haying
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approaches, such as rotational grazing,
that would support both the economic
viability of livestock operations and
butterfly population growth.
Our Response: Conservation of Dakota
skipper and Poweshiek skipperling
populations relies on careful
implementation of management
practices that conserve its habitat while
minimizing adverse effects to
reproduction and survival. Rotational
late-season haying after the adult flight
period, for example, can be beneficial to
the species’ habitat. We have developed
Dakota skipper conservation guidelines
(https://www.fws.gov/midwest/
endangered/insects/dask/
DASKconservationguidelines.html),
which describe those practices in more
detail, and are developing similar
guidelines for the Poweshiek
skipperling. We discuss both the harm
and the benefits that various
management practices may have on
prairie habitats in Factors A and E of
this final listing rule (below).
(133) Comment: A commenter stated
that grassland easements are a broadbrush approach to conserve native
prairies, but there is no targeted
program or recovery plan specific to the
Dakota skipper that would provide
financial incentives and technical
information for ranchers and farmers to
manage habitat in a way that would
expand the population of Dakota
skippers.
Our Response: Service programs,
including Partners for Fish and Wildlife
and State and tribal grant programs, are
available to develop projects and
partnerships to conserve these and other
species. Following listing, the Service
will develop a recovery plan for these
two species.
(134) Comment: A commenter stated
that beaver dams can cause water level
fluctuations in some Poweshiek
skipperling areas in Michigan. The
commenter asked whether these
fluctuations, or the act of returning the
water level to its normal level, harm
Poweshiek skipperling larvae or habitat.
Our Response: It is possible that
higher than normal water levels, for an
extended amount of time, may harm
larvae. We discuss fluctuating water
levels in Factor E of this final listing
rule, below.
Factor A
(135) Comment: A commenter stated
that current Dakota skipper population
sites are already protected, and the
imminent threat to the species is
deemed to be on ‘‘remnant habitat.’’
Our Response: While some Dakota
skipper sites are on land that is
protected from some threats, such as
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conversion of remnant prairies to other
uses, the Dakota skipper populations at
these sites are still exposed to other
stressors, as we detailed in the
Summary of the Factors Affecting the
Species section of this final listing rule,
below.
(136) Comment: A commenter stated
that the Dakota skipper and Poweshiek
skipperling do not warrant listing
because the Service improperly
characterized oil and gas development
as a threat to the Dakota skipper and
Poweshiek skipperling, overstated the
amount of oil and gas development
occurring in the ranges of the Dakota
skipper and Poweshiek skipperling,
incorrectly assumed that the level of oil
and gas development seen in western
North Dakota will occur throughout the
species’ ranges, and erred by concluding
that impacts from oil development in
western North Dakota to the two
butterflies are similar to impacts from
coal-bed natural gas in Wyoming on the
greater sage-grouse. Accordingly, the
Service should withdraw the listing and
critical habitat rules.
Our Response: The Act directs us to
determine whether a species is an
endangered species or a threatened
species because of any factors affecting
its continued existence. Listing actions
may be warranted based on any of the
five factors, singly or in combination.
We completed a comprehensive
assessment of the biological status of the
Dakota skipper and Poweshiek
skipperling, and all factors that might
affect its existence. The effects from oil
and gas activities are just one of the
factors we considered. Our
determinations that the Dakota skipper
is a threatened species and the
Poweshiek skipperling is an endangered
species are based on numerous threats,
acting individually and synergistically,
that are leading to substantial
population declines.
Specifically with regard to our
evaluation of impacts from oil and gas
activities, much of this activity is
currently occurring in areas of native
prairie overlying the Bakken and Three
Forks formations, to the west of known
locations for both butterfly species.
However, current Bakken oil and gas
development is occurring in two
counties that have records of Dakota
skippers (McKenzie and McLean
counties in North Dakota). In those
areas, oil and gas development is a
stressor to the populations that may be
present. Because there are few locations
where the butterflies may still be extant,
significant stressors to these few
populations can be threats to the species
as a whole. Furthermore, although oil
and gas development is unlikely to
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occur throughout the entire range of the
two butterflies in the foreseeable future,
there may be future development or
increases in current activities associated
with the shale-oil formations (such as
the Bakken formation in North Dakota)
that may affect butterfly populations in
those areas. Finally, we used the Naugle
et al. (2011) study and its impacts to
sage grouse as a surrogate to estimate
the impacts of similar energy
development projects to the butterfly
habitat. Because the Powder River Basin
development varies from the
development in the Bakken formation,
we have corrected our estimations and
analysis in this final listing rule (see
Destruction and Conversion of Prairies
to Nonagricultural Development,
below).
(137) Comment: A commenter noted
that wind energy is not a threat to the
species in North Dakota. The Service’s
conclusion that wind energy
development will expand into the
ranges of the Dakota skipper and
Poweshiek skipperling, and thus is a
threat to the species, is based on
outdated data and is poorly supported.
The Service must justify its assumptions
that wind energy will expand into
Dakota skipper and Poweshiek
skipperling range and consequently be a
threat to the species.
Our Response: We have evaluated the
stressors to populations at sites where
we had sufficient information to do so.
Generally, we consider that wind
development will have localized
impacts in a few sites. We know of at
least one site where a proposed wind
development project poses a threat to
the Dakota skipper and its habitat.
Another wind farm is proposed within
2 miles of areas we proposed as critical
habitat, with expansion phases that
could overlap that critical habitat. Both
of these projects are in the draft
Environmental Analysis stage of
development. See Destruction and
Conversion of Prairies to Agricultural
Land, below, for a full discussion on
impacts from wind energy development.
(138) Comment: The proposed listing
determination relies heavily on the
work of McCabe and Royer for North
Dakota, who have both published
generalized statements about impacts of
grazing on the Dakota skipper. These
authors do not discuss the types of
animals, season of use, intensity of
grazing, or whether a grazing system is
involved.
Our Response: The Service used
butterfly surveys and habitat reports
written by Royer, McCabe, Spomer, and
others to inform our determination on
the status of the species in North
Dakota. These authors also often
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reported stressors they observed at sites,
such as invasive species encroachment
or intensive grazing practices. We also
used other reports and publications to
inform the discussion regarding grazing
effects on the butterflies, which
included a discussion regarding types of
animals, intensity of grazing, habitat
type, proximity of nearby populations,
associated herbicide use, and timing. In
the conservation guidelines for the
Dakota skipper (https://www.fws.gov/
midwest/endangered/insects/dask/
DASKconservationguidelines2013.html),
we further discuss grazing in terms of
intensity, duration, season of use, and
type of habitat.
(139) Comment: A commenter stated
that invasive plant control needs to be
done very carefully and in small-scale
treatments to ensure any adverse effects
on the Poweshiek skipperling, or the
vegetative conditions they specifically
require, are minimized, as invasive
plant and brush control is not
automatically beneficial to the butterfly.
Specifically, at the Puchyan Prairie site,
there is greater risk of unintended
negative side effects of invasive plant
control on Poweshiek skipperlings
themselves, or the specific types and
structures of vegetation they require,
than risk of habitat deterioration in the
next several years, if a more cautious
approach is used. More time should be
allowed to assess and describe the full
extent of the kinds of microhabitats
used by the Poweshiek skipperling,
which likely differ among years due to
climatic variation, and the extent of any
change or deterioration in the vegetation
in their core habitat areas.
The commenter also stated that the
Service is also correct that fire
management, without careful planning,
may have significant adverse effects on
these skippers; however, the Service
understates the risks of fire. A number
of areas of good Dakota skipper and
Poweshiek skipperling habitat have
been converted by fire management over
the last several decades from light
agricultural land uses to areas lacking
the features needed by the butterflies.
These converted areas in Iowa,
Minnesota, and westward have few
recent records of either species. Fen
wetland preserves in Michigan do have
recent Poweshiek skipperling records,
but some of these sites have new, not
long-term, fire management. The
Poweshiek skipperling has not fared
well in the working landscape; thus,
deliberate conservation effort is needed.
Our Response: We agree that
conservation of Poweshiek skipperling
populations relies on careful
implementation of management
practices that conserve its habitat, while
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minimizing adverse effects to
reproduction and survival, including
invasive species control at the few sites
where the Poweshiek skipperling
remains, such as Puchyan Prairie. As
discussed in Factor A. The Present or
Threatened Destruction, Modification,
or Curtailment of Its Habitat or Range,
below, encroaching invasive plants may
replace or reduce the coverage of native
forbs and grasses used by adults and
larval butterflies and, therefore, need to
be controlled. However, we further
discuss that control methods (such as
fire and herbicide spraying) may have
their own unintended consequences,
such as reduced native forbs and grasses
and direct mortality of the butterflies, if
not conducted carefully. Furthermore,
various habitat types at these sites may
respond differently to various types of
control treatments. Therefore, when
considering recovery planning for the
species, it will be important to continue
to individually assess sites to determine
the need to control invasive species,
exercise caution when implementing
treatments, monitor the response to any
treatments over the long-term, and
refine or modify treatments as needed to
get desired outcomes. Similarly,
assessment and long-term monitoring of
the species’ needs, such as microhabitat
use, will help inform conservation
efforts at specific locations.
(140) Comment: One commenter
recommended that land managers be
advised as to the appropriateness of
prescribed burns in Poweshiek
skipperling habitat.
Our Response: The Service contacted
all of the landowners within proposed
critical habitat designations as part of
this rulemaking process. We have
developed conservation guidelines for
the Dakota skipper (online at https://
www.fws.gov/midwest/endangered/
insects/dask/
DASKconservationguidelines.html), and
are developing similar guidelines for
Poweshiek skipperling. Contact the
Service’s Ecological Services Field
Office in your State to discuss
prescribed burn practices on land where
one or both species may be present.
(141) Comment: One commenter
recommended that sites with Dakota
skipper populations where fire
management is not already occurring
should remain fire-free, and that fire
management should cease in core
habitat for the Dakota skipper. Instead,
cautious rotational haying or grazing
regimes should be used to rehabilitate
grassland vegetation to the shorter turf
height that Dana (1991) recommends for
the species.
Our Response: We have developed
conservation guidelines for the Dakota
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skipper (https://www.fws.gov/midwest/
endangered/insects/dask/
DASKconservationguidelines.html), and
are developing similar guidelines for
Poweshiek skipperling. The
recommendations will be reviewed for
possible incorporation as we continue to
refine these guidelines.
(142) Comment: A commenter noted
that the proposed rule states that the
negative effects of fire persist for 1 to 5
years, citing Swengel (1996, pp. 73, 79,
81) and Panzer (2002, pp. 1302–3).
These papers, however, include a range
of butterfly species found in prairies,
not just localized prairie specialists like
the Dakota skipper and Poweshiek
skipperling. Panzer’s study contains no
data on the Poweshiek skipperling or
Dakota skipper. Swengel (1996)
includes specific analysis of both
species, but no explicit predictions are
made. Swengel (1996, pp. 73, 79)
describes that the negative effects of fire
persist for specialists for 3 to 5 or more
years. Swengel (1996) does not indicate
an expectation of recovery 1–2 years
post-burn for these species. Thus,
Swengel’s analysis is better used to
define when recovery has certainly not
occurred (within years 0–3), but not
when recovery actually has occurred.
Our Response: We corrected our
interpretation of the Swengel (1996) and
the Panzer (2002) papers as discussed
under Factor A. The Present or
Threatened Destruction, Modification,
or Curtailment of Its Habitat or Range,
below, to better reflect the included data
and information. We also changed our
use of the word ‘‘recovery’’ in this
context to the term ‘‘rebound,’’ which
more accurately describes an upward
trend, but does not imply a stable
recovered trend in populations.
(143) Comment: A commenter noted
that Dana (1991, pp. 55–56) discusses
concern about grass growth structure
and height, namely that fire encourages
taller grass growth, but that Dakota
skippers prefer shorter grass. Therefore,
effectively controlling weeds and brush
does not necessarily mean that the
management is creating suitable habitat
for skippers. In the long run, fire does
not produce a suitable vegetative
structure for skippers. The long-term
compounding indirect effect of fire on
the vegetation (increasing grass height
and thickness) may have a more lasting
impact on the species and be more
difficult to manage.
Our Response: We will consider the
longterm effect of fire on native
vegetation growth and structure when
developing and refining conservation
guidelines for the Dakota skipper and
Poweshiek skipperling.
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(144) Comment: The data used for
North Dakota in the proposed listing
rule relies heavily on the work of
McCabe and Royer, who have both
published generalized statements about
grazing and its effects on the Dakota
skipper. These authors do not discuss
the types of animals, season of use,
intensity of grazing or whether a grazing
system is involved.
Our Response: The Service relied on
butterfly surveys and habitat reports
written by Royer, McCabe, Spomer, and
others to inform species and habitat data
in North Dakota. These authors also
often reported stressors they observed at
sites, such as invasive species
encroachment or intensive grazing
practices. We used various other reports
and publications to inform the
discussion regarding grazing in Factor A
of this final listing rule and included a
discussion regarding types of animals,
intensity of grazing, habitat type,
proximity of nearby populations,
associated herbicide use, and timing. In
our conservation guidelines for Dakota
skipper, we further discuss grazing in
terms of intensity, duration, season of
use, and type of habitat.
(145) Comment: A commenter noted
that low-intensity grazing is mentioned
as a potential management tool to help
maintain habitat and abate other threats
to these two species. In some cases,
high-intensity, short-duration grazing
may have a role in providing the
disturbance that prairies require to
prevent them from being overrun by
woody plants, and invasive species.
Our Response: We have developed
conservation guidelines for the Dakota
skipper’s specific needs. These
guidelines include some grazing
recommendations; however, we are
interested to learn more details about
the effects of grazing practices
implemented in various areas as we
continue to refine our
recommendations, and will take this
information into consideration.
(146) Comment: A commenter noted
that data suggest Poweshiek skipperling
populations at sites that were hayed
prior to preservation did not recover to
the same level following any subsequent
fire.
Our Response: We acknowledge that
fire management may be detrimental to
the Poweshiek skipperling, if not
conducted properly. We are developing
conservation guidelines for the
Poweshiek skipperling that will address
fire management and other actions, and
are interested to learn more about the
implications of fire practices as we
continue to develop and refine our
conservation recommendations.
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(147) Comment: A commenter stated
that the Service should provide data to
support that fire management, even if
applied to most or all of the patch
occupied by the Dakota skipper or
Poweshiek skipperling, has a low effect
on the long-term persistence of these
populations. The Service does not cite
long-term studies of impacts from fire,
but instead provides a list of
assumptions, such as the following: (1)
Fire happens in prairie (although the
extent of that in a natural context is
open to great debate; see literature
review in Swengel and Swengel 2007, p.
264); (2) these skippers live in prairie;
(3) fire has various effects on prairie
plants (although it should not be
assumed that fire controls brush and
weeds; see Swengel et al. 2011, p. 535);
(4) those floristic effects are assumed to
be beneficial to these skippers (although
vigorous tall grass growth caused by fire
may not be; see Dana 1991, pp. 5–56).
Based on these assumptions, the Service
concludes that fire should be fine for
these skippers. The Service needs to
provide direct positive evidence
indicating that the skippers, especially
the larvae, actually succeed in the long
term following a fire.
Our Response: We will consider all
factors and data regarding the effects of
fire on the species during recovery
planning and implementation and in
developing and refining the
conservation guidelines for these two
species. We acknowledge that there are
no long-term (more than two decades)
studies of fire management that
provided data showing long-term
persistence of the populations. We
based our threats analysis and ranking
of stressors as high, medium, and low
based on the studies cited in our
discussion of impacts from fire under
the Summary of the Factors Affecting
the Species section of this final rule,
below. The possibility that we may have
underestimated the stressors of fire
management on the species further
supports our determinations that fire
can be a significant stressor to
populations of Poweshiek skipperlings.
(148) Comment: A commenter stated
that there are problems with some
reports that use McCabe’s 1981
management recommendations, because
McCabe’s paper reflects a point-in-time.
Prairie ecology requires long-term
observations and knowledge of how past
and current management activities
impact plant community dynamics.
Further, prairie management
conclusions based upon observations
made in 1981 are no longer valid, due
to changes in ecological drivers caused
by broad-scale invasion of exotic coolseason grasses and forbs.
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Our Response: McCabe’s 1981 report
is used as a reference to prairie
conditions prior to much habitat
degradation or exotic species invasions
that are common in many locations
today. We acknowledge that an
understanding of prairie ecology
requires long-term observations, as well
as knowledge of how past and current
management activities have impacted
and continue to impact plant
community dynamics.
(149) Comment: One commenter
agreed that annual haying on or after
August 1 presents little or no stress to
Dakota skippers. However, the
commenter went on to point out that
Swengel (1998b) found that Poweshiek
skipperling abundance was strongly
correlated with increasing number of
years since the last management action,
of any management type, including
haying. Thus, annual haying of the
entire habitat patch should be
considered a high stressor for the
Poweshiek skipperling. The Service is
correct that alternate-year haying is
better than annual haying, but it’s even
better when the haying is done
rotationally (half per year, instead of all
every other year). Additionally, the
moderate stressor category for haying is
confusing. As it currently reads, a site
could fall in the moderate category
because you do not know the timing of
the haying, but if you did know the
timing, you would place it in the high
category.
Our Response: We developed the
stressor categories for the purposes of
the threats analysis to inform our listing
determinations; these categories are not
intended to be prescriptive conservation
measures or guidelines. We
acknowledge that there is some
uncertainty in the ‘moderate’ stressor
category for haying, but we wanted to
fairly capture sites where we were
unsure of the timing of haying activities,
but that showed signs indicative of
reduced nectar sources. It is true that
these sites could be moved into the low
or high category if we received more
specifics on the timing of haying in
those locations, and those details will be
more important during the recovery
planning stages for these species.
Factor B
(150) Comment: A commenter noted
that recent publications report that
nonlethal sampling of genetic material
adds an immeasurable or minor effect
on survival or reproductive success of
butterflies compared to handled
individuals that were not also
genetically sampled (Marschalek et al.
2013; Crawford et al. 2013). However,
there is abundant literature on how
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handling has adverse effects on
butterflies, documented for a wide range
of species (e.g., Benson and Emmel
1973; Singer and Wedlake 1981;
Lederhouse 1982; Morton 1984). It is
possible that some types of nonlethal
sampling do not significantly increase
the harm to the butterfly from capture
and handling, but the handling for such
sampling still causes harm compared to
the butterfly not being handled. Thus,
the benefits of such sampling should be
weighed against the harm caused to
individuals.
Our Response: As stated under Factor
B of this final rule, handling stress
during scientific study may affect
individuals of both species. Adverse
effects on butterflies have been
documented for a wide range of species
(e.g., Benson and Emmel 1973, p. 329;
Singer and Wedlake 1981, pp. 215–216;
Lederhouse 1982, pp. 381–382; Morton
1984, pp. 56–57; Mallet et al. 1987, pp.
380–383). The Service will consider
stress and other impacts to the
butterflies from handling when issuing
scientific permits for genetic sampling
and other sampling efforts.
(151) Comment: A commenter noted
that reliably effective captive
propagation has not been demonstrated
for either of these species. However, the
Service should consider and assess the
effect on wild populations of either
species before attempting to develop
captive propagation.
Our Response: The Service will
consider incidental take for otherwise
legal activities in our permitting (e.g.,
section 10 recovery permits) process.
Factor D
(152) Comment: A commenter stated
that as of August 2013, the Minnesota
Department of Natural Resources listed
both the Dakota skipper and the
Poweshiek skipperling as endangered.
The Dakota skipper is also an
‘‘endangered’’ species under Iowa law.
Our Response: We have updated the
State-level protections for Dakota
skipper and Poweshiek skipperling in
Factor D of this final listing rule.
Factor E
(153) Comment: A commenter stated
that herbicides applied in skipper
habitat can negatively affect nectar
resources for the species. However,
herbicide use can have benefits if
carefully targeted to treating brush and
weeds, so long as bare ground does not
subsequently result from the treatment,
as bare ground greatly facilitates
recruitment of new weed and brush
growth.
Our Response: We acknowledge that
carefully targeted herbicide treatments
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may result in the beneficial control of
nonnative or invasive plants and brush,
and have clarified our statements in
Factor E of this final listing rule, below.
(154) Comment: A commenter noted
that results of a preliminary analysis of
the genetic diversity of the Poweshiek
skipperling show limited levels of
genetic diversity in the Wisconsin,
Michigan, and Manitoba populations.
Demographic factors are of greater
concern, specifically, small population
sizes and numbers of populations are
more likely to lead to extinction than
loss of genetic diversity. The
widespread and intensive survey effort
showing continual extirpation of
populations and reduced population
sizes supports the listing of Poweshiek
skipperling as endangered.
Our Response: We have incorporated
information from the preliminary results
of Saarinen (2013, pers. comm.) under
Factor E. Other Natural or Manmade
Factors Affecting Its Continued
Existence, in the discussion on Habitat
Fragmentation and Population Isolation,
below, and look forward to receiving
final results from this research to inform
future conservation efforts for this
species.
(155) Comment: A commenter stated
that weather and climate events, such as
the persistent drought in the Midwest,
and their effects on the Dakota skipper
and Poweshiek skipperling require
further study. Funding and staff are
needed to accomplish these efforts.
Our Response: In this rule, we used
the best available information on
climate and climate change, however we
agree that more study of weather and
climate events will help us with
recovery planning and implementation
for these two species, and will consider
new information when developing the
recovery plan.
(156) Comment: A commenter stated
that, in its assessment of impacts to the
butterflies from climate change, the
Service ignores model uncertainty that
the Intergovernmental Panel on Climate
Change (IPCC) acknowledges.
Our Response: We appreciate your
comment and understand that there are
uncertainties in the climate modeling.
We consider climate change to be a
potential threat to the species, while
acknowledging uncertainty of how
changes may specifically impact these
species or their habitats.
(157) Comment: A commenter stated
that, while it is possible that unknown
threats to the species exist, it is
inappropriate to focus too much effort
on the search for unknown stressors.
This distracts from addressing the
challenges of dealing with the stressors
that have been known for decades
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(isolated populations in fragmented
habitats that are under pressure from
habitat degradation and land
management practices).
Our Response: We acknowledge that
multiple stressors are acting on
populations of both species, and have
been so for many years. In our review,
however, it appears that many sites with
known populations of the Poweshiek
skipperling appear to have
simultaneously declined to undetectable
levels. A similar, but perhaps delayed,
decline is being observed in Dakota
skipper populations. We did not want to
rule out the possibility that this decline
may be due to some unknown cause.
However, we will focus on all potential
factors affecting the species in recovery
planning and implementation, not
simply on any single factor.
Determinations
(158) Comment: A commenter stated
that the Dakota skipper and Poweshiek
skipperling are both threatened by loss
of native prairie vegetation to
agriculture, development, altered fire
patterns, and groundwater depletion.
The Dakota skipper and Poweshiek
skipperling are also threatened by
pesticides, drought, and climate change.
In light of the population declines and
ongoing threats, both butterflies should
be protected as endangered rather than
as threatened.
Our Response: The Dakota skipper is
experiencing population declines and
facing multiple threats. A few
populations in the United States are
doing relatively well, however, and are
in habitats that have low or nonimmediate threats. Furthermore, Canada
has an estimated 15 populations on
lands that are being utilized in a manner
conducive to the conservation of Dakota
skipper, and the threats at those sites are
not imminent. Based on our review of
the best available scientific and
commercial information, we conclude
that the Dakota skipper is likely to
become in danger of extinction in the
foreseeable future throughout all of its
range and, therefore, meets the
definition of a threatened species. For a
detailed discussion, see the
Determination section of this final rule,
below.
(159) Comment: A commenter stated
that the Service should list the Dakota
skipper as endangered, as it is ‘‘in
danger of extinction throughout all or a
significant portion of its range.’’ The
species is present at 91 sites, at least 83
‘‘are subject to one or more threats that
have a moderate to high impact on those
populations.’’ The Service does not
explain why 8 sites that are presumably
secure outweigh 83 sites that are
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experiencing moderate to high threat
levels, especially since ‘‘Dakota skipper
. . . habitat is highly fragmented and
because the species are subject to local
extinction . . . and approximately 84
percent of Dakota skipper sites with
present or unknown status are
effectively isolated.’’
Our Response: We agree that the
Dakota skipper is imperiled, which is
why we determined that the species
warrants listing under the Act.
However, we believe that the Dakota
skipper is not in immediate danger of
going extinct at this point in time.
Instead, we believe that, if trends
continue as they currently are, the
species is likely to get to that point in
the foreseeable future. Because there are
stable populations of the Dakota skipper
that do not appear to be currently
suffering from high-magnitude threats,
and the declining trends are happening
at a slower pace, we determined that
threatened species status is appropriate
for the Dakota skipper (see
Determination, below, for a full
discussion).
(160) Comment: A commenter stated
that the Service determines that the
Dakota skipper is a threatened species
because ‘‘Canada has a fair number of
populations that are being managed in
a manner conducive to the conservation
of Dakota skipper, and the threats at
those sites are not imminent.’’ A ‘‘fair
number’’ is not a biologically
meaningful measure. The Service needs
to explain this contention in a
measurable manner.
Our Response: We are aware of 14
sites in Canada where the species is
considered to be present and one site
where the occupancy is unknown.
Those sites are managed by late-season
haying (after August 1) that is
conducted at least every other year, and
there is no indication that native plant
diversity is declining due to timing or
frequency of mowing.
(161) Comment: A commenter stated
that the Canadian populations are
functionally isolated from each other
and from U.S. populations. The distance
between all these metapopulations
makes interaction or recolonization
unlikely, as Dakota skippers may be
incapable of moving greater than 1 km
(0.6 mi) between patches of prairie
habitat separated by structurally similar
habitats. The Service did not conduct an
adequate analysis of ‘‘significant portion
of range,’’ to determine if the three
metapopulations (U.S., Manitoba, and
Saskatchewan) should each be
considered ‘‘significant,’’ and if one is
‘‘in danger of extinction,’’ then the
species as a whole should be listed as
endangered. The Service must
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separately analyze threats to each
isolated metapopulation because
population isolation and accompanying
loss of genetic diversity are
acknowledged to have significant
impacts on the species.
Our Response: Under the Act and our
implementing regulations, a species
may warrant listing if it is endangered
or threatened throughout all or a
significant portion of its range. Because
we have determined that the Dakota
skipper is a threatened species
throughout all of its range, no portion of
its range can be ‘‘significant’’ for
purposes of the definitions of
‘‘endangered species’’ and ‘‘threatened
species.’’ See the Final Policy on
Interpretation of the Phrase ‘‘Significant
Portion of Its Range’’ in the Endangered
Species Act’s Definitions of
‘‘Endangered Species’’ and ‘‘Threatened
Species’’ (79 FR 37577, July 1, 2014).
(162) Comment: A commenter stated
that the Service has an obligation to
make available the studies that form the
basis of its action. The Service failed to
provide any materials other than its own
draft species assessment and textual
descriptions of proposed critical habit
for either the proposed listing or critical
habitat designation in the
regulations.gov docket or on its Web
sites. The Service did provide a
bibliography; however, many references
cited were unpublished reports or
internal documents.
Our Response: One element of the
transparency and open government
directive encourages executive
departments and agencies to make
information about operations and
decisions readily available to the public.
Supporting documentation used to
prepare the proposed and final rules is
available for public inspection, by
appointment, during normal business
hours, at the U.S. Fish and Wildlife
Service, Twin Cities Ecological Services
Field Office, 4101 American Boulevard
East, Bloomington, Minnesota 55425.
4(d) Rule
(163) Comment: One commenter said
that the 4(d) rule proposed for the
Dakota skipper should be extended to
remove prohibitions for take incidental
to lawfully conducted oil and gas
operations and that this would not
undermine the goal of promoting the
healthy growth of these populations
throughout their entire range. The
commenter indicated that the activities
that were addressed by the proposed
4(d) rule—a variety of routine livestock
ranching activities and mowing of
recreational trails—were far more
widespread in the region and contribute
more directly to the threats listed in the
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proposed rule than were oil and gas
related activities.
Our Response: Although livestock
ranching activities and mowing of
recreational trails may be more
widespread throughout the species
range, livestock grazing also can be a
key factor in the conservation of Dakota
skipper habitat, by helping to ensure
that the species’ habitats are not
subjected to activities that result in their
permanent destruction. That is, lands
are likely to remain unplowed as long
as the landowner chooses to continue to
use them for grazing. In addition,
grazing may also be implemented in a
manner that provides significant
benefits to the species. In these ways oil
and gas production and grazing are
fundamentally different with respect to
Dakota skipper conservation.
Regardless, the Service recognizes that a
variety of interests, including oil and
gas activities, may hold the potential to
contribute to Dakota skipper
conservation.
(164) Comment: One commenter
stated that the 4(d) rule would provide
an important incentive to continue latesummer haying where that practice is
currently being implemented.
Our Response: We agree that the 4(d)
rule will provide this incentive, as
intended. Late-summer haying is
currently the primary management on
numerous sites inhabited by Dakota
skipper that are important for the
species’ conservation.
(165) Comment: One commenter
requested that we also exempt take
caused by ‘‘construction with minimal
disturbance, such as that for
transmission lines, that occurs after July
15th’’ in the 4(d) rule. The same
commenter requested that the Service
‘‘give consideration to exempting
transmission line maintenance activities
and existing right-of-way maintenance
in the same way that section line
maintenance is exempted in the
proposed 4(d) rule.’’
Our Response: It is unclear which
populations could be affected by these
activities, what the effects might be, and
how the effects might be minimized.
Therefore, we have not included these
activities in the 4(d) rule.
(166) Comment: One commenter
stated that ‘‘the proposed 4(d) rule will
undermine, not advance, conservation
of the species’’ and that the 4(d) rule
was not needed to prevent habitat
destruction because it would already be
illegal under section 9 of the Act and
uninhabited areas at risk for conversion
would be protected by designating them
as critical habitat.
Our Response: It is true that take of
Dakota skippers that results from
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destruction of its habitat would be
prohibited under section 9 of the Act,
but there are other reasons to
promulgate the 4(d) rule. As we stated
in the proposed rule, the 4(d) rule will
facilitate cooperation with private
landowners that will be needed to
recover the species. About 47 percent of
the sites where the Dakota skipper has
been recorded in the United States and
that may still harbor the species are on
private land. Almost all of these sites
are working lands managed with grazing
or haying. Conservation of the Dakota
skipper on these sites, and in general,
will require the Service and other
conservation agencies and groups to
develop and maintain cooperative
partnerships with private landowners.
Without that cooperation, we are
unlikely to realize the substantial
improvements in habitat conditions and
public-private partnerships necessary to
conserve the species.
(167) Comment: A commenter stated
that the proposed 4(d) rule does not
provide details as to how the Service
intends to ensure that infrastructure,
such as corrals, loading chutes, and
other livestock working facilities, are
carefully sited so that impacts to the
species are minimized.
Our Response: These types of
facilities are unlikely to have significant
impacts to Dakota skipper populations,
except where the species has been
reduced to only very small areas. In
grazed lands that are typically inhabited
by Dakota skipper, these facilities affect
only small proportions of the available
habitat. Therefore, we do not think that
the small degree of impact posed by
placement of livestock working facilities
would merit site-specific approval and
review by the Service. Instead, by
foregoing any requirement for
landowners to seek Service approval for
siting these facilities, we are likely to
further facilitate continued development
of positive working relationships that
will be essential for recovering the
species. In addition, we can work with
landowners on voluntary methods to
minimize any impacts that might result
from installation of facilities associated
with grazing.
(168) Comment: One commenter
stated that the protections afforded the
Dakota skipper through the 4(d) rule are
not sufficient to reverse the trend
toward extinction because they do not
ensure that the grazing practices
exempted under the rule will benefit the
Dakota skipper.
Our Response: It may not be
practicable to expect broad
implementation of specific mandated
grazing practices on private land to
conserve the Dakota skipper without the
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willingness of the landowner to
implement those practices.
Conservation of Dakota skippers on
grazed lands will require several steps
that include the development of sitespecific grazing recommendations,
monitoring the effects of the recommend
practices on the Dakota skipper and its
habitat, and science-based adaptive
management. Each step will require
access to private and other non-Federal
lands by persons with expertise in
identifying and describing the Dakota
skipper and its key habitat components
and, in at least some cases, by grazing
experts and conservation partners.
Landowners and land managers may be
less likely to grant access for these
activities if we broadly mandate specific
grazing practices. Furthermore, although
the incidental take permitting process
would also provide an avenue by which
to work with private landowners and is
often the best available option for some
species, there is no clear avenue that is
immediately available by which to
engage the large and geographically
widespread group of landowners in
such a process for Dakota skippers. A
permitting process that would involve
more than a few landowners is likely to
take years and would have significant
potential to become contentious and
unwieldy.
(169) Comment: One commenter
suggested that, instead of listing
counties in which take caused by
grazing would not be exempted under
the 4(d) rule, the Service should base
this on habitat.
Our Response: We decided that it is
more appropriate to exempt take of
Dakota skippers caused by grazing on all
non-Federal lands in the United States,
regardless of geographic area, and have
made this change in the final 4(d) rule.
We recommend, however, that lands
where native prairie is currently
maintained by haying continue to be
hayed, and that any change to grazing
on these lands only be done with the
prior input from experts in Dakota
skippers and range conservation. We
suggest contacting the Service’s
Ecological Services Office in your State
for more information.
(170) Comment: A commenter asked
what areas can be treated for weeds or
pests and still be exempted by the 4(d)
rule.
Our Response: The 4(d) rule does not
address control of animal pests;
therefore, it does not exempt take that
may result from treatments that are
applied to control animal pests. The
4(d) rule also does not exempt take of
Dakota skippers that would result from
the broadcast application of
herbicides—that is, application of
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herbicides evenly across all or a portion
of an area. Take of Dakota skippers that
is caused by applications of herbicide
that do not meet this definition of
broadcast spraying would be exempted
by the 4(d) rule.
Take of Dakota skippers is unlikely if
they do not inhabit an area where
broadcast application of herbicides is
proposed. If the presence of Dakota
skippers is suspected in an area where
broadcast application of herbicides is
proposed, we recommend that the
Service be contacted to determine
whether the action may be likely to
cause take of the species, and if
reasonable measures may be adopted
that would avoid take.
Summary of Changes From the
Proposed Rule
Based on our review of the public
comments, comments from other
Federal and State agencies, peer review
comments, issues addressed at the
public hearing, and any new relevant
information that may have become
available since the publication of the
proposal, we reevaluated our proposed
rule and made changes as appropriate.
During the comment periods, the
Service received additional survey
information, minor clarifications, and
additional information on the species
biology. New survey information has
changed the occupancy status at several
sites, for example a site that we
considered to be ‘‘unknown’’ in the
proposed rule may now be considered
‘‘extirpated’’ due to three sequential
years of negative survey data.
Consequently, some sites were dropped
from our analysis of factors affecting the
species because we no longer consider
the species to be present or possibly
present (unknown) at a particular
location. In addition, we included new
information into our analysis of the
factors affecting the species. Neither the
new information nor the updated
occupancy at some sites has
significantly changed our analyses such
that it changed our determinations of
status under the Act for either species.
The 4(d) rule now exempts take of
Dakota skippers caused by grazing on all
non-federal lands in the United States;
the proposed 4(d) rule did not apply to
certain lands in Minnesota and North
Dakota. The final 4(d) rule no longer
exclude some counties from the part of
the rule that exempts take caused by
grazing. Other minor changes to the 4(d)
rule include: Clarifying broadcast versus
spot-spraying of herbicides; defining
‘‘recreational trail’’; and, that take of
Dakota skipper caused by haying in
transportation rights-of-ways and
corridors after July 15 is exempt under
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the 4(d) rule, as long as it is associated
with livestock ranching activities. The
4(d) rule exempts take of Dakota
skippers caused by mowing recreational
trails, a term that is defined in the rule,
even when it is not associated with
livestock grazing.
Summary of the Factors Affecting the
Species
Factor A. The Present or Threatened
Destruction, Modification, or
Curtailment of Its Habitat or Range
Habitat quality is a powerful
determinant of extinction probability in
butterflies such as the Dakota skipper
and Poweshiek skipperling (Thomas et
al. 2001, p. 1795). Among butterfly
species in the United Kingdom, for
example, equilibrium density of
butterflies at sites with optimum habitat
are from 25 to more than 200 times
greater than those for occupied sites
with suboptimal, yet suitable, habitat
(Thomas 1984, cited in Thomas et al.
2001, p. 1794). Consistently good
habitat quality is especially important
for Dakota skipper and Poweshiek
skipperling isolated populations, which
would not be naturally recolonized if
they were extirpated. Protection or
restoration of habitat quality at these
isolated sites is critical to the survival
of both species, although stochastic
events still pose some risk, especially
for smaller populations and at small
sites.
The Poweshiek skipperling and
Dakota skipper depend on a diversity of
native plants endemic to tallgrass
prairies and, for the Poweshiek
skipperling in Michigan, prairie fens.
When nonnative or woody plant species
become dominant, Poweshiek
skipperlings and Dakota skippers
decline due to insufficient sources of
larval food and nectar for adults. For
example, at Wike Waterfowl Production
Area in Roberts County, South Dakota,
the extirpation of Poweshiek skipperling
is attributed to the deterioration of
native vegetation, in particular, the loss
of nectar sources for adult butterflies
due to invasive species encroachment
(Skadsen 2009, p. 9).
Destruction of native tallgrass and
mixed-grass prairie began in 1830
(Samson and Knopf 1994, pp. 418–419).
Extant populations of Dakota skipper
and Poweshiek skipperling are
restricted to native-prairie remnants and
prairie fens; native prairies have been
reduced by 85 to 99.9 percent of their
former area throughout the historical
range of both species (Samson and
Knopf 1994, pp. 418–419). Degradation
and destruction of habitat occurs in
many ways, including but not limited
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to: Conversion of native prairie to
cropland or development; ecological
succession to woody vegetation;
encroachment of invasive species; past
and present fire, haying, or grazing
management that degraded or destroyed
the species’ habitats; flooding; and
groundwater depletion, alteration, and
contamination, which are discussed in
further detail below.
We evaluated the level of impact to
the population at each site of several
habitat-related stressors at 163 Dakota
skipper sites where the occupancy
status of the site is considered to be
present or unknown, as defined in the
Background section of this final rule
(Table 3, above). These 163 sites are
found across the current range of the
species in Minnesota, North Dakota, and
South Dakota. Eight sites with an
unknown or present occupancy were
not evaluated. To determine the levels
of impact to the population at each site,
we used the best available and most
recent information for each site,
including reports, discussions with site
managers, information from natural
heritage databases, etc. (Service 2012,
unpubl. data; Service 2014, unpubl.
geodatabase). We only evaluated a
stressor to the population at any one site
if we had sufficient information to
determine if the level of impact was
high, medium, or low as defined for
each stressor below. Similarly, the level
of impact to the population was
evaluated at 60 Poweshiek skipperling
sites with present or unknown status
(Table 4). Although we did not evaluate
Factor A stressors at all 87 Poweshiek
skipperling sites with present or
unknown occupancy, the 60 sites that
were evaluated are representative of all
the present or unknown Poweshiek
skipperling sites in terms of geography
(range of the species, i.e., sites in Iowa,
Michigan, Minnesota, North Dakota,
South Dakota, and Wisconsin were
evaluated), ownership, and
management. Many sites for both
species (58 sites for Dakota skipper and
26 sites for Poweshiek skipperling)
experience at least two habitat-related
stressors at a medium or high level of
impact (Tables 3 and 4).
TABLE 3—NUMBER OF DAKOTA SKIPPER SITES WITH EACH LEVEL OF IMPACT AND THE TOTAL NUMBER OF SITES THAT
WERE RATED FOR EACH TYPE OF STRESSOR. A TOTAL OF 163 DAKOTA SKIPPER SITES WITH EITHER PRESENT OR
UNKNOWN STATUS WERE EXAMINED; ONLY SITES WITH SUFFICIENT DATA FOR A PARTICULAR STRESSOR WERE
RATED AS HIGH, MEDIUM, OR LOW
[Service 2012 Unpubl. data; Service 2014, unpubl. geodatabase]
High level
of impact
Stressor
Destruction & Conversion (Agricultural & Nonagricultural Development) .......
Wind Development ..........................................................................................
Flooding ...........................................................................................................
Invasive Species ..............................................................................................
Fire ...................................................................................................................
Grazing ............................................................................................................
Haying & Mowing .............................................................................................
Lack of Management .......................................................................................
Size/Isolation ....................................................................................................
Herbicide and/or Pesticide Use .......................................................................
Medium level
of impact
3
1
2
12
10
9
1
9
50
5
Low level
of impact
83
0
6
33
4
29
11
5
50
2
Total number
of rated sites
58
8
6
20
6
14
29
3
63
8
144
9
14
65
20
52
41
17
163
15
TABLE 4—NUMBER OF POWESHIEK SKIPPERLING SITES WITH EACH LEVEL OF IMPACT AND THE TOTAL NUMBER OF SITES
THAT WERE RATED FOR EACH TYPE OF STRESSOR. A TOTAL OF 60 POWESHIEK SKIPPERLING SITES WITH EITHER
PRESENT OR UNKNOWN STATUS WERE EXAMINED; ONLY SITES WITH SUFFICIENT DATA FOR A PARTICULAR
STRESSOR WERE RATED AS HIGH, MEDIUM, OR LOW
[Service 2012 unpubl.; Service 2014, unpubl. data]
High level
of impact
Stressor
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Destruction & Conversion (Agricultural & Nonagricultural Development) .......
Wind Development ..........................................................................................
Flooding/Hydrology ..........................................................................................
Invasive Species ..............................................................................................
Fire ...................................................................................................................
Grazing ............................................................................................................
Haying & Mowing .............................................................................................
Lack of Management .......................................................................................
Size/Isolation ....................................................................................................
Herbicide and/or Pesticide Use .......................................................................
Destruction and Conversion of Prairies
Destruction and Conversion of Prairies
to Agricultural Land
Conversion of prairie for agriculture
may have been the most influential
factor in the decline of the Poweshiek
skipperling and Dakota skipper since
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Medium level
of impact
2
0
2
6
4
4
0
4
21
3
Euro-American settlement, but the
impacts of such conversion on extant
populations is not well known. By 1994,
tallgrass prairie had declined by 99.9
percent in Illinois, Iowa, Indiana, North
Dakota, Wisconsin, and Manitoba; and
by 99.6 percent in Minnesota; and 85
percent in South Dakota (Samson and
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11
0
3
29
2
10
3
6
22
1
Low level
of impact
Total number
of rated sites
28
5
14
11
10
2
3
2
11
5
41
5
19
46
16
16
6
12
54
9
Knof 1994, p. 419). Samson and Knof
(1994, p. 419) did not provide a figure
for the decline of tallgrass prairie in
Saskatchewan, but mention an 81.3
percent decline in mixed grasses from
historical levels. By 1994, mixed-grass
prairie had declined from historical
levels by 99.9 percent in Manitoba and
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71.9 percent in North Dakota (Samson
and Knof 1994, p. 419). Destruction of
tallgrass and mixed-grass prairie began
in 1830, but significant documentation
of the ecosystem’s butterfly fauna did
not begin until about 1960. Therefore,
most of the decline of the Dakota
skipper and Poweshiek skipperling
probably went unrecorded.
Since about 1980, observers have
documented the extinction of several
populations of the Dakota skipper and
Poweshiek skipperling due to habitat
conversion to agricultural use in the
United States and Canada. For example,
four Dakota skipper sites in North
Dakota were converted to irrigated
potato fields, and one in South Dakota
was converted for crop production
(Royer and Marrone 1992a, p. 17). The
Fannystelle site in Manitoba, where the
Dakota skipper was last recorded in
1991, was subsequently converted for
row-crop agriculture (Webster 2003, p.
7). In North Dakota, further conversion
is a stressor to Dakota skippers in the
important Towner-Karlsruhe complex
(Royer and Royer 1998, p. 22; Lenz
1999, p. 13), where the flat topography
and high water table facilitate
conversion to irrigated crop production.
Populations of Dakota skipper in
Manitoba typically occupy flat terrain
that may be vulnerable to conversion to
cropland, although soil conditions may
be unsuitable for row crops at some of
these sites (Webster 2003, p. 10).
Similarly, conversion of native prairie to
cropland continues to be a threat to
Poweshiek skipperling habitat
throughout its range (Royer and
Marrone 1992b, p. 17).
The Dakota skipper, and until
recently, the Poweshiek skipperling,
have largely persisted in areas that are
relatively unsuitable for row crop
agriculture because of their steep terrain
(e.g., in the Prairie Coteau of South
Dakota) or where soils are too wet or
rocky for row-crop agriculture (McCabe
1981, pp. 189–190, Webster 2003, p. 10).
Densely spaced, large glacial rocks, for
example, may have deterred cultivation
at the Chippewa Prairie in Minnesota
and ‘‘spared Chippewa Prairie in
Minnesota from the plow’’ (Dana 2012,
pers. comm.). In areas where Poweshiek
skipperling and Dakota skipper habitat
persists but is adjacent to agriculture,
added nutrients from agricultural runoff
affects groundwater and additional
nutrients in the system contribute to the
dominance of invasive plants (Fiedler
and Landis 2012, p. 51: Michigan
Natural Features Inventory 2012, p. 4).
In summary, conversion for
agriculture on lands suitable for such
purposes is a current, ongoing stressor
of high level of impact to the Poweshiek
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skipperling and Dakota skipper
populations in areas where such lands
still remain. Advances in technology
may also increase the potential of
conversions in areas that are currently
unsuitable for agriculture.
We rated the level of impact to the
populations of the stressor posed by
habitat destruction or conversion for
both agriculture and nonagricultural
purposes (except for conversion for
wind energy development, which was
analyzed separately) at 144 Dakota
skipper and 41 Poweshiek skipperling
sites with present or unknown status
(see Tables 3 and 4) where we had
sufficient information to evaluate the
stressor. In our evaluation of this
stressor, we combined agricultural and
nonagricultural impacts—our analyses
are discussed below (see Destruction
and Conversion of Prairies due to
Nonagricultural Development).
Destruction and Conversion of Prairies
to Nonagricultural Development
Conversion of prairie for
nonagricultural land uses, such as
energy development, gravel mining,
transportation, and housing are stressors
to both Poweshiek skipperling and
Dakota skipper populations. For
example, a site where the Dakota
skipper and Poweshiek skipperling were
recorded in 1997 (Skadsen 1997, pp.
15–16, B–1) in the Bitter Lake area of
Day County, South Dakota, is now a
gravel pit, and the species’ habitat no
longer exists there (Skadsen 2003, pp.
47–48).
Almost all prairie remnants with
Poweshiek skipperling and Dakota
skipper populations are associated with
gravelly glacial till soils (Service 2014,
unpubl. geodatabase); therefore, gravel
mining is a potential stressor to
populations at a large number of sites.
Gravel mining is a stressor to Poweshiek
skipperling and Dakota skipper
populations at several sites in
Minnesota (Dana 1997, p. 15). For
example, gravel mining is a stressor in
at least three of the five sites that
comprise the Felton Prairie complex
(Cochrane and Delphey 2002, pp. 16–
17); however, the Clay County
Stewardship Plan (Felton Prairie
Stewardship Committee 2002) may have
reduced the likelihood of the gravel
mining stressor to populations at this
complex. On at least seven sites in
Minnesota, Dakota skippers inhabit
northern dry prairie plant communities,
which are generally impacted by gravel
mining due to the predominance of
gravel soils (Minnesota DNR 2006, p.
221). Gravel mining is a stressor to
populations of Dakota skipper in central
Manitoba (Rigney 2013a, p. 28). Gravel
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mines are considered a stressor with a
high level of impact to populations of
both species because, where it occurs,
the habitat is completely destroyed.
Potash (salt that contains potassium)
mining is a stressor to Dakota skipper
populations in some Saskatchewan sites
(Westwood 2013, pers. comm.),
although the exact number of sites that
are being considered for potash mining
is unknown and were not included in
our stressor evaluation.
Energy development (oil, gas, and
wind) and associated roads and
facilities result in the loss or
fragmentation of suitable prairie habitat
(Reuber 2011, pers. comm.). Major areas
of recent oil and gas development, such
as that occurring in the Bakken
formation, overlaps with parts of the
Dakota skipper’s range in North Dakota.
North Dakota, for example, is now one
of the top two oil-producing states in
the United States, and new development
is occurring rapidly (MacPherson 2012,
p. 1; North Dakota Petroleum Council
2012, p. 1). The number of drilling
permits in North Dakota nearly doubled
between 2007 and 2008, from 494
permits issued in 2007 to 946 in 2008
(North Dakota Petroleum Council 2009,
p. 2). Permits dropped to 627 in 2009
(North Dakota Petroleum Council 2010,
p. 2), but increased dramatically to
1,676 in 2010 (Ogden 2011, p. 1). While
much of the oil activity is currently
occurring in areas of native prairie
overlaying the Bakken and Three Forks
formations to the west of known
locations for both species, mineral
exploration has occurred in all but one
county in North Dakota (North Dakota
Petroleum Council 2012, p. 1).
McKenzie County falls in the center of
this development and McHenry County
is also within these formations (Mueller
2013, pers. comm.). The oil
development on the Bakken formation
in North Dakota, for example, may be a
future stressor to Dakota skipper
populations in McKenzie County (Royer
and Royer 2012b, p. 16). Oil production
is anticipated to continue to expand at
record levels (MacPherson 2012, p. 1;
MacPherson 2010, entire).
Native-prairie habitat would be
destroyed in the footprint of an oil and
gas well pad, but the pads are relatively
small. However, each oil and gas well
pad requires new road construction, and
evidence suggests that Poweshiek
skipperlings may avoid crossing roads
(Westwood et al. 2012, p. 18). Energy
development can double the density of
roads on range lands (e.g., Naugle et al.
2011, pp. 493–494), increase pipelines,
and increase the number of gravel pits
to accommodate the increased road
construction (Mueller 2013, pers.
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comm.). Development for coal-bed
natural gas (as described in Naugle
2011), for example, in areas with
ranching, tillage agriculture, and oil and
gas development, 70 percent of the
developed land was within 100 m (109
yards (yd)), and 85 percent of the
developed land was within 200 m (218
yd), of a human structure (Naugle et al.
2011, p. 493). Researchers estimated
that, in those areas, every square km
(0.39 square miles) of land may be both
bounded by a road and bisected by a
power line (Naugle et al. 2011, p. 493).
These coal-bed natural gas
developments can be densely located
(e.g., 8 wells per 640 acres) and are
drilled vertically, whereas shale-oil
wells in the Bakken formation are
drilled horizontally and ‘‘relatively far
apart’’ (Conoco Phillips 2013, in litt.).
The habitat fragmentation associated
with oil and gas development may
amplify other stressors to both species,
such as the effects of population
isolation and the impacts of stochastic
events.
Energy development has additional
undesirable and potentially significant
cumulative impacts on wildlife.
Catastrophic events, such as oil and
brine spills, could cause direct mortality
of Dakota skipper or Poweshiek
skipperling larvae that are in shelters at
or below the soil surface. Such spills
may also cause the loss of larval host
and nectar plants in the spill path.
Additional plants may be lost during
spill response, particularly if the
response involves burning. The
likelihood, however, of spills occurring
on the small fraction of land that
remains native tallgrass prairie in North
Dakota (less than one percent according
to Samsom and Knoff 1994, p. 419) is
low.
Wind energy turbines and associated
infrastructure (e.g., maintenance roads)
are likely stressors to Dakota skipper
and Poweshiek skipperling populations,
particularly on private land in South
Dakota (Skadsen 2002, p. 39; Skadsen
2003, p. 47; Skadsen 2012d, pers.
comm.). Similar to oil and gas
development, wind development would
destroy native-prairie habitat in the
footprint of the structure, add access
roads and other infrastructure that may
further fragment prairies, and could be
catalysts for the spread of invasive
species. Further, it is unknown if the
noise and flicker effects associated with
wind turbines may impact Dakota
skipper or Poweshiek skipperling
populations beyond direct impacts from
the turbines and/or infrastructure. Other
wildlife species, such as birds, have
shown significant avoidance of
grasslands where wind development has
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occurred (Pruett et al. 2009, p. 1256;
Shaffer et al. 2012,unpaginated). Wind
development was assessed at nine
Dakota skipper sites and six Poweshiek
skipperling sites where we had
sufficient information. The level of
threat was considered to be low at most
sites because, although the site may be
in an area with the potential for wind
development, there are no specific plans
or proposals to develop wind power on
the site.
Wind development is considered a
stressor of high level of impact to
populations at sites where development
is proposed and there are no actions or
plans to mitigate impacts to the species.
For example, a wind facility was
recently proposed at a Dakota skipper
site in South Dakota (Skadsen 2012d,
pers. comm.), which poses a high-level
threat for the species at that site because
there are no plans to mitigate impacts of
habitat destruction. Although wind
power development currently poses a
high level of impact to the population
at only one site, the extent of this
stressor will likely increase in the
future, due to the high demand for wind
energy and the number of Dakota
skipper and Poweshiek skipperling sites
that are conducive to wind development
(e.g., Skadsen 2003, pp. 47–48).
Furthermore, power transmission lines
may be developed in order to
accommodate the added power of wind
farms, for instance, a new power line is
currently being planned in the Prairie
Coteau in South Dakota for that purpose
(Mueller 2013, pers. comm.).
Housing construction has likely
contributed to the loss of at least two
Poweshiek skipperling populations in
Michigan, and the largest extant
population in Michigan is located in an
area under intense development
pressure (Michigan Natural Features
Inventory 2011, unpubl. data).
Residential wells and drainage disrupt
prairie fen hydrology by reducing water
levels and, thus, facilitating rapid
growth of woody vegetation. In
addition, nutrients added to the
groundwater from leaking septic tanks
contribute to the dominance of invasive
plants, such as narrow-leaved cattail
(Typha angustifolia) and red canary
grass (Phalaris arundinacea) (Michigan
Natural Features Inventory 2012, p. 4).
Road construction impacts Poweshiek
skipperling and Dakota skipper habitat
because it increases the demand for
gravel, and impacts also result from
routine maintenance (e.g., broadcast
herbicide applications, early mowing,
and cleaning out ditches),
improvements (e.g., widening roads or
converting two-lane highways to fourlane highways), or new construction.
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Poweshiek skipperling habitat was
destroyed or degraded on at least two
private properties in Roberts County,
South Dakota, for example, in
association with the widening of U.S.
Highway 12 (Skadsen 2003, p. 47).
Roadside prairie remnants can help
support populations of both species and
serve as dispersal corridors between
larger remnants; therefore, loss of these
areas to road expansion or construction
further reduces and fragments
remaining habitat. In Michigan, at least
one Poweshiek skipperling site and its
habitat has been negatively affected by
recreational ‘mud bogging’, which
destroys vegetation and creates
conditions conducive to invasive
species (Hicks 2014, pers. comm.).
In summary, nonagricultural
development, such as gravel mining,
activities associated with energy
development, or housing and road
development, poses a current stressor of
moderate to high impact to populations
on those lands that are not protected
from destruction or conversion through
a conservation easement or fee title
ownership by a conservation agency.
This type of development may become
more widespread as such practices
increase in the future.
As discussed above in Destruction
and Conversion of Prairies to
Agricultural Land, we rated the level of
impact to the populations of the stressor
posed by habitat destruction or
conversion for both agriculture and
nonagricultural purposes combined
(except for conversion for wind energy
development, which was analyzed
separately) at 144 Dakota skipper sites
with present or unknown status (see
Table 3) where we had sufficient
information to evaluate the stressor. The
level of impact of each stressor to the
population at each site is high at three
of those sites, due to ongoing
destruction of the native prairie, or there
was a high likelihood of conversion
because it is located close to other
converted areas and the land is
conducive for agriculture. The level of
threat is high at 3 sites, moderate at 83
sites, and 58 sites are protected from
destruction or conversion through a
conservation easement or fee title
ownership by a conservation agency
(Table 3). This stressor occurs across the
range of the Dakota skipper; the stressor
has a medium to high level of impact to
Dakota skipper populations in
Minnesota, North Dakota, South Dakota,
Manitoba, and Saskatchewan. The level
of impact was considered to be low if
the site is protected from destruction or
conversion by fee title ownership by a
governmental conservation agency,
nongovernmental conservation
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organization (e.g., The Nature
Conservancy), or educational institution
(e.g., South Dakota State University).
Similarly, 41 Poweshiek skipperling
sites with present or unknown status
were assessed that had sufficient
information: The level of threat was
high at 2 sites and moderate at 11 sites,
and 28 sites are protected from
destruction or conversion through a
conservation easement or fee title
ownership by a conservation agency
(Table 4). At least 6 of the 12 sites where
the Poweshiek skipperling is considered
to still be present have a medium or
high risk of conversion. This stressor
occurs across most of the Poweshiek
skipperling range; the stressor has a
medium to high level of impact to
Poweshiek skipperling populations in
Iowa, Michigan, Minnesota, and South
Dakota; the level of impact is low for the
species at the Manitoba location.
Fluctuating Water Levels
Flooding is a stressor to Poweshiek
skipperlings and Dakota skippers at
sites where too much of the species’
habitat is flooded or where patches are
flooded too frequently. Poweshiek
skipperlings and Dakota skippers must
either survive flooding events in
numbers sufficient to rebuild
populations after the flood or recolonize
the area from nearby areas that had not
flooded. In addition, the return interval
of floods must be infrequent enough to
allow for recovery of the populations
between floods. Changes in hydrology
resulting from wetland draining and
development may permanently alter the
plant community and, therefore, pose a
threat to Poweshiek skipperling and
Dakota skipper due to loss of larval food
and nectar sources.
The Dakota skipper and Poweshiek
skipperling are presumed extirpated
from several sites due to flooding or
draining. For example, one Dakota
skipper site was lost to flooding due to
rising water levels at Bitter Lake, South
Dakota (Skadsen 1997, p. 15). At
Whalen Lake Fen in Michigan, dredging
and channelization disrupted the
hydrology of the site and the fen has
since been invaded by glossy buckthorn
and narrow leaf cattail; Poweshiek
skipperlings are presumed to be
extirpated from the site (Michigan
Natural Features Inventory 2011,
unpubl. data). The loss of a large area
of habitat at two sites in Manitoba,
which were previously suitable for
Dakota skipper, was caused by
prolonged inundation of water that
likely caused larval mortality and
mortality of suitable nectar and larval
food plants (Rigney 2013a, pp. 28, 153).
In addition, flood protection activities
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and associated alteration of the
landscape (e.g., road work that causes
changes to overland drainage) is a
stressor to the species at some sites in
Manitoba (Rigney 2013a, p. 28).
Fluctuating water levels are a current
stressor to populations across both
species’ ranges. Loss of habitat or direct
mortality due to fluctuating water
levels, such as permanent flooding or
wetland draining, is a current stressor to
populations in at least 14 Dakota
skipper sites with present or unknown
status and 19 Poweshiek skipperling
sites with present or unknown status.
For example, one of the three sites with
present or unknown status of Poweshiek
skipperling in Wisconsin, Puchyan
Prairie, is subject to flooding—the entire
prairie portion of the site was
submerged in 1993 (Hoffman 2011, pers.
comm.; Wisconsin DNR 2012, in litt).
The number of Poweshiek skipperling
observed at that site is consistently low.
Flooding is a likely factor that has
contributed to the low numbers
observed in at least part of this site
(Borkin 2012c, pers. comm.).
Conversely, groundwater disruption
and draining is a stressor at all 9 of the
Michigan prairie fen Poweshiek
skipperling sites where the species is
present and high at one site with
unknown occupancy. Interrupted
groundwater flow-through fens can
reduce water levels and facilitate woody
vegetation establishment and growth
(Michigan Natural Features Inventory
2012, p. 4). Agricultural and residential
drains and wells can lower the
groundwater table, thereby reducing the
supply of calcareous seepage, which is
an essential underlying component of
prairie fen hydrology (Michigan Natural
Features Inventory 2012, p. 4).
Furthermore, nutrient additions
associated with drain fields can
contribute to invasive species
encroachment. For instance, if
groundwater flow to prairie wetlands is
severed, fen habitats may convert from
native grasses and flowering forbs to
habitats dominated by invasive species
or woody vegetation (Fiedler and Landis
2012, p. 51, Michigan Natural Features
Inventory 2012, p. 4). The site with the
highest number of Poweshiek
skipperlings in Michigan, for instance,
is partially bordered by residential areas
and is under intense development
pressure (Michigan Natural Features
Inventory2011, unpubl. data). At least 8
of the 11 fen sites with present or
unknown status are at least partially
unprotected from development, and at
least 7 of those are closely bordered by
roads, agriculture, or residential
developments (Michigan Natural
Features Inventory 2011, unpubl. data;
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Service 2014, unpubl. geodatabase). The
status of Poweshiek skipperling is
unknown at one fen site where the
hydrology was likely disrupted by roads
and extensive residential development
in close proximity to the fen (Michigan
Natural Features Inventory 2011,
unpubl. data).
The level of impact to populations
due to flooding was assessed at 12
Dakota skipper sites with present or
unknown status that had sufficient
information to evaluate the stressor
(Table 3); this evaluation only included
sites in North and South Dakota.
Flooding is a stressor of moderate-level
impact to populations at 6 of the sites,
where there is evidence of recent or
pending decrease in the quality or
extent of suitable habitat at the site due
to a change in wetland vegetation,
wetland hydrology, or flooding—all of
these sites occur in North Dakota
(Service 2012 unpubl. data; Service
2014, unpubl. data). Similarly, we
assessed 19 Poweshiek skipperling sites
with present or unknown occupancy for
the level of impact to populations due
to water fluctuations (e.g., flooding or
draining) where we had sufficient
information to evaluate the stressor
(Table 4). Water fluctuations is a
stressor with moderate impact to the
populations at 3 Poweshiek skipperling
sites (including a site in Wisconsin—
one of the 12 Poweshiek skipperling
sites with a present status), and changes
to hydrology is a stressor of moderateto high-level impact to populations at
all 11 Michigan sites (including 9 of 12
Poweshiek skipperling sites that have a
present status) and 1 site in North
Dakota (Service 2012 unpubl. data;
Service 2014, unpubl. geodatabase).
In summary, fluctuating water levels
is a current and ongoing stressor of
moderate level of impact to populations
where the habitat may be temporarily
lost due to intermittent flooding and is
a stressor of high severity where a
change in hydrology may completely
degrade the habitat quality of a site,
particularly prairie fens.
Invasive Species and Secondary
Succession
Poweshiek skipperlings and Dakota
skippers typically occur at sites
embedded in agricultural or developed
landscapes, which make them more
susceptible to nonnative or woody plant
invasion. Nonnative species including
leafy spurge, Kentucky bluegrass,
alfalfa, glossy buckthorn, smooth brome,
purple loosestrife (Lythrum salicaria),
Canada thistle (Cirsium arvense), reed
canary grass, and others, have invaded
Poweshiek skipperling and Dakota
skipper habitat throughout their ranges
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(Orwig 1997, pp. 4, 8; Michigan Natural
Features Inventory 2011, unpubl. data;
Skadsen 2002, p. 52; Royer and Royer
2012b, pp. 15–16, 22–23). Kentucky
bluegrass and leafy spurge (and the
persistent efforts for chemical control of
leafy spurge) have been cited as one of
the major stressors to native-prairie
habitat at several public and privately
owned Dakota skipper sites in North
Dakota (Royer and Royer 2012b, pp. 15–
16, 22–23; Royer 2012, pers. comm.;
Royer 2013, pers. comm.). Once these
plants invade a site, they replace or
reduce the coverage of native forbs and
grasses used by adults and larvae of
both butterflies. Leafy spurge displaces
native plant species, and its invasion is
facilitated by actions that remove native
plant cover and expose mineral soil
(Belcher and Wilson 1989, p. 172). The
seasonal senescence patterns (timing of
growth) of grass species as they relate to
the larval period of Dakota skippers
determine which grass species are
suitable larval host plants. Exotic coolseason grasses, such as Kentucky
bluegrass and smooth brome, are
available when Dakota skipper and
Poweshiek skipperling larvae begin
feeding; however, the morphology and
growth habit of these grasses are likely
major determinants of their
unsuitability to support Dakota skippers
(Dana 1991, pp. 46–47). Thus, a
prevalence of these grasses reduces food
availability for the larvae.
The stressor from nonnative invasive
herbaceous species is compounded by
the encroachment of woody species into
native-prairie habitat. Glossy buckthorn
and gray dogwood encroachment, for
example, is a major stressor to
Poweshiek skipperling populations at
the Brandt Road Fen in Michigan,
which supports the second largest
population of Poweshiek skipperlings in
the State (Michigan Natural Features
Inventory 2011, unpubl. data). Invasion
of tallgrass prairie and prairie fens by
woody vegetation such as glossy
buckthorn reduces light availability,
total plant cover, and the coverage of
grasses and sedges (Fiedler and Landis
2012, pp. 44, 50–51). This in turn
reduces the availability of both nectar
and larval host plants for Poweshiek
skipperlings and Dakota skippers. If
groundwater flow to prairie wetlands is
disrupted (e.g., by development) or
intercepted (e.g., digging a pond in
adjacent uplands or installing wells for
irrigation or drinking water), it can
quickly convert to shrubs or other
invasive species (Fiedler and Landis
2012, p. 51; Michigan Natural Features
Inventory 2012, p. 4). For example,
roads and residential development
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likely disrupted the hydrology of a
prairie fen where the Poweshiek
skipperling was last observed in 2007
and where 2008 and 2009 surveys for
Poweshiek skipperlings were negative
(Michigan Natural Features Inventory
2011, unpubl. data). Furthermore, on
some sites, land managers intentionally
facilitated succession of native-prairie
communities to woody vegetation or
trees, such as Ponderosa pine (Pinus
ponderosa) or spruce (e.g., Dana 1997,
p. 5). This converts prairie to shrubland,
forest, or semi-forested habitat types and
facilitates invasion of adjacent native
prairie by exotic, cool-season grasses,
such as smooth brome. Moreover, the
trees and shrubs provide perches for
birds that may prey on the butterflies
(Royer and Marrone 1992b, p. 15; 1992a,
p. 25).
We rated the level of impact to
populations of invasive species at 65
Dakota skipper sites and 46 Poweshiek
skipperling sites that had sufficient
information to evaluate the stressor
(Table 3 and Table 4; Service 2012
unpubl. data; Service 2014, unpubl.
data). This stressor is considered to have
a low level of impact to the populations
if there was either no information to
indicate a stressor or management was
ongoing to control invasive species
using methods that are unlikely to cause
adverse effects to Dakota skippers or
Poweshiek skipperlings (e.g., spotspraying or hand-pulling). Sites were
assigned a moderate level of impact to
populations if invasive species are
typically a primary driver of
management actions and make it
difficult for managers to specifically
tailor management to conserve Dakota
skipper or Poweshiek skipperling
habitat. The site was assigned a high
level of impact to populations if one or
more nonnative invasive plant species
are abundant or increasing and
management activities are not being
implemented to control their expansion;
or if necessary management actions
cannot be implemented without
themselves causing an additional
stressor to the Dakota skipper or
Poweshiek skipperling populations at
the site.
Invasive species are a current and
ongoing stressor with high levels of
impact to Dakota skipper and
Poweshiek skipperling populations on
sites where land management is
conducive to their invasion or
expansion or where they have become
so pervasive that even favorable
management may not be quickly
effective. Succession is a current and
ongoing stressor of moderate-level
impact to populations at sites where
management is insufficient. The stressor
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of invasive species to populations on
small and isolated sites (e.g., Big Stone
NWR) is a current and ongoing stressor
of high level of impact to populations,
because Dakota skipper and Poweshiek
skipperling populations have little
resilience to the resulting habitat
degradation and to the often aggressive
management needed to control the
invasive plants. Loss of habitat or
degradation of the native plant
community due to encroachment of
invasive species or woody vegetation is
considered a high level of impact to
populations at 12 of the 65 assessed
Dakota skipper sites, a moderate level of
impact to populations at 33 sites, and
low impact to populations at 20 sites.
Sites with high and moderate level of
impact occur throughout the species
range in Minnesota, and North and
South Dakota (Service 2012 unpubl.
data; Service 2014, unpubl. data).
Similarly, invasive species are a stressor
of high level of impact to populations at
6 of the 46 evaluated Poweshiek
skipperling sites, moderate level of
impact to populations at 29 sites, and
low level of impact to populations at 11
sites—sites with high and moderate
levels of impact are throughout the
range of the species in Iowa, Minnesota,
Michigan, North Dakota, South Dakota,
Wisconsin, and Manitoba and include at
least 9 of the 12 sites where the species
is still present (Service 2014, unpubl.
data).
Fire
Dakota skipper and Poweshiek
skipperling populations existed
historically in a vast ecosystem
maintained in part by fire. Due to the
great extent of tallgrass prairie in the
past, fire and other intense disturbances
(e.g., locally intensive bison grazing)
likely affected only a small proportion
of the habitat each year, allowing for
recolonization from unaffected areas
during the subsequent flight period
(Swengel 1998, p. 83). Fire can improve
Poweshiek skipperling (Cuthrell 2009,
pers. comm.) and Dakota skipper habitat
(e.g., by helping to control woody
vegetation encroachment), but it may
also kill most or all of the individuals
in the burned units and alter entire
remnant prairie patches, if not properly
managed (e.g., depends on the timing,
intensity, etc.). Accidental wildfires also
may burn entire prairie tracts (Dana
1997, p. 15) and may hamper plans to
carefully manage Dakota skipper and
Poweshiek skipperling habitat. A
human-set wildfire in late fall 2009 and
another extensive fire in 2011, for
example, burned considerable amounts
of good prairie habitat in The Nature
Conservancy of Canada’s Tall Grass
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Prairie Preserve in Manitoba (Hamel et
al. 2013, p. 1; Westwood 2010, pers.
comm.), which is the only location in
Canada where Poweshiek skipperlings
are present; Dakota skippers are
extirpated from the site. The fires at The
Nature Conservancy of Canada’s Tall
Grass Prairie Preserve may have killed
overwintering larvae, and the
population of Poweshiek skipperling in
Canada ‘‘may have been greatly reduced
as a result of these fires’’ (Hamel et al.
2013, p. 1).
Intentional fires, without careful
planning, may also have significant
adverse effects on populations of Dakota
skippers and Poweshiek skipperlings,
especially after repeated events (McCabe
1981, pp. 190–191; Dana 1991, pp. 41–
45, 54–55; Swengel 1998, p. 83; Orwig
and Schlicht 1999, pp. 6, 8). In
systematic surveys of Minnesota
tallgrass prairies, for example, Dakota
skippers were less abundant on sites
that had been burned, compared with
otherwise similar hayed sites (Swengel
1998, p. 80; Swengel and Swengel 1999,
pp. 278–279). Similarly, Schlicht
(1997b, p. 5) counted fewer Dakota
skippers per hour in burned than on
grazed sites in Minnesota. Orwig and
Schlicht (1999, p. 8) speculated that
inappropriate use of prescribed burning
eliminated Dakota skippers from the last
known occupied site in Iowa, a 65-ha
(160-ac) preserve. The effects of fire on
prairie butterfly populations are
difficult to ascertain (Dana 2008, p. 18),
but the apparent hypersensitivity of
Poweshiek skipperlings and Dakota
skippers indicates that it is a stressor to
both species in habitats burned too
frequently or too broadly. The
Poweshiek skipperling and Dakota
skipper are not known to disperse
widely (Swengel 1996, p. 81; Burke et
al. 2011, p. 2279); therefore, in order to
reap the benefits of fire to habitat
quality, Poweshiek skipperlings and
Dakota skippers must either survive in
numbers sufficient to rebuild
populations after the fire or recolonize
the area from a nearby unburned area.
In addition, the return interval of fires
needs to be infrequent enough to allow
for recovery of the populations between
burns. Therefore, fire is a stressor to
Poweshiek skipperlings and Dakota
skippers at any site where too little of
the species’ habitat is left unburned or
where patches are burned too
frequently.
Panzer (2002, p. 1306) identified four
life-history traits of duff-dwelling
insects (such as the Dakota skipper and
Poweshiek skipperling) that were good
predictors of a negative response to fire:
(1) Remnant dependence (occurring as
small, isolated populations); (2) upland
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inhabitance (dry uplands burn more
thoroughly than wetter habitats); (3)
nonvagility (low recolonization rate);
and (4) univoltine (slower recovery rates
for species with only one generation per
year). Species exhibiting all four traits
should be considered ‘‘hypersensitive’’
to fire (Panzer 2002, p. 1306). While not
specifically included in his study, the
Poweshiek skipperling and Dakota
skipper meet all of Panzer’s criteria for
hypersensitivity (Panzer 2002, p. 1306)
and have additional life-history traits
that further suggest hypersensitivity to
fire. Panzer (2002) observed mean
declines of 67 percent among firenegative species, although actual
mortality was likely higher due to some
immigration into experimental areas
after the burn. When all or large
portions of prairie remnants are burned,
many or all prairie butterflies may be
eliminated at once. Complete
extirpation of a population, however,
may not occur after a single burn event
(Panzer 2002, p. 1306), and the extent of
effects would vary depending on time of
year and fuel load.
Poweshiek skipperlings lay their eggs
near the tips of leaf blades, and they
overwinter as larvae on the host plants
(Borkin 2000, p. 2), where they are
exposed to fires during their larval
stages. Poweshiek skipperlings have
also been documented laying eggs on
the entire length of grass leaf blades and
on low-growing deciduous foliage
(Dupont 2013, p. 133). If larvae are on
prairie dropseed or little bluestem,
which occur in dry prairie, rather than
spike-rush or sedges, which typically
occur in wet prairie, then the larvae are
even more vulnerable to fire (Selby
2005, p. 36). Unlike Dakota skippers,
Poweshiek skipperlings do not burrow
into the soil surface (McAlpine 1972,
pp. 88–92; Borkin 1995, p. 9), which
makes them more vulnerable to fire (and
likely more vulnerable to chemicals
such as herbicides and pesticides)
throughout their larval stages. Species
whose larvae spend more time above
ground, such as Poweshiek skipperlings,
are likely more vulnerable to fire than
species that form underground shelters.
As the spring progresses, however, the
vulnerability of Dakota skippers to fire
increases as larvae shift from buried
shelters to horizontal shelters at the soil
surface (Dana 1991, p. 16).
Studies of all life-stages may be
necessary to fully evaluate these
species’ response to fire. Early spring
burns may be less likely to harm Dakota
skipper populations than late spring
burns, due to larval phenology and
differences in subsurface soil
temperatures during the fire; however,
studies have not conclusively linked the
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relationship of mortality risk to the
timing of spring burns. Experiments to
evaluate the effects of early spring
versus late spring fires and of different
fuel levels on Dakota skipper mortality
found that, despite higher ambient
temperatures during the early spring
burn, temperatures at the average depth
of buried Dakota skipper shelters (Dana
1991, p. 11) were 10 °C (50 °F) higher
during the late-spring burn (Dana 1991,
p. 41). Fuel load was positively related
to subsurface soil temperature (Dana
1991, pp. 41–43). Fuel loads that were
clearly associated with lethal subsoil
temperatures, however, were more
typical of mesic tallgrass prairie, which
had about twice the fuel loads of the
dry-mesic habitats inhabited by Dakota
skippers on the site (Dana 1991, pp. 41,
54). Although Dana’s study was
inconclusive in quantifying the risk of
mortality in relation to the timing of
spring burns, he was able to conclude
that a late-spring burn in ‘‘moderate’’
fuels (430–440 g/m2) would have a
devastating effect on Dakota skipper
populations, and that early spring
burning would afford some amelioration
(Dana 1991, p. 55).
Rotational burning may benefit prairie
butterflies by increasing nectar plant
density and by positively affecting soil
temperature and near-surface humidity
levels due to reductions in litter (Dana
1991, pp. 53–55; Murphy et al. 2005, p.
208; Dana 2008, p. 20). Purple
coneflower and little bluestem, for
example, occurred more frequently on
burned areas than on unburned areas in
mixed-grass prairie at Lostwood
National Wildlife Refuge in
northwestern North Dakota (Murphy et
al. 2005, pp. 208–209). An increase in
purple coneflower, an important nectar
source for Dakota skippers and
Poweshiek skipperlings, may last for 1–
2 years after early spring fires, and
females may preferentially oviposit near
concentrations of this nectar source
(Dana 2008, p. 20).
Although fire tends to increase native
plant diversity in prairies (Murphy et al.
2005, pp. 208–209), several years may
be necessary for Dakota skipper and
Poweshiek skipperling populations to
recover after a burn. Few studies have
documented recovery times for prairie
butterflies after a burn, and even fewer
have measured the relationships
between species abundance in tallgrass
prairies and time since burn. One such
study, however, found lower relative
abundances of Dakota skippers and
Poweshiek skipperlings in burned units
than in otherwise similar hayed units
even 4 years after burns (Swengel 1996,
p. 83). Poweshiek skipperling had the
most negative initial response to fire
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among six species of prairie-obligate
butterfly species (Swengel 1996, p. 83).
Numbers were still lower than expected
1 year post-fire, exceeded expectations
after 2 years, and declined slightly after
3 years (Swengel 1996, p. 83). In
habitats that had not been burned for 4
or more years, Poweshiek skipperling
abundance was about as low as in
habitats sampled less than 1 year after
being burned (Swengel 1996, p. 83). The
2012 spring burn that comprised
approximately 25–30 percent of the
breeding habitat at Scuppernong SNA
may have contributed to the apparent
absence of the species in 2013—the
relatively small population that was also
affected by the 2012 summer drought
and the cold wet spring of 2013 (Borkin
2014, pers. comm.)
Poweshiek skipperling numbers
decline in burned areas for at least 1–
2 years after the burn, and may take
several years to rebound, but may
decline again if management does not
maintain the habitat (Skadsen 2001, p.
37; Webster 2003, p. 12). In general,
rebound times of 1–5 years postburn
have been predicted (Panzer 2002, pp.
1302–1303); however, Vogel et. al (2010,
p. 671) found that habitat-specialist
butterfly abundance rebound time was
approximately 50 months after
prescribed fires. Swengel (1996, pp. 73,
78–79) describes that the negative
effects of fire persist for prairie
specialists for 3 to 5 plus years, and
these species were collectively the most
abundant after 5 or more years since the
last fire. In Manitoba, Poweshiek
skipperling populations were most
numerous in sites burned 5–8 years
previously—the species was absent in
sites that were burned the previous year,
in small numbers in areas that were
burned 2–4 years prior, and absent from
areas that were burned 10 or more years
previous to the survey (Dupont 2013,
pp. 4, 86–87). Recent survey results in
some areas, most notably, Iowa and
Minnesota, indicate that other factors
are acting independently (Dana 2008, p.
18) or in concert with fire to forestall
post-fire rebound.
We assessed the stressor posed by fire
at 20 Dakota skipper sites with present
or unknown status and 16 Poweshiek
skipperling sites with present or
unknown status where we had sufficient
information to evaluate the stressor
(Tables 3 and 4; Service 2012, unpubl.
data; Service 2014, unpubl. data). We
considered fire a stressor of high level
of impact to populations at 10 of the 20
evaluated Dakota skipper sites and 4 of
the 16 Poweshiek skipperling sites. Sites
that face a high level of impact to
populations were primarily those with a
high proportion of Dakota skipper or
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Poweshiek skipperling habitat that may
be burned in a single year or where all
of the species’ habitat is burned with no
likely source of immigrants to sustain
the population. This type of fire
management is a documented cause of
extirpation (Selby 2000, p. 19). Sites
with a moderate level of impact to
populations from fire management were
those where the habitat is divided into
at least three burn units and no unit is
burned more frequently than once every
3 years; or, habitat is divided into two
or more burn units, each unit is burned
no more frequently than once every 3
years, but the entirety of the species’
habitat is never burned in the same year
and the species is present at another site
that is less than 1 km (1.6 mi) away.
Fire is considered to be a stressor of
moderate severity at 4 of the 20
evaluated Dakota skipper sites and 2 of
the 16 Poweshiek skipperling sites. Fire
presents a low level of impact to
populations at sites where the species’
habitat is divided into at least four burn
units and no unit is burned more
frequently than once every 4 years; or,
the species’ habitat is divided into three
or more burn units, at least three units
are burned no more frequently than
once every 4 years, and the site contains
more than 140 ha (346 ac) of native
prairie or where the site is separated
from another occupied site by less than
1 km (1.6 mi). Fire is considered to be
a stressor with a low level of impact to
populations at 6 of the 20 evaluated
Dakota skipper sites and 10 of the 16
Poweshiek skipperling sites.
In summary, fire may be an important
management tool for these butterflies, if
carried out appropriately. However,
where managers burn without ensuring
a sufficient amount of contiguous or
nearby habitat from which immigrants
can re-inhabit burned areas or if not
conducted with conservation of prairie
invertebrates as a primary objective, fire
is a current stressor that can have
moderate impacts on populations.
Uncontrolled wildfires may also have
high or moderate levels of impacts to
populations, and would also depend on
the timing, intensity, and extent of the
burn. Poweshiek skipperlings may be
among the most sensitive of prairie
butterflies to fire, and thus, coordination
between habitat managers and butterfly
experts is necessary to ensure that it is
not implemented in a manner that
degrades population viability. Fire is a
current and ongoing stressor of high
level of impact where burns occur
without ensuring there is a sufficient
amount of contiguous or nearby habitat
from which immigrants can re-inhabit
burned areas. Fire is an ongoing stressor
rangewide for both species and has been
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documented at a high or moderate level
of impact to populations at several sites
in North Dakota, South Dakota,
Minnesota, Wisconsin, and the Tallgrass
Prairie Preserve in Manitoba.
Grazing
As with fire management, grazing may
maintain habitat for the Poweshiek
skipperling and Dakota skipper, but as
with any management practice,
appropriate timing, frequency, and
intensity are important. The level of
impact of grazing on Dakota skipper and
Poweshiek skipperling populations also
depends on the type of habitat that is
being grazed. In contrast to the
permanent habitat destruction and
larval mortality caused by plowing or
mining, for example, some habitats can
remain suitable for the Dakota skipper
and Poweshiek skipperling when grazed
(Dana 1991, p. 54, Schlicht 1997, p. 5,
Skadsen 1997, pp. 24–29), and native
plant diversity in tallgrass prairie may
recover from overgrazing if it has not
been too severe or prolonged. In
addition, grazing may be a valuable tool
for controlling smooth brome invasion
and maintaining native diversity in
prairies, especially where circumstances
make the use of fire difficult or
undesirable (Service 2006, p. 2; Smart et
al. 2013, pp. 685–686). Conversely,
grazing may stimulate brome growth
and reduce native plant diversity.
Grazing may benefit the Dakota
skipper and Poweshiek skipperling
under some management scenarios (e.g.,
adaptive management to adjust grazing
prescriptions according to their effects
on essential features of the prairie
ecosystem). In some habitats, Dakota
skippers benefit from light grazing that
minimizes the area dominated by tall
grasses (e.g., big bluestem and
indiangrass) (Dana 1991, p. 54). Dakota
skippers were relatively abundant on
prairies subjected to light grazing
regimes, but absent on nearby idle
prairies that were no longer used for
grazing; moreover, more Dakota
skippers were observed per hour on the
lightly grazed prairies than on nearby
habitat managed with fire (Schlicht
1997b, p. 5). Similarly, in eastern South
Dakota, Dakota skipper populations
were deemed secure at some sites
managed with rotational grazing light
enough to maintain plant species
diversity (Skadsen 1997, pp. 24–29), but
the species was since extirpated at one
site where a change in ownership
resulted in significant overgrazing
(Skadsen 2006b, p. 5). The economic
benefit of grazing to ranchers may also
benefit the species at some sites by
deterring conversion of remnant prairies
to row crop agriculture; however, recent
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evidence indicates that conversion is
more economically viable (Dowd 2013,
pers. comm.).
Bison (Bison bison) grazed at least
some Dakota skipper and Poweshiek
skipperling habitats historically
(McCabe 1981, p. 190; Bragg 1995, p. 68;
Schlicht and Orwig 1998, pp. 4, 8;
Trager et al. 2004, pp. 237–238), but
cattle (Bos taurus) are now the principal
grazing ungulate in both species’ ranges.
Bison and cattle both feed primarily on
grass, but have some dissimilar effects
on prairie habitats (Damhoureyeh and
Hartnett 1997, pp. 1721–1725; Matlack
et al. 2001, pp. 366–367). Cattle
consume proportionally more grass and
grasslike plants than bison, whereas
bison consume more browse and forbs
(flowering herbaceous plants)
(Damhoureyeh and Hartnett 1997, p.
1719). Grasslands grazed by bison may
also have greater plant species richness
and spatial heterogeneity than those
grazed by cattle (Towne et al. 2005, pp.
1553–1555). Both species remove forage
for larvae (palatable grass tissue) and
adults (nectar-bearing plant parts),
change vegetation structure, trample
larvae, and alter larval microhabitats.
Livestock grazing was identified as a
stressor to populations on most of the
privately owned sites and some public
sites on which Dakota skippers occurred
in 2002 (Cochrane and Delphey 2002,
pp. 62–69). Swengel and Swengel (1999,
p. 286), for example, noted that at the
Sheyenne National Grassland in North
Dakota, grazing appeared to be
unfavorable for the Poweshiek
skipperling and Dakota skipper.
Reduced availability of nectar
resources and larval food plants is likely
the primary factor leading to declines in
Poweshiek skipperling and Dakota
skipper populations on heavily grazed
sites. In South Dakota, for example,
Higgins (1999, p. 15) found lower plant
diversity on privately owned prairies,
which were mostly grazed, than on
publicly owned prairies, which were
almost all idle (no grazing or fire
management). McCabe (1981, p. 189)
observed that grazing eliminated Dakota
skippers on North Dakota wet-mesic
prairies; nectar plants such as yellow
sundrops and bluebell bellflower
rapidly diminished with light grazing,
and heavy grazing eliminated upright
prairie coneflower and purple
coneflower. In Manitoba, certain levels
of grazing are likely to adversely affect
Dakota skipper populations in
proportion to its intensity because it
removes nectar sources (e.g., Rigney
2013a, pp. 143 and 153).
The intensity at which grazing occurs
may dictate the level of impact to the
Dakota skipper and Poweshiek
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skipperling, and grazing may have a
larger impact on the Poweshiek
skipperling than the Dakota skipper
(Westwood 2013, pers. comm.). Grazing
reduces Dakota skipper numbers in
direct proportion to its intensity, due to
the reduction in flowers that provide
nectar and perhaps by influencing adult
behavior (Dana 1997, p. 4). Dana (1997,
p. 5) predicted that privately owned
pastures in Minnesota’s Hole-in-theMountain complex, for example, will
likely only support low densities of
skippers if they continued to be heavily
grazed and sprayed with herbicides.
Surveys at this habitat complex in 2007,
2008, and 2012 failed to record any
Poweshiek skipperlings (Dana 2008, p.
8; Selby 2009a, pp. xxxi–xxxii; Runquist
2012a, pers. comm.; Runquist 2012, pp.
13–14, 18–20), and Dakota skippers
were not detected in 2012 surveys
(Runquist 2012, pp. 13–14, 18–20;
Runquist 2012a, pers. comm.).
While most references to grazing
impacts on prairie butterflies are based
on ancillary observations made during
research focused on other management
impacts, one Minnesota study (Selby
2006b) focused on the effects of grazing
on all life stages of the Dakota skipper,
and also included data for the adult
stage of the Poweshiek skipperling. Both
species were too scarce to collect data
adequate to test the hypotheses (Selby
2006b, p. 2), but observations based on
2 years (2003 and 2004) of surveys
suggested that numbers in the lightly to
moderately grazed pasture were similar
to those in the best portions of nearby
ungrazed habitats (Selby 2006b, p. 30).
Poweshiek skipperlings were almost
absent from the study sites (Selby
2006b, pp. iii–xxiii). Within the grazed
study area, the number of Dakota
skippers declined with increasing
grazing intensity; Dakota skippers were
absent from the most heavily grazed
areas (Selby 2006b, p. 16). Skadsen
(2001, p. 55) found that native forb
diversity was poor on the grazed lands
and predicted the extirpation of both
species unless management practices
were changed. The Dakota skipper is
now extirpated at one of these sites, and
its status is unknown at the other;
Poweshiek skipperling status is
unknown at both sites (Service 2014,
unpubl. geodatabase). Spomer (2004, p.
4) found that larval host plants and
nectar sources were missing from
heavily grazed pastures at Sheyenne
National Grassland, North Dakota.
Grazing intensity combined with
varying habitat type may also affect the
level of grazing impacts. On wet-mesic
habitat in North Dakota, for example,
Dakota skippers and Poweshiek
skipperlings tolerate little to no grazing
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(McCabe and Post 1977, pp. 36–38;
Royer and Marrone 1992a, pp. 10, 17,
28; Royer and Marrone 1992b, pp. 17–
18; Royer and Royer 1998, p. 22).
Webster (2003, pp. 7–8) described very
similar Dakota skipper habitats in
Manitoba and, although grazing
generally does not occur in these
habitats that are occupied by Dakota
skipper, they may be as sensitive to
grazing as similar habitats in North
Dakota; in a later report, he described
the conversion of lands from haying to
grazing as a major stressor to Dakota
skipper in the wet-mesic habitats of
Manitoba (Webster 2007, pp. i–ii, 6).
More recently, it is thought that the
effects of grazing in Manitoba and
Saskatchewan, as stated in Webster
(2007, entire), may not be applicable
under current population sizes, and that
even light grazing may be detrimental
on dry short grass prairie sites prior to
and during the Dakota skipper flight
period (Westwood 2013, pers. comm.).
In the drier and hillier habitats that
the species inhabits, grazing may benefit
Dakota skipper depending on its
intensity. For example, in eastern South
Dakota, Dakota skipper populations
were deemed secure at some sites
managed with rotational grazing that
was sufficiently light to maintain native
plant species diversity (Skadsen 1997,
pp. 24–29), and grazing may also benefit
Dakota skippers by reducing the area
dominated by tall native grasses, such as
big bluestem and Indiangrass (Dana
1991). Proximity of nearby populations
or contiguous habitat may alleviate
some of the negative impacts of grazing.
Royer and Marrone (1992b, p. 29; 1992a,
p. 18) stated that heavy grazing was a
stressor to Dakota skippers and
Poweshiek skipperlings, but that
occasional light grazing is not a longterm stressor in some habitats as long as
there are areas of contiguous habitat that
remain ungrazed. At Chekapa Creek
Ridge and Knapp Pasture in South
Dakota, heavy grazing apparently
extirpated both the Poweshiek
skipperling and Dakota skipper
(Skadsen 2002, p. 38; 2004, p. 7; 2006a,
p. 11). Due to its proximity to other
Poweshiek skipperling populations and
a return to fall haying in 2005, the
Poweshiek skipperling recolonized
Chekapa Creek Ridge in 2006 (Skadsen
2006a, p. 12), but more recent surveys
indicate that the Poweshiek skipperling
has again been extirpated from this site
due to habitat degradation because of a
change from haying to grazing (Skadsen
2012a, pers. comm., Skadsen 2012c,
pers. comm.).
As with fire, Dakota skipper and
Poweshiek skipperling populations may
persist through intense grazing episodes
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or be restored afterwards, if sufficient
numbers survive and reproduce in
lightly grazed patches or if nearby
habitats provide sufficient numbers of
immigrants to reestablish the population
after habitat quality is restored. Years of
grazing without rest, however, may
preclude recovery from the effects of
intense grazing, although the capacity
for restoration of suitable plant
community and other habitat features
may be highly variable among sites. On
some sites, plant diversity may not be
restored when grazing pressure declines
(Dana 1997, p. 30; Jackson 1999, pp.
134–135; Spomer 2004, p. 4). Grazing
intensely (where a high proportion of
plant biomass is removed) or for long
duration leads to native plants being
replaced with exotic, cool-season
European forage grasses and legumes
that are tolerant of continuous grazing
(Jackson 1999, p. 128, Minnesota DNR
2006, p. 232). In overgrazed native
prairie in Minnesota, for example, the
prairie is dominated by exotic grasses
with a low native forb species diversity
and abundance, and foliage height is
less than 10 cm (4 in) (Dana 1997, p. 3);
these prairies lack the native plants
necessary to sustain adult and larval
prairie butterflies. In comparison, sites
less disturbed by grazing have a high
native forb (nectar) species diversity and
abundance foliage height is generally
more conducive to perching and
reproductive activities (between 25 and
40 cm (10 and 16 in)) (Dana 1997, p. 2).
Land managers also frequently use
herbicides, often through broadcast
application, to control weeds and brush
on grazed remnant prairies, which
further reduces native forb diversity and
abundance (Dana 1997, p. 3; Stark et al.
2012, pp. 25, 27) necessary for adult
nectar sources. Skadsen (2006, p. 11),
for example, documented the likely
extirpation of Dakota skippers at Knapp
Ranch in South Dakota after a July 2006
application of broadleaf herbicide in
concert with heavy grazing. Herbicide
and pesticide use is discussed further
under Factor E of this final rule.
While reduced availability of nectar
resources and larval food plants may be
the primary factors leading to declines
in Poweshiek skipperling and Dakota
skipper populations on heavily grazed
sites, changes in vegetation structure
may also be important. For example,
grazing prairie each year during midsummer eliminates nectar plants, such
as purple coneflower, and native warmseason grasses that function as larval
host plants (Skadsen 2007, pers.
comm.). In South Dakota, vegetation
height and litter depth were lower on
prairie remnants that were mostly
grazed (Higgins 1999, pp. 27–29).
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Grazing also causes direct mortality of
larvae due to trampling and altering
larval microhabitats (Royer et al. 2008,
pp. 10–15). In North Dakota, grazing can
compact soils in wet-mesic prairie
inhabited by Dakota skippers and
Poweshiek skipperlings, altering vertical
water movement in the soil, which may
lead to larval desiccation (Royer et al.
2008, p. 16) and may inhibit subsurface
shelter construction, potentially
increasing larval vulnerability to
predators, parasites, and other
environmental stressors (Dana 2013,
pers. comm.). Cattle may also kill larvae
by trampling them, particularly in wetmesic prairies (McCabe 1981, p. 189).
Livestock grazing is the predominant
use of privately owned tallgrass prairie
remnants in South Dakota (Higgins
1999, p. 15) and was identified by the
Service as a stressor on most of the
privately owned sites on which Dakota
skipper occurred when the species was
identified as a candidate species in 2002
(Cochrane and Delphey 2002, pp. 62–
69). The presence and density of purple
coneflower may serve as an indicator of
grazing impacts to Dakota skippers and
Poweshiek skipperlings where the
species occur in dry-mesic prairie
(Skadsen 2006a, p. 2); grazing from midJune through July may reduce purple
coneflower abundance (Skadsen 2007,
pers. comm.)—as discussed in the
Background section of this rule, purple
coneflower has been identified as a
primary source of nectar for both
species, particularly in dry prairie
habitats.
Britten and Glasford (2002, p. 373)
recommended minimizing disturbance
of Dakota skipper habitat during the
flight period (late June to early July) to
maximize genetically effective
population sizes (the number of adults
reproducing) to offset the effects of
genetic drift of small populations
(change in gene frequency over time due
to random sampling or chance, rather
than natural selection). Therefore, a
large portion of the habitat of any
Dakota skipper population should
remain ungrazed or only lightly grazed
during the flight period, and similar
precautions should be taken for the
Poweshiek skipperling.
We assessed the level of impact to
populations from grazing at 52 Dakota
skipper sites and 16 sites currently
occupied by Poweshiek skipperling
with present or unknown status that had
sufficient information to evaluate the
stressor (Tables 3 and 4; Service 2012
unpubl. data; Service 2014, unpubl.
data). This analysis was conducted
differently for different habitat types.
For Type A habitat (Royer et al. 2008,
pp. 14–16) where stocking rates
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(number of cattle or bison over a given
area) have little or no evidence of
grazing effects on Dakota skipper or
Poweshiek skipper habitat quality, we
found the level of impact to populations
of grazing to be low. For Type B habitat
(Royer et al. 2008, p. 14), we assumed
that the level of impact of grazing to
populations would be low if the drymesic slopes were grazed only before
June 1 with at least one year of rest
between rotations and if the pasture
were only spot-sprayed with herbicides
when and where necessary, or, the best
available information does not indicate
that grazing practices are degrading
habitat quality for the species (i.e., no
apparent diminishment of nectar plant
density and diversity and habitat is
good or excellent for Dakota skipper).
At grazed sites where extirpation of
the local population is not imminent,
but habitat quality is fair to poor and the
relative abundance of Dakota skippers
or Poweshiek skipperlings is often low,
we found the level of impact of grazing
to populations to be moderate. Sites
with a moderate level of impact to
populations due to grazing may be
lightly grazed for less than 4 months or
less than 25 percent of the above-ground
biomass of native grasses and forbs is
consumed (Smart et al. 2011, pp. 182–
183), are grazed after June 1, or are not
given a year of rest between grazed
years. At sites where grazing is
conducted season-long, or for more than
4 months during the year, or more than
50 percent of the above-ground biomass
of native grasses and forbs is consumed
and herbicide use is frequent, we found
the level of impact of grazing to
populations to be high. At sites where
grazing is a high-level stressor,
extirpation of the population is likely
imminent and habitat quality is poor.
On public lands inhabited by the
species, grazing is typically used to
control nonnative cool-season grasses
and invasive species. Cattle are often
removed by July 1 to minimize adverse
impacts to warm-season grasses, but this
type of management minimizes the
density of nectar species that are
important to the Dakota skipper and
Poweshiek skipperling. Invasive species
are often present at grazed sites, which
often leads to further management
actions (see Invasive Species and
Secondary Succession).
Of the 52 Dakota skipper sites
assessed, we found the level of impact
to Dakota skipper populations from
grazing to be high at 9 sites, moderate
at 29 sites, and low at 14 sites (Service
2012 unpubl. data; Service 2014,
unpubl. data). Moderate- to high-level
impacts to populations were primarily
at South Dakota sites (N=27)—other
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sites with moderate- to high-level
impacts were in Minnesota (N=7), North
Dakota (N=3), and Manitoba (N=1). As
described above as part of our
assessment of grazing, we examined the
habitat quality ratings that were
primarily assigned by researchers
during surveys for the species, during
separate habitat assessments, or that
were available from State heritage
databases or other sources of scientific
data. The habitat quality was rated as
poor at 7 of the 9 sites where grazing
poses a high level of impact to Dakota
skipper populations. At each of the 14
sites where grazing pressure is low,
habitat quality was good or excellent,
with two exceptions where habitat was
rated as fair to good. Among the 29 sites
where grazing is a moderate level of
impact to Dakota skipper populations, 6
had habitat rated good or excellent.
Of the 16 Poweshiek skipperling sites
for which we had sufficient information
to assess grazing, the level of impact to
populations from grazing is high at 4
sites, moderate at 10 sites, and low at 2
sites—all but 2 of these sites were in
South Dakota. No sites in Wisconsin or
Michigan were assessed for grazing
impacts to populations, where the
grazing does not occur. Among the 10
sites where grazing is a moderate level
of impact to Poweshiek skipperling
populations, 8 have habitat rated as fair
to excellent. The habitat quality was
rated as poor at 2 of the 4 sites where
grazing is having a high level of impact
to Poweshiek skipperling populations.
In summary, grazing may benefit
Dakota skippers and Poweshiek
skipperlings in native tallgrass prairie
by increasing native plant diversity and
patchiness of fires (Minnesota DNR
2006, p. 232). The economic benefit of
grazing to ranchers may also be a benefit
to the species by deterring conversion of
remnant prairies to row crop
agriculture. Grazing is a stressor to these
species, however, if it is not managed
with the goal of conserving nativeprairie vegetation that comprises
suitable habitat for Dakota skipper and
Poweshiek skipperling. Dakota skippers
and Poweshiek skipperlings may benefit
when prairie habitat is rested from
grazing for at least a part of each
growing season, if livestock are
precluded from removing too much
plant material (e.g., are moved when
stubble heights are 6–8 in (15–20 cm)
(Skadsen 2007, pers. comm.), and if the
timing of grazing for each field varies
from year to year (Skadsen 2007, pers.
comm.). Grazing management
recommendations may not be
universally applicable to all locations,
and may depend on the habitat type and
other ecological and physical conditions
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of the site. For instance, stubble heights
of 6–8 inches may be difficult to attain
in certain dry-mesic sites (ND NRCS
2013, pers. comm.).
Conversely, Dakota skipper and
Poweshiek skipperling populations may
be reduced or extirpated when too much
plant material is removed, when fields
are not rested for some portion of the
growing season, or fields are grazed
during the same period each year.
Grazing poses a current and ongoing
stressor of moderate to high level of
impact to populations where its
intensity is such that Dakota skippers
and Poweshiek skipperlings are unlikely
to thrive or even persist. Grazing poses
a likely future stressor where current
management is conducive to Dakota
skipper or Poweshiek skipperling
conservation, but where landowners
may allow excessive grazing in the
future, for example, where management
may change as a result of the changing
market prices of agricultural products.
Unsuitable grazing is an ongoing
stressor throughout much of the range of
the Dakota skipper and Poweshiek
skipperling (primarily in flat wet
prairies of Minnesota, North Dakota,
and South Dakota); grazing is not a
documented stressor at the Poweshiek
skipperling sites with present or
unknown status in Wisconsin,
Michigan, and Iowa or at most Dakota
skipper sites in Canada.
Haying
As with grazing and fire, haying
(mowing grasslands and removing the
cuttings) may maintain habitat for the
Poweshiek skipperling and Dakota
skipper, but as with any management
practice, appropriate timing, frequency,
and intensity are important. Poweshiek
skipperling habitat at Scuppernong
Prairie in Wisconsin, for example,
would have succeeded to shrubby or
forested habitat if it had not been hayed
each fall (Borkin 2011, in litt.)—it is
now one of the few sites in Wisconsin
that is occupied by the Poweshiek
skipperling. Nearly all of the Dakota
skipper sites in Canada where the
species is present are privately owned,
fall-hayed prairies (Westwood 2013,
pers. comm.).
Haying generally maintains prairie
vegetation structure, but it may favor
expansion of invasive species such as
Kentucky bluegrass. If done during the
adult flight period, haying may kill the
adult butterflies or cause them to
emigrate, and if done before or during
the adult flight period, it may reduce
nectar availability (McCabe 1979, pp.
19–20; McCabe 1981, p. 190; Dana 1983,
p. 33; Royer and Marrone 1992a, p. 28;
Royer and Marrone 1992b. p. 14;
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Swengel 1996, p. 79; Webster 2003, p.
10). Royer and Marrone (1992b, p. 14),
for example, ascribed the loss of a North
Dakota Poweshiek skipperling
population to June and July haying.
Several years of July haying may have
led to the Poweshiek skipperling’s
extirpation at Wakidmanwin Prairie in
South Dakota (Skadsen 2006b, p. 13).
The Dakota skipper was observed at the
Wakidmanwin Prairie in 2010 (Skadsen
2010, p. 6); however, it is not clear if the
management has changed since the
observation. Early June haying may have
eliminated Dakota skippers from at least
one site in North Dakota (Royer and
Royer 2012a, p. 72).
Hayed prairies are important
reservoirs of native-prairie plant
diversity; however, long-term annual
haying negatively impacts prairie plant
diversity (Jog et al. 2006, pp. 164–165).
Jog et al. (2006, pp. 164–165)
recommended diversifying management
to include, for example, periodic fire
and to forego annual haying to increase
plant species diversity. In a long-term
study of a prairie in southeastern
Wisconsin, a switch from late-season
haying to fire management led to
increased native plant diversity and
coverage of warm-season grasses,
although woody plant species also
increased (Rooney and Leach 2010, p,
319)—this increased plant diversity was
likely an expression of plants that were
already at that location.
Late-season haying may benefit
Dakota skipper populations (McCabe
1981, p. 190), and Dakota skipper
populations might be more common on
hayed prairies than on idle (not hayed)
prairies (Webster 2003, p. 10). Swengel
and Swengel (1999, p. 279) observed
significantly greater relative abundance
of Dakota skippers on hayed tracts
compared with either idle or burned
tracts in Minnesota, and Skadsen (2004,
p. 7) documented the extirpation of
Dakota skippers from a site after its
management switched from haying to
intensive grazing. Some remnant Dakota
skipper populations in the eastern
Dakotas are found on fall-hayed prairies
(Skadsen 1997, pp. 10–23; Royer and
Royer 2012b) as are many of the sites in
Manitoba (Webster 2003, p. 10). Webster
(2003, p. 8) found ‘‘healthy
populations’’ of Dakota skippers in
Manitoba on sites used as hay fields, as
described by the absence of standing
dead grass, low numbers of shrubs,
shorter bluestem grasses, and abundant
and readily observable nectar flowers, as
compared to un-hayed sites. Scarlet
Fawn Prairie in South Dakota, which is
hayed in the fall, is considered one of
the highest quality prairies in that State
(Skadsen 2012, pers. comm.). In the
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Dakotas, late-season (mid-August to
October) haying appears to minimize
impacts to the prairie butterflies,
although annual haying may diminish
the vigor of native, warm-season grasses
and reduce forb density in north-central
North Dakota (wet-mesic) habitats (Lenz
1999, p. 14; Skadsen 2009, p. 8).
Consistent late-season haying of
Poweshiek skipperling habitat in South
Dakota, appears to have facilitated the
expansion of green needlegrass (Stipa
viridula), a cool-season grass, and
prevented seed development in warmseason plants (Skadsen 2009, p. 8).
We assessed the level of impact of
haying to populations at 41 Dakota
skipper sites and 6 Poweshiek
skipperling sites with present or
unknown status where we had sufficient
information to assess the stressor
(Tables 3 and 4; Service 2012 unpubl.
data; Service 2014, unpubl. data).
Haying was considered to be a stressor
with a low or no negative impact on
populations where it is implemented
after the flight period (after
approximately August 1) and when
there is no reduction in the availability
of native plant species. Haying was
considered to be a stressor with a
moderate level of impact on
populations, where the exact timing or
extent of haying was unknown, but
there are: (1) One or more indications
that haying is resulting in a reduction in
nectar or larval food sources important
to the species due to timing or
frequency of mowing; (2) part of the
Dakota skipper or Poweshiek
skipperling habitat on the site is hayed
before August 1, but a substantial
proportion of habitat is not hayed and
not clearly subject to other stressors,
such as frequent fire or grazing (e.g.,
Smokey Lake site, North Dakota); or (3)
where haying occurs before or after
August 1, but the site is hayed no more
frequently than once every 3 years (e.g.,
Roy West Game Production Area, South
Dakota).
We considered haying to be a stressor
with a high level of impact on
populations where the site was hayed
prior to August 1 (e.g., Oaks Prairie,
North Dakota). At 29 of the 41 evaluated
Dakota skipper sites, current haying
practices are conducive (beneficial) to
Dakota skipper conservation, because it
is conducted after August 1 and is not
reducing native plant species diversity.
One or more indications that current
haying practices are slowly degrading
habitat quality for Dakota skippers has
been documented at 11 of the 41 sites.
At several sites in North Dakota, for
example, Royer and Royer (2012b, pp.
15, 21, 24, 45) noted a decrease in the
diversity and density of forbs at sites
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hayed annually. Haying is a stressor
with a high level of impact on
populations at 1 of the 41 Dakota
skipper sites assessed and a stressor of
moderate-level impacts to the
populations at 11 of the 41 Dakota
skipper sites assessed. Of the 6
Poweshiek skipperling sites evaluated,
haying was a stressor with moderatelevel impacts on populations at 3 sites
and was not considered to have highlevel impacts to the populations at any
of the 6 sites.
In summary, haying is a current and
ongoing stressor of moderate to high
level of impacts to Dakota skippers and
Poweshiek skipperlings at the few sites
where the site is normally hayed before
August and where annual haying is
reducing availability of larval food and
adult nectar plants. However, fall
haying is beneficial to both species,
specifically if it is conducted after the
flight period (after August 1), no more
than every other year, and there is no
indication that native plant species
diversity is declining due to timing or
frequency of haying. Haying is a current
stressor at a small number of sites for
both species; these sites occur primarily
in North Dakota and South Dakota.
Lack of Disturbance
While inappropriate or excessive
grazing, haying, and burning are
stressors to some Poweshiek skipperling
and Dakota skipper populations and
have led to the extirpation of others,
both species are also subject to the stress
of no management practices being
implemented. Prairies that lack periodic
disturbance become unsuitable for
Poweshiek skipperlings and Dakota
skippers due to expansion of woody
plant species (secondary succession),
litter accumulation, reduced densities of
adult nectar and larval food plants, or
invasion by nonnative plant species
(e.g., smooth brome) (McCabe 1981, p.
191; Dana 1983, p. 33; Dana 1997, p. 5;
Higgins et al. 2000, p. 21; Skadsen 2003,
p. 52). For example, Dakota skipper
numbers were reduced at Felton Prairie,
Minnesota, in tracts that had not been
hayed or burned for several years
(Braker 1985, p. 47). Another study also
observed significantly lower Dakota
skipper abundance on unmanaged or
idle sites, compared with hayed sites;
however, Poweshiek skipperlings were
significantly denser with idling
(Swengel and Swengel 1999, p. 285).
Skadsen (1997, pp. 10–23; 2003, pp. 8,
35, 42) reported deterioration of several
unburned and unhayed South Dakota
prairies in just a few years due to
encroachment of woody plants and
invasive species and found lower
species richness of prairie-dependent
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butterflies and lower floristic quality at
sites with no disturbance versus sites
managed by grazing or fall haying
(Skadsen 2006a, p. 3). For example,
Dakota skippers returned to an idle site,
Pickerel Lake State Park, after a burn
conducted in 2007 resulted in a
significant increase in forbs, particularly
purple coneflower (Skadsen 2008, p. 2).
In a separate study, Higgins et al. (2000,
p. 24) found that prairie habitats left
idle had lower plant diversity and
quality than prairies managed with fire.
Populations of Dakota skippers and
Poweshiek skipperlings may also be at
risk at sites where a private landowner
is not aware of the presence or potential
presence of the species, but would
conserve the land if they were made
aware. The land use in some areas in
Canada, for example, are currently
inadvertently used in ways that are
favorable to the species (for example,
fall haying), but the land use may
change in the future (Westwood 2014,
pers. comm.). In the United States, the
Service has notified private landowners
of the presence or potential presence of
one or both species on their land at most
sites with present or unknown
occupancy and many sites that are
considered extirpated or possibly
extirpated but still may have suitable
habitat.
We assessed the stressor posed by
lack of management for populations at
17 Dakota skipper sites and 12
Poweshiek skipperling sites with
present or unknown status where we
had sufficient information to evaluate
the stressor (Tables 3 and 4; Service
2012 unpubl. data; Service 2014,
unpubl. data). Lack of management was
considered to be a stressor of moderatelevel impacts to the population where
the species’ habitat is degraded or likely
to become degraded due to secondary
succession, invasive species, or both,
but actions to restore habitat quality are
planned or ongoing, or where the site is
idle with no evident plans to initiate
management (e.g., fire, grazing, haying),
and there are signs of ongoing or
imminent secondary succession. Lack of
management was considered to be a
stressor with a high level of impact to
the population where the habitat quality
at a site is degraded or likely to become
degraded due to secondary succession
or invasive species, and there are no
ongoing or planned actions to maintain
or restore habitat quality. Lack of
management was considered to be a
stressor of low-level impacts to Dakota
skipper or Poweshiek skipper
populations at sites that are managed by
grazing, haying/mowing, or fire that
precludes loss of Dakota skipper or
Poweshiek skipperling habitat to
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secondary succession and invasive
species (e.g., smooth brome).
Nine of the 17 Dakota skipper sites
assessed are under high level of impact
to population due to lack of
management and 5 sites are under
moderate level of impact to the
population. Four of the 12 Poweshiek
skipperling sites assessed are under
high level of impact to the population
due to lack of management, and 6 sites
are under moderate level of impact to
the population. The Dakota skipper and
Poweshiek skipperling are unlikely to
persist at those sites where the level of
impact to the population due to lack of
management is high. Sites currently
under stress by lack of management
occur throughout the range of both
species; however, most of the present or
unknown sites that lack appropriate
management are in North Dakota, South
Dakota, Minnesota, and Michigan. In
summary, lack of disturbance is a
current and ongoing stressor to Dakota
skipper and Poweshiek skipperling
populations where woody vegetation or
invasive species expansion will reduce
native-prairie grasses and flowering
forbs.
Summary of Factor A
We identified a number of stressors to
the habitat of the Dakota skipper and
Poweshiek skipperling that operated in
the past, are impacting both species
now, and will continue to impact the
species in the future. The decline of
both species is the result of the longlasting effects of habitat loss,
fragmentation, degradation, and
modification from agriculture,
development, invasive species,
secondary succession, grazing, and
haying. Although efforts have been
made to effectively manage habitat in
some areas, the long-term effects of
large-scale and wide-ranging habitat
modification, destruction, and
curtailment will last into the future.
Invasion of the species’ habitat by exotic
species and woody vegetation,
overgrazing, long-lasting or permanent
alterations in water levels or hydrology,
and too frequent or improperly timed
haying remove or significantly reduce
the availability of plants that provide
nectar for adults and food for larvae.
Fire and flooding cause direct mortality
or destroy nectar and food plants if the
intensity, extent, or timing is not
conducive to the species’ biology.
Of the 160 Dakota skipper sites we
evaluated for one or more habitat
stressors, at least 131 sites have at least
one documented stressor with moderate
to high levels of impact to
populations—these sites are found
across the current range of the species
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in Minnesota, North Dakota, South
Dakota, Manitoba, and Saskatchewan
(Service 2012 unpubl. data; Service
2014, unpubl. data). Fifty-eight sites
have 2 or more documented stressors of
moderate to high levels of impact to
populations, and 24 sites have 3 or more
documented stressors of moderate to
high level of impact to populations.
Sites with three or more stressors are
found across most of the current range
of the species; these sites occur in
Minnesota, North Dakota, South Dakota,
and Manitoba (Service 2012 unpubl.
data; Service 2014, unpubl. data).
Furthermore, concurrently acting
stressors may have more intense effects
than any one stressor acting
independently. Therefore, based on our
analysis of the best available
information, present and future loss and
modification of Dakota skipper habitat
is a stressor that has significant impacts
on populations of the species
throughout all of its range. Habitatrelated stressors occur at sites with
Dakota skipper populations within
every State and province of occurrence.
Similarly, of the 60 Poweshiek
skipperling sites with present or
unknown status that we analyzed for
one or more habitat stressors, 46 of them
have at least one stressor at moderate to
high levels of impact to the population.
These sites are found across the current
range of the species and occur in Iowa,
Michigan, Minnesota, North Dakota,
South Dakota, Wisconsin, and Manitoba
(Service 2014, unpubl. data). Twentyfive sites have 2 or more documented
stressors that have moderate to high
levels of impact to the population.
These sites are found across the current
range of the species and occur in Iowa,
Michigan, Minnesota, North Dakota,
South Dakota, Wisconsin, and Manitoba
(Service 2014, unpubl. data). Eleven of
them have at least three documented
stressors that have moderate to high
levels of impact to the population.
These sites are found across the current
range of the species and occur in Iowa,
Michigan, Minnesota, South Dakota,
and Manitoba (Service 2014, unpubl.
data). Furthermore, concurrently acting
stressors may have more intense effects
than any one stressor acting
independently. Therefore, based on our
analysis of the best available
information, present and future loss and
modification of Poweshiek skipperling
habitat is a stressor that has significant
impacts on the species throughout its
range.
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Conservation Efforts To Reduce Habitat
Destruction, Modification, or
Curtailment of Its Range
In the past, funding for conservation
of rare species was primarily directed
toward federally listed or candidate
species, so while the Poweshiek
skipperling may have benefited
indirectly from conservation activities
focused on species such as the Dakota
skipper and Mitchell’s satyr
(Neonympha mitchellii mitchelli), it has
not generally been the primary focus of
those activities. As a result, survey data
and incidental life-history observations
have been accumulated as a part of
projects focused on other species, but
surveys were not necessarily focused on
Poweshiek skipperling sites and
detailed life-history, population, and
demographic data have generally not
been collected for the species. Various
conservation activities directed at the
Dakota skipper also indirectly benefit
the Poweshiek skipperling; these
activities are summarized below.
Conservation agencies have
recognized the need to address the
status of prairie butterflies for more than
30 years beginning with a 1980
workshop held to initiate studies of
Dakota skippers and other prairie
butterflies. In June 1995, the U.S. Fish
and Wildlife Service convened Dakota
skipper experts to outline tasks needed
to preserve enough viable populations
to ensure long-term security for the
species. The group outlined a plan for
surveying populations and
characterizing sites and habitats at
priority areas, identifying and
recommending management needs,
monitoring, and outreach and
education; however, this plan was not
drafted or finalized. In 1999, a Dakota
skipper recovery strategy meeting was
held in South Dakota with State,
Federal, and nongovernmental
biologists attending (Skadsen 1999b,
entire). In 2011, researchers in Canada
organized a Poweshiek Skipperling
Workshop and followup conference call
that brought together researchers and
managers from across the range of the
Poweshiek skipperling to provide
updates on survey data, discuss ongoing
activities, and plan future work. The
workshop resulted in specific
conservation action plans for the
species. The Minnesota Zoo organized a
followup conference during March 2013
to assess progress of the 2011 Poweshiek
Skipperling Workshop Action Plans,
facilitate discussion on the potential
effects of management activities on
prairie butterflies, identify needed
information and data gaps, establish
new priorities for research and a draft
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action plan for 2013, and facilitate
networking and collaborations focused
on the conservation of the Dakota
skipper and Poweshiek skipperling, as
well as other tallgrass prairie butterflies
in the Midwest—the Northern Tallgrass
Prairie Lepidoptera Conservation
Conference Working Group Report
Synthesis is posted at https://
www.mnzoo.org/Prairie
LepidopteraConference/Northern%
20Tallgrass%20Prairie%
20Lepidoptera%20Conservation%
20Conference%20Working%20Group%
20Reports%20-%20Synthesis.pdf.
Research and survey work has
occurred throughout the range of both
species to document populations, to
study the life history of both species,
and to examine the effects of various
management practices, such as fire and
grazing, on the species and their habitat.
For example, research and survey work
on Dakota skippers began with Dana’s
(1991, entire) doctoral study on fire
effects at Hole-in-the-Mountain,
Minnesota, beginning in 1978 and
McCabe’s (1981, entire) 1979 surveys for
the Garrison Diversion project in North
Dakota. Additional work has been
completed on characterizing habitat at
important Dakota skipper sites in
Minnesota (Dana 1997, entire) and
North Dakota (Lenz 1999, entire, Royer
and Royer 1998, entire, Royer and Royer
2012a, entire). Royer (2008, entire)
assessed abiotic habitat parameters of
soil in relation to management and
conservation of Dakota skippers to
complement prior floristic
characterization of these habitats. The
Minnesota DNR and the Service
planned to cooperatively study the
effects of grazing on the Dakota skipper
and Poweshiek skipperling (Selby 2003,
entire; Selby 2006b, entire); however,
skipper numbers were too low to collect
sufficient data to test hypotheses (Selby
2006b, p. 30).
In the past, the Service funded some
management activities intended to
benefit the Dakota skipper, including
habitat management at Big Stone
National Wildlife Refuge, Minnesota
(Olson 2000, entire), landowner contacts
and education on conservation practices
in South Dakota (Skadsen 1999b,
entire), and prairie vegetation
restoration at Chippewa Prairie in 2000
and at Twin Valley Prairie SNA,
Minnesota, in 2001. The results of these
efforts are varied; for instance, the
prairie habitat at Twin Valley Prairie
SNA was recently rated as excellent
quality (Service 2014, unpubl.
geodatabase), but the status of both
species at that site is unknown; the last
positive observation of Dakota skippers
and Poweshiek skipperlings was 1993
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and 1994, respectively. The Dakota
skipper is extirpated from Chippewa
Prairie, and the status of the Poweshiek
skipperling is unknown at the site; the
last positive observations of the species
were in 1995 and 1994, respectively
(Service 2014, unpubl. geodatabase).
The Service purchases easements to
prevent prairie conversion for
agriculture and provide cost-share to
support rotational grazing and other
practices that may benefit Dakota
skippers and Poweshiek skipperlings.
For example, in 12 counties in South
Dakota within the range of the species,
the Service’s grassland easement
program has protected 365,193 ac
(147,788 ha) of grassland that are
primarily native prairie (Larson 2013,
pers. comm.; HAPET 2012, unpubl.
data), although it is not clear whether
these lands are suitable habitat for either
species. Other Service fee title lands,
State lands, and Natural Resources
Conservation Service (NRCS) easement
lands may also protect areas from
conversion, depending on the
protections in those areas (Larson 2013,
pers. comm.). If easements are near
prairie butterfly habitat they can
minimize the impacts of conversion and
may provide dispersal corridors or
buffer sites from external stressors (e.g.,
pesticide drift).
Prairie easements generally prevent
grasslands from being plowed or
destroyed and prevent haying before
July 16, but may not restrict grazing,
pesticide use, or other practices that can
degrade the status of Dakota skipper or
Poweshiek skipperling populations. For
example, one property with a Service
easement was recently overgrazed to the
extent that Dakota skipper was
extirpated from the site (Skadsen 2006b,
p. 5). Cost-share partnerships on
easements and other areas, however,
may further enable landowners to
manage grasslands to benefit Dakota
skippers and other prairie endemic
species. The Service may implement
such actions through the Partners for
Fish and Wildlife program or in
collaboration with NRCS or other
agencies. Since 1990, the Service has
purchased easements to prevent
grassland conversion on millions of
acres in Minnesota, North Dakota, and
South Dakota (HAPET 2012, unpubl.
data). Only some of these areas include
Dakota skipper or Poweshiek
skipperling sites, are within the range of
either species, or include suitable
habitat for either species.
Conservation-interested agencies,
individuals, and Tribes in South Dakota
have made concerted efforts for decades
to conserve native prairie within the
Dakota skipper range. For example,
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there are approximately 54,000 ac
(21,853 ha) of fee title lands in grassland
that are managed by the Service in 12
of the counties within the historical or
current range of the Dakota skipper and
365,000 ac (147,710 ha) protected by the
Services’ grassland easement program
(HAPET 2012, unpubl. data; Larson
2013, pers. comm.). These acreages do
not include an additional 4,000 ac
(1,619 ha) of grass protected by
acquisitions that have occurred in 2012
(HAPET 2012, unpubl. data; Larson
2013, pers. comm.). Not all of these
lands, however, may be managed in
such a manner that is conducive to
Dakota skipper populations.
About one-half of the present or
unknown Dakota skipper sites (total
number of present/unknown sites is
171) in the United States are privately
owned (excluding populations on land
owned by The Nature Conservancy).
Twelve of these populations are on
private land on which the Service has
purchased conservation easements that
preclude plowing and haying before
July 16. Manitoba Habitat Heritage
Corporation has an easement that
overlaps with one Dakota skipper site in
Canada (Friesen 2013, pers. comm.).
Similarly, of the 70 privately owned
sites where Poweshiek skipperling has
been recorded since 1985, 8 sites (all in
Minnesota) have conservation
easements. These easements do not
prescribe grazing practices but are
intended to prevent grassland
conversion to cropland, which is
detrimental to Dakota skippers or
Poweshiek skipperlings. Additional
measures on some easement properties
could ensure grazing practices do not
inadvertently impact either species.
The Nature Conservancy’s Minnesota
and Dakotas offices initiated a Prairie
Coteau Coordinated Conservation
Planning Effort and Plan in 1998 to
facilitate conservation actions by
various landowners, including private,
county, state, tribal and Federal, on high
biodiversity prairie sites (Skadsen
1999b, entire). Additional partners
include conservation organizations,
local conservation districts, and
universities. The Nature Conservancy
acquired a reserve in the Sheyenne
Grassland area, Brown Ranch, which is
a Dakota skipper site with an unknown
status, and manages some of the most
significant habitats for the two species
in Minnesota, including the Hole-in-theMountain Prairie preserve. Based on
intensive surveys in 2007, Dana (2008,
p. 19) found ‘‘considerable reassurance’’
that the rotational burning approach
used at Prairie Coteau SNA and Hole-inthe-Mountain Preserve is compatible
with long-term persistence of the Dakota
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skipper, for example, by controlling
woody vegetation encroachment. The
Minnesota DNR also manages the Prairie
Coteau SNA with rotational burning
(Dana 2008, p. 19), which may control
woody vegetation encroachment. The
Clay County Stewardship Plan (Felton
Prairie Stewardship Committee 2002)
may have reduced the likelihood and
severity of gravel mining within the
Felton Prairie complex in Minnesota.
Many of the best sites for Dakota
skipper and Poweshiek skipperling in
South Dakota are on tribal lands
managed by the Sisseton-Wahpeton
Sioux Tribe (e.g., Scarlet Fawn and Oak
Island Prairies) (Skadsen 1997, Skadsen
2012b, p. 3), with late-season haying.
According to Skadsen (2012, p. 3) ‘‘. . .
as in prior years, the fall hayed prairies
held in trust by the Sisseton Wahpeton
Oyate had the most diverse native flora
and thus the largest numbers of Dakota
skippers.’’ Although these lands
generally contain high-quality habitat
for prairie butterflies in eastern South
Dakota (Skadsen 2012b, p. 3), a change
to alternate year haying—instead of
annual haying—may further improve
habitat quality by ensuring that plants
that flower during the Dakota skipper
and Poweshiek skipperling flight
periods are able to produce seed (Royer
and Royer 2012b, p. 15).
The Day County Conservation
District, South Dakota, places a high
priority on implementing prescribed
grazing on rangelands known to support
Dakota skippers and bordering sites in
the Upper Waubay Basin Watershed
(Skadsen 1999b, p. 3). Their efforts
include soliciting grants and providing
education on grazing management,
controlled burning, and integrated pest
management to control leafy spurge,
through workshops and a demonstration
site. There are five Poweshiek
skipperling sites in Day County with
unknown occupancy and no sites where
the species is considered to be present.
There are a total of 24 Dakota skipper
sites in Day County: 3 sites where the
species is considered to be present, 11
sites that have an unknown occupancy,
and the remaining are extirpated or
possibly extirpated. It is not known how
many of these sites are benefiting from
these efforts and to what degree.
In South Dakota, completed
management plans guide habitat
restoration at Hartford Beach State Park
and Pickerel Lake State Recreation Area
(Skadsen 2008, pp. 4–7; Skadsen 2011,
pp. 1–4). At each site, the lack of
haying, grazing, or fire had allowed
plant succession to degrade and reduce
the extent of Dakota skipper habitat.
Dakota skipper habitat at these sites is
divided into 3–4 management units. A
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controlled burn was conducted in one
unit at Hartford Beach State Park in
2008, and shrubs were removed from
two of the units (Skadsen 2008, p. 4). At
Pickerel Lake State Recreation Area, a
controlled burn was conducted in 2007,
and in 2008 the site was hayed and
shrubs were removed. The Dakota
skipper was present in the burned unit
for the first time since 2002 after ‘‘a
dramatic increase in forbs, especially
purple coneflower, occurred after the
burn’’ and ‘‘apparently attracted Dakota
skippers from a nearby site’’ (Skadsen
2008, p. 2). The Poweshiek skipperling
is extirpated from both sites, but the
reasons for its disappearance are not
known (Service 2012, unpubl. data). At
each site, prescribed fire and brush
control are implemented on a rotational
basis (Skadsen 2011, pp. 1–4); at
Pickerel Lake State Recreation Area,
forbs were planted in 2011 to diversify
nectar resources for prairie butterflies
(Skadsen 2011, pp. 2–4).
A privately owned ranch with Dakota
skippers in Day County, South Dakota,
is managed with a patch-burn grazing
system in which each grazing unit is
rested for a full year (Skadsen 2008, p.
10), which may be beneficial to the
species. The effects of patch-burn
grazing at this site are being studied
jointly by The Nature Conservancy and
South Dakota State University (Skadsen
2008, p. 10).
In 2005, the Service’s National
Wildlife Refuge System in North Dakota
and South Dakota adopted the
Conservation Strategy and Guidelines
for Dakota Skippers on Service Lands in
the Dakotas, which are based on the
Service’s Dakota Skipper Conservation
Strategy and Guidelines and on versions
of the Service’s conservation guidelines
for Dakota skipper. The guidelines were
revised in March 2013 (https://
www.fws.gov/midwest/endangered/
insects/dask/DASKconservation
guidelines2013.html). In the Dakotas,
the Service plans to implement the
conservation guidelines on all of its
lands where the Dakota skipper is
known to occur—the Service owns 12
Dakota skipper sites in the Dakotas
where the species is considered present
or has unknown occupancy. The
guidelines also suggest that the Service
examine other lands under its
ownership to determine whether
unrecorded populations of Dakota
skippers may be present and to conduct
surveys in those areas or manage the site
in accordance with the Dakota Skipper
Conservation Strategy and Guidelines.
These guidelines will be reviewed and
updated to reflect new information as it
is developed.
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In Manitoba, August 1st is the
recommended earliest haying and
grazing date at Dakota skipper sites. The
recommended intensity of grazing is to
be as low as economically feasible to
prevent permanent damage to sites (e.g.,
destruction of nectar plants). In
Manitoba, it is recommended that sites
that have burned or have been impacted
by other factors such as extensive
flooding, should not be grazed for at
least one year following these events.
Poweshiek Skipperling
Most of the conservation initiatives
discussed above were put in place to
benefit the Dakota skipper, but may also
benefit the Poweshiek skipperling.
Conservation initiatives are also in place
at several Poweshiek skipperling sites in
Wisconsin and one or two sites in
Michigan.
At least two sites occupied by
Poweshiek skipperling in Michigan are
at least partially owned and managed by
the Michigan Nature Association
(MNA); however, the MNA does not
specifically manage for Poweshiek
skipperling conservation. The State of
Michigan owns part or all of four
occupied Poweshiek skipperling sites;
however, most of those lands are
managed as State recreational areas, not
for prairie butterfly conservation.
Landowners at one fen site are
participating in a Michigan DNR Land
Incentive Program, and a portion of
another occupied site is part of the Burr
Memorial Prairie Plant Preserve
(Michigan Natural Features Inventory
2011, unpubl. data). The Poweshiek
skipperling may benefit from
conservation activities in place for the
federally endangered Mitchell’s satyr at
one Michigan site.
Poweshiek skipperling sites in
Wisconsin are owned and managed by
the Wisconsin DNR, who manage the
land to maintain and improve prairie
habitat. The Wisconsin DNR recently
received a Sustain Our Great Lakes
(SOGL) grant to conduct invasive
species management on several SNAs,
including Puchyan Prairie (Wisconsin
DNR 2012, in litt.). The Scuppernong
Prairie SNA, Wilton Road, and Kettle
Moraine Low Prairie SNA are managed
primarily through fire and invasive
species control.
Furthermore, the Minnesota Zoo
recently initiated a propagation research
program for the Poweshiek skipperling
and Dakota skipper to develop methods
to propagate these and other species in
the future. If this program is successful,
a conservation benefit could be possible
if the program could facilitate
reintroduction and augmentation efforts
into areas where the species has
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declined or disappeared. Furthermore,
this propagation effort may lead to
increased knowledge of basic biology
and life history of both species.
To summarize, the conservation
initiatives discussed above may
ameliorate one or more stressors on
populations of Dakota skipper and
Poweshiek skipperling at a relatively
small number of sites. Approximately
12 Dakota skipper sites and 8 Poweshiek
skipperling sites benefit from
conservation easements; an additional
12 Dakota skipper sites are owned by
the Service and may benefit from
implementation of Dakota skipper
conservation guidelines; 2 sites in State
parks are undergoing prairie restoration
and management; approximately 5
additional Dakota skipper sites and 4
Poweshiek skipperling sites are
managed to benefit prairie butterflies,
such as rotational fire management.
Since numerous sites have two or more
stressors of moderate to high-level
impacts to one or both species, all
stressors are likely not completely
ameliorated at many sites. Initiatives
such as captive propagation and studies
of the effects of various management
techniques may be applied broadly and
may be beneficial to each species as a
whole—the timeframe for these benefits
to be realized, however, will not be
immediate.
Factor B. Overutilization for
Commercial, Recreational, Scientific, or
Educational Purposes
Although its biology could make the
Dakota skipper sensitive to collection at
some locations, the present level of
scientific collection is minimal and
recreational collecting is unlikely (Royer
and Marrone 1992a, p. 27). Collection is
not known to be a stressor for the
Poweshiek skipperling (Royer and
Marrone 1992b, p. 16). Collection is not
currently a stressor to either species in
Canada (COSEWIC 2003, p. 18).
Scientific Collectors Permits are
required in states where both species
have legal protection, and permission is
often required to collect specimens on
protected areas. Furthermore, these
species are not collected for commercial
purposes; the drab coloration likely
makes both species less desirable for
collectors and the remoteness of
occupied habitat and limited flight
period would make recreational
collections difficult (Borkin 2012, pers.
comm.). Therefore, overutilization for
commercial, recreational, scientific, or
educational purposes is not currently a
threat to Dakota skipper and Poweshiek
skipperling.
Handling stress during scientific
study may be stressors to individuals of
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both species. Adverse effects on
butterflies have been documented for a
wide range of species (e.g., Benson and
Emmel 1973, p. 329; Singer and
Wedlake 1981, pp. 215–216; Lederhouse
1982, pp. 381–382; Morton 1984, pp.
56–57; Mallet et al. 1987, pp. 380–383).
Although recreational collection is
not a threat to these species at this time,
due to the few populations, small
population size, and restricted range, if
any recreational collecting did occur in
the future, even limited collection from
the remaining small and isolated
populations could have deleterious
effects on these species’ reproductive
and genetic viability.
Factor C. Disease or Predation
Diseases or parasites that are specific
to the Dakota skipper or Poweshiek
skipperling are not known, but some
parasitism or predation likely occurs
during each of the life stages. Disease
and predation are part of the natural
population dynamics of any insect,
including the Dakota skipper and
Poweshiek skipperling—without high
rates of mortality before reproduction,
populations would increase
exponentially. The small amount of
observations of predation and
parasitism makes documenting those
phenomenons difficult (Dana 2013,
pers. comm.). Only a few studies have
attempted to document parasitism and
predation. For example, 10 of 130 eggs
tagged for field observation in a 1994
study of a Wisconsin Poweshiek
skipperling population appeared to have
suffered from predation or parasitism
(Borkin 1995, p. 5); some were
punctured and had the contents
extracted, and others turned black and
dried up. Dana (1991, pp. 19–21)
documented some parasitism of Dakota
skipper and Ottoe skipper (Hesperia
ottoe) eggs and larvae by various wasp
species and predation by various
insects, such as ants, but escaping his
observation would have been predation
by birds and small mammals on these
immature stages (Dana 2013, pers.
comm.).
Wolbachia, ubiquitous intercellular
bacteria estimated to affect 20–70
percent of all insect species, including
many butterfly species, affects the
reproductive ecology of its host
(Kodandaramaiah 2011, pp. 343–350). It
is uncertain if Wolbachia are affecting
the Dakota skipper or Poweshiek
skipperling. An infection of Wolbachia
may reduce already small population
sizes and increase the probability of
extirpation (Nice et al. 2009, pp. 3137–
3138), particularly if the population is
infected with a novel strain (Runquist
2013, pers. comm.). The Minnesota Zoo
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plans to conduct Wolbachia screening
and strain identification of genomic
DNA samples that the University of
Michigan (at Dearborn) extracted from
both species. The effects of predation by
birds or insects on Dakota skipper or
Poweshiek skipperling population
dynamics are not known and may
impact the species.
McCabe (1981, p. 187), noted three
kinds of predators to Dakota skippers,
including Ambush bugs (Hemiptera:
Phymata sp.), flower spiders (Aranaea:
Misumena spp.), and orb weavers
(various Araneldae). Flower spiders and
ambush bugs are effective predators of
nectar-feeding insects (McCabe 1981,
pp. 187–188) and may cause mortality
to some individuals, but it is difficult to
quantify the population-level impacts of
predators to either the Dakota skipper or
Poweshiek skipperling. Dana
documented predation on adult
skippers by robber flies (Asilidae),
which are common in upland prairie
habitats, and noted the incidence of
wing damage indicative of an
unsuccessful attack by a bird or similar
predator (Dana 1991, pp. 26–27; Dana
2013, pers. comm.). Several incidences
of predation by crab spiders and robber
flies on both the Dakota skipper and
Poweshiek skipperling have been
documented in Canada, although it is
not thought to be a common occurrence
(Westwood 2013, pers. comm.). McCabe
(1981) failed to observe bird or
dragonfly predation; however these
events are difficult to observe (Dana
2013, pers. comm.). Orb weaver spiders
appear to be successful predators of
‘‘old, worn individuals’’ (McCabe 1981,
p. 188), but bird and other animal
predation on young and old adults
likely occurs when the butterflies are
roosting or torpid and unable to escape
(Dana 1991, p. 27).
Disease, parasitism, and predation are
important parts of population dynamics
of normal populations of insects, but
may have an amplified effect on small
populations. Furthermore, as we discuss
in the possibility of unknown factors
that may be affecting the species (in
Factor E of this final rule), it is possible
that a new virulent pathogen or
parasitoid may have increased mortality
above normal levels and may be causing
the rapid decline in the Poweshiek
skipperling and possibly also the Dakota
skipper (Dana 2013, pers. comm.).
Disease and parasitism are a serious
hypothesis that may explain the rapid
decline of the Poweshiek skipperling,
and perhaps the Dakota skipper, and
these factors, along with predation, are
extremely difficult to observe.
Therefore, we are unsure if either
disease, parasitism, or predation are
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significant stressors to the Dakota
skipper or Poweshiek skipperling
populations at this time, and we are not
certain if these stressors will contribute
to significant population-level impacts
in the future. However, in the future,
disease, parasitism, and predation may
have an amplified effect on these small
and isolated populations.
asabaliauskas on DSK5VPTVN1PROD with RULES
Factor D. The Inadequacy of Existing
Regulatory Mechanisms
Existing regulatory mechanisms vary
by location, but generally do not
mitigate for the numerous stressors that
the Dakota skipper and Poweshiek
skipperling face.
State Regulations
The Dakota skipper is listed as
endangered under Minnesota’s
endangered species statute. Under the
Minnesota statute, a person may not
take, import, transport, or sell any
portion of an endangered species of
wild animal or plant, or sell or possess
with intent to sell an article made with
any part of . . . an endangered species
of wild animal or plant’’ except as
permitted by the Minnesota DNR
(Minnesota Statutes 2012, 84.0895). The
Poweshiek skipperling was listed as
State-endangered in Minnesota, and the
status of Dakota skipper was changed
from threatened to endangered on
August 19, 2013 (Minnesota DNR 2013).
The Poweshiek skipperling is listed as
threatened under State endangered
species statutes in Iowa and Michigan
and as endangered in Wisconsin. The
Dakota skipper is listed as endangered
under State endangered species statutes
in Iowa. South Dakota has an
endangered species act, but no
invertebrates are currently listed. South
Dakota put forth a proposal to add the
Dakota skipper to the State endangered
species act list, but it was not finalized.
Although the Dakota skipper is not
listed as threatened or endangered
under South Dakota’s endangered
species statute, the State natural
heritage program considers the species
to be imperiled because of rarity due to
very restricted range and very few
populations. North Dakota does not
have a mechanism for conferring
protection to threatened or endangered
species at the State level.
State endangered species statutes
provide State natural resource or
conservation agencies with the authority
to regulate collection of individuals and
related activities (for Poweshiek
skipperling in Iowa, Michigan, and
Wisconsin and Dakota skipper in
Minnesota and Iowa), but we have no
information to suggest that collection is
a stressor that impacts populations of
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the species. With the exception of the
regulation of some incidental take in
Wisconsin and Minnesota, the statutory
protections afforded by these State
statutes may do little to protect or
mitigate Poweshiek skipperling or
Dakota skipper from non-collection
threats. While some stressors may result
in direct mortality of both species, such
as ill-timed fires, most stressors to the
species are indirect and State laws that
regulate direct harm to the species do
not address these factors. In Iowa, for
example, Poweshiek skipperling
populations are likely now extirpated
due to habitat destruction and
conversion and other undetermined
stressors, despite the species’ presence
on the State’s list of threatened species
since 1994. In Wisconsin, where
stressors from actions that may
incidentally take Poweshiek
skipperlings may be addressed in
conservation plans, State endangered
species protections do not protect the
species from stochastic events and
habitat fragmentation that are stressors
to the State’s small and isolated
populations.
In North Dakota, the fundamental
purpose of the North Dakota Trustlands
(e.g., State school lands) management is
to obtain a ‘‘fair market’’ return from the
lands while maintaining or improving
their condition and value (ND
Department of Trustlands Web site
https://www.land.nd.gov/surface/
About.aspx). Consequently, if such land
does not produce income for the State,
it may be subjected to deliberate change
in management strategy or ownership
(e.g., sale at auction). The major source
of income on the North Dakota
Trustlands is from grazing and
agricultural leases, with additional
revenue generated from rights-of-way,
salt water disposal, and gravel and
scoria mining (ND Department of
Trustlands Web site https://
www.land.nd.gov/surface/About.aspx).
At least two Dakota skipper sites are
under North Dakota State School
management and are managed as hay
lands.
Federal Regulations
The U.S. Forest Service (Forest
Service or USFS) has designated the
Poweshiek skipperling and the Dakota
skipper as sensitive species (a species
identified by a Regional Forester for
which population viability is a concern)
in North Dakota (Forest Service 2011).
The Forest Service’s objectives for
sensitive species benefit Dakota skipper
and Poweshiek skipperling where they
occur (or could occur) on USFS lands;
however, the majority of populations of
both species do not occur within USFS
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63733
lands. The Poweshiek skipperling has
been documented at two sites on the
Sheyenne National Grasslands;
however, it has not been observed since
2001 at one site and 1996 at the other.
Therefore, these Forest Service
objectives, although promising, have
little ability to affect the rangewide
status of the species. If Forest Service
lands were to be occupied by either
species in the future, these objectives
may benefit the species at a local scale.
Canadian Regulations
Dakota skipper and Poweshiek
skipperling are listed as threatened
under Canada’s Species at Risk Act
(SARA) (Environment Canada 2012.
Species at Risk Act Public Registry.
<https://www.registrelepsararegistry.gc.ca/sar/index/default_
e.cfm>. Accessed September 19, 2014).
Under SARA, take of both species is
prohibited on Canadian Federal lands,
but the Poweshiek skipperling occurs
only on non-Federal lands in Canada,
and only four or five Dakota skipper
sites are on Federal lands (Coalfields
Community Pasture) in Canada. The
Federal Cabinet may create an order
extending SARA’s powers (e.g., to
private lands) if a species is
insufficiently protected by provincial
laws; however, such action has not been
taken for either of these species. In May
2014, the COSEWIC status designation
of Dakota skipper was changed from
threatened to endangered (https://
www.cosewic.gc.ca/rpts/detailed_
species_assessments_e.html accessed
September 19, 2014). The Dakota
skipper is listed as threatened under the
Manitoba Endangered Species Act, and
it is, therefore, unlawful to kill, injure,
possess, disturb, or interfere with the
Dakota skipper; destroy, disturb, or
interfere with its habitat; or damage,
destroy, obstruct, or remove a natural
resource on which the species depends
for its life and propagation (Manitoba
Endangered Species Act https://
www.gov.mb.ca/conservation/wildlife/
legislation/endang_act.html, accessed
February 7, 2012). The Poweshiek
skipperling was recently listed as
endangered in Manitoba (https://
www.gov.mb.ca/conservation/wildlife/
sar/sarlist.html, accessed December 28,
2012). There is no legal basis for
protecting threatened or endangered
invertebrates in Saskatchewan, but since
both species are listed under SARA, the
national government could step in to
protect the species in the province if the
province does not act to protect the
species (Environment Canada. 2012.
Species at Risk Act: A Guide. https://
www.sararegistry.gc.ca/approach/act/
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Guide_e.cfm, accessed February 7,
2012).
To summarize, some of the regulatory
mechanisms discussed above are
beneficial to populations of Dakota
skipper and Poweshiek skipperling at a
local scale; however, most do not
ameliorate stressors except for harm to
individuals in certain States. With the
exception of the regulation of some
incidental take in Wisconsin,
Minnesota, and Canada, the statutory
protections afforded by these statutes
may do little to protect Poweshiek
skipperling or Dakota skipper from noncollection stressors.
asabaliauskas on DSK5VPTVN1PROD with RULES
Factor E. Other Natural or Manmade
Factors Affecting Its Continued
Existence
Habitat Fragmentation and Population
Isolation
As habitat specialists, habitat
fragmentation has a strong negative
effect on the distribution and abundance
of the Dakota skipper and Poweshiek
skipperling because both are dependent
on remnant native tallgrass prairie or
native mixed-grass prairie, and, in
Michigan, Poweshiek skipperling
depends on native prairie fens. Habitat
fragmentation reduced once-extensive
areas of these habitats to a collection of
patches of varying quality and isolation.
The probability of extinction within
patches can be determined primarily by
degradation of habitat quality,
management techniques (e.g., haying,
prescribed burns), and likelihood of
stochastic events, such as wildfire or
floods.
Fragmentation of tallgrass prairie has
degraded the genetic diversity of
remaining Dakota skipper populations
(Britten and Glasford 2002, pp. 371–
372). What may have once been a single
population of Dakota skippers spread
across formerly extensive tallgrass and
mixed-grass prairie (McCabe 1981, p.
184) is now fragmented into about 171
separate sites where the species is
known to be or may still be present
(sites with present (83) or unknown (88)
status). The small genetic differences
among seven Dakota skipper
populations in the southern portion of
the species’ range suggest that they were
formerly connected (Britten and
Glasford 2002, pp. 371–372). Each
Dakota skipper population is now
subject to genetic drift that may erode
its genetic variability over time and
possesses genetic qualities indicative of
inbreeding (Britten and Glasford 2002,
pp. 371–372). Inbreeding lowers the
capacity of local populations to adapt to
environmental changes and may
magnify the effect of deleterious alleles
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(genes with undesirable effects on
individuals or populations) (Nieminen
et al. 2001, pp. 242–243).
Preliminary results of genetic studies
on the Poweshiek skipperling show that
there appears to be limited levels of
genetic diversity in the 32 tissue
samples that were collected from the
Scuppernong Prairie site in Wisconsin,
7 samples from Manitoba, and 93 from
6 Michigan populations in 2012
(Saarinen 2013, pers. comm.). Of greater
concern than loss of genetic diversity,
however, may be demographics,
specifically the limited number of
populations and population sizes that
may be too small to persist (Saarinen
2013, pers. comm.) compounded by
other stressors.
Poweshiek skipperlings are not wide
dispersers (Burke et al. 2011, p. 2279;
Fitzsimmons 2012, pers. comm.);
species experts have estimated
maximum dispersal distance to be less
than 1.6 km (1.0 mi) (Westwood 2012b,
pers. comm; Dana 2012b, pers. comm.).
Its mobility, however, has been ranked
as less than that of Dakota skipper
(Burke et al. 2011, p. 2279; Fitzsimmons
2012, pers. comm.); therefore, a more
conservative maximum dispersal
distance may be more similar to that of
the Dakota skipper (less than 1 km (0.6
mi)). Most individuals may remain
within a single habitat patch during
their 5–7 day adult life span; therefore,
local extinctions of the Poweshiek
skipperling on isolated habitat
fragments are likely permanent unless
one or more populations located within
1.0–1.6 km (0.6–1.0 mi) are large enough
to produce immigrants to reestablish
populations. Furthermore,
fragmentation of tallgrass prairie began
in about 1830, and at least 85 to 99
percent of the original prairie is now
gone across the species’ ranges (Samson
and Knopf 1994, p. 419). As a result,
Poweshiek skipperling and Dakota
skipper populations are now scattered
in fragments of this once-vast
ecosystem. The Poweshiek skipperling
may not move across barriers; for
instance, in Manitoba, Poweshiek
skipperlings have been observed
avoiding dispersal over short distances,
even to suitable habitat, if a barrier such
as a road exists between suitable prairie
habitat or nectar sources (Westwood et
al. 2012, p.18). Repopulation of
Poweshiek skipperling sites after
extirpation has been observed (e.g., after
a flood) (Saunders 1995, p. 15), but
source populations need to be adjacent
or very close.
Similarly, adult Dakota skippers have
a short (5- to 7-day) life span (Dana
1991, p. 32) and an estimated maximum
dispersal distance to be no greater than
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1 km (0.6 mi) between patches of prairie
habitat separated by structurally similar
habitats (Cochrane and Delphey 2002,
pp. 6, 32). Therefore, Dakota skipper
and Poweshiek skipperling habitat
patches separated by more than 1 km
(0.6 mi) are effectively isolated from one
another (McCabe 1981, p. 190; Swengel
1998). Extirpation of small, isolated
populations may occur over many years
in some cases, but may be inevitable
where immigration from nearby
populations is not possible (Hanski et
al. 1996, p. 535).
Because Dakota skipper and
Poweshiek skipperling habitat is highly
fragmented and because the species are
subject to local extinction, their ability
to disperse to reoccupy vacant habitat
patches may be crucial for their longterm persistence. Patch isolation and
decreased permeability of surrounding
habitat acts as a dispersal barrier
between patches, ultimately decreasing
genetic diversity within the patch
through genetic drift and inbreeding. If
we assume isolation occurs when a
patch is more than 1.6 km (1.0 mi) from
another patch, then about 45 percent of
Poweshiek skipperling locations with
present or unknown status are
effectively isolated, and would not be
recolonized if extirpated (Service 2012
unpubl. data; Service 2014, unpubl.
data). Using a more conservative
maximum dispersal of 1.0 km (0.6 mi),
approximately 55 percent of Poweshiek
skipperling locations with present or
unknown status are effectively isolated.
Isolation was a factor in loss of a site at
Hartford Beach State Park, South
Dakota, where the Poweshiek
skipperling was extirpated due to
habitat succession and exotic plant
invasion (Skadsen 2009, p. 4; Skadsen
2010, pers. comm.), but was located too
far from a source population for natural
recolonization to occur. Improved
prairie management has since markedly
improved habitat quality, but the
species has not been detected since
2006 at Hartford Beach State Park
(Skadsen 2009, p. 4; Skadsen 2012, p. 4;
Service 2014, unpubl. geodatabase). For
Dakota skipper, if we use a maximum
dispersal distance of 1 km (0.6 miles),
approximately 63 percent of Dakota
skipper sites with present or unknown
status are effectively isolated (Service
2014, unpubl. geodatabase).
This simple analysis, however,
probably underestimates the impacts of
habitat fragmentation on the species.
Populations of both species may only be
near others that are too small to produce
sufficient numbers of immigrants. This
is true for the Poweshiek skipperling in
Scuppernong Prairie in Wisconsin, for
example, which is about 0.3 km (0.2 mi)
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from the Wilton Road population; fewer
than 100 individuals have been counted
at this site each year, and the species
was not observed in 2013 (See
Population Distribution and Status).
Numbers at Wilton Road are currently
too small (fewer than 12 individuals
counted each year) to produce sufficient
numbers of emigrants to Scuppernong
Prairie to reestablish a viable population
in the event of the latter’s extirpation.
There is no population of Poweshiek
skipperlings near the Puchyan Prairie
site (which is about 115 km (71 mi) from
the nearest site in Wisconsin);
additionally, only a few individuals
have been observed at this site each
year. In North Dakota, Orwig (1997, p.
3) found that a 6-ha (15-ac) patch of
Poweshiek skipperling habitat at
Hartleben Prairie was connected by
grassland to another Poweshiek
skipperling population, but neither was
considered a robust population at the
time and the species was not observed
at either location in 2013. Only 2 of the
9 Poweshiek skipperling sites with
present status in Michigan are located
within 1.6 km (1 mi) of another site; the
rest are completely isolated from other
populations. Furthermore, most of these
populations consist of few individuals
(see Population Distribution and
Status). Poweshiek skipperlings at Little
Goose Lake Fen, for example, are
separated from other populations by at
least 8 km (5 mi)—too far for immigrants
to repopulate the site. Furthermore,
Little Goose Lake Fen may contain too
few Poweshiek skipperlings (Michigan
Natural Features Inventory 2011,
unpubl. data; Cuthrell 2013, pers.
comm.) to generate sufficient numbers
of immigrants. In addition, poor habitat
quality negatively influences the
number and quality of emigrants
(Thomas et al. 2001, p. 1795; Matter et
al. 2009, p. 1467). Isolation is not likely
alleviated by connections to low-quality
habitats that are not capable of
producing emigrants at the numbers or
frequency sufficient to reliably
repopulate nearby patches.
Even with proper prairie management
at individual sites, extreme weather
patterns or severe weather events may
significantly impact Poweshiek
skipperling and Dakota skipper
populations, because they can occur
across a large geographic area. These
events include extremely harsh winters,
late hard frosts following a spring thaw,
severe storms, flooding, fire, or cool
damp conditions. Habitats isolated as a
result of fragmentation will not be
recolonized naturally after local
extirpations, as described above. Dakota
skipper and Poweshiek skipperling
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numbers may decline due to the
extirpation of isolated local populations
where recolonization is no longer
possible, even without further habitat
destruction (Schweitzer 1989,
unpaginated). The likelihood of
population extirpation may be directly
related to the size of habitat fragments.
For example, in systematic surveys on
Minnesota prairies, Swengel and
Swengel (1997, pp. 134–137; 1999, p.
284) found no Dakota skippers on the
smallest remnants (less than 20 ha (49
ac)), and significantly lower abundance
on intermediate size (30–130 ha (74–321
ac)) than on larger tracts (greater than
140 ha (346 ac)). These differences were
unrelated to vegetation characteristics;
habitat area did not correlate
significantly with vegetation type,
quality, or topographic diversity
(Swengel and Swengel 1999, p. 284).
We assessed the stressor of small size
and isolation of habitat for 163 Dakota
skipper sites and 54 Poweshiek
skipperling sites with present or
unknown status (Service 2012 unpubl.
data; Service 2014, unpubl. data). We
considered small size and isolation of
habitat to be a stressor with a low-level
impact on populations at sites that
contain more than 140 ha (346 ac) of
native prairie or the species’ habitat
onsite is located less than 1 km (0.6 mi)
from habitat occupied by the species on
another site. If the sum of native prairie
on the site under review plus that on the
nearby site(s) is less than 140 ha (346
ac), then this stressor was considered to
have a moderate or high impact on
populations. We considered small size
and isolation of habitat to be a stressor
with moderate impacts on populations
at sites where the species’ habitat is
greater than 1 km (0.6 mi) from any
other area where the species is present,
but contains more than 30 ha (74 ac) of
habitat for the species; or where the
species’ habitat is less than 1 km (0.6
mi) from occupied Dakota skipper and
Poweshiek skipperling habitat on
another site, but the sum of native
prairie on the site under review plus
that on the nearby site(s) is less than 140
ha (346 ac) and greater than 30 ha (74
ac). Sites that contain a small area of
Dakota skipper and Poweshiek
skipperling habitat—no more than 30 ha
(74 ac)—and that are not within the 1km (0.6-mi) estimated maximum
dispersal distance of occupied Dakota
skipper habitat are considered to have a
stressor of high magnitude to those
populations due to a combination of
their small size and isolation.
Although we were unsure of the size
of many sites in Canada, most sites were
separated by more than 1 km (0.6 mi).
Dakota skipper sites in central Manitoba
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63735
are generally greater than 158 ac (64 ha),
but all of the sites are separated by more
than 1 km (0.6 mi), and many sites are
separated by many kilometers
(Westwood 2013 pers. comm.).
Therefore, about 25 of the sites
evaluated in Canada were thought to
have at least a moderate level of stressor
from size and isolation. The Canada
sites where Dakota skippers are
considered to be present are
approximately 200 km (125 mi) from the
nearest North Dakota site, and the
Manitoba site is 166 km (103 mi) from
the nearest Poweshiek skipperling site
in Minnesota.
Dakota skipper populations on about
31 percent of the evaluated sites (50 of
163 sites) face a high level of impact due
to a combination of size and isolation
(Service 2012 unpubl. data, 2014
unpubl. data). Approximately 31
percent of evaluated sites (50 sites) face
a moderate level of impact to
populations due to small size and
isolation. About 39 percent of Dakota
skipper sites (63 of the 163 evaluated
sites) in the United States are either
sufficiently large (greater than 130 ha
(346 ac)) or are close enough to other
Dakota skipper populations that small
size and isolation is not a stressor.
Similarly, the stressor of small size and
isolation has a high level of impact on
Poweshiek skipperling populations on
about 39 percent of rated sites (25 of 54
sites), on 22 sites (41 percent) the
stressor is considered to have a
moderate level of impact to populations,
and on 20 percent (11 of the 54
evaluated sites) of the sites, we do not
consider a small size and isolation to be
a stressor. In a separate analysis strictly
looking at distances between Poweshiek
skipperling sites where the species is
present, we found that only 4 sites are
within 1 km (0.6 mi) of another site
where the species is present (Service
2014, unpubl geodatabase).
In summary, small, isolated
populations face a current and ongoing
stressor of moderate to high severity to
both the Dakota skipper and Poweshiek
skipperling. The stressor has a high
impact to populations when isolation is
combined with small habitat fragments
or small populations; for example,
where the population is too small to
supplement nearby populations without
adverse genetic consequences to the
source population. Isolated populations
occur throughout both species’ entire
ranges; only 4 of the 12 Poweshiek sites
with present status are within the
estimated maximum dispersal distance
from one another as are about 40
percent (64–69 of 171 sites) of Dakota
skipper sites with present or unknown
occupancy. The small populations are
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subject to erosion of genetic variability
leading to inbreeding, which lowers the
ability of the species to adapt to
environmental change. Small
populations occur rangewide for both
species; for example, surveyors have
counted fewer than 100 individuals in
all but 4 Poweshiek skipperling sites in
2011, all but one site surveyed in 2012,
and all sites surveyed in 2013.
Climate Change
Our analyses under the Act include
consideration of the likely effects of
ongoing and projected changes in
climate. The terms ‘‘climate’’ and
‘‘climate change’’ are defined by the
Intergovernmental Panel on Climate
Change (IPCC). ‘‘Climate’’ refers to the
mean and variability of different types
of weather conditions over time, with 30
years being a typical period for such
measurements, although shorter or
longer periods also may be used (IPCC
2013, p. 1450). The term ‘‘climate
change’’ thus refers to a change in the
mean or variability of one or more
measures of climate (e.g., temperature or
precipitation) that persists for an
extended period, typically decades or
longer, whether the change is due to
natural variability, human activity, or
both (IPCC 2013, p. 1450). Various types
of changes in climate can have direct or
indirect effects on species. These effects
may be positive, neutral, or negative and
they may change over time, depending
on the species and other relevant
considerations, such as the effects of
interactions of climate with other
variables (e.g., habitat fragmentation)
(IPCC 2007, pp. 8–14, 18–19). We use
our expert judgment and appropriate
analytical approaches to weigh relevant
information, including uncertainty, in
our consideration of various aspects of
climate change.
As is the case with all stressors that
we assess, even if we conclude that a
species is currently affected or is likely
to be affected in a negative way by one
or more climate-related impacts, it does
not necessarily follow that the species
meets the definition of an ‘‘endangered
species’’ or a ‘‘threatened species’’
under the Act. If a species is listed as
endangered or threatened, knowledge
regarding the vulnerability of the
species to, and known or anticipated
impacts from, climate-associated
changes in environmental conditions
can be used to help devise appropriate
strategies for its recovery.
Global climate change, with
projections of increased variability in
weather patterns and greater frequency
of severe weather events, as well as
warmer average temperatures, would
affect remnant prairie habitats and
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prairie fen habitats and may be a
stressor that has significant impacts on
prairie butterflies such as Dakota
skippers and Poweshiek skipperling
(Royer and Marrone 1992b, p. 12; Royer
and Marrone 1992a, pp. 22–23; Swengel
et al. 2011, p. 336; Landis et al. 2012,
p. 140). For example, climatic factors,
particularly precipitation and
evaporation, play an important role in
defining suitable Dakota skipper habitat
(McCabe 1981, pp. 189–192). Larval
Dakota skipper have ‘‘hydrofuge glands’’
that suggest an historical or present
need of the species for protection from
flooding (McCabe 1981, p. 181). Royer et
al. (2008, p. 2) hypothesize that
temperature and relative humidity at or
near the soil surface may be important
factors dictating larval survival,
particularly since early stages live in a
silken nest within a few centimeters (2–
3) (0.8–1.2 in) of the soil surface during
most of the summer (McCabe 1981, pp.
180–181, 189; Dana 1991, p. 16).
Furthermore, both species and their
habitats may experience the effects of
gradual shifts in plant communities and
an increase in catastrophic events (such
as severe storms, flooding, and fire) due
to climate change, which are
exacerbated by habitat fragmentation.
Isolated populations, specifically,
Dakota skipper populations and
Poweshiek skipperling populations that
are separated by more than about 1 km
(0.6 miles), are unlikely to recover from
local catastrophes unless sufficient
numbers are successfully reintroduced,
for instance, through artificial
propagation efforts.
Documentation of climate-related
changes that have already occurred
throughout the range of the Dakota
skipper and Poweshiek skipperling
(Johnson et al. 2005, pp. 863–871) and
predictions of changes in annual
temperature and precipitation in the
Midwest region of the United States,
such as Minnesota prairies
(Galatowitsch et al. 2009, pp. 2017),
Michigan fens (Landis et al. 2012, p.
140), South Dakota (Cochrane and
Moran 2011, entire), and throughout
North America (IPCC 2007, p. 9)
indicate that increased severity and
frequency of droughts, floods, fires, and
other climate-related changes will
continue in the future. Recent studies
have linked climate change to observed
or predicted changes in distribution or
population size of insects, particularly
Lepidoptera (Wilson and Maclean 2011,
p. 262). Native remnant prairies have
been reduced by 85 to 99.9 percent
across the range of both species (Samson
and Knof 1994, p. 419)—this fact,
coupled with the low dispersal ability of
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both species, makes it unlikely that
populations may expand to new areas,
for example, in a northward direction,
to adapt to changing climate. Climate
change is a stressor that has the
potential to have severe impacts on the
species; however, at this time our
knowledge of how these impacts may
play out is limited. All of the sites
within the range of both species are in
an area that will experience the effects
of climate change, but how those effects
will be manifested is uncertain.
Prairie Plant Harvesting
A potential, future stressor to the
Dakota skipper and Poweshiek
skipperling is collection of purple
coneflower (also known as black samson
echinacea), a predominate nectar source
for both species, for the commercial
herbal remedy market (Skadsen 1997, p.
30). Biologists surveying skipper
habitats have not reported signs of plant
collecting, but illegal or unregulated
harvest could become a problem in
Dakota skipper and Poweshiek
skipperling habitats due to economic
demand (Skadsen 1997, p. 30).
Currently, prairie plant harvesting is not
considered a threat that impacts the
species; however, this situation may
change if the demand for echinacea
increases.
Management for Invasive Species and
Succession
Native prairie and native prairie fens
must be managed to prevent the indirect
effects of invasive species and
succession (processes of change in
species structure to an ecological
community over time; secondary
succession is a disruption to succession
that occurs due to an event such as fire)
to Dakota skippers and Poweshiek
skipperlings. If succession progresses
too far, established shrubs or trees must
be removed in a way that avoids or
minimizes damage to the native prairie.
When succession is well advanced,
managers must use intensive methods,
such as fire management, to restore
prairie plant communities. If not done
carefully, these actions may themselves
harm local populations of the butterflies
(for example, see Factor A. The Present
or Threatened Destruction,
Modification, or Curtailment of Its
Habitat or Range). For example, once
smooth brome has invaded Poweshiek
skipperling or Dakota skipper habitat, it
is challenging to eradicate it while
minimizing harm to the butterflies.
Willson and Stubbendiecks (2000, p. 36)
recommended burning prairie habitats,
annually in some cases, to control
smooth brome at the stage when the
lateral shoots are elongating.
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In southwestern Minnesota and in
other parts of Dakota skipper’s range,
the optimum time to burn to control
smooth brome may occur during the
time that the adult butterflies are active.
Cutting or grazing to remove smooth
brome may have less intensive effects
on Poweshiek skipperling and Dakota
skipper larvae and could be used as an
alternative to fire, although these
techniques also pose a risk to both
species if carried out annually at
isolated sites. Puchyan Prairie is another
example of a small and isolated
population that is susceptible to
invasive species control efforts, if they
are not conducted properly (Swengel
and Swengel 2012, p. 6), although the
Wisconsin DNR proposed control efforts
that may improve habitat by removing
reed canary grass, Canada thistle, and
glossy buckthorn (Wisconsin DNR 2012
in litt.; Carnes 2012, in litt.).
If not appropriately managed with
fire, grazing, or haying, Poweshiek
skipperling and Dakota skipper habitat
is degraded due to reduced diversity of
native-prairie plants and eventually
succeeds to shrubby or forested habitats
that are not suitable for either species.
At Hartford Beach State Park in South
Dakota, for example, the Poweshiek
skipperling was extirpated (Skadsen
2009, p. 4) after lack of management led
to invasion by smooth sumac (Rhus
glabra) and quaking aspen (Populus
tremuloides) (Skadsen 2006a, p. 5). Lack
of management may also increase the
likelihood of invasion of exotic coolseason grasses, such as Kentucky
bluegrass and smooth brome (Mueller
2013, pers. comm.), which do not grow
when Dakota skipper and Poweshiek
skipperling larvae are feeding; thus a
prevalence of these grasses reduces food
availability for the larvae.
As with invasive species, actions
intended to reverse secondary
succession may be intensive and can
themselves affect Poweshiek skipperling
and Dakota skipper populations. For
example, Poweshiek skipperling
populations failed to recover after
prescribed burns were carried out at
Kettle Moraine Low Prairie SNA after it
had become overgrown (Borkin 2011, in
litt.).
Although carefully targeted herbicide
treatments result in beneficial control of
undesired plants, broadcast chemical
control of exotic plants such as aerial
spraying of leafy spurge and application
of broad-spectrum herbicides to control
weeds in pastures also eliminates native
forbs that are important nectar sources
for both species (Royer and Marrone
1992a, pp. 10, 16, 28, 29, 33, 1992b, p.
17, Orwig 1997, p. 7). For example,
invasion of native prairie by exotic
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species, primarily leafy spurge and
Kentucky bluegrass, as well as chemical
control of exotic species, are
documented stressors to Dakota
skippers at about 12 sites in North
Dakota (Royer and Royer 2012b, pp. 15–
16, 22–23). In repeated surveys, Royer
and Marrone (1992a, p. 33) observed a
correlation between the disappearance
of the Dakota skipper and the advent of
chemical weed control methods in
North Dakota, including the Sheyenne
National Grasslands. Royer and Marrone
(1992b, p. 17) cited the combination of
drought and grasshopper control
programs along the Red River Valley as
having serious impacts on the
Poweshiek skipperling. Dana (1997, p.
5) concluded that herbicide use for
weed and brush control on private lands
is the principal stressor to the Hole-inthe-Mountain complex in Minnesota,
where both butterfly species have been
documented.
Furthermore, herbicide or pesticide
use in concert with other management
types may amplify other stressors to the
butterflies. Skadsen (2006b, p. 11), for
example, documented the likely
extirpation of the Poweshiek skipperling
at Knapp Ranch in South Dakota after a
July 2006 application of broadleaf
herbicide associated with heavy grazing.
The degree and immediacy of the
impact posed by broadcast application
of herbicides or pesticides is not
precisely understood, but may be mostly
tied to the use of herbicides to control
invasive species on rangelands. If broad
applications of herbicides are used in
ways that remove plants from
rangelands that are important for
Poweshiek skipperling or Dakota
skipper, then this is a potential stressor
on all privately owned sites where
broadcast applications may occur.
Indiscriminant use of insecticides for
pest control on rangeland, adjacent
cropland, or forests is a stressor to
populations of Poweshiek skipperling
and Dakota skipper. Insecticides used in
agriculture, urban gardens, and forests
are a suspected cause of Colony
Collapse Disorder in bees by reducing
resistance to parasites and pathogens
and may have similar effects on other
insects (Beyers 2012, p. 1). Neonicotinyl
pesticides, such as the imidacloprid
compound, for example, are a
commonly used seed dressing that
spreads to nectar and pollen of
flowering crops (Whitehorn 2012, p. 1).
The use of neonicotinoids on
agricultural crops has dramatically
increased in the last ten years and they
are now the most widely used group of
insecticides in the world (Jeschke et al.
2011, pp. 2897–2898; Main et al. 2014,
p. 2; Goulson 2013, pp. 1–2).
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Neonicotinoids persist in the
environment (Goulson 2013, p. 1) and
are thought to accumulate in the soil
from repeated applications over time
(Hopwood et al. 2013, p. 4). Insects can
be exposed through multiple routes—
neonicotinoids are used in seed
dressings, foliar spray, soil irrigation
water, soil drench, granular in pastures,
tree injections, and topical applications
to pets.
In the United States, six
neonicotinoids are approved for use—
imidacloprid, thiamethoxam,
clothianidin, dinotefuran, thiacloprid,
and acetamiprid (EPA 2014 Web site)—
and it is estimated that more than 3.5
million pounds (56 million ounces) of
neonicotinoids were applied to nearly
127 million acres (51 million hectares)
of agricultural crops each year from
2009 to 2011. The presence and
concentrations of neonicotinoids at
Dakota skipper and Poweshiek
skipperling sites or nearby agricultural
fields that use neonicotinoid seed
treatments or other such treatments has
not been assessed, however, in general,
nearly 100 percent of corn is known to
be treated, and about 75 percent of
soybean seeds are known to be treated
with neonicotinoids, for example.
Similarly, soybean aphid spraying
occurs during the adult flight period, is
widespread, and applied aerially—this
spray can drift to nearby Dakota skipper
or Poweshiek skipperling habitat. The
presence and concentrations of
insecticides at Dakota skipper and
Poweshiek skipperling sites or nearby
agricultural fields that utilize soybean
aphid spraying has not been assessed.
The Minnesota Zoo has proposed a
study to investigate the levels of
neonicotinoids, aphid pesticides, and
other insecticides that may be present at
several skipper sites in Minnesota and
South Dakota.
The spread of nonnative gypsy moths
(Lymantria dispar dispar) has increased
efforts to control this damaging species
and may also be a stressor, especially in
the range of Poweshiek skipperling.
Insecticides used in the gypsy moth
suppression programs typically include
Foray, a formulation of the bacterial
insecticide Bacillus thuringiensis
kurstakii (Btk), or Gypchek, a viral
insecticide specific to gypsy moth
caterpillars. Btk is known to be lethal to
butterfly larvae (e.g., Karner blue
butterfly) (Carnes 2011, p. 1). In
Wisconsin, the gypsy moth suppression
program is managed under State Statute
26.30 and Natural Resources Board Rule
number 47, and Gypchek is used when
endangered or threatened moths or
butterflies are present (Wisconsin DNR,
https://dnr.wi.gov/topic/ForestHealth/
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GypsyMothPesticides.html, accessed
May 24, 2012).
Herbicide and pesticide use was
assessed at 15 present and unknown
Dakota skipper sites and 9 Poweshiek
skipperling sites occupied with present
or unknown occupancy where we had
sufficient information to evaluate the
stressor (Service 2012 unpubl.; 2014,
unpubl. data). We considered the level
of impact to populations posed by
herbicide and pesticide use to be low if
the site is only spot sprayed with
herbicides or pesticides when and
where necessary (Smart et al. 2011, p.
182) and their use is not expected to
change in the future. The level of
stressor was considered to be moderate
if the use of herbicides is likely to
increase at a site (e.g., in response to
new or expanding invasive species), but
Dakota skipper and Poweshiek
skipperling habitat is unlikely to be
exposed to broadcast applications. The
level of impact to populations posed by
herbicide and pesticide use was
considered to be high at sites where
herbicides are likely to be broadcast
over the entire site at least once every
4 years, or herbicide use has
significantly reduced forb or nectar
plant density and diversity or is likely
to in the future. The level of impact to
populations posed by herbicide and
pesticide use was high at 5 of the 16
assessed Dakota skipper sites (2 in
North Dakota and 3 in South Dakota)
and moderate at 2 sites—1 in North
Dakota and 1 in South Dakota. The level
of impact to populations posed by
herbicide and pesticide use was
considered to be high at 3 of the 9
assessed Poweshiek skipperling sites
(all 3 in South Dakota), and 1 site in
North Dakota had a moderate level of
impact to populations.
In summary, some efforts to manage
woody encroachment and invasive
species, such as herbicide use, can be a
stressor to both Dakota skipper and
Poweshiek skipperling populations.
Invasive species management is a
current and ongoing stressor of low to
high impact to populations, depending
on the intensity and extent of the use,
types of techniques, and the
compounding effects that may occur
from varying management. Medium- to
high-level impacts of herbicide or
pesticide use to Dakota skipper and
Poweshiek skipperling populations have
been documented in North and South
Dakota. This stressor has a high impact
to populations when it is combined
with other stressors, such as
management, that reduces or eliminates
nectar food sources, or small habitat
fragments that are isolated from other
source populations that may replenish
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individuals killed by pesticides.
Herbicide and pesticide use may have
direct or indirect effects on Dakota
skipper and Poweshiek skipperling.
Although such activities occur, there is
no evidence that these activities alone
have significant impacts on either
species, since their effects are often
localized. However, these factors may
have a cumulative effect on the Dakota
skipper and Poweshiek skipperling
when added to habitat curtailment and
destruction because dramatic
population declines have occurred in
both species (discussed in Factor A).
Invasive species and woody vegetation
management helps to maintain prairie
habitats and can also be beneficial to
populations of both species, for
example, when concentrated on affected
areas through spot spraying.
Pharmaceuticals
The effect of pharmaceutical residues
in the environment on nontarget
animals is an emerging concern (Lange
et al. 2009). Ivermectin, a widely used
and persistent veterinary
pharmaceutical used to treat cattle, is a
chemical of emerging concern to the
Dakota skipper and Poweshiek
skipperling. Ivermectin is an
anthelmintic (drugs that are used to
treat infections with parasitic worms)
that is spread to prairie environments
via the dung of grazing cattle (Lange et
al. 2009, p. 2238). Lange et al. (2009, pp.
2234, 2238) found that skipper
butterflies are particularly vulnerable to
ivermectin, due to their low dispersive
capacities and habitat preferences for
soil. The extirpation of the Dakota
skipper in at least one South Dakota site
(Sica Hollow West) is possibly due to
ivermectin that has leached into the
environment (Skadsen 2010, pers.
comm.).
Pharmaceutical use is a stressor that
has the potential to have high-level
impacts on populations of the Dakota
skipper and Poweshiek skipperling;
however, at this time our knowledge of
these impacts is limited. Sites within
the range of both species could
experience the effects of
pharmaceuticals. Sites that experience
grazing, however, are particularly
vulnerable to ivermectin use; these sites
are primarily in South Dakota, North
Dakota, and Minnesota. The use of
pharmaceuticals such as ivermectin may
have a cumulative effect on the Dakota
skipper and Poweshiek skipperling
when added to habitat curtailment or
destruction, because habitat destruction
leads to population declines in
populations of both species (discussed
in Factor A).
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Unknown Stressors Causing Population
Declines
The sharp and broad declines of
Poweshiek skipperling documented in
Iowa, Minnesota, North Dakota, and
South Dakota are indicative of a
response to one or more stressors that
have yet to be ascertained. These
unknown factors may consist of a
combination of one or more of the
stressors described throughout Factors
A, C, and E of this final rule, or may be
something that has not yet been
identified. These declines are
reminiscent of the widely publicized
decline of honey bees (Apis mellifera) in
that they seem sudden and mysterious
(Spivak et al. 2011, p. 34). One
hypothesis to explain the rapid decline
of the Poweshiek skipperling, and
possibly the Dakota skipper, is that a
newly virulent pathogen or a new
parasitoid has increased mortality above
normal levels (Dana 2013, pers. comm.).
One or more unidentified stressors
have strongly impacted Poweshiek
skipperling populations in the western
portion of its range, which contains
more than 80 percent of the species’ site
records. Unknown stressors may be the
current factor with the most significant
impacts to Poweshiek skipperling in
Minnesota, North Dakota, and South
Dakota, where populations experienced
a sudden decline to undetectable
numbers after about 2003. Until about
2003, Poweshiek skipperling was
regarded as the most frequently and
reliably encountered prairie-obligate
skipper in Minnesota, which contains
nearly 50 percent of all known
Poweshiek skipperling locations.
Numbers and distribution dropped
dramatically in subsequent years,
however, and the species has not been
seen in Minnesota since 2007, with the
exception of 2 individuals observed at
one location in 2013 (Weber 2014, in
litt.; Dana 2014, pers. comm.). Similar
recent dramatic declines were observed
in North Dakota, South Dakota, and
Iowa (See Background of this rule).
Recent declines of Dakota skippers
indicate that this species may also be
impacted by unknown stressors. The
Dakota skipper was last detected at one
site in Iowa in 1992. Only one
individual was detected in Minnesota
during 2012 surveys, which included 18
sites with previous records; surveys for
undiscovered populations were also
carried out on 23 prairie remnants
without previous records for the
species. Only six individual Dakota
skippers were detected at one site in
Minnesota during 2013 surveys, which
included 15 sites with previous records
and 12 prairie remnants without
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previous records for the species (Service
2014, unpubl. geodatabase.). Based on
similar conditions in other parts of the
species’ range, similar trends are
anticipated outside of Minnesota.
Indications of recent declining trends
have been observed in South Dakota and
North Dakota. In South Dakota, for
example, the proportion of positive
surveys at known sites has fluctuated
over time; however, the 2012 and 2013
surveys had the lowest positive
detection rate (38 percent and 32
percent, respectively) for the last 15
years (since 1996)—much less than
comparable survey years in South
Dakota (for years with more than 20
surveys). The Dakota skipper was
detected at 12 of the 23 sites surveyed
during 2012 in North Dakota (and 2
additional sites with no previous Dakota
skipper records); average encounter
frequencies observed across the State in
2012 (9.4 encounters per hour),
however, were about half of those
observed during the 1996–1997 Statewide surveys (ND State average = 17.4
encounters per hour). The Dakota
skipper was not detected at the three
sites that were surveyed in 2013 in
North Dakota with previous records of
the species. Recent survey results and
similar life histories suggest that the
Dakota skipper can be reasonably
compared to the Poweshiek skipperling
in their potential rate of decline—that
is, it is reasonable to assume that Dakota
skipper may be vulnerable to the same
unidentified factors that have caused
dramatic declines in the Poweshiek
skipperling, with a slight delay in
timing.
In summary, the results of extensive
surveys in the western portion of the
Poweshiek skipperling’s range have
documented the species’ response to
unknown factors and indicate that they
are a current stressor of high severity.
Although to date the Dakota skipper has
not experienced such dramatic declines
as the Poweshiek skipperling, similar
unknown stressors on Dakota skipper
populations likely have affected the
species in Minnesota and Iowa, where
recent surveys indicate that the species
may be largely absent or at undetectable
levels.
Summary of Factor E
Based on our analysis of the best
available information, we have
identified several natural and manmade
factors affecting the continued existence
of the Dakota skipper and Poweshiek
skipperling. Effects of small population
size, population isolation, and loss of
genetic diversity are likely stressors that
have significant impacts on both
species. Environmental effects resulting
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from climatic change, including
increased flooding and drought, are
expected to become severe in the future
and result in additional habitat losses;
however, we have limited information
on how this stressor may affect either
species. Possibly the stressor with the
most significant impacts to the
Poweshiek skipperling are one or more
unknown factors that have led to
widespread and sharp population
declines in the western portion of the
species’ range. These unknown stressors
may also be the cause of the recent
declines observed in Dakota skipper
populations over much of its range.
Anthropogenic factors such as
insecticide, herbicide, and pesticide use
are also stressors to both species, and
unregulated prairie plant harvest has the
potential to become a stressor in the
future (See Factor E). Collectively, these
stressors have operated in the past, are
impacting both species now, and will
continue to impact the Dakota skipper
and Poweshiek skipperling in the
future.
Conservation Efforts To Reduce Other
Natural or Manmade Factors Affecting
Its Continued Existence
Several of the conservation activities
discussed under Factor A. in this rule
may address some factors discussed
under Factor E, for example, life-history
studies of both species, studies to
examine the effects of various
management strategies on the species
and its habitat, and habitat restoration
techniques such as controlled burns on
sites divided into several management
units.
The Minnesota Zoo has initiated a
new program to research Poweshiek
skipperling and Dakota skipper
propagation. If this program is
successful, it could facilitate
reintroduction and augmentation into
areas where the species has declined or
disappeared, to bolster the small genetic
pool and small numbers. In 2012,
researchers at the Minnesota Zoo and
the University of Michigan initiated a
genetics study of Dakota skipper and
Poweshiek skipperling using specimens
at some of the few sites where either
species was observed in 2012,
specifically a few sites in Michigan,
Wisconsin, and Manitoba for the
Poweshiek skipperling and sites in
North Dakota, South Dakota, and
Manitoba for Dakota skipper. Too few
(one adult male) Dakota skipper were
observed in Minnesota to obtain
samples from that State in 2012.
Similarly, only six individuals were
observed at one Minnesota site in 2013.
The genetics studies will help inform
captive propagation and reintroduction
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63739
efforts, which may help alleviate
stressors associated with small and
isolated populations.
In 2011, researchers collected 32 adult
Dakota skippers from a combination of
4 sites in South Dakota and translocated
them to Pickerel Lake State Park, where
the species was last detected in 2008
(Skadsen 2011, pp. 7–9). The phenology
of the adult flight period and purple
coneflower blooms did not coincide,
and no Dakota skippers were observed
at the release site during subsequent
visits in 2011 or 2012 (Skadsen 2011,
pp. 8–9, Skadsen 2012, p. 4).
Researchers and managers continue to
develop prairie restoration and
management goals for this and the
Hartford Beach State Park site in South
Dakota (Skadsen 2011, p. 9; Skadsen
2012b, p. 7).
The Minnesota Zoo has also begun a
study to investigate the levels of
neonicotinoids, aphid pesticides, and
other insecticides present at several
skipper sites in Minnesota and at least
one site in South Dakota.
We are unaware of any conservation
efforts that directly address the impacts
of climate change to Dakota skippers or
Poweshiek skipperlings. We are
unaware of any conservation efforts that
address the possible effects of
pharmaceuticals on the Poweshiek
skipperling and Dakota skipper.
Cumulative Effects From Factors A
Through E
Many of the stressors described in this
final rule may cumulatively or
synergistically impact the Dakota
skipper and Poweshiek skipperling
beyond the scope of each individual
stressor. For example, improper grazing
management alone may only affect
portions of Dakota skipper or Poweshiek
skipperling habitat; however, improper
grazing combined with invasive plants,
herbicide use, and drought may
collectively result in substantial habitat
loss, degradation, or fragmentation
across large portions of the species’
ranges. In turn, climate change may
exacerbate those effects, further
diminishing habitat and increasing the
isolation of already declining and
isolated populations, making them more
susceptible to genetic drift or
catastrophic events such as fire,
flooding, and drought. Further,
nonagricultural development such as
gravel mining or housing development
not only can directly destroy habitat,
but also can increase fragmentation of
habitat by increasing associated road
development. Additionally, draining
prairie fens will increase invasive plant
and woody vegetation encroachment.
Numerous stressors are likely acting
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cumulatively to further increase impacts
on the already vulnerable, small, and
isolated populations of Poweshiek
skipperling and Dakota skipper.
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Determination
Dakota Skipper
We carefully assessed the best
scientific and commercial information
available regarding the past, present,
and future threats to the Dakota skipper.
Dakota skippers are obligate residents of
undisturbed (remnant, untilled) highquality prairie, ranging from wet-mesic
tallgrass prairie to dry-mesic mixedgrass prairie. Native tallgrass prairies
have been reduced by 85 to 99.9 percent
of their former area, and native mixedgrass prairies have been reduced by 71.9
to 99 percent of their former area in
North Dakota, Manitoba, and
Saskatchewan. The Dakota skipper was
once a common prairie butterfly widely
dispersed in five States, extending from
Illinois to North Dakota, and portions of
two Canadian provinces. However, its
range is now substantially reduced such
that the Dakota skipper is restricted to
small patches of fragmented nativeprairie remnants in portions of three
States and two Canadian provinces.
Recent survey data indicate that the
Dakota skipper has declined to zero or
to undetectable levels in approximately
77 percent of sites where it had been
recorded rangewide. It is presumed
extirpated from Illinois and Iowa and no
longer occurs in eastern Minnesota.
Much of the rangewide decline in the
species has been observed in the last
few years. Since 1988, researchers have
surveyed 10 or more sites in 25 years;
the average positive detection rate for
those years is 63 percent rangewide.
Since 2009, the percent of surveyed
sites with positive detections of the
species has dropped from 63 percent in
2009, to 41 percent in 2010, 36 percent
in 2011, 37 percent in 2012, and 22
percent in 2013. While these types of
lows in detections have been observed
in past years, for example, in the early
1990s, the numbers of individuals
observed in 2013 were the lowest ever
recorded, despite extensive survey
effort. Dakota skippers currently occupy
sites in northeastern South Dakota,
North Dakota, western Minnesota,
southern Manitoba, and southeastern
Saskatchewan.
Of the 264 historical locations, the
species is presumed extirpated or
possibly extirpated from at least 93 (35
percent) of those sites, and the
occupancy of the species is unknown at
approximately 88 (33 percent) sites. Of
the 88 sites where the occupancy is
unknown, at least 78 sites are subject to
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one or more stressors that have a
moderate to high impact on those
populations—these sites are distributed
across Minnesota, North Dakota, and
South Dakota. Three sites with
unknown occupancy were not evaluated
for stressors, due to lack of information.
The 7 sites with unknown occupancy
without moderate- to high-level
stressors are scattered in various
counties in Minnesota and South
Dakota, and the skipper is thought to
still be present at approximately 83 (31
percent) of the 264 historical locations,
although 22 of these sites have not been
surveyed since 2002. Of those 83 sites,
at least 73 sites are subject to one or
more stressors that have a moderate to
high impact on those populations, such
as conversion to agriculture, lack of
management, and small size and
isolation. Four sites were not evaluated
due to lack of information, and the
remaining six sites that do not have
stressors with moderate- to high-level
impacts to populations occur in
scattered counties in Minnesota and
South Dakota.
Approximately half (40 of 83) of the
locations where the species is
considered to be present are primarily
located on privately owned fall-hayed
prairies in Canada, mostly within 2
isolated complexes, and have not been
surveyed since 2007. All 40 of those
Canadian sites have one or more
stressors of moderate to high level of
impact to populations. Approximately
15 populations in Canada are on lands
that are being used in ways that are
favorable to the Dakota skipper (i.e.,
late-season haying conducted at least
every other year and there is no
indication that native plant species
diversity is declining due to timing or
frequency of mowing), and the stressors
at those sites are not immediate.
However, we are aware of only one of
these Canadian populations that is
protected (on Federal land). The
remaining sites where the species is
considered to be present are about
equally distributed among Minnesota
(11 sites), North Dakota (16 sites), and
South Dakota (14 sites). Sites with
stressors with moderate to high level of
impacts to populations occur in all three
States.
Many factors likely contributed to the
Dakota skipper’s decline, and numerous
factors, acting individually or
synergistically, continue today (see
Summary of Factors Affecting the
Species). We identified many stressors
to the species, some of which rise to the
level of threats that contribute to the
listing status for each species. Habitat
loss and degradation have impacted the
Dakota skipper, curtailing the ranges of
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the species (see Factor A). Extensive
historical conversion of prairie and
associated habitats, nearly complete in
some areas, has isolated many Dakota
skipper populations. These small and
isolated populations are subject to loss
of genetic diversity through genetic drift
(see Factor E) and are susceptible to a
variety of stochastic (e.g., wildfires,
droughts, and floods) and deterministic
(e.g., overgrazing, invasive species)
factors (see Factor A) that may kill all
or a substantial proportion of a
population.
Although much of the habitat
conversion occurred in the past, the
effects of the dramatic reduction and
fragmentation of habitat have persistent
and ongoing effects on the viability of
populations; furthermore, conversion of
native prairies to agriculture or other
uses is still occurring today. The life
history of the species exacerbates the
threats caused by the fragmentation and
degradation of the species’ habitat (see
Factors A and E) as the Dakota skipper
is not likely to recolonize distant sites
due to its short adult life span, single
annual flight, and limited dispersal
ability. Therefore, the species’
extirpation from a site is likely
permanent unless it is near another site
from which it can emigrate.
Furthermore, because the larvae are
located at or near the soil surface, they
are more vulnerable to fire (Factor A);
herbicides, pesticides, and other
chemicals (see Factor E); desiccation
due to changing climate (see Factor E);
or flooding (see Factor A).
Within the remaining native-prairie
patches, degradation of habitat quality is
now the primary threat to the Dakota
skipper (see Factor A). Of the various
threats to Dakota skipper habitat,
conversion, invasive species, secondary
succession, and reduction in the
diversity of native-prairie plant
communities have moderate- to highlevel impacts to populations throughout
the range of the Dakota skipper. An
array of other factors including
nonagricultural development, chemical
contaminants, pesticides, and intensive
grazing are also current and ongoing
threats to the Dakota skipper and its
habitat (see Factors A and E). Current
and ongoing prairie management
practices, such as indiscriminate use of
herbicides or intensive grazing that
reduces or eliminates food sources,
contribute to the species’ imperilment at
sites throughout the range of the species
(see Factors A and E).
Unknown factors may be the current
threat that has the most significant
impacts to the Dakota skipper in Iowa
and Minnesota, where populations
experienced a sudden decline to
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undetectable numbers in the most
recent years (see Factor E). Based on
recent data, similar conditions in other
parts of the Dakota skipper’s range, and
the similarities in life histories between
Poweshiek skipperling and Dakota
skipper, similar declining trends are
anticipated in other parts of the Dakota
skipper’s range due to unknown factors,
and may only be a few years behind
those declines experienced by other
species, such as the Poweshiek
skipperling (see Factor E). Existing
regulatory mechanisms vary across the
species’ ranges, and although
mechanisms do exist that protect the
species from direct take in Iowa and
Minnesota, these mechanisms do not
sufficiently mitigate threats to the
species (see Factor D). Climate change
may affect Dakota skipper, especially
increased frequency of extreme climatic
conditions such as flooding and
drought, but there is limited information
on the exact nature of impacts that these
species may experience. Recent
temperature and precipitation trends
indicate that certain aspects of climate
change may be occurring in Dakota
skipper range now (see Factor E).
The Act defines an endangered
species as any species that is ‘‘in danger
of extinction throughout all or a
significant portion of its range’’ and a
threatened species as any species ‘‘that
is likely to become endangered
throughout all or a significant portion of
its range within the foreseeable future.’’
We find that the Dakota skipper is likely
to become endangered throughout all of
its range within the foreseeable future,
based on the immediacy, severity, and
scope of the threats described above.
These threats are exacerbated by small
population sizes, the loss of redundancy
and resiliency of these species, and the
continued inadequacy of existing
protective regulations. A few scattered
populations of Dakota skipper are doing
relatively well, however, and are in
habitats that have low or non-immediate
threats.
Canada has approximately 15
populations on lands that are being
utilized in a manner conducive to the
conservation of Dakota skipper, and the
threats at those sites are not imminent.
However, few of these populations are
protected, many are vulnerable to
changes in land use, landowners may
not be aware of the species presence and
may change land use, and the sites have
not been surveyed in the last 5 years.
While a few new locations of Dakota
skipper populations continue to be
discovered in North and South Dakota,
the numbers of individuals observed at
those sites is generally low, and
extirpation at previously known sites
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seems to be occurring at a faster rate
than new discoveries. The decreasing
numbers of sites with positive
detections and the decreasing numbers
of individuals observed at each site
throughout its range, including known
sites in Minnesota, North Dakota, and
South Dakota, is likely to continue.
Therefore, on the basis of the best
available scientific and commercial
information, we are listing the Dakota
skipper as a threatened species in
accordance with sections 3(20) and
4(a)(1) of the Act.
We find that an endangered species
status is not appropriate for the Dakota
skipper because some Dakota skipper
populations still appear to be doing
relatively well (populations detected
during the last survey year, numbers
appear stable, lower levels of threats
and stressors)—primarily in North
Dakota, South Dakota, Manitoba, and
Saskatchewan. About 14 to 15 sites in
Manitoba are used in a manner
conducive to the conservation of Dakota
skipper (haying after the adult flight
period), and the threats at those sites are
not imminent. Furthermore, we believe
the species to be present in at least 6
sites that do not have documented
stressors of a moderate- to high-level
impact to populations, primarily in
scattered counties in Minnesota and
South Dakota. Additionally, a few new
Dakota skipper sites continue to be
discovered in suitable prairie habitat in
North Dakota and South Dakota.
Under the Act and our implementing
regulations, a species may warrant
listing if it is endangered or threatened
throughout all or a significant portion of
its range. Because we have determined
that the Dakota skipper is a threatened
species throughout all of its range, no
portion of its range can be ‘‘significant’’
for purposes of the definitions of
‘‘endangered species’’ and ‘‘threatened
species.’’ See the Final Policy on
Interpretation of the Phrase ‘‘Significant
Portion of Its Range’’ in the Endangered
Species Act’s Definitions of
‘‘Endangered Species’’ and ‘‘Threatened
Species’’ (79 FR 37577).
Poweshiek Skipperling
We carefully assessed the best
scientific and commercial information
available regarding the past, present,
and future threats to the Poweshiek
skipperling. Poweshiek skipperling are
obligate residents of undisturbed
(remnant, untilled) high-quality prairie,
ranging from wet-mesic tallgrass prairie
to dry-mesic mixed-grass prairie. Native
tallgrass prairies have been reduced by
85 to 99.9 percent of their former area,
and native mixed-grass prairies have
been reduced by 72 to 99 percent of
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their former area in North Dakota,
Manitoba, and Saskatchewan. The
Poweshiek skipperling was once a
common prairie butterfly widely
dispersed in eight States, extended from
Michigan to North Dakota, and portions
of Manitoba, Canada. However, its range
is now substantially reduced such that
the Poweshiek skipperling is restricted
to small patches of fragmented nativeprairie remnants in portions of two
States and one Canadian province. The
species is presumed extirpated from
Illinois and Indiana, and the status of
the species is unknown in four of the six
States with relatively recent records
(within the last 20 years). Recent survey
data indicate that the Poweshiek
skipperling has declined to zero or to
undetectable levels in approximately 96
percent of sites where it has ever been
recorded.
A drastic decline in this species has
been observed rangewide very recently.
Between 1985 and 2003, researchers
surveyed 10 or more sites in 7 different
years (excluding new sites in the first
year); the average positive detection rate
for those years is 71 percent rangewide.
Since 2003, the percent of surveyed
sites with positive detections of the
species has dropped to an average of 31
percent each year (2004–2013), with a
low of 12 percent at sites surveyed in
2012 and 2013. Despite recent
substantial survey efforts in those
States, the Poweshiek skipperling has
not been recorded in Iowa since 2007,
when it was observed at 1 site; in North
Dakota since 2001, when it was
observed at 1 site, nor in South Dakota
since 2008, when it was observed at 3
sites. The species was not observed in
North Dakota, South Dakota, or
Minnesota during 2012 surveys, for
example. The Poweshiek skipperling
was observed at one site in Minnesota
in 2007 and there was a sighting of a
Poweshiek skipperling at one site in
2013, although no photographs or
specimens were taken to confirm the
sighting. Iowa sites were not surveyed
in 2012, and the species was not
detected in 2013. Poweshiek skipperling
have historically been documented at
approximately 296 sites; now we
consider the species to be present at
only 12 of those sites—one of these is
considered a sub-site of a larger site.
The only confirmed extant (present)
populations of Poweshiek skipperling
are currently restricted to 1 small and
isolated native-prairie remnant in
Wisconsin, 9 small and isolated prairie
fen remnants in Michigan, and a prairie
complex in Manitoba. The species may
also be present at one site in Minnesota.
These sites represent less than 5 percent
of the total number of sites ever
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documented for the species. The
numbers observed at these sites are
relatively small (fewer than 100
individuals at all sites surveyed in
2013), and all of these sites have at least
one documented threat that has
moderate to high impacts on those
populations. The strongest population
in the United States, a prairie fen in
Michigan with relatively high and fairly
consistent numbers observed each year
(numbers observed per minute ranged
from 0.2 to 2.2 during the last 6 survey
years), for instance, is under threat from
intense development pressure. The
Tallgrass Prairie Preserve site in
Manitoba also has relatively high
numbers observed each year; however,
this site is impacted by several
immediate, moderate- to high-level
threats, including the encroachment of
invasive plants and woody vegetation,
flooding, and isolation from the nearest
site by hundreds of kilometers. In
addition, recent unplanned fires in 2009
and 2011 affected large portions of the
site. Poweshiek skipperling is
considered to have unknown occupancy
at 75 sites—throughout the range of the
species (Iowa, Michigan, Minnesota,
North Dakota, and South Dakota), 49 of
these sites were included in the threats
assessment. Of the 49 sites where the
occupancy is unknown that had
sufficient information to assess, at least
42 sites are subject to one or more
threats that have a moderate to high
impact on those populations. These
sites are throughout the range of the
species in Iowa, Michigan, Minnesota,
North Dakota, and South Dakota.
Many factors likely contributed to the
Poweshiek skipperling’s decline, and
numerous major threats, acting
individually or synergistically, continue
today (see Summary of Factors Affecting
the Species). Habitat loss and
degradation have impacted the
Poweshiek skipperling, curtailing the
ranges of both species (see Factor A).
Extensive historical conversion of
prairie and associated habitats, nearly
complete in some areas, has isolated
many Poweshiek skipperling
populations. These small and isolated
populations are subject to loss of genetic
diversity through genetic drift (see
Factor E) and are susceptible to a variety
of stochastic (e.g., wildfires, droughts,
and floods) and deterministic (e.g.,
overgrazing, invasive species) factors
(see Factor A) that may kill all or a
substantial proportion of a population.
Although much of the habitat
conversion occurred in the past, the
effects of the dramatic reduction and
fragmentation of habitat have persistent
and ongoing effects on the viability of
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populations; furthermore, conversion of
native prairies to agriculture or other
uses is still occurring today. The life
history of the species exacerbates the
threats caused by the fragmentation and
degradation of its habitat (see Factors A
and E) as Poweshiek skipperlings are
not likely to recolonize distant sites due
to their short adult life span, single
annual flight, and limited dispersal
ability. Therefore, the Poweshiek
skipperling’s extirpation from a site is
likely permanent unless it is near
another site from which it can emigrate.
Furthermore, because the larvae are
located at or near the soil surface, they
are more vulnerable to fire (Factor A),
herbicides, pesticides, and other
chemicals (see Factor E); desiccation
due to changing climate (see Factor E);
or changes in hydrology (see Factor A).
Within the remaining native-prairie
patches, degradation of habitat quality is
now the primary threat to the
Poweshiek skipperling (see Factor A).
Of the various threats to Poweshiek
skipperling habitat, conversion, invasive
species, secondary succession, and
reduction in the diversity of nativeprairie plant communities have
moderate- to high-level impacts to
populations throughout the range of the
Poweshiek skipperling. An array of
other factors including nonagricultural
development, chemical contaminants,
pesticides, and intensive grazing are
also current and ongoing threats to the
Poweshiek skipperling and its habitat
(see Factors A and E). Current and
ongoing prairie management practices,
such as indiscriminate use of herbicides
or intensive grazing that reduces or
eliminates food sources, contribute to
the species’ imperilment, particularly in
North Dakota, South Dakota, and
Minnesota (see Factors A and E).
Unknown factors may be the current
threat that has the most significant
impacts to the Poweshiek skipperling
species in Iowa, Minnesota, North
Dakota, and South Dakota, where
populations experienced a sudden
decline to undetectable numbers in the
most recent years (see Factor E).
Existing regulatory mechanisms vary
across the species’ ranges, and although
mechanisms do exist in Iowa, Michigan,
Minnesota, and Wisconsin that protect
the species from direct take, these
mechanisms do not sufficiently mitigate
threats to the Poweshiek skipperling
(see Factor D). Climate change may
affect the Poweshiek skipperling,
especially increased frequency of
extreme climatic conditions such as
flooding and drought, but there is
limited information on the exact nature
of impacts that the species may
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experience. Recent temperature and
precipitation trends indicate that certain
aspects of climate change may be
occurring in Poweshiek skipperling
range now (see Factor E).
The Act defines an endangered
species as any species that is ‘‘in danger
of extinction throughout all or a
significant portion of its range’’ and a
threatened species as any species ‘‘that
is likely to become endangered
throughout all or a significant portion of
its range within the foreseeable future.’’
We find that the Poweshiek skipperling
is presently in danger of extinction
throughout its entire range, based on the
immediacy, severity, and scope of the
threats described above. These threats
are exacerbated by small population
sizes, the loss of redundancy and
resiliency of these species, and the
continued inadequacy of existing
protective regulations. There are only 12
locations where we believe the species
to be present, and all of those sites are
subject to at least one or more ongoing
and immediate threats that have
moderate- to high-level effects on those
populations. Therefore, on the basis of
the best available scientific and
commercial information, we are listing
the Poweshiek skipperling as
endangered in accordance with sections
3(6) and 4(a)(1) of the Act.
We find that a threatened species
status is not appropriate for the
Poweshiek skipperling because the
unknown factors have significant
impacts to the species throughout most
of its range and have occurred in a short
timeframe. Sharp population declines
have not been detected at the few
remaining sites where the species is still
present, but all of these sites are
currently experiencing one or more
threats that have moderate- to high-level
impacts to populations. Based on recent
data and similar conditions in other
parts of Poweshiek skipperling range,
similar declining trends are anticipated
in other parts of the range of the species,
and may only be a few years behind
those declines experienced by the
species in Iowa, Minnesota, North
Dakota, and South Dakota (see Factor E).
The impacts of the unknown factors on
populations are exacerbated by habitat
curtailment and destruction and other
factors such as the effects of small and
isolated populations due to habitat
fragmentation.
Under the Act and our implementing
regulations, a species may warrant
listing if it is endangered or threatened
throughout all or a significant portion of
its range. Because we have determined
that the Poweshiek skipperling is an
endangered species throughout all of its
range, no portion of its range can be
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‘‘significant’’ for purposes of the
definitions of ‘‘endangered species’’ and
‘‘threatened species.’’ See the Final
Policy on Interpretation of the Phrase
‘‘Significant Portion of Its Range’’ in the
Endangered Species Act’s Definitions of
‘‘Endangered Species’’ and ‘‘Threatened
Species’’ (79 FR 37577).
Available Conservation Measures
Conservation measures provided to
species listed as endangered or
threatened under the Act include
recognition, recovery actions,
requirements for Federal protection, and
prohibitions against certain practices.
Recognition through listing results in
public awareness and conservation by
Federal, State, Tribal, and local
agencies, private organizations, and
individuals. The Act encourages
cooperation with the States and requires
that recovery actions be carried out for
all listed species. The protection
required by Federal agencies and the
prohibitions against certain activities
are discussed, in part, below.
The primary purpose of the Act is the
conservation of endangered and
threatened species and the ecosystems
upon which they depend. The ultimate
goal of such conservation efforts is the
recovery of these listed species, so that
they no longer need the protective
measures of the Act. Subsection 4(f) of
the Act requires the Service to develop
and implement recovery plans for the
conservation of endangered and
threatened species. The recovery
planning process involves the
identification of actions that are
necessary to halt or reverse the species’
decline by addressing the threats to its
survival and recovery. The goal of this
process is to restore listed species to a
point where they are secure, selfsustaining, and functioning components
of their ecosystems.
Recovery planning includes the
development of a recovery outline
shortly after a species is listed,
preparation of a draft and final recovery
plan, and revisions to the plan as
significant new information becomes
available. The recovery outline guides
the immediate implementation of urgent
recovery actions and describes the
process to be used to develop a recovery
plan. The recovery plan identifies sitespecific management actions that will
achieve recovery of the species,
measurable criteria that determine when
a species may be downlisted or delisted,
and methods for monitoring recovery
progress. Recovery plans also establish
a framework for agencies to coordinate
their recovery efforts and provide
estimates of the cost of implementing
recovery tasks. Recovery teams
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(comprising species experts, Federal
and State agencies, nongovernmental
organizations, and stakeholders) are
often established to develop recovery
plans. When completed, the recovery
outlines, draft recovery plans, and the
final recovery plans will be available on
our Web site (https://www.fws.gov/
endangered), or from our Twin Cities
Ecological Services Fish and Wildlife
Office (see FOR FURTHER INFORMATION
CONTACT).
Implementation of recovery actions
generally requires the participation of a
broad range of partners, including other
Federal agencies, States, Tribes,
nongovernmental organizations,
businesses, and private landowners.
Examples of recovery actions include
habitat restoration (e.g., restoration of
native vegetation), research, captive
propagation and reintroduction, and
outreach and education. The recovery of
many listed species cannot be
accomplished solely on Federal lands
because their range may occur primarily
or solely on non-Federal lands. To
achieve recovery of these species
requires cooperative conservation efforts
on private, State, and Tribal lands.
When species are listed, funding for
recovery actions will be available from
a variety of sources, including Federal
budgets, State programs, and cost-share
grants for non-Federal landowners, the
academic community, and
nongovernmental organizations. In
addition, pursuant to section 6 of the
Act, the States of Iowa, Michigan,
Minnesota, North Dakota, South Dakota,
and Wisconsin would be eligible for
Federal funds to implement
management actions that promote the
protection and recovery of the
Poweshiek skipperling and Dakota
skipper. Information on our grant
programs that are available to aid
species recovery can be found at:
https://www.fws.gov/grants.
Please let us know if you are
interested in participating in recovery
efforts for the Dakota skipper or
Poweshiek skipperling. Additionally,
we invite you to submit any new
information on these species whenever
it becomes available and any
information you may have for recovery
planning purposes (see FOR FURTHER
INFORMATION CONTACT).
Section 7(a) of the Act requires
Federal agencies to evaluate their
actions with respect to any species that
is proposed or listed as endangered or
threatened and with respect to its
critical habitat, if any is designated.
Regulations implementing this
interagency cooperation provision of the
Act are codified at 50 CFR part 402. If
a species is listed subsequently, section
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7(a)(2) of the Act requires Federal
agencies to ensure that activities they
authorize, fund, or carry out are not
likely to jeopardize the continued
existence of the species or destroy or
adversely modify its critical habitat. If a
Federal action may adversely affect a
listed species or its critical habitat, the
responsible Federal agency must enter
into formal consultation with the
Service.
Federal agency actions within the
species habitat that may require
conference or consultation or both as
described in the preceding paragraph
include, but are not limited to,
management and any other landscapealtering activities on Federal lands such
as actions within the jurisdiction of the
NRCS; land management by the U.S.
Forest Service; issuance of section 404
Clean Water Act permits by the U.S.
Army Corps of Engineers; land
management by the U.S. Fish and
Wildlife Service; construction and
management of gas pipeline, wind
facilities and associated infrastructure,
and power line rights-of-way by the
Federal Energy Regulatory Commission;
construction and maintenance of roads
or highways by the Federal Highway
Administration; and land management
within branches of the Department of
Defense (DOD). Examples of these types
of actions include activities funded or
authorized under the Farm Bill Program,
Environmental Quality Incentives
Program, Clean Water Act (33 U.S.C.
1251 et seq.), Partners for Fish and
Wildlife Program, and DOD
construction activities related to
training or other military missions.
Poweshiek Skipperling
The Act and its implementing
regulations set forth a series of general
prohibitions and exceptions that apply
to all endangered wildlife. The
prohibitions of section 9(a)(2) of the Act,
codified at 50 CFR 17.21 for endangered
wildlife, in part, make it illegal for any
person subject to the jurisdiction of the
United States to take (includes harass,
harm, pursue, hunt, shoot, wound, kill,
trap, capture, or collect; or to attempt
any of these), import, export, ship in
interstate commerce in the course of
commercial activity, or sell or offer for
sale in interstate or foreign commerce
any listed species. Under the Lacey Act
(18 U.S.C. 42–43; 16 U.S.C. 3371–3378),
it is also illegal to possess, sell, deliver,
carry, transport, or ship any such
wildlife that has been taken illegally.
Certain exceptions apply to agents of the
Service and State conservation agencies.
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Dakota Skipper
Under section 4(d) of the Act, the
Service has discretion to issue
regulations that we find necessary and
advisable to provide for the
conservation of threatened wildlife. We
may also prohibit by regulation with
respect to threatened wildlife any act
prohibited by section 9(a)(1) of the Act
for endangered wildlife. Exercising this
discretion, the Service has developed a
4(d) rule containing all the general
prohibitions and exceptions to those
prohibitions; these are found at 50 CFR
17.31 and 50 CFR 17.32. For the Dakota
skipper, the Service has developed a
4(d) rule that is tailored to the specific
threats and conservation needs of this
species. As a means to promote
conservation efforts on behalf of the
Dakota skipper, we are finalizing a 4(d)
rule for this species that modifies the
standard protections for threatened
wildlife found at 50 CFR 17.31. In the
case of a 4(d) rule, the general
regulations (50 CFR 17.31 and 17.71)
applying most prohibitions under
section 9 of the Act to threatened
species do not apply to that species, and
the 4(d) rule contains the prohibitions
necessary and advisable to conserve that
species.
As discussed above, the primary
factors supporting the determination of
threatened species status for the Dakota
skipper are habitat loss and degradation
of native prairies, including conversion
of native prairie for agriculture or other
development; ecological succession and
encroachment of invasive species and
woody vegetation; certain fire, haying,
and grazing management that reduces
the availability of certain native-prairie
grasses and flowering herbaceous plants
to the Dakota skipper; some fire
management; flooding; existing
regulatory mechanisms that are
inadequate to mitigate threats to the
species; loss of genetic diversity; small
size and isolation of remnant patches of
native prairie; indiscriminate use of
herbicides that reduces or eliminates
nectar sources; climate conditions such
as drought; and other unknown factors.
The Act does not specify particular
prohibitions, or exceptions to those
prohibitions, for threatened species.
Instead, under section 4(d) of the Act,
the Secretary of the Interior has the
discretion to issue such regulations as
she deems necessary and advisable to
provide for the conservation of such
species. The Secretary also has the
discretion to prohibit by regulation with
respect to any threatened species, any
act prohibited under section 9(a)(1) of
the Act. Exercising this discretion, the
Service has developed general
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prohibitions (50 CFR 17.31) and
exceptions to those prohibitions (50
CFR 17.32) under the Act that apply to
most threatened species. Alternately, for
other threatened species, the Service
develops specific prohibitions and
exceptions that are tailored to the
specific conservation needs of the
species. In such cases, some of the
prohibitions and authorizations under
50 CFR 17.31 and 17.32 may be
appropriate for the species and
incorporated into a rule under section
4(d) of the Act, but the section 4(d) rule
will also include provisions that are
tailored to the specific conservation
needs of the threatened species and may
be more or less restrictive than the
general provisions at 50 CFR 17.31.
In recognition of efforts that provide
for conservation and management of the
Dakota skipper and its habitat in a
manner consistent with the purposes of
the Act, this 4(d) rule outlines the
prohibitions, and exceptions to those
prohibitions, necessary and advisable
for the conservation of the Dakota
skipper.
Conversion of grasslands for the
production of agricultural crops poses a
threat to the Dakota skipper because it
may directly destroy the species’
habitat, increase isolation of
populations by impeding dispersal, and
increase the risk posed by drift of
herbicides and pesticides. A wide
variety of peer-reviewed publications
and government reports have
documented recent conversion of native
grassland. In addition, economic and
policy incentives are likely to continue
to place pressure on landowners to
convert native grassland from ranching
to agricultural cropland (Doherty et al.
2013, p. 14); Sylvester et al. 2013, p. 13;
Rashford et al. 2011, p. 282; Stephens et
al. 2008, p. 6; (Congressional Research
Service (CRS) 2007, p. 5, United States
Government Accountability Office
(USGAO) 2007, p. 15, Stephens et al.
2008, p. 6, Rashford et al. 2011, p. 282,
Sylvester et al. 2013, p. 13). Grassland
loss in the western corn belt may be
occurring at the fastest rate observed
since the 1920s and 1930s and at a rate
comparable to that of deforestation in
Brazil, Malaysia, and Indonesia (Wright
and Wimberly 2013, p. 5). Between 2006
and 2011, destruction of native
grassland was mostly concentrated in
North Dakota and South Dakota, east of
the Missouri River, an area
corresponding closely to the range of the
Dakota skipper (Wright and Wimberly
2013, p. 2). In northeastern South
Dakota, one of the few remaining
strongholds for the Dakota skipper,
about 269,000 acres (108,907 ha) of
grassland was lost—primarily to
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cropland—between 2006 and 2012
(Reitsma et al. 2014, p. 3).
As with agricultural policies (Doherty
et al. 2013, p. 15), prohibitions against
take of Dakota skippers could interact
with other factors to affect the rates at
which native grassland is converted in
the range of the species. Less than 20
percent of the grassland in the Prairie
Pothole Region of the United States is
permanently protected (Doherty et al.
2013, p. 7), and the vast majority of
remaining grassland is privately owned.
The conservation of ‘‘working
landscapes’’ based on ranching and
livestock operations (‘grass-based
farming’) is frequently a priority of
programs to conserve native grassland
ecosystems in the northern Great Plains
(e.g., U.S. Fish and Wildlife Service
2011, p. 5). Exempting incidental take of
Dakota skippers that may result from
grazing and other routine livestock
ranching activities will afford us more
time to protect the species’ habitats in
these areas and will facilitate the
cooperation and partnerships with
livestock producers necessary to recover
the species.
Three primary factors have led us to
determine that it is necessary and
advisable to exempt take of Dakota
skippers caused by certain ranching
activities, including grazing. First, a
variety of socioeconomic and policy
factors are leading to the conversion of
native grasslands for the production of
agricultural crops, as summarized
above. Whereas conversion of native
grassland for crop production would
result in a permanent loss of Dakota
skipper habitat and may also exacerbate
other threats (e.g., pesticide drift) to the
species, grasslands can remain suitable
for Dakota skippers when grazed (see
below and Dana 1991, p. 54; Schlicht
1997, p. 5; Skadsen 1997, pp. 24–29). By
exempting take of Dakota skippers
caused by grazing, we acknowledge the
positive role that some ranchers have
already played in conserving Dakota
skippers and the importance of
preventing any additional loss and
fragmentation of native grasslands as the
result of activities in areas that could
support the species.
Second, although some grazing
practices pose a threat to Dakota
skipper, grazing may also be an effective
tool to improve Dakota skipper habitat
when carefully applied in cooperation
and consultation with private
landowners, public land managers, and
grazing experts. In eastern South
Dakota, Dakota skipper populations
were deemed secure at some sites
managed with rotational grazing that
was sufficiently light to maintain native
plant species diversity (Skadsen 1997,
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pp. 24–29), and grazing may also benefit
Dakota skippers by increasing coverage
of mid-height grasses, such as little
bluestem, relative to tallgrasses, such as
big bluestem and Indiangrass (Dana
1991, p. 54). Intensive early-season
grazing can reduce the extent of
Kentucky bluegrass, a nonnative species
that invades prairie habitats and
competes with native plant species
(DeKeyser et al. 2013, p. 86). In
addition, grazing may also inhibit the
establishment of smooth brome and
help to enhance coverage and diversity
of native plants in prairies that have
been invaded by nonnative cool-season
grasses (U.S. Fish and Wildlife Service
2006, p. 2; DeKeyser et al. 2009, p. 18;
Smart et al. 2013, p. 686). Because
grazing can lead to adverse conditions
for the Dakota skipper, however, the
Service encourages collaboration with
private landowners, public land
managers (e.g., Skadsen 2006, p. 5),
State and Federal conservation agencies,
and nongovernmental organizations to
identify, implement, monitor, and refine
grazing practices that are conducive to
the species’ conservation.
Third, recovery of the Dakota skipper
will depend on the protection and
restoration of high-quality habitats for
the species on private lands and on
public lands that are grazed or hayed by
private individuals under lease or other
agreements. Conservation of Dakota
skippers on these lands will require the
development and implementation of
complex, individualized, and long-term
management agreements that rely on
robust monitoring of Dakota skipper
populations and habitat features. All of
these agreements will require a
willingness on the part of the private
ranchers to collaborate with the Service
and our partners to implement, monitor,
and adapt conservation grazing
practices in a manner that allows for
stable or growing Dakota skipper
populations. This type of cooperative
approach is more likely to take place
and to be successful if we exempt take
caused by grazing and the other
activities that we specify in the 4(d)
rule.
In some geographic areas, such as
McHenry County, North Dakota, the
Dakota skipper almost exclusively
inhabits relatively flat and moist prairie
habitats that are mowed for hay. In these
areas we do not encourage a switch to
grazing without careful consideration of
the potential consequences to the
Dakota skipper. These habitats, referred
to as calcareous or ‘‘alkaline prairies’’ by
McCabe (1979, p. 17; 1981, p. 179); ‘‘wet
mesic’’ by Royer and Marrone (1992, p.
21); and ‘‘Type A’’ by Royer et al. (2008,
p. 14), are distinguished from other
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Dakota skipper habitats by relatively flat
topography and certain plant
community and soil characteristics
(Lenz 1999, pp. 5–7; Royer et al. 2008,
pp. 14–15). Dakota skippers appear to be
generally absent from this type of
habitat in North Dakota where it is
grazed, due to a shift away from a plant
community that is suitable for the
species (McCabe 1979, p. 17; 1981, p.
179). The shift in plant community
composition and adverse effects to
Dakota skipper populations may occur
rapidly (McCabe 1981, p. 179; Royer
and Royer 1998, p. 23). The conversion
of similar habitats in Manitoba from
haying to grazing may be a major threat
to the Dakota skipper there as well
(Webster 2007, pp. i–ii, 6). In contrast,
limited or ‘‘light rotational grazing’’ of
habitats on steep dry-mesic slopes in
Saskatchewan may not conflict with
Dakota skipper conservation (Webster
2007, p. ii).
The reduced vulnerability of habitats
on dry-mesic slopes to the effects of
grazing may be due, in part, to the
tendency for grazing pressure to be
lighter in sloped areas. The steepness of
habitats occupied by Dakota skippers in
Saskatchewan, for example, limits their
use for grazing (Webster 2007, p. ii).
Steep slopes may also play a role in
reducing the adverse effects of grazing at
some sites in South Dakota—at one
grazed site inhabited by the Dakota
skipper, for example, habitat on steep
slopes was ‘‘in good condition,’’
whereas ‘‘lesser slopes’’ were
‘‘moderately grazed’’ and some areas
were ‘‘overgrazed’’ (Skadsen 1999a, p.
29).
In the proposed rule, we cited the lack
of any examples of strong populations of
Dakota skippers where the relatively
moist and flat (‘Type A’) habitats are
grazed as evidence that it would not be
necessary and advisable to exempt take
caused by grazing in certain counties
where ‘Type A’ habitats are found. As
stated above, we still do not recommend
a change to grazing on ‘Type A’ habitats
occupied by the Dakota skipper unless
a cooperative plan is developed to
ensure that it will be done in a manner
that conserves the species in the
affected habitats. Nevertheless, in light
of the great importance that cooperative
relationships with certain public land
management agencies and private
livestock producers will play in
conserving the Dakota skipper, we find
that it is necessary and advisable to
exempt take that may be caused by
grazing on non-Federal lands regardless
of geographic area. We do not expect
this to result in a significant change in
management from haying to grazing
because other factors, such as the costs
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63745
of building fences and developing
livestock watering facilities, are more
important factors that will influence this
land management decision.
Provisions of the 4(d) Rule for the
Dakota Skipper
Section 4(d) of the Act states that ‘‘the
Secretary shall issue such regulations as
[s]he deems necessary and advisable to
provide for the conservation’’ of species
listed as a threatened species.
Conservation is defined in the Act to
mean ‘‘to use and the use of all methods
and procedures which are necessary to
bring any endangered species or
threatened species to the point at which
the measures provided pursuant to [the
Act] are no longer necessary.’’
Additionally, section 4(d) states that the
Secretary ‘‘may by regulation prohibit
with respect to any threatened species
any act prohibited under section
9(a)(1).’’
The courts have recognized the extent
of the Secretary’s discretion under this
standard to develop rules that are
appropriate for the conservation of a
species. For example, the Secretary may
find that it is necessary and advisable
not to include a taking prohibition, or to
include a limited taking prohibition. See
Alsea Valley Alliance v. Lautenbacher,
2007 U.S. Dist. Lexis 60203 (D. Or.
2007); Washington Environmental
Council v. National Marine Fisheries
Service, and 2002 U.S. Dist. Lexis 5432
(W.D. Wash. 2002). In addition, as
affirmed in State of Louisiana v. Verity,
853 F.2d 322 (5th Cir. 1988), the rule
need not address all the threats to the
species. As noted by Congress when the
Act was initially enacted, ‘‘once an
animal is on the threatened list, the
Secretary has an almost infinite number
of options available to him with regard
to the permitted activities for those
species. [S]he may, for example, permit
taking, but not importation of such
species,’’ or [s]he may choose to forbid
both taking and importation but allow
the transportation of such species, as
long as the measures will ‘‘serve to
conserve, protect, or restore the species
concerned in accordance with the
purposes of the Act’’ (H.R. Rep. No. 412,
93rd Cong., 1st Sess. 1973).
Section 9 prohibitions make it illegal
for any person subject to the jurisdiction
of the United States to take (including
harass, harm, pursue, shoot, wound,
kill, trap, capture, or collect; or attempt
any of these), import or export, ship in
interstate commerce in the course of
commercial activity, or sell or offer for
sale in interstate or foreign commerce
any wildlife species listed as an
endangered species, without written
authorization. It also is illegal under
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asabaliauskas on DSK5VPTVN1PROD with RULES
section 9(a)(1) of the Act to possess, sell,
deliver, carry, transport, or ship any
such wildlife that is taken illegally.
Prohibited actions consistent with
section 9 of the Act are outlined for
threatened species in 50 CFR 17.31(a)
and (b). Through this 4(d) rule, all
prohibitions in 50 CFR 17.31(a) and (b)
apply to the Dakota skipper except in
the specific instances as outlined below.
The 4(d) rule will not remove or alter in
any way the consultation requirements
under section 7 of the Act.
Routine Livestock Operations and
Maintenance of Recreational Trails and
Rights-of-Way
Incidental take that is caused by the
routine livestock ranching and other
specified trail and rights-of-way
maintenance activities described below
and that are implemented on private,
State, and tribal lands and on other
lands not under Federal jurisdiction
(e.g. lands owned by county
governments or local governments) will
not be prohibited, as long as those
activities are otherwise legal and
conducted in accordance with
applicable State, Federal, tribal, and
local laws and regulations. For the
purposes of this 4(d) rule, routine
livestock ranching and recreational trail
and rights-of-way maintenance activities
include the items listed below. Except
as explicitly stated below, these
activities must be associated with
livestock ranching for this 4(d) rule to
apply.
(1) Fence Construction and
Maintenance: Fences are an essential
tool for livestock and ranch
management. In addition, the strategic
distribution of fencing is also necessary
to implement multi-cell rotational
grazing systems, which may be
necessary to improve grazing
management and provide a conservation
benefit to Dakota skipper habitat.
(2) Livestock Gathering and
Management: The installation and
maintenance of corrals, loading chutes,
and other livestock working facilities
are critical to ranch operations. These
activities may be carried out with only
minimal impacts to Dakota skipper if
carefully sited with respect to the
location and distribution of important
Dakota skipper habitat.
(3) Development and Maintenance of
Livestock Watering Facilities: Without a
suitable water source in a pasture,
livestock ranching is impossible. The
proper distribution of livestock watering
sources is also a prerequisite to
implementing improved grazing
management via the use of multi-cell
rotational grazing systems that may be
necessary to conserve Dakota skipper
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habitat and to provide a conservation
benefit to the species on grazed sites.
This activity includes both the initial
development of water sources and their
maintenance. Dugout ponds, for
example, typically require a cleanout
after 15 to 20 years.
(4) Noxious Weed Control: State and
county laws require landowners to
control noxious weeds on their
property, and the timing of control
actions is usually dependent on the
growth stage of the weed species.
Control of noxious weeds may also be
important to protect Dakota skipper
habitat because native plant diversity
declines when nonnative plant species
invade and become established in
prairies (Boettcher et al. 1993, p. 35).
Broadcast application of herbicides,
however, may result in significant
deterioration of native plant diversity in
prairies (Smart et al. 2011, p. 184).
Therefore, incidental take of Dakota
skipper that may result from spraying of
herbicides would be exempt except as a
result of broadcast spraying, which we
define as the application of herbicides
evenly across the entire application
area. Note that herbicide applications
would not affect the Dakota skipper if
they do not affect the limited areas
where the species is present. Broadcast
applications of herbicides that do not
affect habitats occupied by the Dakota
skipper would not result in take of the
species, and thus would not result in
violation of section 9 of the Act. Take
that may occur as a result of mowing
that is carried out for the purpose of
controlling one or more noxious weed
species is also exempted from the take
prohibitions under section 9 of the Act
by issuance of this 4(d) rule.
(5) Haying: Stock cows need to be
maintained through the non-growing
season though supplemental feeding
with hay; thus, haying (cutting grass and
other vegetation for drying and use as
livestock feed) is a critical component of
ranch activity. Dakota skippers occur on
several native hayland sites—sites
where the native-prairie vegetation is
mowed for hay. For the purposes of this
rule, native hayland does not include
lands that had previously been plowed
and were then replanted to native or
nonnative vegetation. Native hayland
may include, however, areas within
transportation (e.g., road, highway,
railroad) rights-of-ways and corridors
where native grassland is mowed for
hay. Native haylands are typically cut in
August, after the needlegrass
(Hesperostipa spp. or Nassella viridula,
or both) awns drop. Incidental take of
Dakota skippers that occurs as a result
of haying no earlier than July 16 (after
July 15) is exempted from the take
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Fmt 4701
Sfmt 4700
prohibitions under section 9 of the Act
by issuance of this 4(d) rule. Dakota
skippers are unlikely to occur in
replanted grasslands (grasslands
replanted on formerly plowed or
cultivated lands) or in tame hayland or
grassland (hayland or grassland planted
to and comprising primarily nonnative
grass species, such as smooth brome
(Bromus inermis inermis)). Therefore,
mowing replanted and tame grasslands
before July 16 would not result in take
of Dakota skippers and would thus not
result in a violation of section 9 of the
Act.
(6) Mowing Section Line Rights-ofWay and Recreational Trails: Section
line rights-of-way and some recreational
trails need to be mowed several times
during the growing season to ensure that
snow will not catch and block vehicle
access and that they are suitable for
hiking and other intended recreational
activities, respectively. Section line
rights-of-way typically comprise
disturbed soil that has been contoured
for a roadway and are likely to contain
only small proportions of Dakota
skipper habitat at any affected site.
Therefore, impacts to Dakota skipper
populations are likely to be minimal,
and any incidental take that is a result
of mowing of section line rights-of-way
and recreational trails will be exempt
from the take prohibitions of section 9
of the Act. Recreational trails are travel
ways established either through
construction or use that are intended for
and passable by at least one or more of
the following: foot traffic, bicycles, inline skates, wheelchairs, or crosscountry skis. Incidental take that may be
caused by mowing recreational trails
does not need to be associated with
livestock ranching for the 4(d) rule to
apply.
(7) Livestock (Cattle, Bison, or Horse)
Grazing: Incidental take of Dakota
skippers that may result from grazing on
private, State, or tribal land is exempt
from the take prohibitions of section 9
of the Act.
We may issue permits to carry out
otherwise prohibited activities
involving endangered and threatened
wildlife species under certain
circumstances. Regulations governing
permits are codified at 50 CFR 17.22 for
endangered species, and at 17.32 for
threatened species. With regard to
endangered wildlife, a permit must be
issued for the following purposes: For
scientific purposes, to enhance the
propagation or survival of the species,
and for incidental take in connection
with otherwise lawful activities.
It is our policy, as published in the
Federal Register on July 1, 1994 (59 FR
34272), to identify to the maximum
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extent practicable at the time a species
is listed, those activities that would or
would not constitute a violation of
section 9 of the Act. The intent of this
policy is to increase public awareness of
the effect of a final listing on proposed
and ongoing activities within the range
of a listed species. Based on the best
available information, the following
actions are unlikely to result in a
violation of section 9, if these activities
are carried out in accordance with
existing regulations and permit
requirements; this list is not
comprehensive:
(1) Unauthorized collecting, handling,
possessing, selling, delivering, carrying,
or transporting of the species, including
import or export across State lines and
international boundaries, except for
properly documented antique
specimens of these taxa at least 100
years old, as defined by section 10(h)(1)
of the Act;
(2) Unauthorized modification,
removal, or destruction of the prairie
vegetation, soils, or hydrology in which
the Dakota skipper and Poweshiek
skipperling are known to occur;
(3) The unauthorized release of
biological control agents that attack any
life stage of these species, including the
unauthorized use of herbicides,
pesticides, or other chemicals in
habitats in which the Poweshiek
skipperling or Dakota skipper is known
to occur;
(4) Introduction of nonnative species
that compete with or prey upon the
Dakota skipper and Poweshiek
skipperling or their food sources, such
as the introduction of nonnative leafy
spurge, reed canary grass, or glossy
buckthorn, to the State of Iowa,
Michigan, Minnesota, North Dakota,
South Dakota, and Wisconsin; and
(5) Unauthorized discharge of
chemicals or fill material into any
wetlands in which the Poweshiek
skipperling or Dakota skipper are
known to occur.
Questions regarding whether specific
activities would constitute a violation of
section 9 of the Act should be directed
to the Twin Cities Ecological Services
Fish and Wildlife Office (see FOR
FURTHER INFORMATION CONTACT).
Requests for copies of the regulations
concerning listed animals and general
inquiries regarding prohibitions and
permits may be addressed to the U.S.
Fish and Wildlife Service, Endangered
Species Permits, 5600 American Blvd.,
West, Suite 990, Bloomington, MN
(telephone 612–713–5350; facsimile
612–713–5292).
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Required Determinations
National Environmental Policy Act (42
U.S.C. 4321 et seq.)
We have determined that
environmental assessments and
environmental impact statements, as
defined under the authority of the
National Environmental Policy Act
(NEPA; 42 U.S.C. 4321 et seq.), need not
be prepared in connection with listing
a species as an endangered or
threatened species under the
Endangered Species Act. We published
a notice outlining our reasons for this
determination in the Federal Register
on October 25, 1983 (48 FR 49244).
Government-to-Government
Relationship With Tribes
In accordance with the President’s
memorandum of April 29, 1994
(Government-to-Government Relations
with Native American Tribal
Governments; 59 FR 22951), Executive
Order 13175 (Consultation and
Coordination With Indian Tribal
Governments), and the Department of
the Interior’s manual at 512 DM 2, we
readily acknowledge our responsibility
to communicate meaningfully with
recognized Federal Tribes on a
government-to-government basis. In
accordance with Secretarial Order 3206
of June 5, 1997 (American Indian Tribal
Rights, Federal-Tribal Trust
Responsibilities, and the Endangered
Species Act), we readily acknowledge
our responsibilities to work directly
with tribes in developing programs for
healthy ecosystems, to acknowledge that
tribal lands are not subject to the same
controls as Federal public lands, to
remain sensitive to Indian culture, and
to make information available to tribes.
The Sisseton-Wahpeton Oyate,
Flandreau Santee Sioux Tribe, Turtle
Mountain Band of Chippewa, Three
Affiliated Tribes, Spirit Lake Sioux
Tribe, and Standing Rock Sioux Tribe
are the main Tribes affected by this final
rule. We began government-togovernment consultation with these
tribes prior to the publication of the
proposed rule, through the public
comment period, and during the
development of the final listing
determination.
We sent letters in September 2012 to
each Tribe seeking early input regarding
the species status review and to offer
government-to-government
consultation. We sent notification letters
in October and November of 2013 to
each Tribe describing the critical habitat
exclusion process under section 4(b)(2)
of the Act, and we engaged in
conversation with the Tribes about the
proposed listing and critical habitat
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63747
rules to the extent possible. We have
maintained contact with Flandreau
Santee Sioux Tribe, Turtle Mountain
Chippewa, Three Affiliated Tribes,
Spirit Lake Sioux Tribe, and Standing
Rock Sioux Tribe through letters, phone
calls, and emails, and we notified each
tribe when documents pertaining to the
listing and critical habitat rules were
made available.
We have coordinated several survey
efforts with Sisseton-Wahpeton Oyate
since 1995 and held an informational
meeting for the Tribe in April 2014, to
better explain the proposed listing and
designation of critical habitat. We met
with representatives from the Turtle
Mountain Chippewa in May 2014, and
conducted a site visit at that time to
evaluate areas proposed for designation
as critical habitat. We did not receive
comments from the Sisseton-Wahpeton
Oyate, Three Affiliated Tribes, Standing
Rock Sioux Tribe, Flandreau Santee
Sioux Tribe, Turtle Mountain
Chippewa, or the Spirit Lake Nation.
However, notification of the available
economic analysis screening
memorandum for the critical habitat
proposal was provided to all Tribes in
the species’ ranges at the time it was
made available to the public.
References Cited
A complete list of references cited in
this rulemaking is available on the
Internet at https://www.regulations.gov
and upon request from the Twin Cities
Ecological Services Field Office (see FOR
FURTHER INFORMATION CONTACT).
Authors
The primary authors of this final rule
are the staff members of the Twin Cities
Ecological Services Field Office.
List of Subjects in 50 CFR Part 17
Endangered and threatened species,
Exports, Imports, Reporting and
recordkeeping requirements,
Transportation.
Regulation Promulgation
Accordingly, we amend part 17,
subchapter B of chapter I, title 50 of the
Code of Federal Regulations, as follows:
PART 17—[AMENDED]
1. The authority citation for part 17
continues to read as follows:
■
Authority: 16 U.S.C. 1361–1407; 1531–
1544; 4201–4245; unless otherwise noted.
2. Amend § 17.11(h) by adding entries
for ‘‘Skipper, Dakota’’ and ‘‘Skipperling,
Poweshiek’’ to the List of Endangered
and Threatened Wildlife in alphabetical
order under ‘‘Insects’’ to read as follows:
■
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Federal Register / Vol. 79, No. 206 / Friday, October 24, 2014 / Rules and Regulations
§ 17.11 Endangered and threatened
wildlife.
*
*
*
*
(h) * * *
*
Species
Historic range
Common name
*
INSECTS
Scientific name
*
*
*
Hesperia dacotae
*
U.S.A. (IA, IL,
MN, ND, SD);
Canada (Manitoba, Saskatchewan).
*
Skipperling,
Poweshiek.
*
Oarisma
poweshiek.
*
U.S.A. (IA, IL, IN,
MI, MN, ND,
SD, WI,); Canada (Manitoba).
*
*
*
*
*
*
*
3. Amend § 17.47 by adding paragraph
(b) to read as follows:
■
§ 17.47
Special rules—insects.
*
*
*
*
*
(b) Dakota skipper (Hesperia dacotae).
(1) Which populations of the Dakota
skipper are covered by this special rule?
This rule covers the distribution of
Dakota skipper in the United States.
(2) Prohibitions. Except as noted in
paragraph (b)(3) of this section, all
prohibitions and provisions of §§ 17.31
and 17.32 apply to the Dakota skipper.
(3) Exemptions from prohibitions.
Incidental take of Dakota skipper will
not be a violation of section 9 of the Act
if it occurs as a result of the following
activities (except where explicitly stated
otherwise, these activities must be
associated with livestock ranching):
(i) Fence construction and
maintenance.
(ii) Livestock gathering and
management. The installation and
maintenance of corrals, loading chutes,
and other livestock working facilities
must be carefully sited with respect to
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When listed
*
*
*
*
851
*
851
NA
T
*
*
NA
E
*
*
the location and distribution of
important Dakota skipper habitat.
(iii) Development and maintenance of
livestock watering facilities.
(iv) Noxious weed control. Incidental
take of Dakota skipper that results from
spraying of herbicides is not a violation
of section 9 of the Act, except such take
that results from broadcast spraying,
which is the application of herbicides
evenly across the entire application
area. Incidental take that results from
mowing to control one or more noxious
weed species would also not be a
violation of section 9 of the Act.
(v) Haying. For the purposes of this
rule, native haylands do not include
lands that had previously been plowed
and were then replanted to native or
nonnative vegetation, but native
haylands do include areas within
transportation (e.g., road, highway,
railroad) rights-of-ways and corridors
where native grasses are mowed for hay.
Haying of native haylands no earlier
than July 16 (after July 15) would not be
a violation of section 9 of the Act.
Mowing of replanted grasslands
(grasslands replanted on formerly
plowed or cultivated lands) or tame
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Special
rules
NA
*
NA
*
Critical
habitat
Status
*
*
Skipper, Dakota ...
asabaliauskas on DSK5VPTVN1PROD with RULES
Vertebrate
population where
endangered or
threatened
*
*
*
17.47(b)
*
NA
*
haylands or grasslands (planted hayland
or grassland comprising primarily
nonnative grass species, such as smooth
brome (Bromus inermis inermis)) would
also not be a violation of section 9 of the
Act at any time of the year.
(vi) Mowing section line rights-of-way
and recreational trails. Mowing of
section line rights-of-way (typically
disturbed soil that has been contoured
for a roadway) would not be a violation
of section 9 of the Act. Mowing of
recreational trails (travelways
established either through construction
or use that are intended for and passable
by foot traffic, bicycles, in-line skates,
wheelchairs, or cross-country skis)
would not be a violation of section 9 of
the Act, regardless of whether the trails
are associated with livestock ranching.
(vii) Livestock (cattle, bison, or horse)
grazing on private, State, or tribal land.
Dated: October 15, 2014.
Stephen Guertin,
Acting Director, U.S. Fish and Wildlife
Service.
[FR Doc. 2014–25190 Filed 10–23–14; 8:45 am]
BILLING CODE 4310–55–P
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[Federal Register Volume 79, Number 206 (Friday, October 24, 2014)]
[Rules and Regulations]
[Pages 63671-63748]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-25190]
[[Page 63671]]
Vol. 79
Friday,
No. 206
October 24, 2014
Part II
Department of the Interior
-----------------------------------------------------------------------
Fish and Wildlife Service
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50 CFR Part 17
Endangered and Threatened Wildlife and Plants; Threatened Species
Status for Dakota Skipper and Endangered Species Status for Poweshiek
Skipperling; Final Rule
Federal Register / Vol. 79 , No. 206 / Friday, October 24, 2014 /
Rules and Regulations
[[Page 63672]]
-----------------------------------------------------------------------
DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R3-ES-2013-0043; 4500030113: 4500030113]
RIN 1018-AY01
Endangered and Threatened Wildlife and Plants; Threatened Species
Status for Dakota Skipper and Endangered Species Status for Poweshiek
Skipperling
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Final rule.
-----------------------------------------------------------------------
SUMMARY: We, the U.S. Fish and Wildlife Service (Service), determine
threatened species status under the Endangered Species Act of 1973
(Act), as amended, for the Dakota skipper (Hesperia dacotae), a
butterfly currently found in Minnesota, North Dakota, South Dakota,
Manitoba, and Saskatchewan and endangered species status for the
Poweshiek skipperling (Oarisma poweshiek), a butterfly currently found
in Michigan, Minnesota, Wisconsin, and Manitoba. The effect of this
regulation will be to add these species to the List of Endangered and
Threatened Wildlife.
DATES: This rule becomes effective November 24, 2014.
ADDRESSES: This final rule is available on the internet at https://www.regulations.gov and https://www.fws.gov/midwest/Endangered/.
Comments and materials we received, as well as supporting documentation
we used in preparing this rule, are available for public inspection at
https://www.regulations.gov. All of the comments, materials, and
documentation that we considered in this rulemaking are available by
appointment, during normal business hours at: U.S. Fish and Wildlife
Service, Twin Cities Field Office, 4101 American Boulevard East,
Bloomington, Minnesota 55425; (612) 725-3548; (612) 725-3609
(facsimile).
FOR FURTHER INFORMATION CONTACT: Peter Fasbender, Field Supervisor,
Twin Cities Field Office, 4101 American Boulevard East, Bloomington,
Minnesota 55425; (612) 725-3548; (612) 725-3609 (facsimile). Persons
who use a telecommunications device for the deaf (TDD) may call the
Federal Information Relay Service (FIRS) at 800-877-8339.
SUPPLEMENTARY INFORMATION:
Executive Summary
Why we need to publish a rule. Under the Endangered Species Act, a
species may warrant protection through listing if it is endangered or
threatened throughout all or a significant portion of its range.
Listing a species as an endangered or threatened species can only be
completed by issuing a rule.
This rule will finalize the listing of the Dakota skipper (Hesperia
dacotae) as a threatened species and the Poweshiek skipperling (Oarisma
poweshiek) as an endangered species.
The basis for our action. Under the Endangered Species Act, we can
determine that a species is an endangered or threatened species based
on any of five factors: (A) The present or threatened destruction,
modification, or curtailment of its habitat or range; (B)
Overutilization for commercial, recreational, scientific, or
educational purposes; (C) Disease or predation; (D) The inadequacy of
existing regulatory mechanisms; or (E) Other natural or manmade factors
affecting its continued existence. We have determined the threats to
both species include:
Habitat loss and degradation of native prairies and
prairie fens, resulting from conversion to agriculture or other
development; ecological succession and encroachment of invasive species
and woody vegetation primarily due to lack of management; past and
present fire, haying, or grazing management that degrades or eliminates
native prairie grasses and flowering forbs; flooding; and groundwater
depletion, alteration, and contamination.
Other natural or manmade factors, including loss of
genetic diversity, small size and isolation of sites, indiscriminate
use of herbicides such that it reduces or eliminates nectar sources,
climate conditions such as drought, direct mortality from fire and
other management activities or natural occurrences, direct or indirect
mortality from indiscriminate use of pesticides, and other unknown
stressors.
Existing regulatory mechanisms are inadequate to mitigate
these threats to both species.
Peer review and public comment. We sought comments from independent
specialists to ensure that our designation is based on scientifically
sound data, assumptions, and analyses. We invited these peer reviewers
to comment on our listing proposal. We also considered all other
comments and information received during the comment period.
Previous Federal Action
Please refer to the proposed listing rule for the Dakota skipper
and Poweshiek skipperling (78 FR 63574; October 24, 2013) for a
detailed description of previous Federal actions concerning this
species.
Background
Please refer to the proposed listing rule for the Dakota skipper
and the Poweshiek skipperling (78 FR 63574; October 24, 2013) for a
summary of species information.
Status Assessments for Dakota Skipper and Poweshiek Skipperling Dakota
Skipper
Species Description
The Dakota skipper (Hesperia dacotae) is a member of the skipper
family Hesperiidae and was first described in 1911 from collections
taken at Volga, South Dakota, and Grinnell, Iowa (Skinner 1911 in Royer
and Marrone 1992a, p. 1). The family Hesperiidae comprises seven
subfamilies worldwide, four of which occur in North America, north of
Mexico (Brower and Warren at https://tolweb.org/Hesperiidae). There are
21 recognized species in the genus Hesperia (ibid). Dakota skipper is
the accepted common name for H. dacotae.
The Dakota skipper is a small to medium-sized butterfly with a
wingspan of 2.4-3.2 centimeters (cm) (0.9-1.3 inches (in)) and hooked
antennae (Royer and Marrone 1992a, p. 3). Like other Hesperiidae
species, Dakota skippers have a faster and more powerful flight than
most butterflies because of a thick, well-muscled thorax (Scott 1986,
p. 415).
Adult Dakota skippers have variable markings. The dorsal surface of
adult male wings ranges in color from tawny-orange to brown and has a
prominent mark on the forewing; the ventral surface is dusty yellow-
orange (Royer and Marrone 1992a, p. 3). The dorsal surface of adult
females is darker brown with diffused tawny orange spots and a few
diffused white spots restricted to the margin of the forewing; the
ventral surfaces are dusty gray-brown with a faint white spotband
across the middle of the wing (Royer and Marrone 1992a, p. 3). Adult
Dakota skippers may be confused with the Ottoe skipper (H. ottoe),
which is somewhat larger with slightly longer wings (Royer and Marrone
1992a, p. 3). Dakota skipper pupae are reddish-brown, and the larvae
are light brown with a black collar and dark brown head (McCabe 1981,
p. 181).
[[Page 63673]]
General Life History
Dakota skippers are univoltine (having a single flight per year),
with an adult flight period that may occur from the middle of June
through the end of July (McCabe 1979, p. 6; McCabe 1981, p. 180; Dana
1991, p. 1; Royer and Marrone 1992a, p. 26; Skadsen 1997, p. 3; Swengel
and Swengel 1999, p. 282). The actual flight period varies somewhat
across the range of each species and can also vary significantly from
year to year (e.g., Rigney 2013a, p. 138), depending on temperature
patterns (Bink and Bik 2009, Koda and Nakamura 2012). Females emerge
slightly later than males (Dana 1991, p. 15, Rigney 2013a, p. 138), and
the observed sex ratio of Dakota skippers was roughly equal during peak
flight periods (Dana 1991, p. 15; Swengel and Swengel 1999, pp. 274,
283).
The Dakota skipper flight period in a locality lasts 2 to 4 weeks,
and mating occurs throughout this period (Braker 1985, p. 46; McCabe
and Post 1977, pp. 36-38; McCabe 1979, p. 6; McCabe 1981, p. 180; Dana
1991, p. 15; Swengel and Swengel 1999, p. 282; Rigney 2013a, p. 138).
Adult male Dakota skippers exhibit perching behavior (perch on tall
plants to search for females), but occasionally appear to patrol in
search of mating opportunities (Royer and Marrone 1992a, p. 25).
Dakota skippers lay eggs on broadleaf plants (McCabe 1981, p. 180)
and grasses (Dana 1991, p. 17), although larvae feed only on grasses.
Potential lifetime fecundity is between 180 and 250 eggs per female
Dakota skipper; realized fecundity depends upon longevity (Dana 1991,
p. 26). Female Dakota skippers lay eggs daily in diminishing numbers as
they age (Dana 1991, pp. 25-26). Dana (1991, p. 32) estimated the
potential adult life span of Dakota skipper to be 3 weeks and the
average life span (or residence on site before death or emigration) to
be 3 to 10 days on one Minnesota prairie.
Dakota skippers overwinter as larvae and complete one generation
per year. Dakota skipper eggs hatch after incubating for 7-20 days;
therefore, hatching is likely completed before the end of July. Recent
research at the Minnesota Zoo demonstrated that, under controlled
conditions in the laboratory, Dakota skippers eggs hatched after 11 to
16 days, and the majority of the caterpillars hatched on the 13th and
14th days (Runquist 2014, pers. comm.). After hatching, Dakota skipper
larvae crawl to the bases of grass plants where they form shelters at
or below the ground surface with silk, fastened together with plant
tissue (Dana 1991, p. 16). They construct 2-3 successively larger
shelters as they grow (Dana 1991, p. 16). The larvae emerge from their
shelters at night to forage (McCabe 1979, p. 6; McCabe 1981, p. 181;
Royer and Marrone 1992a, p. 25) and appear to clip blades of grass and
bring them back to their shelters to consume (Dana 2012a, pers. comm.).
Dakota skippers have six or seven larval stages (instars) (Dana
1991, pp. 14-15) and overwinter (diapause) in ground-level or
subsurface shelters during either the fourth or fifth instar (McCabe
1979, p. 6; McCabe 1981, pp. 180, 189; Dana 1991, p. 15; Royer and
Marrone 1992a, pp. 25-26). In the spring, larvae resume feeding and
undergo two additional molts before they pupate. During the last two
instars, larvae shift from buried shelters to horizontal shelters at
the soil surface (Dana 1991, p. 16).
Food and Water
Nectar and water sources for adult Dakota skippers vary regionally
and include purple coneflower (Echinacea angustifolia), blanketflower
(Gaillardia aristata), black-eyed Susan (Rudbeckia hirta), purple
locoweed (Oxytropis lambertii), bluebell bellflower (Campanula
rotundifolia), prairie milkvetch (Astragalus adsurgens) (syn. A.
laxmannii), and yellow sundrops (Calylophus serrulatus) (Dana 1991;
McCabe and Post 1977, pp. 36-38; Royer and Marrone 1992a, p. 21; Rigney
2013a, p. 142). Plant species likely vary in their value as nectar
sources due to the amount of nectar available during the adult flight
period (Dana 1991, p. 48). Nectar source preferences are typically
indicated as the relative proportion of plants selected for nectaring
among all the available species in a particular area. Swengel and
Swengel (1999, pp. 280-281) observed nectaring at 25 plant species,
however, most of the nectaring was at purple coneflower and
blanketflower. Dana (1991, p. 21) reported the use of 25 nectar species
in Minnesota with purple coneflower most frequented; McCabe (1979, p.
42; McCabe 1981, p. 187) observed Dakota skippers using eight nectar
plants. Dakota skippers in Manitoba were recently observed nectaring on
12 species of plants, primarily black-eyed Susan, but also including 6
species that were previously unrecorded as nectar flowers: White
sweetclover (Melilotus alba), purple prairie clover (Petalostemon
purpureus), yellow evening-primrose (Oenothera biennis), palespike
lobelia (Lobelia spicata), fiddleleaf hawksbeard (Crepis runcinata),
and upland white aster (Solidago ptarmicoides) (Rigney 2013a, pp. 4,
57). In addition to nutrition, the nectar of flowering forbs provides
water for Dakota skipper, which is necessary to avoid desiccation
during flight activity (Dana 1991, p. 47; Dana 2013, pers. comm.). Some
plant species listed in some studies as nectar flowers are likely used
for perching and patrolling rather than as nectar sources.
The flight of the adult female typically extends beyond that of
males (Dana 2014, pers. comm.; Dana 1991, pp. 1,15; Rigney 2013a, p.
138); therefore the two sexes can visit the same nectar plant species
at different rates (e.g., if the flowering period is more coincident
with either the male or the female flight period). For example, Dana
(1991, p. 21) observed a greater number of males than females visiting
purple locoweed--this plant is already past its flowering peak at the
beginning of the male flight and nearly finished flowering by the peak
female flight (Dana 2014, pers. comm.).
Dakota skipper larvae feed on several native grass species; little
bluestem (Schizachyrium scoparium) is a frequent food source of the
larvae (Dana 1991, p. 17; Royer and Marrone 1992a, p. 25), although
they have been found on Dichanthelium spp., and other native grasses
(Royer and Marrone 1992a, p. 25). When presented with no other choice,
Dakota skipper larvae may feed on a variety of native and nonnative
grasses (e.g., Kentucky bluegrass (Poa pratensis)) at least until
diapause (Dana 1991, p. 17). The timing of growth and development of
grasses relative to the larval period of Dakota skippers are likely
important in determining the suitability of grass species as larval
host plants. Large leaf blades, leaf hairs, and the distance from
larval ground shelters to palatable leaf parts preclude the value of
big bluestem and Indian grass as larval food plants, particularly at
younger larval stages (Dana 1991, p. 46). In captivity, Dakota skipper
larvae ate big bluestem (Andropogon gerardii), at older larval stages,
and prairie dropseed (Sporobolus heterolepis) (Runquist 2014, pers.
comm.). Captive larvae also fed on smooth brome (Bromus inermis) (Dana
1991, p 17), but this was not tested in a natural setting and the
structural features of this grass would hinder or prevent larval
survival (Dana 2013, pers. comm.). The tight empirical correlation
between occurrence of Dakota skippers and the dominance of native
grasses in the habitat, indicates that population persistence requires
native grasses for survival (Dana 2013, pers. comm.).
[[Page 63674]]
Dispersal
Dakota skipper are not known to disperse widely; the species was
evaluated among 291 butterfly species in Canada as having relatively
low mobility. Experts estimated Dakota skipper to have a mean mobility
of 3.5 (standard deviation = 0.7) on a scale of 0 (sedentary) to 10
(highly mobile) (Burke et al. 2011, p. 2279; Fitzsimmons 2012, pers.
comm.). Dakota skippers may be incapable of moving greater than 1
kilometer (km) (0.6 miles (mi)) between patches of prairie habitat
separated by structurally similar habitats (e.g., crop fields, grass-
dominated fields or pasture, but not necessarily native prairie)
(Cochrane and Delphey 2002, p. 6). Royer and Marrone (1992a, p. 25)
concluded that Dakota skippers are not inclined to disperse, although
they did not describe individual ranges or dispersal distances. McCabe
(1979, p. 9; 1981, p. 186) found that concentrated activity areas for
Dakota skippers shift annually in response to local nectar sources and
disturbance.
In a mark-recapture study, average adult movements of Dakota
skipper were less than 300 meters (m) (984 feet (ft)) over 3-7 days;
marked adults crossed less than 200 m (656 ft) of unsuitable habitat
between two prairie patches and moved along ridges more frequently than
across valleys (Dana 1991, pp. 38-40). Dana (1997, p. 5) later observed
reduced movement rates across a small valley dominated by exotic
grasses compared with movements in adjacent widespread prairie habitat.
Roads and crop fields were suspected as impediments for movement among
prairie patches along two sites of the main valley (Dana 1997, p. 5),
although movements beyond the study area were beyond the scope of the
1997 mark-recapture study (Dana 2013, pers. comm.). Skadsen (1999, p.
2) reported possible movement of Dakota skippers in 1998 from a known
population at least 800 m (2625 ft) away to a site with an unusually
heavy growth of purple coneflower; he had not found Dakota skippers in
three previous years when coneflower production was sparse. The two
sites were connected by native vegetation of varying quality,
interspersed by a few asphalt and gravel roads (Skadsen 2001, pers.
comm.).
In summary, the best information we have suggests that dispersal of
Dakota skipper is very limited due in part to its short adult life span
and single annual flight. Therefore, the species' extirpation from a
site is likely permanent unless it is within about 1 km (0.6 mi) of a
site that generates a sufficient number of emigrants or is artificially
reintroduced to a site; however, the capability to propagate the Dakota
skipper is currently lacking.
Habitat
Dakota skippers are obligate residents of undisturbed (remnant,
untilled) high-quality prairie, ranging from wet-mesic tallgrass
prairie to dry-mesic mixed-grass prairie (Royer and Marrone 1992a, pp.
8, 21). High-quality prairie contains a high diversity of native plant
species, including flowering herbaceous plants (forbs). Royer and
Marrone (1992a, p. 21) categorized Dakota skipper habitat into two main
types that were once intermixed on a landscape scale, but are now
mostly segregated. The first, referred to as ``Type A'' by Royer et al.
(2008, pp. 14-16), is low wet-mesic prairie that occurs on near-shore
glacial lake deposits. Type A Dakota skipper habitat is dominated by
bluestem grasses, with three other plant species almost always present
and blooming during Dakota skipper's flight period: Wood lily (Lilium
philadelphicum), bluebell bellflower, and mountain deathcamas (smooth
camas; Zigadenus elegans) (McCabe 1981, p. 190). This habitat type has
a high water table and is subject to intermittent flooding in the
spring, but provides ``sufficient relief to provide segments of non-
inundated habitat during the spring larval growth period within any
single season'' (Royer et al. 2008, p. 15). Common forbs in bloom
during the late season in Type A habitat include Rocky Mountain blazing
star (Liatris ligulistylis), Canada goldenrod (Solidago canadensis),
strict blue-eyed grass (Sisyrinchium montanum), common goldstar
(Hypoxis hirsuta), and black-eyed Susan (Lenz 1999, p. 6). Type A
habitats also contain small patches of dry-mesic prairie inhabited by
Dakota skippers. Common forb species in these dry-mesic areas include
stiff sunflower (Helianthus pauciflorus Nutt. ssp. pauciflorus) and
candle anenome (Anemone cylindrica), although purple coneflower was
rare in these habitats (Lenz 1999, pp. 6-11). Dakota skipper inhabits
Type A habitat in north-central North Dakota, southeast North Dakota,
and Manitoba.
The second Dakota skipper habitat type, referred to as ``Type B''
by Royer et al. (2008, p. 14), occurs on rolling terrain over gravelly
glacial moraine deposits and is dominated by bluestems and needle
grasses (Heterostipa spp.). As with Type A habitat, bluebell bellflower
and wood lily are also present in Type B habitats, but Type B habitats
also support more extensive stands of purple coneflower, upright
prairie coneflower, and common gaillardia (Royer and Marrone 1992a, p.
22). Both Type A and Type B prairies may contain slightly depressional
(low topographical areas that allow for the collection of surface
water) wetlands with extensive flat areas and slightly convex hummocks,
which are dryer than the wet areas (Lenz 1999, pp. 4, 8).
In northeastern South Dakota, Dakota skippers inhabit primarily
Type B habitats with abundant purple coneflower, but they also occur in
nearby Type A habitats in some areas (Skadsen 1997, p. 4). All Type A
habitats occupied by Dakota skipper in South Dakota are near hill-
prairie (Type B) habitats that are managed with fall haying (Skadsen
2006b, p. 2).
Little bluestem and porcupine grass (Hesperostipa spartea) are the
predominant grass species in Dakota skipper habitat in South Dakota
(Skadsen 2006b, p. 2). Dry-mesic prairies suitable for Dakota skippers
in South Dakota typically include little bluestem, side oats grama,
porcupine grass, needle-and-thread grass (Hesperostipa comata), and
prairie dropseed, and a high diversity and abundance of forbs,
including purple coneflower, purple prairie clover, white prairie
clover, yellow sundrops, prairie groundsel (Packera plattensis),
prairie milkvetch, eastern pasqueflower (Pulsatilla patens), old man's
whiskers (prairie smoke, Geum triflorum), western silver aster
(Symphyotrichum sericeum), dotted blazing star (Liatris punctata), tall
blazing star (L. asper), meadow zizia (Zizia aptera), blanket flower,
prairie sagewort (Artemisia frigida), and leadplant (Amorpha canescens)
(Skadsen 2006b, pp. 1-2). Purple coneflower occurs at all sites where
the Dakota skipper has been recorded in South Dakota, although it is
absent at some sites where Dakota skipper is abundant in other States
(Skadsen 2006b, p. 2).
In Minnesota, Dakota skippers often inhabit Type B habitats,
however, the species has been documented in Type A habitats,
particularly in Kittson and Stearns counties. Dana (1997, p. 8)
described typical habitat in Minnesota as dry-mesic prairie dominated
by mid-height grasses with an abundance of nectar sources including
purple coneflower and prairie milkvetch (Astragalus laxmannii Jacq.
var. robustior). Southern dry prairies in Minnesota are described as
having sparse shrub cover (less than 5 percent) composed primarily of
leadplant, with prairie rose (Rosa arkansana), wormwood sage, or smooth
sumac (Rhus glabra) present and few, if any, trees (Minnesota DNR
2012a). Dana (1991, p. 21) never encountered Dakota
[[Page 63675]]
skippers in wet or wet-mesic prairies in Minnesota, despite abundance
of suitable plants and the frequent use of these habitats by similar
skipper species. In systematic surveys at 12 Minnesota sites, Swengel
and Swengel (1999, pp. 278-279) found that Dakota skippers were
significantly more abundant on dry prairie than on either wet-mesic
prairie.
In Manitoba, Dakota skipper habitat has been described as Type A
prairies, where the species tends to occupy the slightly higher, drier
areas of wet-mesic prairie where nectar sources are more abundant
(Webster 2003, p. 7). Recent studies classify Dakota Skipper sites in
Manitoba as tallgrass or medium to tallgrass prairies that have been
subject to minimal disturbance, generally consisting of higher, dryer
prairies adjacent to lower areas with sedges (Rigney 2013a, p. 155).
Inhabited areas are dominated by native grasses and sites are generally
characterized as having the following plant species: Big bluestem,
little bluestem (Schizachyrium scoparius), tufted hair grass
(Deschampsia caespitosa), switchgrass (Panicum virgatum), Cusick's
bluegrass (Poa cusickii), porcupine grass, common spikerush (Eleocharis
palustris), wood lily (Lilim philadelphicum), wild onion (Allium
stellatum), mountain death camas (Zygadenus elegans), death camas
(Zygadenus gramineus), common gold star (Hypoxis hirsute), wild prairie
rose, American licorice (Glycyrrhiza lepidota), white prairie clover
(Petalostemon candidum), purple prairie clover, Seneca snake root
(Polygala senega), meadow zizia, northern bedstraw (Galium boreale),
harebell, palespike lobelia, common yarrow (Achillea millefolium), pale
agoseris (Agoseris glauca), heath aster (Aster ericodes) or white
prairie aster (A. falcatus), smooth aster (Aster laevis), Flodman's
thistle (Cirsium flodmanii), fiddle leaf hawksbeard, eastern daisy
fleabane (Erigeron annuus), Maximilian sunflower (Helianthus
maximilianii), Nuttall's sunflower (Helianthus nuttallii), meadow
blazing star, black-eyed Susan, upland white aster, and stiff goldenrod
(Solidago rigida) (Rigney 2013a, pp. 155-156).
Occupied habitats in Saskatchewan are similar to the drier upland
dry-mesic mixed-grass prairie hillside habitats in Manitoba, which is
dominated by bluestems and needlegrass. The Dakota skipper was most
common on ridgetops and hillsides near purple coneflower (Webster 2003,
p. 8).
In North Dakota, an association of bluestems (Schizachyrium
scoparium, Andropogon gerardii) and needlegrasses, typically invaded by
Kentucky bluegrass, typifies dry-mesic Dakota skipper habitat in the
rolling terrain of river valleys and the Missouri Coteau (Royer and
Marrone 1992a, p. 22). These prairies, located on the western edge of
the species' known range, typically contain wood lily, bluebell
bellflower, coneflowers, and other asters as nectar sources; in some
areas, mountain deathcamas also occurs (Royer and Marrone 1992a, p.
22). The location of larval food plants rarely seems to affect Dakota
skipper distribution within habitats because these warm-season grasses
are usually dominant and evenly dispersed (Swengel 1994, p. 6),
although invasion by smooth brome grass and other invasive species may
displace or extirpate native larval food plants (Culliney 2005, p. 134;
Bahm et al. 2011, p. 240; LaBar and Schultz 2012, p. 177).
Two key factors, soils unsuitable for agriculture and steep
topography, have allowed remnant native-prairie habitats inhabited by
Dakota skippers to persist (Royer and Marrone 1992a, p. 22). McCabe
(1979, pp. 17-18; 1981, p. 192) and Royer et al. (2008, p. 16) have
linked the historical distribution of Dakota skippers to surface
geological features and soils that are glacial in origin and, possibly,
regional precipitation-evaporation ratios (ratio of evaporation
occurring naturally in one location over a given area compared to the
amount of precipitation, such as rain and snow, falling over the same
area). Soil types typical of Dakota skipper sites were described as
sandy loams, loamy sand, or loams (Lord 1988 in Royer et al. 2008, pp.
3, 10). Additional edaphic (soil) features, such as soil moisture,
compaction, surface temperature, pH, and humidity, may be contributing
factors in larval survival and, thus, important limiting factors for
Dakota skipper populations (Royer et al. 2008, p. 2). For example,
edaphic parameters measured in sites throughout the range of Dakota
skipper and occupied by the species included a bulk density (an
indicator of soil compaction) that ranged from 0.9g/cm\3\ to 1.3 g/
cm\3\ and mean soil pH that ranged from 6.3 to 6.7 with high micro-
scale variation (variation on a small scale) (Royer et al. 2008, p.
10). Soil texture ranged from 4 to 12 percent clay, 53 to 74 percent
sand, and 14 to 39 percent silt (Royer et al. 2008, p. 12). Seasonal
soil temperatures, measured at three depths (20, 40, and 60 cm (8, 16,
and 24 in)) were the same at all depths within a site; occupied
Minnesota sites generally had higher soil temperatures at all depths
than occupied sites in North Dakota or South Dakota (Royer et al. 2008,
p. 11). Royer did not measure these parameters in unoccupied sites.
Rigney (2013a, pp. 108-109) measured edaphic features at 8 sites in
Manitoba occupied by the species and broadly characterized the soil
compaction (at 10 cm) as 570 to 990 kPA, bulk density ranging from 0.75
to 1.30 kg/L, mean soil surface air temperature at 18 [deg]C during
Julian weeks 28-39 (continuous count of weeks since the beginning of
the calendar year), and mean relative humidity at 85 percent during the
same time period. Soils were classified as clay loams and sandy loams,
with generally low to moderate compaction (<1375 kPA) and bulk
densities, which is indicative of little or no compacting forces from
cattle grazing, tilling, or agricultural vehicles (Rigney 2013a, pp.
104, 119).
Royer (2008, pp. 2, 16) hypothesized that Dakota skipper larvae are
particularly vulnerable to desiccation (drying out) during dry summer
months and require ``vertical water distribution'' (movement of shallow
groundwater to the soil surface) in the soils or wet low areas to
provide relief from high summer temperatures. Humidity may also be
essential for larval survival during winter months since the larvae
cannot take in water during that time and depend on humid air to
minimize water loss through respiration (Dana 2013, pers. comm.). Royer
(2008, pp. 14-15) measured microclimalogical levels (climate in a small
space, such as at or near the soil surface) within ``primary larval
nesting zones'' (0 to 2 cm (0 to 0.8 inches) above the soil surface)
throughout the range of Dakota skippers, and found an acceptable
rangewide seasonal (summer) mean temperature range of 18 to 21 [deg]C
(64 to 70 [deg]F), rangewide seasonal mean dew point ranging from 14 to
17 [deg]C (57 to 63 [deg]F), and rangewide seasonal mean relative
humidity between 73 and 85 percent. Royer (2008) only examined occupied
areas for these parameters; therefore, the statistical and biological
significance of these edaphic variables cannot be determined from his
study.
Species Occupancy
We generally consider the Dakota skipper or Poweshiek skipperling
to be ``present'' at sites where the species was detected during the
most recent survey, if the survey was conducted in 2002 or more
recently and there is no evidence to suggest the species is now
extirpated from the site (e.g., no destruction or obvious and
significant degradation of the species' habitat), with the exception
[[Page 63676]]
of the following four sites. We consider the species to be present at
one Poweshiek skipperling site in Michigan where the species was
observed at the site in 1996, and no further surveys have been
conducted. This site, however, still has suitable habitat for the
species according to species experts in the State and at least one
other species of prairie-fen-dependent butterfly is present (Hosler
2013, pers. comm.). Therefore, the Poweshiek skipperling is most likely
still present at this site. We also consider the Dakota skipper to be
present at one site (Chanarambie Creek in Minnesota) where the most
recent survey was from 1994. At this site, no evidence suggests the
species is not still present because, based on a species-expert review
of the site, the habitat and management is still conducive to the
species (Dana 2013, pers. comm.). Additional sites where we consider
Dakota skipper to be present include two sites in Minnesota with 1996
records (Bluestem Prairie and Buffalo River State Park). Although no
survey for the species has taken place at Bluestem Prairie since 1996,
a 2012 assessment of the habitat at the site indicates that this site
is a high-quality prairie that contains the native prairie flora
conducive to the Dakota skipper (Selby 2012, p. 9). The site at Buffalo
River State park, which adjoins Bluestem Prairie, has not been surveyed
since 1996, but recent habitat assessments show that it still contains
prairie habitats with the native prairie flora conducive to the species
(MN DNR 2013, unpubl.). Furthermore, the species expert in Minnesota
supports that the species is most likely still present at these sites.
We assigned a status of ``unknown'' if the species was found in
1993 or more recently, but not in the most recent one to two sequential
survey year(s) since 1993 and there is no evidence to suggest the
species is now extirpated from the site (e.g., no destruction or
obvious and significant degradation of the species' habitat). We
considered a species to be ``possibly extirpated'' at sites where it
was detected at least once prior to 1993, but not in the most recent
one to two sequential survey years(s). A species is also considered
``possibly extirpated'' at sites where it was found prior to 1993 and
no surveys have been conducted in 1993 or more recently. At least three
sequential years of negative surveys, no matter what years they were
conducted, were necessary for us to consider the species ``extirpated''
from a site, because of the difficulty of detecting these species, as
explained further in this section. A species is also considered
``extirpated'' at sites where habitat for the species is no longer
present. If the species is considered to be extirpated from a site, the
occupancy status would not change unless the species is detected at
that location during future surveys.
When determining whether the species occupancy is unknown, possibly
extirpated, or extirpated at a particular site, we used the survey year
1993 as a cut-off date, because most known sites (more than 81 percent
of known Poweshiek skipperling sites and more than 86 percent of known
Dakota skipper sites) have been surveyed at least once since 1993, and
survey data more than 20 years old may not reflect the current status
of a species or its habitat at a site (for example, due to habitat loss
from secondary succession of woody vegetation or a change in plant
communities due to invasive species). Although it cannot be presumed
that the species is absent at sites not surveyed since 1993, the
likelihood of occupancy of these sites should be considered differently
than sites with more recent survey data (e.g., due to woody vegetation
succession over time). When analyzing survey results, we disregarded
negative surveys conducted outside of the species' flight period
(outside of June or July) or under unsuitable conditions (e.g., high
wind speeds over approximately 16 miles-per-hour). We accepted survey
data from those surveyors with whom we were confident in their ability
to identify the species in the field.
After we applied these standards to initially ascertain the status
of the species, we asked species experts and Service personnel to help
verify, modify, or correct species' occupancy at each site
(particularly for sites with questionable habitat quality or those that
have not been surveyed recently). In most cases, we used the status
confirmed during expert review, unless we received additional
information (e.g., additional survey or habitat data provided after the
expert reviews) that suggests a different status at a particular site.
Timing of surveys is based on initial field checks of nectar plant
blooms and sightings of butterfly species with synchronous emergence
(sightings of butterfly species that emerge at the same time as Dakota
skipper and Poweshiek skipperling), and, more recently, emergence
estimated by a degree-day emergence model using high and low daily
temperature data from weather stations near the survey sites (Selby,
undated, unpublished dissertation). Surveys are conducted during flight
periods when the species' abundance is expected to be at levels at
which the species can be detected. However, as with many rare species,
detection probabilities are imperfect and some uncertainty remains
between non-detection and true absence (Gross et al. 2007, pp. 192,
197-198; Pellet 2008, pp. 155-156). Three sequential years of negative
surveys is sufficient to capture variable detection probabilities,
since each survey year typically encompasses more than one visit (e.g.,
the average number of visits per Dakota skipper site per year ranges
from 1 to 11), and the probability of false absence after 5-6 visits
drops below 5 percent for studied butterfly species with varying
average detection probabilities (Pellet 2008, p. 159). Therefore, the
site is considered ``extirpated'' if there are three sequential years
of negative surveys (preferably, each year has more than one survey
date).
It cannot be presumed that the species is not persisting at a site
only because there have not been recent surveys. At several sites, the
species has persisted for longer than 20 years; for example, Dakota
skipper was first recorded at Scarlet Fawn Prairie in South Dakota in
1985 and has had positive detections (the species was detected during a
survey) every survey since that date. The most recent detection was in
2013. The year 1993 was chosen based on habitat-related inferences,
specifically, the estimated time for prairie habitat to degrade to non-
habitat due to woody encroachment and invasive species. For example,
native prairies with previous light-grazing management that were
subsequently left idle transitioned from mixed grass to a mix of woody
vegetation and mixed grass in 13 years and it was predicted that these
idle prairies would be completely lost due to woody succession in a 30-
year timeframe (Penfound 1964, pp. 260-261). The time for succession of
idle prairie depends on numerous factors, such as the size of the site,
edge effects (the changes that occur on the boundary of two habitat
types), and the plant composition of adjacent areas.
This approach is the most objective way to evaluate the data range-
wide. Most sites have been surveyed over multiple years, although the
frequency and type of surveys varied among sites and years. Surveys
were conducted using various protocols (e.g., Pollard walks (Pollard
1975), modified Pollard walks, wandering transects, timed transects)
depending on the objective of the survey, funding or available
resources, and staff. In several cases, species experts provided input
on occupancy based on their familiarity
[[Page 63677]]
with the habitat quality and stressors to populations at particular
sites.
To summarize, there are few sites with relatively older data where
we consider the species to still be present. In general, most Poweshiek
skipperling sites with a present status have had a positive detection
in 2008, or more recently with a few exceptions. At one Poweshiek
skipperling site, the species was observed at the site in 1996, and no
further surveys have been conducted. The remaining Poweshiek
skipperling sites where the species is considered present have had
detections in 2013, except four sites where the species was detected in
2008, 2010, 2011, or 2012, and no further surveys have occurred.
Likewise, in general, most Dakota skipper sites with a present status
have had a positive detection in 2002, or more recently, with a few
exceptions. At four Dakota skipper sites we consider the species to be
present with the most recent record from 2001 or earlier including one
site where the most recent survey was from 1994, and two sites with
1996 records. No evidence suggests that the species is not still
present at these sites because the best information indicates that the
site's habitat is still conducive to the butterfly, and, therefore, the
species may still be present there. We also consider Dakota skipper to
be present at the following sites: 17 sites in Canada that were
surveyed most recently in 2002; 1 additional site with a 2002 detection
of the species and a favorable habitat assessment in 2012; 1 site with
a 2003 detection; 1 site with a 2005 detection; 1 site with a 2006
detection; 19 sites in Canada that were surveyed most recently in 2007;
2 additional sites with a 2007 detection; 1 site with a positive
detection in 2008; 3 sites with a positive detection in 2009; 23 sites
with positive detections in 2012; and 10 sites with positive detections
in 2013.
Population Distribution and Occupancy Status
Once found in native prairies in five States and two Canadian
provinces, the Dakota skipper and its habitat have undergone dramatic
declines; the species is now limited to native prairie remnants in
three States and two Canadian provinces. The Dakota skipper is presumed
extirpated from Illinois and Iowa and no longer found in eastern
Minnesota. Populations persist in a few locations in western Minnesota,
northeastern South Dakota, North Dakota, southern Manitoba, and
southeastern Saskatchewan. Royer and Marrone (1992a, p. 5) speculated
that Dakota skippers may also occur in far eastern Montana and
southeastern Saskatchewan, in habitats similar to those occupied by the
species in northwestern North Dakota. The Dakota skipper was
subsequently found in Saskatchewan in 2001 after 40 years of searching
(Hooper 2002, pers. comm.), but no actual records have been found in
Montana and Royer (2002, pers. comm.) no longer thinks that the species
ever occured in Montana.
From its earliest identification, the Dakota skipper was considered
rare (Royer and Marrone 1992a, p. 1), although considerable destruction
of its habitat likely occurred even before the species was first
described in 1911. Habitat destruction and degradation has greatly
fragmented Dakota skipper's range from its core through its northern
and western fringes (McCabe 1981, p. 179; Royer and Marrone 1992a, p.
28; Schlicht and Saunders 1994, p. 1; Royer 1997, p. 2; Schlicht 1997a,
p. 2; Schlicht 1997b, p. 2; Skadsen 1997, pp. 25-26; Skadsen 1999c, p.
15; Swengel and Swengel 1999, p. 267). The historical distribution of
Dakota skippers may never be precisely known because ``much of
tallgrass prairie was extirpated prior to extensive ecological study''
(Steinauer and Collins 1994, p. 42), such as butterfly surveys.
Destruction of tallgrass and mixed-grass prairie began in 1830 (Samson
and Knopf 1994, p. 418), but significant documentation of the
ecosystem's butterfly fauna did not begin until about 1960. Therefore,
most of the species' decline probably went unrecorded. Based on records
of vouchered specimens, however, we know that Dakota skipper range has
contracted northward out of Illinois and Iowa. The species was last
recorded in Illinois in 1888 (McCabe 1981, p. 191) and in Iowa in 1992
(Orwig and Schlicht 1999, p. 6). Britten and Glasford's (2002, pp. 363,
372) genetic analyses support the presumption that this species
formerly had a relatively continuous distribution; the small genetic
divergence (genetic distance) among seven sites in Minnesota and South
Dakota indicate that populations there were once connected. Dakota
skipper dispersal is very limited due in part to its short adult life
span and single annual flight. Therefore, the species' extirpation from
a site is likely permanent unless it is within about 1 km (0.62 mi) of
a site that generates a sufficient number of emigrants or is
artificially reintroduced to a site.
The Dakota skipper's range once comprised native prairie in five
States and Canada, extending from Illinois to Saskatchewan; it now
occurs only in native prairie remnants in portions of three States and
two Canadian provinces. Of the 264 historically documented sites, there
are 83 sites where we consider the Dakota skipper to be present, 88
sites with unknown status, 41 possibly extirpated sites, and 52 that
are considered extirpated (Table 1). Approximately 47 percent (39 of
83) of the sites where the species is considered to be present are
located in Canada, mostly within three isolated complexes, and were
observed in 2002, or in 2007 with no subsequent surveys. Four
additional locations where we consider the species to be present in
Manitoba had positive detections of the species as recently as 2012
(Rigney 2013a, p. 117). The remaining 42 sites where the species is
considered to be present are about equally distributed among Minnesota
(11 sites), North Dakota (16 sites), and South Dakota (14 sites).
Researchers made positive detections of the species in 10 of these
sites in 2013. The species was observed at 19 of these sites in 2012.
Other U.S. sites with a present status with relatively older positive
detections and no subsequent surveys for the species include one site
with a positive detection in 1994, two sites with positive detections
in 1996, one site with a positive detection in 2002, one site with a
positive detection in 2005, one site with a positive detection in 2006,
two sites with a positive detection in 2007, one site with a positive
detection in 2008, and three sites with a positive detection in 2009.
At several of these sites, the habitat has been assessed more recently
than they were surveyed for the species. The distribution and status of
Dakota skipper in each State of known historical or extant occurrence
are described in detail below.
[[Page 63678]]
Table 1--Number of Historically Documented Dakota Skipper Sites Within Each State and the Number of Sites Where
the Species Is Thought To Be Present, Unknown, Possibly Extirpated, or Extirpated
----------------------------------------------------------------------------------------------------------------
State's
percentage
of the
State total Present Unknown Possibly Extirpated Total
number of extirpated
historical
sites
----------------------------------------------------------------------------------------------------------------
Illinois.......................... 0.4 ........... ........... ........... 1 1
Iowa.............................. 1.1 3 3
Minnesota......................... 26.1 11 28 18 12 69
North Dakota...................... 20.5 16 14 11 13 54
South Dakota...................... 32.6 14 45 10 17 86
Manitoba.......................... 14.0 28 1 2 6 37
Saskatchewan...................... 5.3 14 0 0 0 14
-----------------------------------------------------------------------------
Total Number of Historically ........... 83 88 41 52 264
Documented Sites.................
Percent of the Total Number of ........... 32 33 15 20 ...........
Historical Sites by Occupancy
----------------------------------------------------------------------------------------------------------------
Illinois
Dakota skippers are considered to be extirpated from Illinois. The
species was last recorded near Chicago in 1888 (McCabe 1981, p. 191).
Iowa
There are three historical records of Dakota skippers in three
counties in Iowa (Dickinson, Poweshiek, and Woodbury), but the species
is presumed extirpated from the State (Schlicht and Orwig 1998, pp. 84-
85; Selby 2004a, pp. 1, 5; Selby 2012, pers. comm.; Nekola and Schlicht
2007, p. 9). The species was last seen at Cayler Prairie (Dickinson
County) in 1992, but surveys of this site in 2000, 2004, 2005, and 2007
were negative, so we presume it to be extirpated from that site
(Schlicht and Orwig 1998, p. 85; Selby 2004a, p. 5; Selby 2006a, p. 5;
Selby 2008, p. 6). The species was not observed at eight sites surveyed
in the period 1988-1997 (Swengel and Swengel 1999, pp. 288-289), at
eight sites surveyed in 2004 (Selby 2004a, p. 5), nor during extensive
surveys at 32 sites in 2007 (Selby 2008, p. 6).
Minnesota
Minnesota historically contained about 26 percent of the sites
where the Dakota skipper has been recorded (Table 1) (Service 2014,
unpubl. geodatabase). Since the earliest known record (1965) of the
species in Minnesota, 66 sites have been recorded in the State, but
recent surveys indicate that the species is declining in the State
(Service 2014, unpubl. geodatabase). Of the 69 known locations of
Dakota skipper in Minnesota; the species is extirpated or possibly
extirpated from 30 of those sites, and the status is unknown at 28
others (Service 2014, unpubl. geodatabase). The Dakota skipper is
considered to be present at 11 sites in Minnesota in 3 counties: Clay,
Lincoln, and Murray, although 2 of those sites have not been surveyed
since 1996, and 1 site has not been surveyed since 1994.
McCabe (1981, p. 187) observed very stable population numbers in
Minnesota prairies that he visited repeatedly 1968-1979. On dry-mesic
prairie in Lincoln County, Minnesota, Dana (Dana 1997, pp. 3-5) also
observed stable numbers into the thousands during his intensive studies
from 1978 to 1983. Schlicht (1997a, p. 13) and Reiser (1997, p. 16)
reported more variable numbers on the same sites in 1995-1996, and
based on these more recent observations, Dana (1997, pp. 3-5) suggested
that populations could experience significant size fluctuations between
years. At Hole-in-the-Mountain preserve, Minnesota, Dana (1991, pp. 36-
37) found peak abundance of approximately 1,000 Dakota skippers over
about 40 ha (98 ac); he estimated that 2,000-3,000 individuals may have
been alive at various times during the flight period and that only one-
third to one-half of adults were alive simultaneously. Where they
occur, these high adult densities persist for only about a week to 10
days during the single annual flight period (Selby and Glenn-Lewin
1989, pp. 24-28).
The percentage of sites surveyed each year in Minnesota with
positive detections remained relatively stable from 1985 to 2005, with
an average detection rate of 67 percent for all survey years with more
than one site surveyed (excluding sites newly discovered in the first
year it was discovered), an average of 70 percent detection rate for
survey years with 5 or more sites surveyed and an average of 66 percent
detection rate for survey years with 10 or more sites surveyed. One
exception to the high detection rates was 1994; only 26 percent (5 of
19 sites) of sites surveyed in 1994 resulted in positive detections.
Recent surveys of the species resulted in significantly lower than
average positive detections. The percent of sites surveyed each year
with positive detections has recently decreased from 70 percent (7 of
10 sites) in 2005, to 47 percent (8 of 17 sites) in 2007, 56 percent
(10 of 18 sites) in 2008, 6 percent (1 of 16 sites) in 2012, and to 7
percent (1 of 15 sites) in 2013 (for years with greater than 10 sites
surveyed, see Figure 1). Only one individual was detected in Minnesota
during 2012 surveys, which included 18 sites with previous records and
23 prairie remnants without previous records for the species (Dana
2012c, pers. comm.; Runquist 2012a, pers. comm.; Olsen 2012, pers.
comm.). Dakota skippers were detected at 1 site in Minnesota during
2013 surveys, which included 15 sites with previous records and 12
prairie remnants without previous records for the species (Runquist
2014, pp. 3-6; Selby 2014, pp. 2-5; Rigney 2013b, p. Appendix B;
Service 2014, unpubl. geodatabase.). The cause for this sharp decline
is unknown.
[[Page 63679]]
[GRAPHIC] [TIFF OMITTED] TR24OC14.009
The Dakota skipper is presumed extirpated at 12 sites in Minnesota;
at 7 of these sites the species has not been observed since 1984 or
earlier. Four sites at which the species is now presumed to be
extirpated have had fairly recent positive observations. The species
was last observed at Prairie Waterfowl Production Area (WPA) in Big
Stone County in 2000 (Skadsen 2000, p. 1), for example, but was not
found in 2008 (Selby 2009a, p. i), 2010, and 2012 (Service 2014,
unpubl. geodatabase). Dakota skippers were observed at the Glacial
Lakes WPA in 2001 (Schlicht 2001b, p. 18), but the species was not
observed in 2003, 2004, and 2005 (Selby 2006b, p. Appendix A xii); the
species is now considered to be extirpated at that site (Service 2014,
unpubl. geodatabase). The last observation of Dakota skipper at the Big
Stone National Wildlife Refuge (NWR) in Lac Qui Parle County was in
2000, and it was not observed during surveys in 2009, 2011, or 2012
(Skadsen 2012a, p. 5). Dakota skippers were observed at Chippewa
Prairie in 1995, but not in 1996, 2005, and 2012 (Service 2014, unpubl.
geodatabase). Of the 18 sites where the species is possibly extirpated,
4 have not been surveyed since the species was last seen in 1989 or
earlier. Dakota skippers at two of the sites where the species is
possibly extirpated have not been observed since 1991 (Service 2014,
unpubl. geodatabase). One site, with a positive detection in 1998, was
ranked as ``possibly extirpated'' based on expert opinion. The
remaining 11 sites had positive observations prior to 1993, were
surveyed once more recently, and had a negative observation (Service
2014, unpubl. geodatabase).
The status of the Dakota skipper is unknown at 28 sites; Dakota
skipper have not been observed at 14 of these sites since the mid- to
late 1990s, despite one or two years of survey effort at several sites.
The remaining 14 sites with unknown status have had positive
observations in 2007 or more recently, but are given this designation
due to one or two subsequent negative surveys. For example, Dakota
skipper was documented at the Gens Prairie in Murray County and
Woodstock Prairie in Pipestone County in 2007, but the species was not
observed during surveys in 2008 or 2013 (Selby 2009a, p. Appendix 5 li,
xxxiii and Appendix 4 xlix; Selby 2014, p. 5).
In 2007 and 2008, the Minnesota DNR carried out a broad survey
effort to assess the status of Dakota skipper and other prairie
butterflies in the State after experts noted significant declines in
these species in west-central Minnesota beginning in 2003 (Selby 2006b,
p. 30). Researchers surveyed 17 and 19 sites with previous Dakota
skipper records in 2007 and 2008, respectively; Dakota skipper was
found at 8 sites each year and at 1 site where it had not previously
been recorded (Selby 2009a, p. 6). The surveys confirmed Dakota
skipper's extirpation from one site in Cottonwood County, where it was
last recorded in 1970.
A parallel study in 2007 (Dana 2008) consisted of more intensive
work at a few sites thought to contain some of the State's most viable
populations of Dakota skipper. Among these sites was The Nature
Conservancy's Hole-in-the-Mountain preserve in Lincoln County, which
was the only Minnesota population rated as secure in 2002 (Cochrane and
Delphey 2002, p. 16). The 2007 surveys indicated that the site still
supported a substantial population, but that it may have decreased in
size since earlier studies were conducted (Dana 1991, p. 36; Dana 2008,
p. 18). Dakota skippers were not detected during the 2012 or 2013
flight periods (Runquist 2012, pp. 13-14, 18-20; Runquist 2012a, pers.
comm., Selby 2014, p. 5); therefore, we consider the status of the
species at the Hole-in-the-Mountain preserve to be unknown.
[[Page 63680]]
Relatively important populations of Dakota skipper in Minnesota may
still occur at the Prairie Coteau, Felton Prairie, and Glacial Lakes
complexes, but the 2012 and 2013 survey results raised concern for the
species' status at Prairie Coteau. The number of Dakota skippers
encountered per 100 m (328 ft) of transect at Prairie Coteau State
Natural Area (SNA) were 1.7 in 1990 and 1.1 in 2007 (Dana 2008, p. 19).
No Dakota skippers were observed at Prairie Coteau SNA during the 2012
or 2013 flight periods (Runquist 2012, pp. 9-10); therefore, we
consider the status of the species to be unknown at that site. Selby
(2009b, Appendix 4, p. iv) recorded 14 Dakota skippers during a 5-hour
survey in 2007 at the Felton Prairie SNA. During a 1-hour survey in
2008, nine Dakota skippers were recorded and with little indication of
any substantial change since the previous year (Selby 2009b, Appendix
5, p. iv); Felton Prairie was resurveyed in 2013, and no Dakota
skippers were observed (Service 2014, unpubl. geodatabase). The number
of Dakota skippers recorded during recent surveys at Glacial Lakes
State Park has been low despite good habitat conditions. An apparently
widespread population was present as recently as 2001 when Skadsen
(2001, p. 24) found Dakota skippers along almost all of 40 km (25 mi)
of transect in and around the park--he recorded as many as 31 Dakota
skippers along one transect (Skadsen 2001, p. 24). Selby (2009a, p. 1
and 1iv) surveyed the same areas in 2007 and 2008, describing habitat
at survey sites as good to excellent, but recorded only eight Dakota
skippers during about 7 hours of surveys in and around the park (Selby
2009a, p. 1 and 1iv). Glacial Lakes State Park surveys conducted in
2012 were outside of the Dakota skipper flight period (Runquist 2012a,
pers. comm.), and the species was not detected in 2013 (Selby 2014, p.
5).
In summary, the Dakota skipper is now considered to be extirpated
or possibly extirpated from at least 30 of the 69 sites in Minnesota,
which historically contained approximately 26 percent of all known
historical Dakota skipper locations rangewide (Table 1). The species is
considered to be present and unknown at 12 and 27 sites, respectively.
However, only one individual male was detected in the State during 2012
surveys, which included 18 sites with previous records; 2012 surveys
for undiscovered populations were also carried out on 23 prairie
remnants without previous records for the species. Only 6 individual
Dakota skipper were observed in 2013 surveys in Minnesota, which
included 15 sites with previous records; 2013 surveys for undiscovered
populations were also carried out on 12 prairie remnants without
previous records for the species (Service 2014, unpubl. geodatabase).
Similar surveys of prairie remnants with no previous documentation of
Dakota skipper were completed in Minnesota in 2007 and 2008. Based on
these surveys, the likelihood that significant undiscovered Dakota
skipper populations occur in Minnesota is low.
North Dakota
North Dakota historically contained approximately 21 percent of all
known historical locations of Dakota skippers rangewide (Table 1); the
State contained 54 historical sites distributed among 18 counties
(Service 2014, unpubl. geodatabase). The Dakota skipper is currently
present at 16 sites in 5 North Dakota counties, of these, 11 occur
within the Towner-Karlsruhe complex in McHenry County, 1 is within the
Sheyenne National Grasslands complex in Ransom County, 2 are in
northern McKenzie County, and 1 site is in Wells County. Of the 16
sites where we consider the Dakota skipper to be present, 15 sites had
positive observations of the species in 2012. The remaining site had
positive observations in 2002. The status of the species is unknown at
14 sites; 10 of these sites have not had positive records since the
mid- to late 1990s, and the other 4 sites had positive records between
2001 and 2003. The Dakota skipper is presumed extirpated from 13 sites
and 4 counties, primarily due to heavy grazing, weed control, and other
disturbances (e.g., bulldozing at Killdeer Mountain to reduce aspen
growth, Royer 1997). The species is possibly extirpated from 11
additional sites and 3 additional counties.
Researchers surveyed 25 sites, believed to possibly have Dakota
skipper populations, in 2012; of these sites, 23 had previous records
of the species (Royer and Royer 2012a, entire). Thirteen of the 25
surveyed sites had Dakota skipper present (Royer and Royer 2012a, pp.
3-4; Royer and Royer 2012b, pp. 2-3). One new site was found in 2012
(Royer and Royer 2012a, p. 33), adjacent to a site with previous
records but with different land-ownership, so the researcher considered
it a new site. Another new site was found in North Dakota in 2012, in
Wells County, where two observations were made--possibly the same
individual (HDR, Inc. 2012, pp. 21-23). At sites with Dakota skipper,
lower average encounter frequencies were observed across the State in
2012 (State average = 9.4 encounters per hour) than during the 1996-
1997 statewide surveys (State average = 17.4 encounters per hour)
(Royer and Royer 2012b, p. 5; Royer and Royer 2012a. pp. 7-8). Three
sites with previous Dakota skipper records in North Dakota were
surveyed during the 2013 flight period; the species was not detected in
any of those surveys (Fauske 2013 data (in ND National Guard 2013, in
litt.; HDR Engineering 2013, pp. 10-11).
Of the Dakota skipper populations in North Dakota, none may be
secure, although the Towner-Karlsruhe complex was considered to be the
stronghold for the species in the State in 2002 (Cochrane and Delphey
2002, p. 17), and most of the sites where the species is currently
present are still occupied by ``viable populations'' (Royer 2012a,
pers. comm.). All of the habitat where the species is present in the
Towner-Karlsruhe complex is Type A (wet-mesic) habitat (Royer and
Marrone 1992a, pp. 21-22; Royer et al. 2008, pp. 14-16). Three sites
within the Towner-Karlsruhe complex are owned by the North Dakota State
Land Department, and the remaining nine sites with extant populations
are privately owned. Some Towner-Karlsruhe sites are linked by highway
rights-of-way that contain native prairie vegetation and by other
prairie remnants (Royer and Royer 2012a, p. 18). In 2002, none of these
sites were described as secure (Cochrane and Delphey 2002, pp. 66-67)
since each is subject to private or State management options that could
extirpate Dakota skipper from the site. In 1999, it was estimated that
about 30 percent of the Towner-Karlsruhe area still contained native
prairie (Lenz 1999, p. 2); more recent observations indicate that
several native prairie sites have been invaded to varying extents by
nonnative species, such as leafy spurge, Kentucky bluegrass, and
alfalfa (Medicago sativa), and several are subject to intense grazing
or early haying (Royer and Royer 2012b, pp. 5-6, 7-10, 13-16, 18-19,
22-23; Royer 2012, in litt.).
Dakota skipper populations in the Sheyenne National Grasslands
complex have experienced intensive grazing, leafy spurge (Euphorbia
esula) invasion, and the effects of herbicides used to control leafy
spurge and grasshoppers (Royer 1997, pp. 15 and 27). For example,
McCabe (1979, p. 36) cited the McLeod Prairie in the Sheyenne
Grasslands in southeastern North Dakota as the best site for Dakota
skippers in North Dakota. Since then, however, leafy spurge invasion
has significantly modified the habitat, and the Dakota skipper is now
extirpated
[[Page 63681]]
from the site (Royer 1997, p. 14). Swengel and Swengel (1999, p. 286)
did not find Dakota skippers at eight survey sites in the Sheyenne
grasslands during 1988-1997, although Royer did observe a few isolated
Dakota skippers in the Sheyenne National Grasslands during this period
(e.g., Royer 1997, pp. 14-15). Dakota skippers were recorded at one new
site (Gregor) in the Sheyenne National Grasslands in 2001 (Spomer 2004,
pp. 14-15). The status of Dakota skipper at the Gregor site is
currently unknown, since the species was not observed during the 2002
survey (Royer and Royer 2012a, pp. 3-4).
Orwig (1996, p. 3) suggested that Brown's Ranch in Ransom County,
owned by The Nature Conservancy, had potential to support a
metapopulation (groups of local populations interconnected by dispersal
habitat) in the Sheyenne River watershed. More recently, however,
Spomer (2004, p. 36) found that the population there was not doing
well, and Royer failed to find the species in 2012 (Royer and Royer
2012a, p. 3). Therefore, the status of the species at the Brown Ranch
site is unknown. Royer (1997, pp. 15 and 27) claimed that, throughout
the Sheyenne Grasslands, both public and private lands have been so
heavily grazed and altered by grasshopper and leafy spurge control that
extirpation of Dakota skippers from the area is almost certain to
occur. The population at Venlo Prairie, for example, deteriorated from
good/fair in 2001 to poor in 2003 due to intense grazing and
disappearance of flowers (Spomer 2004, pp. 9, 12); the species is now
considered to be extirpated at that site. The population at Garrison
Training Area in McLean County is now considered unknown due to
negative surveys in 2004 and 2013 (Fauske 2004, p. 1; Fauske 2013 in ND
National Guard 2013, in litt.).
In 2002, experts ranked all sites outside of the two complexes
discussed above as threatened or vulnerable; most were small and
isolated populations threatened by conversion and invasive species
(Cochrane and Delphey 2002, pp. 66-67). Most of these sites are now
considered extirpated or possibly extirpated. Today, only 3 sites
outside of the Towner-Karsruhe Complex and Sheyenne National Grasslands
complexes are thought to have extant (present) Dakota skipper
populations. In addition to the Towner-Karsruhe Habitat Complex sites
in McHenry County, only 2 of the 25 sites surveyed by Royer in 2012,
both in northern McKenzie County, may have ``viable populations''
(Royer 2012b, pers. comm.), although only one individual was observed
at each site in 2012 (Royer and Royer 2012b, pp. 16-17). Only three
sites with previous records were surveyed in North Dakota during the
2013 flight period, and the Dakota skipper was not observed (Fauske
2013 in ND National Guard 2013, in litt.; HDR Engineering 2013, pp. 10-
11).
In summary, North Dakota contains approximately 21 percent (N = 54)
of all known historical locations of the species rangewide; however,
the current occupancy status of the Dakota skipper is unknown at 14
sites, and it is considered to be extirpated or possibly extirpated
from at least 24 of the 54 known sites in the State (Table 1). The
species is considered to be present at 16 sites in the State. North-
central North Dakota may hold hope for the species' long-term
conservation. Dakota skipper was detected at 13 of the 25 sites
surveyed during 2012 (23 of the sites had previous Dakota skipper
records); average encounter frequencies observed across the State in
2012 (9.4 encounters per hour), however, were lower than during the
1996-1997 State-wide surveys (ND State average = 17.4 encounters per
hour) using the same methodology. The species was not detected at the
three sites surveyed in 2013.
Although only a small fraction of all grassland in North Dakota has
been surveyed for Dakota skippers, a significant proportion of the un-
surveyed area is likely not suitable for Dakota skipper. The species
was never detected at approximately 108 additional locations in North
Dakota that were surveyed for the species in the period 1991-2013
(USFWS 2014, unpubl. geodatabase). Many of these sites have been
surveyed multiple times over multiple years (USFWS 2014, unpubl.
geodatabase). Surveys for the Dakota skipper are typically conducted
only in areas where floristic characteristics are indicative of their
presence. New potential sites surveyed are generally focused on prairie
habitat that appears suitable for the species and has a good potential
of hosting the species, in other words, sites are not randomly selected
across the landscape. Therefore, researchers have a higher likelihood
of detecting the species at these sites than at sites randomly selected
across the landscape. Based on these surveys, the likelihood that
significant numbers of undiscovered Dakota skipper populations occur in
North Dakota is low. Moreover, data available from the numerous sites
that have been surveyed are likely to be representative of areas that
have not been surveyed--that is, population trends and the nature and
extent of stressors that may impact the populations in un-surveyed
areas can reasonably be inferred by analyzing data collected from the
sites that have been surveyed.
South Dakota
South Dakota historically contained approximately 33 percent of all
known locations of Dakota skippers rangewide (Table 1). Since the
earliest known record of Dakota skipper (1905) in South Dakota, 86
sites have been documented across 11 counties in the State, but recent
surveys indicate that the species is declining in the State (Service
2014, unpubl. geodatabase). Of the 86 historical sites, Dakota skipper
is presumed extirpated from 17 sites and 2 counties (Brown and Moody),
and is possibly extirpated from 10 additional sites. Dakota skipper is
considered present at 14 sites, and the status of the species is
unknown at 45 sites. Twenty-seven sites in South Dakota with previous
Dakota skipper records were surveyed in 2012; the species was detected
at 9 of those sites (Service 2014, unpubl. geodatabase). Eight
additional sites within the species' historical range were surveyed
during the 2012 flight period, which resulted in the discovery of two
new nearby Dakota skipper sites (Service 2014, unpubl. geodatabase;
Skadsen 2012a, pers. comm.). Twenty-eight sites in South Dakota with
previous Dakota skipper records were surveyed in 2013; the species was
detected at 9 of those sites (Service 2014, unpubl. geodatabase). Ten
additional sites within the species' historical range were surveyed
during the 2013 flight period, which resulted in no new Dakota skipper
sites discovered (Service 2014, unpubl. geodatabase). The proportion of
positive surveys at known sites has fluctuated over time; however, the
2012 and 2013 surveys had the lowest positive detection rate (35
percent and 32 percent, respectively) for the last 16 years (since
1996), much less than comparable survey years (years with 10 or more
sites surveyed) in South Dakota.
While there are some sites with earlier records, most South Dakota
sites were initially documented during extensive surveys conducted
during 1996 to 1998. Forty-eight locations without previous records
were surveyed during 2002-2004, which resulted in the discovery of 20
new Dakota skipper sites in northeastern South Dakota (Skadsen 2003, p.
8; Skadsen 2004, pp. 3-6), but due to more recent negative surveys, the
occupancy of the species is currently unknown or extirpated at many of
these sites (Skadsen 2011, p. 5; Skadsen 2012b, pp. 4-5; Skadsen, 2012,
pers. comm.; Skadsen 2003, p. 10; Skadsen
[[Page 63682]]
2004, p. 2; Skadsen 2006a, p. 2, 10; Skadsen 2006b, p. 5; Skadsen 2007,
p. 3; Skadsen 2008, p. 3, 12; Skadsen 2009, p. 3). Additional survey
effort resulted in the discovery of nine new sites between 2005 and
2012, with a maximum of three new sites discovered in 2006 (Skadsen
2010a, p. 6; Skadsen 2012b, pp. 4-5; Skadsen 2012, pers. comm.; Skadsen
2005, pp. 5-6, Skadsen 2006a, p. 12; Skadsen 2006b, p. 5; Skadsen 2007,
p. 3; Skadsen 2008, p. 9; Skadsen 2009, p. 2). Eight additional sites
without previous documentation of the species were surveyed in 2012,
which resulted in the discovery of two nearby sites (Service 2014,
unpubl. geodatabase). To summarize, new sites have been discovered in
South Dakota during most survey years since 2002, however, the number
of new sites discovered each year has been low recently; two or three
new sites have been discovered each survey year since 2005 (three sites
in 2005, two sites in 2006, two sites in 2007, zero sites in 2010, two
sites in 2012, and zero sites in 2013). The rate that known sites are
becoming extirpated is higher than the rate of new discovery--the
occupancy of the species at many sites is now unknown or extirpated due
to more recent negative surveys.
The species has never been documented in Clark County, but because
few surveys have been conducted there, the county may contain
undiscovered populations (Skadsen 2006b, p. 1). Skadsen (2012b, pers.
comm.) doubts the existence of public lands with suitable Dakota
skipper habitat in Clark County and has not received permission to
survey a few possible suitable locations that are privately owned.
Although only a small fraction of all grassland in eastern South
Dakota has been surveyed for Dakota skippers (e.g., Dakota skipper
surveys have been conducted on less than approximately 30,000 acres
(12,140 ha) in South Dakota within the species range (Service 2014,
unpubl. geodatabase)), a significant proportion of the un-surveyed area
may not be suitable for the Dakota skipper, based on surveys in
additional areas of possible habitat where the species was not detected
. For example, there is an estimated 1,620,549 acres (ac) (655,813
hectares (ha)) of unbroken (untilled) grasslands that may provide
habitat for the Dakota skipper in the nine counties where the Dakota
skipper is considered be present or to have unknown occupancy in South
Dakota (HAPET 2012, unpubl. data). Additional areas of unbroken prairie
were estimated in three other counties where the species may have
occurred historically (HAPET 2012, unpubl. data). While these lands
represent unbroken grassland in South Dakota, the models used to
identify unbroken grassland are not able to identify plant species,
plant species composition, floristic quality, or presence of invasive
species (Loesch 2013, pers. comm.). Therefore, it is not known if these
unbroken grasslands contain the specific native prairie plants that the
Dakota skipper requires (as discussed in detail in the Background
section of this proposed rule) and, therefore, may not equate to
suitable habitat for the species.
The species was never detected at approximately 79 additional
locations in South Dakota that were surveyed from 1991 through 2013
(USFWS 2014, unpubl. geodatabase). Several of these sites have been
surveyed multiple times in one year or during multiple years (USFWS
2014, unpubl. geodatabase). Surveys for Dakota skipper are typically
conducted only in areas where floristic characteristics are indicative
of their presence. For example, in South Dakota, Skadsen (1997, p. 2)
selected for surveys dry-mesic prairie that supported purple coneflower
and wet-mesic prairie that supported wood lily and mountain deathcamas
based on searches for these sites by car and reports from resource
managers. Only sites with landowner permission are accessed for
surveys, however, new potential sites surveyed are generally focused on
prairie habitat that appears suitable for the species and has a good
potential of hosting the species, in other words, sites are not
randomly selected across the landscape. Therefore, researchers have a
higher likelihood of detecting the species at these sites than at sites
randomly selected across the landscape. Based on these surveys, the
likelihood that significant undiscovered Dakota skipper populations
occur in South Dakota is low. Moreover, data available from the
numerous sites that have been surveyed are likely to be representative
of areas that have not been surveyed--that is, population trends and
the nature and extent of stressors that may impact the populations in
un-surveyed areas can reasonably be inferred by analyzing data
collected from the sites that have been surveyed.
Since there is little long-term quantitative data for sites in
South Dakota, we examined presence-absence (non-detection) data over
time. The percent of sites surveyed each year with positive detections
of the species remained relatively stable from 1985 to 2010, with an
average positive detection rate of 63 percent for all survey years with
more than one site surveyed (excluding new sites for the first year of
discovery), an average positive detection rate of 60 percent for survey
years with at least 5 sites surveyed, and an average positive detection
rate of 71 percent for survey years with at least 10 sites surveyed.
One exception to the high detection rates was during the 1991 survey
year when none (0 of 7 sites) of the sites surveyed in 1991 resulted in
positive detections of the species, excluding 3 new sites that were
discovered that year. Another exception was in 1996, when 2 of the 8
sites with previous records surveyed had a positive detection; however,
6 new sites were discovered that year. The detection rate remained
relatively stable until 2010, when the percent of sites with positive
detections fell from 89 percent (8 of 9 sites) in 2010, to 46 percent
(5 of 11 sites) in 2011, 35 percent (9 of 26 sites) in 2012, and 32
percent (9 of 28 sites) in 2013 (Figure 2). These types of fluctuations
had been observed in prior years; therefore, it is difficult to
determine a clear trend in the data using positive detections--the last
two survey years may fall within the normal range of variation.
[[Page 63683]]
[GRAPHIC] [TIFF OMITTED] TR24OC14.010
The Outer Coteau des Prairies subsection of the North Central
Glaciated Plains section of Bailey's Eco-regions is thought to be a
stronghold for Dakota skipper, since nearly 34 percent of the total
documented Dakota skipper sites are within that subsection (89 of the
264 documented sites--Service 2014, unpubl. geodatabase). Most of these
Outer Coteau des Prairie sites are in South Dakota; 73 of the 86 Dakota
skipper sites in South Dakota are within the Outer Coteau des Prairies
subsection (Service 2014, unpubl. geodatabase). Dakota skipper is
considered to be present at only 9 of those 73 sites--the species
status is unknown at 40 of those sites, possibly extirpated at 8 sites,
and extirpated at the remaining 16 sites within that ecoregion
subsection in South Dakota (Service 2014, unpubl. geodatabase).
In summary, South Dakota historically contained approximately 33
percent of all known locations of the species rangewide. The current
occupancy status of the Dakota skipper is unknown at 45 sites, and it
is considered to be extirpated or possibly extirpated from at least 27
of the 86 known sites in the State, although large areas of grasslands
remain in South Dakota we don't expect significant additional
populations to be found if more surveys were conducted. Furthermore,
downward trends and threats impacting populations at known sites are
also likely occurring at potentially undiscovered sites. The species is
considered to be present at 14 of the 86 documented sites in the State.
Twenty-six sites in South Dakota with previous Dakota skipper records
were surveyed in 2012; the species was detected at nine of those sites;
eight sites with no previous records for the species were surveyed
during the 2012 flight period, which resulted in the discovery of two
nearby sites. Twenty-eight sites in South Dakota with previous Dakota
skipper records were surveyed in 2013; the species was detected at 9 of
those sites (Service 2014, unpubl. geodatabase). Ten additional sites
within the species' historical range were surveyed during the 2013
flight period, which resulted in no new Dakota skipper sites discovered
(Service 2014, unpubl. geodatabase). The proportion of positive surveys
at known sites has fluctuated over time; however, the 2012 and 2013
surveys had the lowest positive detection rate (35 percent and 32
percent, respectively) for the last 16 years (since 1996)--much less
than comparable survey years in South Dakota.
Manitoba
Manitoba historically contained approximately 14 percent (N = 37)
of the known locations of the Dakota skipper rangewide. The Dakota
skipper is considered present at 1 isolated site and 28 sites split
between 2 distinct complexes, 12 sites near Griswold and 16 sites along
Lake Manitoba. The 12 sites near Griswold are located approximately 200
km (124 mi) southwest of the populations along Lake Manitoba (at 16
sites) and about 125 km (78 mi) northeast of the nearest population in
Saskatchewan (Webster 2003, pp. 5-6; Webster 2007, p. 4). The species
is considered to be unknown at one site near Griswold where the species
was detected in 2007 and 2011, but not during the most recent survey
year (2012) (Rigney 2013a, p.117). The species is presumed extirpated
or possibly extirpated from eight sites in Manitoba, including from the
Tallgrass Prairie Preserve, where it has not been
[[Page 63684]]
found in the seven most recent survey years (Webster 2003, p. 5;
Westwood et al. 2012, p. 1; Westwood 2007, pers. comm.; Hamel et al.
2013, pp. 8-16)--(the later surveys were focused on Poweshiek
skipperlings, but other species were recorded), and one site that was
converted to a flaxseed field (Webster 2003, p. 7).
In 2007, researchers surveyed 16 sites for the Dakota skipper near
Griswold, Manitoba (Webster 2007, p. 4), and found Dakota skippers at
14 of the 16 sites; 12 of these represent new sites for the species in
Manitoba (Webster 2007, p. 4). Four of these sites were resurveyed in
subsequent years (2010, 2011, and 2012)--the species is considered to
be present at two sites, is unknown at one site due to a recent
negative survey, and extirpated at the fourth site due to 3 consecutive
negative survey years (Rigney 2013a, p. 117; Service 2014 unpublished
database). The species is considered to be present at the remaining 10
sites that have not been surveyed since 2007.
Until recently, population estimates and trends at the sites near
Griswold in south west Manitoba have not been examined quantitatively;
however, the population appears to be relatively stable at one site,
may be declining at a second site, and is considered extirpated from
two sites with repeated survey years. Numbers observed during searches
at a site near Griswold in 2007 did not appear to change appreciably
since 2002 surveys, when the population was estimated (non-
quantitatively) to be approximately 750 individuals (Webster 2003, p.
5; Webster 2007, p. 4). A total of 273 adults were observed during a
3.3-hour survey at the second site, where the population was estimated
non-quantitatively to be about 2,000 individuals (Webster 2007, p. 4).
Survey methodology changes in the years since 2007 (two to five surveys
per site per flight period in the timeframe 2009-2013 compared to
single site visits per year prior to 2008) have provided more rigorous
population estimates at four Manitoba sites near Griswold and have
shown a marked reduction in densities since 2002 or 2007 at three of
the four sites (Rigney 2013a, p. 117). The Dakota skipper is present at
two of the four sites near Griswold with repeated survey years. The
estimated densities (mean number of individuals observed per hour) at
one site remained at 1/hour in 2011 and 2012 and was approximately 30/
hour in 2011 and 33/hour in 2012 at a second site. The species is
considered extirpated at one of these sites, because it was not
detected during 2010, 2011, and 2012 surveys. The status of the species
is unknown at another site where the estimated numbers fell from 2/hour
to zero detected in 2012 (Rigney 2013a, p. 117).
The Dakota skipper was first recorded near Winnipeg in 1933 and
near Miniota in 1944 and then at two additional sites in the early
1990s. The species is considered to be extirpated or possibly
extirpated at all of these sites (Service 2014 unpubl. geodatabase).
In 2002, the species was observed at 19 sites near Lundar, within
about 25 km (16 mi) east of Lake Manitoba (Interlake region) (Webster
2003, p. 4); however, most of these sites have not been surveyed since.
Similar to the Griswold sites, the survey methodology changes in years
since 2007 (two to five surveys per site per flight period during 2009-
2013 compared to single site visits per year prior to 2008) have
provided more rigorous population estimates at four Manitoba sites near
Lake Manitoba (Interlake region) and have shown a marked reduction in
densities since 2002 or 2007 at two of the four sites (Rigney 2013a, p.
117). The species is considered present at two of four sites that have
been surveyed since 2002 in this area; the species is considered
extirpated from the other two sites due to three consecutive negative
survey years (2010, 2011, and 2012) (Rigney 2013a, p. 117). The mean
number of individuals observed per hour at one site has declined from
2/hour in 2011 to 1/hour in 2012 (Rigney 2013a, p. 117). The mean
number per hour increased from approximately 1/hour to 6/hour at
another site (Rigney 2013a, p. 117). The species is considered to be
present at the remaining 14 Interlake sites that have not been
resurveyed since 2002 (Service 2014, unpublished database).
Several additional areas were examined for potential Dakota skipper
habitat in 2007, including areas east of Hwy 21, within the Lauder
Sandhills Wildlife Management Area, north of Oak Lake and near Tilston,
Sinclair, Cromer, and Brandon, as well as other locations. Most of the
areas examined were under row crop agriculture, were heavily grazed,
were dry scrub prairies, or were otherwise habitats unsuitable for
Dakota skipper (Webster 2007, p. 6). In 2007, the areas near Brandon
and the high ground within the wetland complexes near Oak Lake still
contained potentially suitable habitat (Webster 2007, p. 6).
The nearest known extant (present) population of Dakota skippers in
Manitoba is approximately 120 km (75 mi) from the closest extant
(present) population in North Dakota and about 111 km (69 mi) from the
closest Saskatchewan population. Britten and Glasford (2002, pp. 367,
372) suggested that Manitoba populations are genetically distinct from
a group of populations in Minnesota and South Dakota, although
populations in additional intervening locations should be sampled to
confirm this hypothesis (Runquist 2012b, pers. comm.).
Saskatchewan
Saskatchewan historically contained approximately 5 percent (N=14)
of all known records of Dakota skippers rangewide. In Saskatchewan, the
Dakota skipper is restricted to undisturbed or lightly grazed, steep,
south-facing hills near the Souris River (Webster 2007, p. ii). The
Dakota skipper was first recorded south of Oxbow, Saskatchewan, in 2001
where three males were collected (Hooper 2003, p. 124) on an ungrazed
knoll within a patch of mixed-grass prairie that was approximately 1 ha
(2 ac) in extent. Dakota skippers were found at three additional sites
during 2002 surveys (Webster 2003, pp. 6-7). In 2007, researchers
surveyed 16 sites in southeastern Saskatchewan and found Dakota
skippers at 10 of these sites (including Oxbow); 8 of these represent
new sites for the species in Saskatchewan (Webster 2007, p. i). During
2007 surveys, which were conducted late in the flight period, only a
few individuals were observed at each site where the species was
present (Webster 2007, p. ii). Nine of these sites where the species
was found in 2007 were surveyed along an approximate 50-km (31-mi)
stretch of steep hillsides along the ridgeline north of Souris River;
distances between sites range from 1 to 28 km (0.8 mi to 17 mi). We
consider Dakota skipper to be present at all 14 sites in Saskatchewan,
although 3 of those sites have not been surveyed since 2002. The
nearest known extant population of Dakota skippers in Saskatchewan is
approximately 111 km (69 mi) from the closest extant (present)
population in North Dakota and 200 km (125 mi) from the closest
Manitoba population.
Poweshiek Skipperling
Species Description
The Poweshiek skipperling (Oarisma poweshiek) is a member of the
skipper family, Hesperiidae, and was first described by Parker (1870,
pp. 271-272). Parker (1870, pp. 271-272) provided the original
description of this species from his type series collected near
Grinnell, Iowa. It was named for the county in which it was found
(Poweshiek County), but it was misspelled, Powesheik, in the original
[[Page 63685]]
description. This spelling was retained by most early authorities
(Lindsey 1922, p. 61; Holland 1931, p. 360). Miller and Brown (1981, p.
31) used the corrected spelling, Poweshiek, but then Miller and Ferris
(1989, p. 31) changed it back in their supplement. Current usage is
mixed, with many authorities retaining the original spelling (e.g.,
Miller 1992, p. 20), while others have opted for the corrected spelling
(Layberry et al. 1998, p. 48; Opler et al. 1998, p. 363; Glassberg
1999, p. 167; Brock and Kaufman 2003, p. 306). Layberry et al. (1998,
p. 48) state ``. . . since it is a clear case of an original incorrect
spelling it can be corrected [rule 32(c)ii of the International Code of
Zoological Nomenclature].''
Poweshiek skipperlings are small and slender-bodied, with a
wingspan generally ranging from 2.3 to 3.0 cm (0.9 to 1.2 in). The size
of Poweshiek skipperlings appears to vary somewhat across their range
(Royer and Marrone 1992b, p. 3). North Dakota and South Dakota
specimens tend to be slightly smaller than the 2.9 to 3.2 cm (1.1 to
1.3 in) range given by Parker (1870) for the type specimens from
Grinnell, Iowa (Royer and Marrone 1992b, p. 3). A sample of Richland
County, North Dakota, specimens from Royer's collection had an average
wingspan of 2.8 cm (1.1 in) for males and 3.0 cm (1.2 in) for females.
South Dakota specimens in Marrone's collection had an average wingspan
of 2.6 cm (1.0 in) for males and 2.7 cm (1.1 in) for females. The upper
wing surface is dark brown with a band of orange along the leading edge
of the forewing. Ground color of the lower surface is also dark brown,
but the veins of all but the anal third of the hindwing are outlined in
hoary white, giving an overall white appearance to the undersurface.
The Poweshiek skipperling is most easily confused with the Garita
skipperling (Oarisma garita), which can be distinguished from Poweshiek
skipperling by their smaller size, quicker flight, and overall golden-
bronze color (Royer and Marrone 1992b, p. 3). Another distinguishing
feature is the color of the anal area of the ventral hindwing (orange
in Garita; dark brown in Poweshiek). The Garita skipperling generally
occurs west of Poweshiek skipperling range, although there are records
of both species from two counties in southeastern North Dakota and two
counties in northwestern Minnesota (Montana State University--Big Sky
Institute 2012, Butterflies of North America https://www.butterfliesandmoths.org, Accessed 5/14/12; Minnesota Department of
Natural Resources (DNR) 2012, Rare features database. Accessed 5/14/
12).
McAlpine (1972, pp. 85-92) described Poweshiek skipperling eggs as
pale yellowish green, mushroom shaped with a flattened bottom, a
slightly depressed micropyle (pore in the egg's membrane through which
the sperm enter) and smooth surfaced. They were 0.8 millimeters (mm)
(0.01 in) long, 0.7 mm (0.03 in) wide and 0.5 mm (0.02 in) high. The
overall color of the head and body of the larvae is pale grass-green,
with a distinctive darker green mid-dorsal stripe and seven cream-
colored stripes on each side. First instars were 1.8 mm (0.07 in) at
hatching, and the lone 7th instar survivor was 23.6 mm (1.0 in) near
the end of that stage. McAlpine did not have any observations past the
7th instar (the stage between successive molts, the first instar being
between hatching and the first molt) (McAlpine 1972, pp. 85-93).
General Life History
Poweshiek skipperlings lay their eggs near the tips of leaf blades
and overwinter as larvae on the host plants (Bureau of Endangered
Resources in Swengel and Swengel 1999, p. 285, Borkin 2000, p. 7).
Poweshiek skipperlings have also been documented laying eggs on the
entire length of grass leaf blades and on low-growing deciduous foliage
(Dupont 2013, p. 133). McAlpine (1972, pp. 85-92) described the various
life-history stages of Poweshiek skipperling, and recent studies of
captive Poweshiek skipperlings at the Minnesota Zoo provide additional
information (Runquist 2013, pers. comm.). McAlpine (1972, pp. 85-93)
observed hatching of larval Poweshiek skipperling after about 9 days.
McAlpine's records were incomplete, and he did not have any
observations past the 7th instar, but he believed that there should
have been one or two additional instars, followed by the chrysalis
(pupa) and then the imago (adult) stages (McAlpine 1972, pp. 85-93).
Captive Poweshiek skipperling eggs hatched 8 to 9 days after
oviposition (Runquist 2013, pers. comm.). After hatching, Poweshiek
skipperling larvae crawl out near the tip of grasses and may remain
stationary, with their head usually pointing downward (McAlpine 1972,
pp. 88-92). Unlike Dakota skippers, Poweshiek skipperling do not form
shelters underground (McAlpine 1972, pp. 88-92; Borkin 1995, p. 9;
Borkin 2008, pers. comm.), instead the larvae overwinter up on the
blades of grasses and on the stem near the base of the plant (Borkin
2008, pers. comm.; Dana 2008, pers. comm.). Borkin (2008, pers. comm.)
observed larvae moving to the tips of grass blades to feed on the outer
and thinner edges of the blades, with later movement down and among
blades. Mature Poweshiek skipperling caterpillars reared in captivity
ranged in size from approximately 22 to 25 mm (0.9 to 1 inch) in length
just prior to pupation (Runquist 2013, pers. comm.).
Food and Water
For the Poweshiek skipperling, nectar plants vary across its
geographic range. Smooth ox-eye (Heliopsis helianthoides) and purple
coneflower were noted as the frequently visited nectar plants in Iowa,
Minnesota, and North Dakota (Swengel and Swengel 1999, p. 280). Other
nectar species used were stiff tickseed (Coreopsis palmata), black-eyed
Susan, and palespike lobelia (Swengel and Swengel 1999, p. 280). On
drier prairie habitats in Iowa and Minnesota, purple coneflower is used
almost exclusively, and the emergence of the adults corresponds closely
to the early maturity of this species' disk florets (Selby 2005, p. 5).
On the wetter prairie habitats of Canada and the fen habitats of
Michigan, favored nectar plants are black-eyed Susan, palespike
lobelia, sticky tofieldia (Triantha glutinosa), and shrubby cinquefoil
(Dasiphora fruticosa ssp. floribunda) (Nielsen 1970, p. 46; Holzman
1972, p. 111; Catling and Lafontaine 1986, p. 65; Bess 1988, p. 13;
Summerville and Clampitt 1999, p. 231). Recent studies in Manitoba
indicate that the most frequently used nectar plants are black-eyed
Susan, upland white aster, and self-heal (Prunella vulgaris) (Dupont
2013, pp. 70-71). In addition to nutrition, the nectar of flowering
forbs provides water for Poweshiek skipperling, which is necessary to
avoid desiccation during flight activity (Dana 2013, pers. comm.).
Until recently, the larval food plant was presumed to be elliptic
spikerush (Eleocharis elliptica) or sedges, but this was based on
limited observations, primarily from the Michigan populations (e.g.,
Holzman 1972, p. 113). More recent observations show that the preferred
larval food plant for some populations of Poweshiek skipperling is
prairie dropseed (Borkin 1995, p. 6); larvae have also been observed
feeding on little bluestem (Schizachyrium scoparium) (Borkin 1995, pp.
5-6) and sideoats grama (Bouteloua curtipendula) (Dana 2005a, pers.
comm.). Poweshiek skipperling larvae have been observed feeding on
Carex sp. (Borkin 1994, p. 6; Borkin 1996, p. 2), although not through
the entire larval development (Borkin 2014, pers. comm.). Poweshiek
skipperling
[[Page 63686]]
have been observed laying eggs (ovipositing) on mat muhly (Muhlenbergia
richardsonis) (Cuthrell 2012a, pers. comm.), a grass in Michigan's
prairie fens (Penskar and Higman 1999, p. 1). Captive-reared
caterpillars fed most successfully on prairie dropseed, and older
caterpillars (late 2-day instar and older) successfully fed on little
bluestem, big bluestem, and side-oats gramma (Runquist 2013, pers.
comm.). One post-diapause Poweshiek skipperling was successfully reared
to adulthood on Pennsylvania sedge (Carex pensylvanica) (Runquist 2013,
pers. comm.).
In southwestern Minnesota dry hill prairies, Poweshiek skipperling
oviposition was observed on prairie dropseed, little bluestem, big
bluestem, porcupine grass, and a couple unidentified species; a larva
was observed feeding on sideoats grama (Dana 2005a, pers. comm.).
Poweshiek skipperlings were observed to oviposit on big bluestem in
Wisconsin (Borkin 2012a, pers. comm.), although indiscriminate
oviposition on unsuitable larval plants has been observed during high
summer temperatures (Borkin 1995, p. 6). Borkin (1995, p. 4) also
observed oviposition on an unidentified sedge (Eleocharis sp.), but
only 2 eggs were found on the sedge in comparison to more than 100 eggs
found on prairie dropseed. In Manitoba, Poweshiek skipperlings were
observed ovipositing on big bluestem, white sweet clover, an
unidentified goldenrod (Solidago spp.), and juvenile bur oak (Quercus
macrocarpa) leaves (Dupont 2013, p. 73). Poweshiek skipperlings have
also been documented laying eggs on the entire length of grass leaf
blades, including the tips, and on low-growing deciduous foliage
(Dupont 2013, p. 133). Dana (2013, pers. comm.) noted that larvae seem
to begin feeding at a very fine, threadlike blade tip and females
placed eggs on fine blade tips of grasses during some observed
ovipositions. Consistent with field observations of female oviposition
on fine blades of grass, captive-reared caterpillars (early instars)
preferred feeding on finer leaf blades (Runquist 2013, pers. comm.).
Dispersal
Poweshiek skipperlings are also not known to disperse widely; the
species was evaluated among 291 butterfly species in Canada as having
relatively low mobility; experts estimated Poweshiek skipperling to
have a mean mobility of 2 (standard deviation = 1.4) on a scale of 0
(sedentary) to 10 (highly mobile) (Burke et al. 2011, p. 2279;
Fitzsimmons 2012, pers. comm.). A mark-recapture study was conducted in
Manitoba in 2008 and 2009; however, only 2 of the 56 marked individuals
in 2008 were recaptured and none of the 16 marked individuals in 2009
were recaptured, so available data are insufficient to examine within
and between site dispersal (Dupont 2013, pp. 68-70). After 2 days, the
two recaptured individuals were within 50 m (165 ft) of their initial
capture location (Dupont 2013, p. 69).
Besides this study in Manitoba, which had too few recaptures to
make any statistically significant conclusions, we are unaware of any
other studies that documented the dispersal distance of the species.
Therefore, we used the Dakota skipper as a surrogate species to
estimate the maximum dispersal distance of Poweshiek skipperlings and
verified our assumptions with expert review. In a mark-recapture study,
average adult movements of Dakota skippers were less than 300 meters
(m) (984 feet (ft)) during a period of 3-7 days; marked adults crossed
less than 200 m (656 ft) of unsuitable habitat between two prairie
patches and moved along ridges more frequently than across valleys
(Dana 1991, pp. 38-40). Dana (1997, p. 5) later observed reduced
movement rates across a small valley dominated by exotic grasses with
roads and crop fields compared with movements in adjacent widespread
prairie habitat. Roads and crop fields were suspected as impediments
for movement among prairie patches along two sites of the main valley
(Dana 1997, p. 5), although movements beyond the study area were beyond
the scope of the 1997 mark-recapture study (Dana 2013, pers. comm.).
Skadsen (1999, p. 2) reported possible movement of Dakota skippers in
1998 from a known population at least 800 m (2,625 ft) away to a site
with an unusually heavy growth of purple coneflower; he had not found
Dakota skippers in three previous years when coneflower production was
sparse.
Based on expert opinion, a maximum dispersal distance of 1.6 km
(1.0 mi) was estimated to be a reasonable and likely distance for male
Poweshiek skipperling to travel between patches of prairie habitat
separated by structurally similar habitats (e.g., perennial grasslands
but not necessarily native prairie) (Westwood 2012a and 2012b, pers.
comm.; Dana 2012b, pers. comm.). The species, however, will not likely
disperse across habitat that is not structurally similar to native
prairies, such as certain types of row crops or anywhere not dominated
by grasses (Westwood 2012a and 2012b, pers. comm.; Dana 2012b, pers.
comm.). In Manitoba, Poweshiek skipperling have been observed avoiding
dispersal over short distances, even to suitable habitat, if a barrier
such as a road exists between suitable prairie habitat and nectar
sources (Westwood et al. 2012, p. 18).
Since experts estimated Dakota skippers to have a mean mobility of
3.5 (standard deviation = 0.7) on a scale of 0 (sedentary) to 10
(highly mobile), which is higher than the estimate for the Poweshiek
skipperling (mean mobility of 2) (Burke et al. 2011, p. 2279;
Fitzsimmons 2012, pers. comm.), we used the estimated dispersal
distance of the Dakota skipper, approximately 1 km (0.6 mi) (Cochrane
and Delphey 2002, p. 6), which is more conservative than the 1.6 km
(1.0 mi) estimated for the Poweshiek skipperling by expert opinion
(Westwood 2012b, pers. comm., Dana 2012b, pers. comm.). One kilometer
is a reasonable maximum dispersal distance, since no data documents the
species that document a greater distance travelled.
In summary, using the best information available, dispersal of
Poweshiek skipperling is very limited due in part to its short adult
life span and single annual flight. Therefore, the species' extirpation
from a site is likely permanent unless it is within about 1 km (0.6 mi)
of a site that generates a sufficient number of emigrants or is
artificially reintroduced to a site; however, the capability to
propagate the Poweshiek skipperling is currently lacking.
Habitat
Poweshiek skipperling habitats include prairie fens, grassy lake
and stream margins, moist meadows, sedge meadow, and wet-to-dry
prairie. McCabe and Post (McCabe and Post 1977, pp. 36-38) describe the
species' habitat in North Dakota as ``. . . high dry prairie and low,
moist prairie stretches as well as old fields and meadows.'' Royer and
Marrone (1992b, p. 12) describe Poweshiek skipperling habitat in North
Dakota and South Dakota as moist ground in undisturbed native tallgrass
prairies. Poweshiek skipperling habitat throughout Iowa and Minnesota
is described as both ``high dry'' and ``low wet'' prairie (McCabe and
Post 1977, pp. 36-38). The only documented Illinois record was
associated with high rolling prairie (Dodge 1872, p. 218); the only
documented Indiana record was from marshy lakeshores and wetlands
(Blatchley 1891, p. 398; Shull 1987, p. 29).
Southern dry prairies in Minnesota are described as having sparse
shrub cover (less than 5 percent) composed primarily of leadplant, with
prairie rose,
[[Page 63687]]
wormwood sage, or smooth sumac present and few, if any, trees
(Minnesota DNR 2012a, p. 1). Southern mesic prairies also have sparse
shrubs (5-25 percent cover) consisting of leadplant and prairie rose
with occasional wolfberry (Symphoricarpos occidentalis) and few, if
any, trees (Minnesota DNR 2012b, p. 1).
The disjunct populations of Poweshiek skipperlings in Michigan have
more narrowly defined habitat preferences, variously described as wet
marshy meadows (Holzman 1972, p. 114), bog fen meadows or carrs (Shuey
1985, p. 181), sedge fens (Bess 1988, p. 13), and prairie fens
(Michigan Natural Features Inventory 2011, unpubl. data; Michigan
Natural Features Inventory 2012, unpubl. data); prairie fen is the
currently accepted name for this habitat type. Bess (1988, p. 13) found
the species primarily in the drier portions of Liberty Fen, Jackson
County, dominated by ``low sedges'' and an abundance of nectar sources.
Summerville and Clampitt (1999, p. 231) noted that the population was
concentrated in areas dominated by spikerush and that only 10-15
percent of the fen area was occupied despite the abundance of nectar
sources throughout. Poweshiek skipperling have been described as
occupying peat domes within larger prairie fen complexes in areas
either dominated by mat muhly or prairie dropseed (Cuthrell 2013a,
pers. comm.). A few prairie fens in Michigan also contain other rare
butterflies, such as Mitchell's satyr and swamp metalmark (Cuthrell
2013a, pers. comm.).
Poweshiek skipperling populations in Wisconsin are also disjunct
from the population to the west and are associated with areas that
contain intermixed wet prairie, wet-mesic, and dry-mesic prairie
habitats (Borkin 1995, p. 6; Swengel 2013, pers. comm.). The dry-mesic
habitats in the Scuppernong Prairie contain ``extensive patches of
prairie dropseed and little bluestem grasses'' (Borkin 1995, p. 7).
Survival in wetter areas, which tend to burn cooler and less
completely, coupled with low recolonization rates, or the
disproportionate loss of wet versus dry prairie could give the false
impression that the wet areas were their preferred habitat (Borkin
1995, p. 7). Puchyan Prairie consists of wet-mesic prairie that grades
lower into sedge meadow (WI DNR Web site https://dnr.wi.gov/topic/Lands/naturalareas/index.asp?SNA=172; Swengel 2013, pers. comm.) and adult
Poweshiek Skipperlings have been observed in wet prairie there,
although it is not known if these areas function as successful larval
habitat (Swengel 2013, pers. comm.).
Like the Dakota skipper, it has been hypothesized that Poweshiek
skipperling larvae may be vulnerable to desiccation during dry summer
months (Borkin 2012a, pers. comm.) and require movement of shallow
groundwater to the soil surface or wet low areas to provide relief from
high summer temperatures or dry conditions (Royer et al. 2008, pp. 2,
16; Borkin 2012a, pers. comm.). Humidity may also be an essential
factor to larval survival during winter months since the larvae cannot
take in water during that time and depend on humid air to minimize
water loss through respiration (Dana 2013, pers. comm.).
Royer (2008, pp. 14-15) measured microclimatological (climate in a
small space, such as at or near the soil surface) levels within
``larval nesting zones'' (0 to 2 cm above the soil surface) at six
known Poweshiek skipperling sites, and found an acceptable rangewide
seasonal (summer) mean temperature range of 18 to 21 [deg]C (64 to
70[emsp14][deg]F), rangewide seasonal mean dew point ranging from 14 to
17 [deg]C (57 to 63[emsp14][deg]F), and rangewide seasonal mean
relative humidity between 73 and 85 percent. Royer (2008) examined only
occupied areas for these parameters; therefore, the statistical and
biological significance of these edaphic variables cannot be determined
from his study.
Canadian populations of Poweshiek skipperlings are restricted to a
single 2,300-ha (5,683-ac) area in southeastern Manitoba (COSEWIC 2003,
p. 5). The wet to mesic tallgrass prairie in this area is characterized
by low relief (1-2 m (3-7 ft)), with alternating lower, wetter areas
and higher, drier prairie; Poweshiek skipperlings tend to be
concentrated on or near the edge of the higher, drier prairie (COSEWIC
2003, p. 8). Spikerush is frequent in the wetter areas, and prairie
dropseed, black-eyed Susan, and palespike lobelia are frequent in the
drier areas (COSEWIC 2003, pp. 7-8). The wet-mesic tallgrass prairies
in Manitoba vary in size and occur along bluffs of Bur oak and
trembling aspen (Populus tremuloides Michx.) (Catling and Lafontaine
1986; Dupont 2013, p. 17). Little bluestem, big bluestem, and Indian
grass were the three most common grasses in managed study plots in
Manitoba (Dupont 2013, p. 85). Plant species generally associated with
upland, drier portions of the mesic tallgrass prairies in Manitoba
include: Big bluestem, pale-spike lobelia, prairie dropseed, mountain
death camas, stiff goldenrod, black-eyed Susan, and meadow blazing-star
(Environment Canada 2012, p. 6). In lower, wetter prairies with
Poweshiek skipperlings, the following species are listed as often seen:
Willow (Salix spp.), sedges (Carex spp.), rushes (Juncus spp.),
groundsels (Pakera spp.), tufted hairgrass, creeping bentgrass
(Agrostis stolonifera), mat muhly, elliptic spike-rush, four-flowered
yellow loosestrife (Lysimachia quadriflora), and common self-heal
(Environment Canada 2012, p. 6). Most of these plants were also
commonly observed in study plots surveyed in 2008-2009 (Dupont 2013, p.
86). The soils where the Poweshiek skipperling occurs in Manitoba are
described as shallow, rocky, and highly calcareous (Westwood and
Borkowsky 2004 in Dupont 2013, p. 19).
Prairie fen habitat soils in Michigan are described as saturated
organic soils (sedge peat and wood peat) and marl, a calcium carbonate
(CaCO3) precipitate (MINFI Web site accessed August 3,
2012). In other States, soil textures in Poweshiek skipperling habitats
are classified as loam, sandy loam, or loamy sand (Royer et al. 2008,
pp. 3, 10); soils in moraine deposits are described as gravelly, except
the deposits associated with glacial lakes.
Population Distribution and Occupancy
The Poweshiek skipperling is historically known from eight States,
ranging widely over the native wet-mesic to dry tallgrass prairies from
eastern North and South Dakota (Royer and Marrone 1992b, pp. 4-5)
through Iowa (Nekola and Schlicht 2007, p. 7) and Minnesota (Minnesota
DNR, Division of Ecological Resources, unpubl. data), with occurrences
also documented in northern Illinois (Dodge 1872, p. 218), Indiana
(Blatchley 1891, p. 898), Michigan (Holzman 1972, p. 111; McAlpine
1972, p. 83), and Wisconsin (Borkin 2011, in litt.; Selby 2010, p. 22).
The relatively recent discovery of Poweshiek skipperling populations in
the Canadian province of Manitoba further extends its known historical
northern distribution (Westwood 2010, pp. 7-22; Dupont 2010, pers.
comm.). Additional historical accounts of Poweshiek skipperling from
the States of Montana, Colorado, and Nebraska are likely
misidentifications of its western congener, the Garita skipperling.
Once common and abundant throughout native prairies in eight States
and at least one Canadian province, the Poweshiek skipperling and its
habitat have experienced significant declines. The species is
considered to be present at a few native prairie remnants in two States
and one location in Manitoba, Canada. The species is presumed
extirpated from
[[Page 63688]]
Illinois and Indiana, and the status of the species is uncertain in
four of the six States with relatively recent records (within the last
20 years). The historical distribution of Poweshiek skipperling may
never be precisely known because ``much of tallgrass prairie was
extirpated prior to extensive ecological study'' (Steinauer and Collins
1994, p. 42), such as butterfly surveys. Destruction of tallgrass and
mixed-grass prairie began in 1830 (Sampson and Knopf 1994, p. 418), but
significant documentation of the ecosystem's butterfly fauna did not
begin until about 1960. Therefore, most of the decline of the Poweshiek
skipperling probably went unrecorded. Poweshiek skipperling dispersal
is very limited due in part to its short adult life span and single
annual flight. Therefore, the species' extirpation from a site is
likely permanent unless it is within about 1 km (0.6 mi) of a site that
generates a sufficient number of emigrants or is artificially
reintroduced to a site.
Recent survey data indicate that Poweshiek skipperling has declined
to zero or to undetectable levels at 96 percent of sites where it has
ever been recorded. Until about 2003, Poweshiek skipperling was
regarded as the most frequently and reliably encountered prairie-
obligate skipper butterfly in Minnesota, which contains approximately
48 percent of all known Poweshiek skipperling locations rangewide.
Numbers and distribution dropped dramatically in subsequent years,
however, and the species was not seen in Minnesota from 2007 through
2012. Two individuals were observed at one site in 2013 (Weber 2014, in
litt.; Dana 2014, pers. comm.). In Iowa, the Poweshiek skipperling was
found at 2 of 33 sites with previous records surveyed in 2007; the
species was last observed at one site in 2008. Iowa contains about 14
percent of documented sites rangewide. Unidentified threats to the
species have acted to extirpate or sharply diminish populations at all
or the vast majority of sites in Iowa and Minnesota (Dana 2008, p. 16;
Selby 2010, p. 7).
South Dakota historically contained about 23 percent of the
rangewide sites with documented presence of Poweshiek skipperling,
although recent surveys in that State also suggest an emergent and
mysterious decline. The species was last observed in South Dakota in
2008, at three sites. Surveys conducted in 2009-2013 flight seasons in
South Dakota resulted in zero detections of the species. North Dakota
historically contained about six percent of the rangewide sites with
documented presence of Poweshiek skipperling; the species was last
observed in North Dakota in 2001. Survey efforts in North Dakota have
been minimal between 1998 and 2011, but surveys conducted in 1997
documented more than 10 Poweshiek skipperlings at 1 site; 6 individuals
were counted at 1 site, and 0 were detected at 6 other sites. Surveys
conducted during the 2012 and 2013 flight seasons in North Dakota
resulted in zero detections of the species.
Seven Michigan sites were recently ranked as having good or better
``viability,'' a habitat-based element occurrence rank assigned by the
Michigan Natural Features Inventory (2011); however, the number of
individuals observed at a few of those sites has declined in recent
years, and the species is presumed extirpated from one of those sites.
Currently, four of the ten extant occurrences of Poweshiek skipperling
in Michigan are considered to have good or better viability (Michigan
Natural Features Inventory (2011, unpubl. data). Each of those faces
threats of at least low to moderate magnitude, and the State contains
only about 6 percent of all known historical Poweshiek skipperling
records. One population of Poweshiek skipperlings in Wisconsin had
fairly consistent numbers observed over the last 5 years (17 to 63
individuals counted using modified Pollard transect covering 15 ac (6
ha) in approximately 40 minutes), but the species was not observed in
2013 surveys. One population in Manitoba has fairly consistent numbers
(typically hundreds of individuals observed each year). To summarize,
of the 298 documented sites, there are 12 sites where we consider the
Poweshiek skipperling to be present, 111 sites with unknown status, 96
possibly extirpated sites, and 79 where we consider the species to be
extirpated (Table 2). The distribution and status of Poweshiek
skipperling in each State of known historical or extant occurrence are
described in detail below.
Table 2--Number of Historically Documented Poweshiek Skipperling Sites Within Each State and the Number of Sites
Where the Species Is Thought To Be Present, Unknown, Possibly Extirpated, or Extirpated
----------------------------------------------------------------------------------------------------------------
State's
percentage
of the
State total Present Unknown Possibly Extirpated Total
number of extirpated
historical
sites
----------------------------------------------------------------------------------------------------------------
Illinois.......................... 1.3 ........... ........... ........... 4 4
Indiana........................... 0.3 ........... ........... ........... 1 1
Iowa.............................. 13.8 ........... 4 24 13 41
Michigan.......................... 5.7 9 2 ........... 6 17
Minnesota......................... 48.3 1 58 64 21 144
North Dakota...................... 5.7 ........... 8 6 3 17
South Dakota...................... 23.2 ........... 36 2 31 69
Wisconsin......................... 1.3 1 3 ........... ........... 4
Manitoba.......................... 0.3 1 ........... ........... ........... 1
-----------------------------------------------------------------------------
Total Number of Historically ........... 12 111 96 79 298
Documented Sites.............
Percent of the Total Number of ........... 4% 37% 32% 27% ...........
Historical Sites by Occupancy....
----------------------------------------------------------------------------------------------------------------
Illinois
The Poweshiek skipperling historically occurred in Illinois,
although only one historical occurrence is supported (Table 2). In the
early 1870s, Dodge (1872, p. 218) reported abundant Poweshiek
skipperling occupying ``the high rolling prairie that forms the divide
between the Illinois
[[Page 63689]]
and Rock rivers'' in Bureau County, Illinois. In addition to Bureau
County, the Web site Butterflies and Moths of North America lists
Poweshiek skipperling historical occurrences for Lake and Mason
Counties, which were submitted to the Web site before the date field
was required, so a default date of January 1, 1950, was assigned, which
is outside of the typical flight period (https://www.butterfliesandmoths.org/species/Oarisma-poweshiek; accessed August
16, 2012). The Web site maintains a verifiable database on species
occurrences, but there is no accessible supporting data for the Lake
and Mason Counties records (Lundh 2012, pers. comm.). One additional
record, housed at University of Wisconsin-Oshkosh, was collected in
DuPage County in 1968 and was recently identified as a Poweshiek
skipperling. The location where the specimen was collected has since
been converted and is no longer a prairie, and it is presumed that the
species is extirpated from that location (Borkin 2014, pers. comm.).
Poweshiek skipperling is, therefore, presumed to be extirpated from
Illinois.
Indiana
There is one supported historical occurrence of Poweshiek
skipperlings in Indiana (Table 2). Blatchley (1891, p. 898) reported
small numbers of Poweshiek skipperlings near Whiting, Indiana; Shull
(1987, p. 49) expressed confidence that this record is authentic. The
Poweshiek skipperling is considered extirpated from Indiana.
Iowa
Iowa historically contained approximately 14 percent (N=41) of all
known records of Poweshiek skipperlings rangewide (Table 2). The
Poweshiek skipperling was historically known to occur at 38 sites in 13
counties in Iowa (Nekola 1995, p. 8; Saunders 1995, pp. 27-28; Selby
2005, p. 18; Nekola and Schlicht 2007, p. 7; Selby 2010, p. 6);
however, this number may vary slightly (up to 41 sites) depending on
how one divides sites along the Little Sioux River in the Freda-Cayler
area (Selby 2012a, pers. comm.). Early reports from Parker (1870, p.
271) described Poweshiek skipperling as abundant on a prairie slope at
Grinnell, Iowa, while Lindsey (1917, p. 352; 1920, p. 320) noted
additional rare occurrences in Story, Dickinson, Poweshiek, and
Woodbury Counties, Iowa--among these, habitat has long since been
destroyed in all but Dickinson County.
In 1993-1994, 65 sites were surveyed in 17 counties where Dakota
skipper or Poweshiek skipperling had been previously recorded or where
prairie and butterfly surveys or infra-red photography suggested the
presence of Poweshiek skipperling habitat (Saunders 1995, pp. 7-8).
Among the 65 sites surveyed, Poweshiek skipperlings were found at 29
sites in 10 counties (Saunders 1995, p. 27). In 2000, Poweshiek
skipperlings were found at six sites surveyed in and near Cayler
Prairie and Freda Haffner Kettlehole State preserves in Dickinson
County (Selby 2000, p. 19). Followup surveys of this complex in 2004,
2005, and 2007, however, produced no confirmed sightings (Selby 2010,
p. 6). Extensive surveys were conducted in 2007, and included 32 of the
38 sites in the State with post-1990 records (Selby 2008, pp. 4, 6).
Poweshiek skipperlings were found at 2 of the 38 sites surveyed--
Hoffman Prairie State Preserve in Cerro Gordo County and Highway 60
Railroad Prairie in Osceola County (Selby 2008, pp. 6-7). Five of the
six sites not included in the 2007 surveys had very little quality
prairie (Selby 2012a, pers. comm.). Supplementary surveys conducted
further west along U.S. Highway 18 in Hancock County also produced no
confirmed sightings (Selby 2010, p. 7). No surveys were conducted at
previously known Poweshiek skipperling sites in the State during the
2012 flight season. No Poweshiek skipperlings were observed in surveys
in 2013 at two sites with relatively recent records of the species
(2005 and 2008) (Olsen 2013, p. 2).
The Poweshiek skipperling is presumed extirpated or possibly
extirpated from all but four of the known sites in Iowa. The status of
the Poweshiek skipperling is unknown at four sites: Highway 60 Railroad
Prairie, Floete Prairie in Dickinson County, Florenceville Prairie, and
Hayden Prairie in Howard County. There have been no surveys at Highway
60 Railroad Prairie since the species was observed there in 2007 (Selby
2012a, pers. comm.). The last observation of Poweshiek skipperling at
Floete Prairie was in 1994, and the habitat ``did not appear to be very
good quality'' in 2007, although the site was not surveyed for
butterflies that year (Selby 2012a, pers. comm.) or in subsequent
years. The Poweshiek skipperling was last observed at the Florenceville
Prairie in 1994 (Saunders 1995, p. 27), but not during the 2007 survey
year (Selby 2010, pp. 8-11). The species was last observed at Hayden
Prairie in 2005, but not during surveys conducted in 2007 (Selby 2010,
p. 10) or 2013 (Olsen 2013, p. 2). Four Poweshiek skipperlings were
found at Hoffman Prairie in Cerro Gordo County in 2008 (Selby 2009b, p.
3), but none were found during surveys in 2009 (Selby 2009b, p. 7) and
2010 (Selby 2010, p. 7). We initially assigned an unknown status to the
Hoffman Prairie site because the species had not been seen in the 2009
and 2010 survey years; however, Selby believes that the species may be
extirpated from this site (Selby 2012a, pers. comm.), so we assigned a
status of extirpated to this site, which was confirmed with negative
surveys in the 2013 flight season (Olsen 2013, p. 2).
To summarize, the Poweshiek skipperling was historically documented
in 41 sites in Iowa. The species occupancy is unknown at 4 of those
sites, and the species is considered to be extirpated or possibly
extirpated at 13 and 24 sites, respectively (Table 2). The species is
not considered to be present at any of the sites in Iowa.
Michigan
Michigan historically contained approximately 6 percent (N=17) of
all known records of Poweshiek skipperlings rangewide (Table 2).
Poweshiek skipperling has been historically documented at 17 sites in 6
counties in Michigan. The species was first recorded in Michigan in
1893 at Lamberton Lake near Grand Rapids in Kent County (Holzman 1972,
p. 111) and then at nearby Button Lake Fen (also known as Emerald Lake
Fen) in 1944 (McAlpine 1972, p. 83). Shrubs have invaded both sites,
however, and no Poweshiek skipperlings have been found at either of
these two western Michigan sites since 1944 and 1968, respectively
(Michigan Natural Features Inventory 2011, unpubl. data). Holzman
(1972, p. 111) documented Poweshiek skipperling in Oakland County in
1970, and the species has since been found at a total of 15 locations
in eastern Michigan.
The Poweshiek skipperling is currently considered to be present at
nine sites (Table 2) in four counties in Michigan: Jackson, Lenawee,
Oakland, and Washtenaw. The species has been observed recently (2008-
2013) at most of those sites, except at the Liberty Bowl Fen in Jackson
County, which has not been surveyed since one individual was observed
in 1996. The status of the species is unknown at two sites; Bullard
Lake in Livingston County, where Poweshiek skipperlings were last seen
in 2007, but not in subsequent surveys in 2008 and 2009 (Cuthrell
2012a, pers. comm.), and Liberty Fen (Grand River Fen) in Jackson
County, where Poweshiek skipperlings were observed in 2012 but not in
2013 surveys
[[Page 63690]]
(Cuthrell 2013, pers. comm.). The species is presumed extirpated from
six sites including the only two sites in Kent County and three sites
in Oakland County: Rattalee Road, Fenton Road, and Rattalee Lake Fen
(Call C Burr Preserve) fens. The species has not been observed at the
Rattalee Road and Fenton Road sites since 1970 and 1973, respectively
(Michigan Natural Features Inventory 2011, unpubl. data). Four
Poweshiek skipperlings were seen in 2009 at the Rattalee Lake Fen
(Calla C Burr Preserve), but none were observed during surveys
conducted in 2010, 2011, and 2012 (Cuthrell 2012a, pers. comm.;
Michigan Natural Features Inventory 2011, unpubl. data). The Michigan
Natural Features Inventory (MNFI) also considers the two sites in Kent
County to be extirpated due to habitat loss and destruction, Lamberton
Lake and Button Lake (also known as Emerald Lake); the species has not
been observed at either site since 1968 and 1944, respectively. The
species is presumed to be extirpated at Whalen Lake Fen in Livingston
County, where the species has not been observed since 1998 despite
three subsequent years of surveys (Michigan Natural Features Inventory
2011, unpubl. data).
Four of Michigan's nine extant (present) Poweshiek skipperling
occurrences were recently considered to have at least good viability
(Michigan Natural Features Inventory 2011, unpubl. data); however, 2013
survey results have put the viability in question. Three of these
sites, Buckhorn Lake also known as Big Valley), Brandt Road Fen (also
known as Holly Fen) and Long Lake Fen, are within 20 km (12 mi) of one
another in Oakland County; all with relatively large numbers (61-389)
of the species recorded in 2010-2012 surveys (Michigan Natural Features
Inventory 2011, unpubl. data; Cuthrell 2012a, pers. comm.). In 2013,
however, 2 individuals (0.008/hr.) were recorded at Buckhorn Lake,
which was down from 84 individuals (0.35/hr.) recorded the previous
survey year (2012) with similar effort, and 53 individuals (0.33/hr.)
were recorded at Brandt Road in 2013, down from 71 individuals (0.59/
hr.) recorded the previous survey year (2012) with similar effort. The
largest extant (present) Poweshiek skipperling population in Michigan
may be at Long Lake Fen, where 25 individuals (0.2/hr.) were counted
during 2013 surveys, down from 389 individuals (2.2/hr.) and 225
individuals (1.3/hr.) observed in the previous two survey years (2011
and 2012, respectively) with similar sampling effort. In 2012, Long
Lake Fen was thought to be the largest population of Poweshiek
skipperling in the United States. However, it is subjected to intense
development pressure, and results from 2013 surveys show low numbers. A
fourth site, Grand River Fen (also known as Liberty Fen) in Jackson
County, is approximately 100 km (62 mi) from the other three sites, and
was also considered to have good viability in 2011, but the viability
is questionable since 2013 surveys for the species were negative. In
2010, researchers counted 54 (0.3/hr.) Poweshiek skipperling at Grand
River Fen, and 114 (0.6/hr.) in 2011 (Michigan Natural Features
Inventory 2011, unpubl. data; Cuthrell 2012a, pers. comm.). This number
fell to 14 (0.1/hr.) in 2012 and zero in 2013 (Cuthrell, 2012a, pers.
comm.; 2012b, pers. comm.; 2013, pers. comm.).
Small populations, immediate threats that have significant impacts
on the species, or both limit the viability of the remaining five sites
where we consider Poweshiek skipperling to still be present in
Michigan. In 2010, eight (0.1/hr.) Poweshiek skipperlings were recorded
at Park Lydon in Washtenaw County; 12 individuals were counted in 2011
(0.1/hr.), 22 were counted in 2012 (0.2/hr.), and 1 individual was
counted in 2013 (Cuthrell 2012a, pers. comm.; 2013, pers. comm.). Two
individuals (0.02/hr.) were recorded at Goose Creek Grasslands (also
known as Little Goose Lake Fen) in Lenawee County in 2010, and nine
(0.07/hr.) were seen in 2011 (Cuthrell 2012a, pers. comm.; 2012b, pers.
comm.). Only one Poweshiek skipperling was seen during a 15-minute 3-
person survey in 2007 at the Snyder Lake site. Fourteen individuals
were observed during 2008 surveys at Halstead Lake Fen (Michigan
Natural Features Inventory 2011, unpubl. data), and 18 were observed in
2012 (Cuthrell 2012a, pers. comm.); neither survey year had units of
effort associated with the counts at this site. One individual was
counted at Bullard Lake fen in 2007, but the species was not observed
in the two most recent survey years (2008 and 2009); therefore, the
status is unknown at that site. We have only one year of data from
Liberty Bowl Fen, where the species was recorded in 1996. The Eaton
Road Fen is thought to be fairly viable, where 15-20 individuals were
observed on multiple occasions in 2005, and a high of 68 individuals
were observed in 2011 (Cuthrell 2012b, pers. comm.). The Eaton Road
site is approximately 0.6 km (1 mi) from the Long Lake Fen site and is
considered a sub-site within Long Lake Fen (Cuthrell 2012b, pers.
comm.), but we consider it to be a separate site for the purposes of
this rule.
To summarize, Poweshiek skipperling was historically documented in
17 sites in Michigan (Table 2). The species is considered to be present
at 9 of the sites, although the numbers observed in 2013 were
substantially less than in previous years with similar survey effort.
The occupancy is unknown at 2 sites, and the species is considered to
be extirpated at 6 sites.
Minnesota
Minnesota historically contained approximately 48 percent (N=144)
of all known records of Poweshiek skipperlings rangewide (Table 2).
There are approximately 189 historical Poweshiek skipperling occurrence
records in 32 counties in Minnesota [Minnesota Natural Heritage
Inventory (MN NHI) database accessed June 19, 2013, plus additional
surveys]. Clusters of records occur within five general areas from the
State's southwest corner to near the Canadian border in the north.
Based on the proximity of some occurrences to one another (e.g.,
overlapping or occurrences in close proximity to one another in one
general location), there appear to be approximately 144 distinct
historical site records in the State (Dana 2012d, pers. comm; Service
2014, unpubl. geodatabase). Poweshiek skipperling are presumed
extirpated or possibly extirpated from at least 85 of these known
sites. The status of the species is unknown at 58 sites, although 27 of
those locations have not been surveyed since 2003, and the species has
undergone a sharp decline in the State since then.
An extensive survey effort was completed in 1993 and 1994 (Schlicht
and Saunders 1994, entire; Schlicht and Saunders 1995, entire). During
those surveys, Poweshiek skipperlings were found in 11 of 19 sites on
which the species had been previously recorded and in 13 new sites, for
a total of 25 of 63 surveyed prairie sites; the species was present at
30 and 39 percent of the sites in 1993 and 1994, respectively (Schlicht
and Saunders 1995, pp. 5-7). These results contrast sharply with those
from the surveys conducted in 2007 and 2008, when the species was found
at four and zero percent of sites, respectively. Although the species
was apparently more common in 1993 and 1994, numbers of Poweshiek
skipperling found during surveys were typically low. Large numbers were
observed at only three sites (Schlicht and Saunders 1995, p. 4). At one
of these sites, Glynn Prairie, 25 Poweshiek skipperling were recorded
during a 50-minute survey in July 1993 (Schlicht and Saunders 1995,
data sheet); no Poweshiek skipperling were observed at this site during
the
[[Page 63691]]
2007 survey despite good survey conditions (Selby 2009a, p. xxxv).
Until about 2003, the Poweshiek skipperling was regarded as ``the
most frequently and reliably encountered prairie-obligate skipper in
Minnesota'' (Dana 2008, p. 1). Signs of the species' decline in
Minnesota were noted in 2003 when Selby (2005, p. 20) found sharply
lower numbers in and near Glacial Lakes State Park (Selby 2005, p. 20)
compared to those observed in 2001 (Skadsen 2001, pp. 22-24). For
example, numbers recorded along four transects that were surveyed in
both years decreased from 104 to 2 individuals (Selby 2006b, Appendix
2, p. ii). In 2004 and 2005, Selby (2006b, Appendix 2, p. 2) did not
record a single Poweshiek skipperling on any of these transects in and
around the park during 11 separate surveys.
An extensive survey effort was conducted in 2007 and 2008
throughout most of the species' known range in the State (Selby 2009a,
entire). Sites with previous Poweshiek skipperling records that were
considered to have the greatest conservation importance to the species
(large, high-quality prairie remnants) were surveyed, as well as sites
with no previous records that appeared likely to support the species
(Selby 2009a, p. 2). In 2007, 70 sites in 15 counties were surveyed,
including 26 sites with previous Poweshiek skipperling records (Selby
2009a, pp. 1, 6). In 2008, 58 sites were surveyed in 13 counties,
including 22 sites with prior records (Selby 2009a, pp. 1, 6). A total
of 34 sites with previous Poweshiek skipperling records were surveyed
in both years combined. Poweshiek skipperling presence was recorded on
only three of the 70 surveyed sites in 2007; each of these three sites
had just one confirmed individual (Selby 2009a, p. 1). No Poweshiek
skipperlings were observed on any of the 58 sites surveyed during the
2008 flight period (Selby 2009a, p. 1).
In 2007, multiple transect surveys were conducted in four sites
with previously well-documented Poweshiek skipperling populations--
transects totaling 52,985 m (33 mi) were surveyed without observing a
single Poweshiek skipperling (Dana 2008, p. 5). About half of these
transects (totaling 20,959 m (13 mi)) were in the Prairie Coteau
Scientific and Natural Area (SNA), where in 1990 Selby recorded 116
Poweshiek skipperlings during the flight peak (Selby and Glenn-Lewin
1990, pp. 19-20) along a total of about 6,250 m (4 mi) of transects
(Dana 2008, p. 16). No Poweshiek skipperling were observed during
surveys of the Prairie Coteau SNA in 2012 (Runquist 2012, pp. 9-10).
Additional surveys were conducted in 2012; however, Poweshiek
skipperling were not observed at any of the 18 sites with relatively
recent records (Runquist 2012, pp. 4-25; Selby 2012, p. 2; Selby 2013,
p. 2; Dana 2012c, pers. comm.; Runquist 2012a, pers. comm.; Olsen
2012a, pers. comm.). Fifteen additional prairie sites with potential
habitat or records of other skippers were surveyed in 2012, but no
Poweshiek skipperling were observed (Runquist 2012, pp. 4-25; Selby
2012, p. 2; Selby 2013, p. 2; Dana 2012c, pers. comm.; Runquist 2012a,
pers. comm.; Olsen 2012a, pers. comm.). Twenty-one sites with previous
records of the species were resurveyed in 2013 and 7 additional sites,
with no previous records, were also surveyed for the species (Runquist
2014, pp. 3-6; Selby 2014, pp. 2-5; Rigney 2013b, p. Appendix B). Three
individual Poweshiek skipperlings were observed at one site in Polk
County--this is the first credible sighting of the species in the State
since 2007 (Webster 2013, pers. comm.; Dana 2014, pers. comm.; Service
2014, unpub. database).
Nearly half (approximately 48 percent) of all documented Poweshiek
skipperling sites rangewide are in Minnesota, thus the apparent
collapse of large numbers of Poweshiek skipperling populations across
the State may pose a significant challenge for the long-term existence
of this species. Although the possibility remains that the species is
extant at some sites where recent (2007, 2008, 2012, or 2013) surveys
were negative, it seems unlikely that it is present at those sites in
any significant numbers. Extensive surveys in 1993 and 1994 documented
the species at about 35 percent of all surveyed sites, whereas the 2007
effort found them at only about 2 percent of all sites surveyed; no
Poweshiek skipperling were detected despite widespread and robust
survey efforts involving multiple observers in 2008 or 2012 (Dana 2008,
p. 8; Selby 2009a, p. 1; Dana 2012c, pers. comm.; Runquist 2012a, pers.
comm.; Olsen 2012, pers. comm.; Runquist 2012, pp. 4-25; Selby 2012, p.
2, 2013, p. 2). Three individuals were sighted at one location in 2013
(Webster 2013, pers. comm.; Dana 2014, pers. comm.).
To summarize, Poweshiek skipperling was historically documented in
approximately 144 sites in Minnesota (Table 2). The species is not
considered to be present at any of these sites, except at one location
(Table 2). The occupancy is unknown at 58 sites, and the species is
considered to be extirpated or possibly extirpated at 21 and 64 sites,
respectively (Table 2).
North Dakota
North Dakota historically contained approximately 6 percent (N=17)
of all known records of Poweshiek skipperlings rangewide (Table 2).
Poweshiek skipperlings have been historically documented at 17 sites
(Table 2) in 7 North Dakota counties (Selby 2010, p. 18; Service 2014,
unpubl. geodatabase): Cass, Dickey, LaMoure, Ransom, Richland, and
Sargent in the southeastern corner of the State and Grand Forks County
in the Northeast. Poweshiek skipperling are now considered extirpated
or possibly extirpated from nine sites and four counties (Cass, Dickey,
LaMoure, and Grand Forks) in North Dakota. The status of the species is
unknown at 8 sites, where the species was last observed between 1996
and 2001, but not during the most recent 1-2 year(s) surveyed. Four
sites with fairly recent Poweshiek skipperling records were surveyed in
2012; Poweshiek skipperling were not found at any of those sites (Royer
and Royer 2012b, pp. 21-24; Royer and Royer 2012a, p. 6). One
additional site was surveyed, which had the potential for Poweshiek
skipperling presence because of its proximity to a known site for the
species; however, no Poweshiek skipperling were found (Royer and Royer
2012b, pp. 18-19; Royer and Royer 2012a, p. 6; Royer 2012b, pers.
comm.). The species was not observed at six sites with previous records
of Poweshiek skipperlings that were surveyed in 2013. The species
occupancy at two of these sites with 2013 surveys was updated from
unknown to extirpated based on three consecutive years of negative
surveys (Service 2014, unpubl. geodatabase).
The Poweshiek skipperling was known from seven North Dakota sites
across six counties in the 1990s; however, only two of those sites were
considered to have extant populations at that time; three records were
represented by incomplete or ambiguous locality data, and the species
was assumed to be extirpated at one site (Royer and Marrone 1992b, pp.
8-11). Surveys conducted in the State after 1992 documented additional
populations, but the most recent surveys at these sites were mostly
negative. Orwig discovered eight new populations of Poweshiek
skipperling (six in Richland County and two in Sargent County) during 3
years of survey work (1995-1997) in southeastern North Dakota (Orwig
1995, pp. 3-4; Orwig 1996, pp. 4-6, 9-12; Orwig 1997, p. 2). The
species was found at two of the eight sites surveyed in 1997 (Orwig
[[Page 63692]]
1997, p. 2) and at two additional sites in 1996 (Spomer 2004, p. 11).
Once abundant at several known sites in North Dakota, Poweshiek
skipperlings have experienced a dramatic decline over the last few
decades. In 1977, McCabe and Post (1977a, p. 38), for example, found
Poweshiek skipperling to be abundant at McLeod Prairie in Ransom
County, stating that they could ``be collected two at a time on the
blossoms of Long-headed coneflower . . .'' In 6 years of subsequent
monitoring (1986-1991), however, Royer failed to find a single
Poweshiek skipperling at the site after it was converted to a cattle-
loading area (Royer and Marrone 1992b, p. 10). Royer and Marrone
(1992b, pp. 10-11) assumed the species had been extirpated at this
site. Similarly, the number of Poweshiek skipperlings recorded during
surveys at the West Prairie Church site along the boundary of Cass and
Richland counties, fell from hundreds in 1986, to four in 1990, and
zero in 1991 and 2012 (Royer and Marrone 1992b, p. 8; Royer and Royer
2012b, p. 21). Poweshiek skipperlings are unlikely to persist at this
small and isolated site (Royer and Royer 2012b, p. 21; Royer 2012c,
pers. comm.).
The last observation of a live Poweshiek skipperling in North
Dakota was in 2001, at a new site discovered by Spomer (2001, p. 9) in
Ransom County. Poweshiek skipperlings were not found in subsequent
surveys at this site in 2002, 2003, and 2012 (Spomer 2001, p. 2; Spomer
2002, p. 3; Spomer 2004 p. 36; Selby 2010, p. 18; Royer and Royer
2012b, p. 22), although the 2012 survey may have been conducted too
late in the year to detect the species at that site (Royer 2012b, pers.
comm; Royer 2012d, pers. comm.). Therefore, the status of the species
at this site is unknown.
To summarize, Poweshiek skipperling was historically documented in
17 sites in North Dakota (Table 2). The species is not considered to be
present at any of these sites (Table 2). The occupancy is unknown at
eight sites, and the species is considered to be extirpated or possibly
extirpated at three and six sites, respectively (Table 2).
South Dakota
South Dakota historically contained approximately 24 percent (N=69)
of all known records of Poweshiek skipperlings rangewide (Table 2). The
Poweshiek skipperling has been historically documented at approximately
69 sites (Table 2) across 10 counties in South Dakota (Selby 2010, p.
19). Based on expert review and additional survey and habitat
information, the status of the species was determined to be unknown at
36 sites, possibly extirpated at 2 sites, and presumed extirpated at
the remaining 31 sites (Table 2); at least 8 of the extirpated sites
have been destroyed by conversion, gravel mining, loss of native
vegetation, flooding, or heavy grazing (Skadsen 2012c, pers. comm.).
The Poweshiek skipperling was not detected at any site that was
surveyed between 2009 and 2013: 6 sites in 2009, 10 sites in 2010, 1
site in 2011, 10 sites in 2012, and 25 sites in 2013 (Skadsen 2009, p.
12; Skadsen 2011, p. 5; Skadsen 2010, pers. comm.; Skadsen 2012a, pers.
comm.; Skadsen 2012b, p. 3; Skadsen 2013, pp. 3-4). The 2009 to 2013
results are in marked contrast to surveys conducted in 2002 when the
species was recorded at 23 of 24 sites surveyed (Skadsen 2003, pp. 11-
45). Cool and wet weather may have depressed butterfly populations, in
general, in eastern South Dakota and west-central Minnesota in 2009 as
it apparently did in 2004 (Skadsen 2004, p. 2; Skadsen 2009, p. 2). In
2012 and 2013, five and nine additional sites, respectively, with
potentially suitable native-prairie habitat but with no previous
records of the species were surveyed, but no Poweshiek skipperling were
observed (Service 2014, unpubl. geodatabase).
Wisconsin
Wisconsin historically contained approximately 1 percent (N=4) of
all known records of Poweshiek skipperlings rangewide (Table 2).
Naturalists reported Poweshiek skipperling to be common to abundant on
prairies in southeastern Wisconsin in the late 1800s (e.g., in
Milwaukee and Racine Counties), although exact localities are unknown
(Borkin 2011, in litt.; Selby 2010, p. 22). By 1989, however, the
species was listed as State endangered (Borkin 2011, in litt.). The
Poweshiek skipperling is considered to be present at one site in
Wisconsin (Table 2); Puchyan Prairie State Natural Area (SNA) is
approximately 100 km (62 mi) to the northwest of the Kettle Moraine
State Forest in Green Lake County. The status of the species is unknown
at three sites within the Southern Unit of the Kettle Moraine State
Forest in Waukesha County. An additional 2010 record of a butterfly was
incorrectly identified as a Poweshiek skipperling at Melendy's Prairie
Unit of the Scuppernong Prairie SNA (Borkin 2012b, pers. comm.).
The two occurrences of Poweshiek skipperling in the Kettle Moraine
State Forest inhabit small areas that were once part of a larger
prairie complex, which was fragmented by conversion to agriculture,
other human development, and encroachment of woody vegetation (Borkin
2011, in litt.). Up until 2013, the largest population in Wisconsin was
within a 6-ha (15-ac) prairie remnant on Scuppernong Prairie SNA at
Kettle Moraine State Forest, which had record counts exceeding 100
individuals in 1994, 1995, 1998, and 1999 (Borkin 1995, p. 10; Borkin
1996, p. 7; Borkin 2000, p. 4; Borkin 2011, in litt.). Four were found
in 2007 (Borkin 2008, in litt., p. 1), although these data were
collected during a single transect survey that may have been early in
the flight season and are, therefore, not comparable to other survey
years (Borkin 2012a, pers. comm.). A maximum count of 42, 17, 63, and
45 were counted in 2009, 2010, 2011, and 2012, respectively (Borkin
2011a, pers. comm.; Borkin 2012c, pers. comm.). The relatively low
maximum count in 2010 may be due to the timing of the flight (early)
and the timing of the survey effort (late); therefore, the peak flight
may have been missed (Borkin 2013, pers. comm.). A controlled burn in
late March of 2012 may correlate with lower numbers observed during the
2012 flight (Borkin 2012a, pers. comm.). While this difference may be
within the range of variation observed over the previous 4 years
(Wisconsin DNR 2012, in litt.), the range in variation may be skewed
due to the low numbers observed in 2010 due to the timing of the flight
and the survey effort (Borkin 2013, pers. comm.). No Poweshiek
skipperlings were observed at Scuppernong during repeated surveys in
2013 (Borkin 2013, pers. comm.)--this is the first time no individuals
have been observed there since regular surveys began in the 1990s
(Borkin 2014 pers. comm.). Each year, surveys were conducted with
similar effort--modified Pollard transect covering 15 ac (6 ha) in
approximately 40 minutes (Borkin 2014, pers. comm.).
After brush was cleared from the area in 2002, a small number of
Poweshiek skipperlings were discovered the following year in a small
isolated prairie remnant patch at a second site in the Kettle Moraine
State Forest, (Borkin in litt 2008). Once the intervening woody growth
was removed, individuals presumably dispersed from the Scuppernong SNA
remnant prairie to a small habitat patch about 200 ft (61 m) away
(Borkin 2012a, pers. comm.). Surveys at each habitat patch have
consistently yielded counts of less than 10 (Borkin 2008, in litt.),
with a combined high count of 11 to 15 individuals in 2011. A total of
six individuals, with a high single day count of three, were observed
in eight surveys during 2012 (Borkin 2012c,
[[Page 63693]]
pers. comm.; Borkin 2012a, pers. comm.). No Poweshiek skipperlings were
observed in 2013 (Borkin 2013, pers. comm).
The status of the Poweshiek skipperling is unknown at a third and
much larger fragment of Kettle Moraine State Forest, the Kettle Moraine
Low Prairie SNA, which is adjacent to the Wilton Road site. The Kettle
Moraine Low Prairie SNA was overgrown by shrubs including willows
(Salix spp.), quaking aspen (Populus tremuloides), and glossy buckthorn
(Frangula alnus) and has been managed with a series of controlled
burns, in addition to a 1975 wildfire (Borkin 2011, in litt; Borkin
2012a, pers. comm.; Wisconsin DNR 2012, in litt). The highest number
recorded at the Kettle Moraine Low Prairie SNA was 28 on July 8, 1995
(Borkin 2012a, pers. comm.). Preliminary attempts in 2000 to 2003 to
augment the population with adults from Scuppernong SNA and captive-
reared larvae were not successful (Borkin 2012a, pers. comm.). A single
Poweshiek skipperling was sighted there on July 2, 2004, but none were
found in surveys conducted in 2007-2009 and 2011-2012 (Borkin 2011b,
pers. comm.; Borkin 2012a and 2012c, pers. comm.). Two Poweshiek
skipperlings were recorded in 2010 at this site (Wisconsin DNR2012, in
litt.); however, no photographs or voucher specimens confirm the
sighting. This site was surveyed less intensively than Scuppernong
Prairie, because of the species' relatively low density and abundance
at Kettle Moraine Low Prairie SNA (Borkin 2012a, pers. comm.).
Extensive brush cutting, additional burns, and restoration of the
hydrology have been undertaken in recent years (Borkin 2012a, pers.
comm.).
Poweshiek skipperlings are present at a third site in Wisconsin,
Puchyan Prairie SNA, in Green Lake County, although this population is
small and declining (Borkin 2009, pers. comm.). The Poweshiek
skipperling was first discovered at Puchyan Prairie in 1995, and 6 to
30 individuals have been recorded in subsequent surveys (Borkin 2008,
in litt.; Swengel 2012, pers. comm). In 2012, Swengel (2012, pers.
comm.) found a maximum of three individuals, despite several hours of
searching over 3 days. In 2013, Swengel (2013, pers. comm.) found a
total of three individuals during 2 days of searching.
Additional sites in eight counties (Crawford, Grant, Iowa,
Jefferson, Monroe, Rock, Sauk, and Walworth) have been surveyed in an
attempt to find undiscovered Poweshiek skipperling populations. Four of
the eight sites surveyed in 1998 and 1999 seemed to have adequate host
plants, nectar resources, and size typical of Poweshiek skipperling
habitat, but Poweshiek skipperling were not present at any of the sites
(Borkin 2000, pp. 5-7).
To summarize, Poweshiek skipperling was historically documented in
4 sites in Wisconsin (Table 2). The species is considered to be present
at one site and the occupancy is unknown at three sites (Table 2).
Manitoba
Manitoba historically contained less than 1 percent (N=1) of all
known records of Poweshiek skipperlings rangewide (Table 2); however,
multiple Poweshiek skipperling historical records occur in one general
location--a complex of several nearby small sites within the Tallgrass
Prairie Preserve--in far southern Manitoba, near the United States
border. Poweshiek skipperlings were first recorded in Canada near Vita,
Manitoba, in 1985 at each of seven prairies surveyed, and populations
were described as abundant but localized (Catling and Lafontaine 1986,
p. 63). Poweshiek skipperlings were found at 15 of 18 locations
surveyed within the same area in 2002 (COSEWIC 2003, p. 5).
The Poweshiek skipperling is currently present at one location in
Canada, The Nature Conservancy of Canada Tall Grass Prairie Preserve
near Vita, Manitoba (Westwood 2010, p. 2; Westwood et al. 2012, p. 1;
Hamel et al. 2013, p. 1). Poweshiek skipperlings were historically
moderately common in areas of the preserve (Klassen et al. 1989, p.
27). In 2002, Webster (2003, p. 5) counted approximately 150
individuals, and in 2006, approximately 126 individuals were sighted
across 10 sites (Westwood 2010, p. 3). Surveys of 10 sites in 2008 and
2009 yielded 281 and 79 Poweshiek skipperlings, respectively (Dupont
2010, pers. comm.). Poweshiek skipperling numbers in the preserve
declined sharply after a 647-ha (1,600-ac) wildfire in fall 2009 burned
much of the species' habitat, including areas that likely contained the
largest and highest density populations (Westwood 2010, p. 2); surveys
of comparable effort to the 2008 and 2009 surveys yielded only 13
Poweshiek skipperlings on the preserve in 2010 (Westwood 2010, pp. 7-
22). Surveys of 45 sites within the Tall Grass Prairie Reserve during
2011 resulted in 13 sites with positive sightings, 9 of which were new
sites (Westwood et al. 2012, p. 11; Dupont 2011, pers. comm.). The
average number of Poweshiek skipperlings found at each site ranged from
10 to 15 per hour. These numbers are up considerably from 2010, but not
as high as observed in 2008 (Dupont 2011, pers. comm.). In 2012, a
total of 50 individuals were observed, which was ``low when compared to
historic densities'' (Hamel et al. 2013, p. 17). Poweshiek skipperling
sites in Manitoba are often surveyed up to 7 times during the flight
period each year (Westwood 2013, pers. comm.). The preserve has
detailed management recommendations to facilitate recovery of the
Poweshiek skipperling (Westwood 2010, p. 5).
Following an assessment and status report completed in 2003 under
the Committee on the Status of Endangered Wildlife in Canada (COSEWIC),
the Poweshiek skipperling was listed under the Species at Risk Act as
Threatened in Canada in July 2005 (COSEWIC 2003). A recovery strategy
is now in place for the species in Canada (Environment Canada 2012),
which includes critical habitat designations within and adjacent to The
Nature Conservancy of Canada Tall Grass Prairie Preserve (Environment
Canada 2012, p. ii).
Summary of Comments and Recommendations
In the proposed rule published on October 24, 2013 (78 FR 63574),
we requested that all interested parties submit written comments on the
proposal by December 23, 2013, during which we held public meetings on
November 5, 2013, in Minot, North Dakota; November 6, 2013, in Milbank,
South Dakota; November 7, 2013, in Milford, Iowa; November 13, 2013, in
Holly, Michigan; and November 14, 2013, in Berlin, Wisconsin. We also
contacted appropriate Federal and State agencies, scientific experts
and organizations, and other interested parties and invited them to
comment on the proposal. Newspaper notices inviting general public
comment were published in the following papers: Detroit Free Press,
Detroit, MI; The Detroit News, Detroit, MI; Berlin Journal, Berlin, WI;
The Forum of Fargo-Moorhead, Fargo, ND; Minneapolis Star-Tribune,
Minneapolis, MN; Mukwonago Chief, Mukwonago, WI; The Des Moines
Register, Des Moines, IA; Bismark Tribune, Bismark, ND; The Argus
Leader, Sioux Falls, SD. We did not receive any requests for a public
hearing. All substantive information provided during comment periods
has either been incorporated directly into this final determination or
addressed below. Comments specific to the proposed designation of
critical habitat for the two species (78 FR 63625) will
[[Page 63694]]
be addressed in the final critical habitat determination.
Peer Reviewer Comments
In accordance with our peer review policy published on July 1, 1994
(59 FR 34270), we solicited expert opinion from ten knowledgeable
individuals with scientific expertise that included familiarity with
the Dakota skipper or the Poweshiek skipperling and its habitat,
biological needs, and threats. We received responses from seven of the
peer reviewers.
We reviewed all comments received from the peer reviewers for
substantive issues and new information regarding the listing of the
Dakota skipper or the Poweshiek skipperling. The peer reviewers
generally concurred with our methods and conclusions and provided
additional information, clarifications, and suggestions to improve the
final rule. Peer reviewer comments are addressed in the following
summary and incorporated into the final rule as appropriate.
General
(1) Comment: Peer reviewers thought that the Service's
interpretation of literature addressing threats to these species was
well researched. However, some peer reviewers suggested that further
research would strengthen or refine our understanding of these
butterflies.
Our Response: The Act requires us to make a determination on the
status of species based on the best available information. However, we
agree that that further studies of these species would further our
understanding and help us with the recovery planning and
implementation. We will consider further research needs in our recovery
planning efforts.
(2) Comment: One peer reviewer stated that, in the Executive
Summary, the Service did not describe the effects of habitat management
on butterflies, but rather focused on the impacts to native vegetation.
Our Response: We have updated the executive summary to include the
direct mortality that may occur due to management activities or natural
occurrences. This subject is discussed in further detail in the
Background section of this final listing rule.
Taxonomy
(3) Comment: One peer reviewer provided a correction to the number
of subfamilies in the family Hesperiidae and the number of species in
the genus Hesperia. Specifically, the family comprises 7 subfamilies
world-wide, 4 of which occur in North America, north of Mexico. There
are 21 recognized species in the genus Hesperia (ibid), not 18 as cited
in the proposal.
Our Response: We corrected the statements in the Background section
of this final listing rule.
Species Biology
(4) Comment: One peer reviewer provided details on Dakota skipper
and Poweshiek skipperling biology, specifically, information pertaining
to early life stages and larval food choices, which were learned from
captive-rearing trials at the Minnesota Zoo.
Our Response: We have incorporated the updated information into the
Background section of this final listing rule.
(5) Comment: Two peer reviewers suggested that we incorporate the
findings of two recently published Master's theses (Dupont 2013, Rigney
2013a) that have new information on the Dakota skipper and Poweshiek
skipperling, including data from surveys at several locations for both
species in Manitoba. These studies also show a greater decline in both
species in Canada over the last 10 years than is indicated in the
proposed listing rule.
Our Response: We incorporated data from the referenced Master's
theses in the Dakota skipper Background section in this final listing
rule. The new information, although important to our full understanding
of the status of the species throughout their ranges, does not change
our listing determinations for the two species.
(6) Comment: A peer reviewer stated that based on personal
observations and McAlpine's 1972 report, upon hatching, Poweshiek
skipperling larvae crawl out near the tip of grasses, and do not crawl
to the base of grasses, as was stated in the proposal.
Our Response: We corrected the statement regarding Poweshiek
skipperling larval behavior in the Background section of this final
listing rule.
(7) Comment: A peer reviewer noted that a species' nectar
preference is usually indicated by selection in greater frequency
rather than the proportion of the species among all available nectar
sources (because random selection would be expected to result in
selection frequency equal to the species' proportion of the available
choices). All of the references cited in the rule report nectar
preferences as the relative proportion among observed choices.
Our Response: We clarified this point in the Background section of
this final listing rule.
Food and Water
(8) Comment: Peer reviewers provided corrections to the lists of
flowers used as nectar sources and the importance of several plants as
nectar sources for the butterflies.
Our Response: We corrected the nectar flowers for Dakota skipper
accordingly in the Background section of this final listing rule. Also,
we removed upright prairie coneflower, fleabane, and white prairie
clover from our list of important nectar species. We did not remove
black-eyed Susan, because Rigney (2013a, p. 142) reported Dakota
skippers were frequently observed nectaring on that species in Canada.
(9) Comment: One peer reviewer stated that the assertion that
Dakota skipper larvae feed only on native grasses has not been
established, and further stated that when confined with no other
choice, Dakota skipper larvae may feed on a variety of native and
nonnative grasses. Exotic cool-season grasses, such as Kentucky
bluegrass and smooth brome are available, and generally of good
nutritional quality, when overwintering larvae emerge from hibernation
and begin feeding. The tight empirical correlation between occurrence
of this skipper and the dominance of native plants in the habitat,
however, indicates that the species requires native grasses.
Our Response: We have incorporated this information into the final
listing rule, and recognize that Dakota skipper larvae can use both
native and nonnative plants as food during certain stages of larval
development. Some exotic cool-season grasses may be suitable larval
food plants during limited times of larval development; however, the
morphology and growth of these grasses may determine the suitability
for the species, and if those grasses dominate a site, the chances for
larvae finding suitable food sources is decreased.
(10) Comment: One peer reviewer provided additional information on
observations of Poweshiek skipperling oviposition and larval food use
in Wisconsin.
Our Response: We have incorporated the information into the
Background section of this final listing rule.
(11) Comment: One peer reviewer corrected our interpretation of his
observations on Poweshiek skipperling oviposition (egg-laying) to state
that larvae need to begin feeding on very fine, threadlike blade tips,
and that females placed eggs on fine blade tips of grasses during some
observed ovipositions.
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Our Response: We have incorporated this information into the
Background section of this final listing rule.
(12) Comment: One peer reviewer stated that the summary of the best
available information for Dakota skipper dispersal is adequate and
incorporates all of the information of which the reviewer is aware. The
reviewer did correct our interpretation of Dana's 1997 mark-and-
recapture study. The reviewer stated that roads and crop-fields were
suspected to be impediments to Dakota skipper movement; however, this
was not explicitly tested during the study. Another reviewer wanted
clarification on our basis for the estimated maximum dispersal distance
of the Poweshiek skipperling.
Our Response: We corrected the dispersal section of this final rule
to accurately present Dana's 1997 mark-and-recapture study findings,
and added information from an additional study. In one mark-and-
recapture study in Manitoba, the Poweshiek skipperling was found within
50 m (165 ft) of its original capture location (Dupont 2013, p. 69).
Besides this study in Manitoba, which had too few recaptures to make
any statistically significant conclusions, we are unaware of any other
dispersal studies for the species. Therefore, we used Dakota skipper
(and dispersal studies on this species) as a surrogate species to
estimate the maximum dispersal distance of the Poweshiek skipperling
(e.g., Dana 1991, Dana 1997, Skadsen 1999a), and verified our
assumptions with expert opinion and Burke (2011). Experts generally
agreed that 1.6 km (1.0 mi) was a reasonable estimate for Poweshiek
skipperling dispersal distance (Westwood 2012b, pers. comm.; Dana
2012b, pers. comm.). However, according to Burke et al. (2011), the
Poweshiek skipperling was less mobile than the Dakota skipper. Since
experts generally assumed the maximum dispersal distance of the Dakota
skipper was 1 km (0.6 mi), we used 1 km (0.6 mi) as a conservative
maximum dispersal distance for the Poweshiek skipperling.
(13) Comment: One peer reviewer questioned the accuracy of the
mobility value assigned to the Dakota skipper from the Burke et al.
(2011) publication. The reviewer suggested that the strongest evidence
for limited dispersal capabilities is the absence of observations
outside of native-prairie habitat. Butterflies that are highly mobile
are occasionally observed in unsuitable habitat; however, factors such
as the rarity of the species, its small size and inconspicuous
appearance, and the rarity of observers that are both interested in
skippers and capable of identifying them, makes the absence of
observations in unsuitable habitats weak evidence for the absence of
movement over long distances. The reviewer further stated that, since
we have little basis for measuring dispersal in this species, but we
have no evidence that it does much dispersing, we should assume that
dispersal is very limited.
Our Response: The Burke et al. (2011) paper was published in a
peer-reviewed scientific journal (using expert interviews); however, we
recognize the limitations of the data therein and, therefore, have
arrived at our conclusion that the Dakota skipper has low dispersal
capability based on this paper in conjunction with other reports and
observations.
Habitat
(14) Comment: One peer reviewer corrected the statement that Type B
habitat (as explained in the Background section above) was the only
habitat type inhabited by the Dakota skipper in Minnesota, as the
species has been documented in other habitat types, particularly in
Type A habitat in Kittson and Stearns Counties.
Our Response: We corrected the statement regarding Dakota skipper
habitat types in Minnesota in this final listing rule. It should be
noted, however, that there is only one recent (2009) record of a Dakota
skipper in Kittison County, Minnesota, and two sites in Stearns County
where the species is possibly extirpated.
(15) Comment: One peer reviewer stated that the assertion in our
proposed rule that Dakota skipper larvae are ``particularly vulnerable
to desiccation during dry summer months'' was a hypothesis, with no
confirming evidence. The paper cited only surveyed occupied habitat and
did not test unoccupied areas for the same parameters.
Our Response: We realize the limitations of Royer's 2008 study, and
have corrected our interpretations accordingly in this final rule;
specifically, the sampling design (edaphic parameters were measured
only in occupied areas, and no unoccupied areas were examined to test
the significance of the findings) does not allow for statistically
significant conclusions.
(16) Comment: One peer reviewer corrected the definition given for
``larval nesting zones'' measured for edaphic characteristics in Royer
(2008). The ``primary larval nest zone'' in which they measured
temperature and humidity is described as 0-2 cm above the soil surface,
not between the soil surface and 2 cm deep as stated in the proposed
rule.
Our Response: We have corrected the statement regarding larval
nesting zones in the Background section of this final rule.
Occupancy
(17) Comment: Ane peer reviewer commented on the adequacy of the
categorization of population status, and stated that it was done in an
appropriately conservative way, but did not think this would affect the
ultimate decision for either species
Our Response: We developed the occupancy criteria to be as
objective as possible in light of the information we had, which was
complicated by the variability of the frequency and lack of error
quantification of the survey data. We applied the occupancy rules
consistently, in the same way throughout the range of each species,
with discretion given to species experts who were familiar (e.g., who
had conducted relatively recent site visits or butterfly surveys) with
the sites within their State. Using the best information available, we
attempted to balance our determination as to whether the species was
likely present or not at a particular location. We determined that at
sites where the species was detected during the most recent survey, if
the survey was conducted in 2002 or more recently, this was a
reasonable timeframe to assume its presence, if there was no evidence
of habitat destruction or significant degradation of the habitat. Some
other comments, however, indicated that the 10-year timeframe was too
long to assume presence of an annual species, such as these
butterflies, while others thought we should still be assuming presence
at locations with detections much farther back (prior to 1993), if we
had no evidence that the habitat hadn't been destroyed there. However,
we believe that we have taken the most reasonable approach to defining
occupancy, used the best available scientific information
appropriately, and have been consistent in making this determination.
(18) Comment: One peer reviewer noted that it would be useful to
clarify the importance of unknown sites and to determine if habitat in
``unknown'' sites, and sites where extirpation has presumed to have
occurred, is actually in a condition to support future populations,
particularly for future reintroductions.
Our Response: It is important to distinguish among sites where the
species is likely extirpated, where the species is still present, and
where we are unsure of the species' presence, in
[[Page 63696]]
order to determine the current status of these species. The habitat at
individual sites varies, but where we had evidence that the habitat was
destroyed, we considered those sites to be extirpated (and, thus,
unsuitable for future reintroductions). The habitat at other sites may
still be suitable for one or both species, and its role in future
recovery efforts, such as reintroductions, will be considered during
the recovery planning and implementation phase for these species.
(19) Comment: One peer reviewer requested that we define some terms
used in the proposed rule; in particular, the terms ``positive
detections,'' ``detection rate,'' and ``liv''.
Our Response: Positive detections refers to the number of times the
species was detected during a survey. Detection rate is calculated as
the number of times the species was detected (at a singular site or
groups of sites), divided by the number of surveys (at a singular site
or groups of sites). Finally, ``liv'' refers to the page number in the
preface of a cited publication (Roman numeral for page 54).
(20) Comment: Does the definition of species extirpation from a
site apply to surveys conducted in 1993, or to those done more
recently?
Our Response: We considered the species to be extirpated from a
site if there were at least three sequential years of negative surveys,
no matter the year those sites were surveyed, and the species has not
subsequently been documented at the site. For example, if a site was
only surveyed in 1991, 1995, and 1999, and there were no positive
detections of the species during all 3 years, we assumed that the
species is extirpated from that site. The species occupancy at that
site would not change unless the species is detected at that site in
the future. We have clarified this definition in the Background section
of this final listing rule.
(21) Comment: One peer reviewer wanted further clarification on our
justification for including four Dakota skipper sites with older
records in the present occupancy category. The reviewer suggested we
review the previous densities of the species at the four sites and the
proximity of nearby sites from which individuals could recolonize the
sites in question.
Our Response: The species occupancy at one of four South Dakota
sites has been updated to ``unknown'' after further review of the
information available for the site, including 2013 survey data that
were not available to us at the time we drafted the proposed rule.
However, there is no evidence to suggest that the species is not still
present at the remaining three sites (all in Minnesota), because the
best information indicates that the sites' habitats are still suitable
for the butterfly, and, therefore, despite the lack of recent surveys,
the species may still be present there.
(22) Comment: A peer reviewer noted that at several points the
proposed rule indicates that survey efforts may vary in number of
visits, but that certain survey results were not considered, because
they were not conducted at the appropriate time. The peer reviewer
questioned whether we can presume that the surveys that were considered
are comparable, regardless of the number of visits visits, whether
those surveys all meet some minimum criteria, and whether there was a
standard survey effort measurement.
Our Response: Since the purpose of site surveys differed by site,
the amount of effort also varied. For example, if the goal of the
survey was to verify if the species was present at a particular
location, a surveyor may have stopped the survey effort as soon as the
first individual was detected, which may have occurred after a short,
one-time visit. On the other hand, if the survey purpose was to count
individuals during the peak flight of a species, the site may have been
visited every day throughout the adult flight period, and more
quantitative measurements, such as number of individuals observed per
hour, may have been recorded. We used all types of surveys, as long as
they were conducted during the appropriate time of the year (mid-June
through mid- to late July), and during appropriate conditions (e.g.,
generally wind speeds less than 16 mph, unless the species was detected
at higher speeds). Furthermore, we only considered surveys from
individual surveyors who are able to reliably identify the species in
the field.
(23) Comment: A peer reviewer noted that the proposed rule states
that existing models are unable to identify specific plant species,
invasive species, and floristic quality, and the Service concludes that
unbroken grasslands ``may not contain the specific native prairie
plants that the Dakota skipper requires. . . .'' This statement appears
to be contradicted later in the document.
Our Response: We clarified the statements in this final listing
rule. The intent of the first statement is to acknowledge that existing
habitat models cannot identify specific species or determine floristic
quality necessary to support Dakota skipper populations. The models may
be useful in narrowing down areas that may contain the necessary nectar
plants and larval food plants, but presence of specific plant species
and suitability for the Dakota skipper must be verified by other means
(e.g., on the ground plant surveys). The second statement refers to the
possibility of yet undiscovered areas of suitable habitat where the
Dakota skipper may exist, because not every area that is suitable has
been surveyed for the species.
(24) Comment: A peer reviewer noted that survey site selection may
be influenced by the expert's knowledge of potential habitats, land
ownership, and the ability to gain landowner permission to access areas
for surveys.
Our Response: We acknowledge that survey sites may be selected for
a variety of reasons. A site may be surveyed because there is known
suitable prairie habitat in an area, but the exact survey location may
depend on other variables, such as the ability to gain landowner
permission to survey.
Status and Trends
(25) Comment: One peer reviewer provided additional 2009 data for
the Felton Prairie site in Minnesota.
Our Response: We incorporated this data into this final listing
rule.
(26) Comment: One peer reviewer requested clarification on the
butterfly survey methodology and how floristic diversity was rated at
some of the survey locations.
Our Response: The survey methodology varied among locations, years,
surveyors, and by other factors, and it is difficult to succinctly
describe the methodology used for more than 20 years of surveys for
hundreds of survey sites. For that reason, we examined the data in
terms of the rate of positive detections over the years at each survey
location as a way to compare data across multiple survey methods and
years. We applied certain standards that each survey must meet (see
response to comment 22, above). In this final listing, we describe
survey methods or floristic quality determination methods for specific
locations when it is necessary to understand the results for a
particular survey, and describe typical survey and floristic
methodologies in the Background section of this final rule.
(27) Comment: A peer reviewer commented that the number of
historical populations of Dakota skipper that remain extant is probably
overestimated, given the results of recent resurvey efforts. In
particular, this peer reviewer questioned whether it was realistic to
assume species presence at five Minnesota sites, given the dramatic
declines and apparent extirpation of populations at some of the
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best sites within recent years. The reviewer suggested assigning those
sites as ``possibly present'' or ``status unknown'' category, and
targeting these sites for future surveys to determine the species'
presence, particularly because recent declines do not appear to be due
to habitat degradation or loss.
Our Response: Based on 2013 survey data, we changed the occupancy
for several sites. When determining species occupancy at a site, we
balanced information on habitat succession with the available survey
data to avoid falsely assuming the species is absent from less-surveyed
sites that still have suitable habitat.
(28) Comment: A peer reviewer commented that, based on surveys
conducted in 2013, the status of both the Dakota skipper and the
Poweshiek skipperling in Minnesota is likely more dire than suggested
in the proposal. No Dakota skippers or Poweshiek skipperlings were
observed during duplicate surveys conducted at 13 sites. During single
surveys conducted later in the flight period (the time when adult
butterflies are able to fly) at two additional sites in Clay County,
MN, six Dakota skippers were seen at one of those sites and no
Poweshiek skipperling were observed at either site. Both sites had
fairly good numbers during 2008 surveys. Additionally, one peer
reviewer suggested that we incorporate results from 2013 surveys of
sites in Kittson County, Minnesota. No Dakota skippers were observed at
Lake Bronson in 2013; however, there was one highly likely sighting,
and the area contains moderate-quality habitat. The Frenchman's Bluff
sites in Minnesota were surveyed on July 11, 2013, which was during the
period of peak abundance in the phenologically (relationship between a
periodic biological phenomenon and climatic conditions) delayed year,
but the Dakota skipper was not observed. The estimated probability of
the species presence at the site is 90 percent, based on the abundance
of habitat and purple coneflower in bloom.
Our Response: We incorporated the 2013 data into this final listing
rule. Due to several negative results from 2013 surveys, particularly
in Minnesota, the occupancy status at several sites has been updated in
this final listing rule. We still determine that the Dakota skipper
should be listed as threatened, and provide justification for our
determination in this final listing rule.
(29) Comment: One peer reviewer suggested that we incorporate
information from a 2013 report of butterfly surveys in South Dakota.
Our Response: We incorporated 2013 survey results in this final
listing rule.
(30) Comment: A peer reviewer suggested that the Dakota skipper
population densities as described in 2003 and 2007 status assessments
may no longer accurately describe the populations and the threats
causing population declines. For example, reported sightings of Dakota
skippers within the Riding Mountain National Park in Manitoba (Walleyn
2002) are likely not valid; there are no voucher specimens to confirm
the report. There are no known sites that are owned by the Government
in Canada.
Our Response: We incorporated updated information regarding several
sites in Manitoba and Saskatchewan. We have no records of any confirmed
Dakota skipper sites within the Riding Mountain National Park in
Manitoba.
(31) Comment: One peer reviewer noted that there has been a decline
in the number of individual Dakota skippers observed during the flight
period compared to the populations observed in 2002 and 2007. The
current population estimates are much lower than those described in
Webster's 2002 and 2007 reports. Furthermore, the methods for
estimating densities have changed; survey methodology has become more
rigorous, with 2 to 5 visits per site per year from 2009-2013 compared
to single visits prior to 2008.
Our Response: We incorporated 2013 data into this final listing
rule. Due to largely negative results from 2013 surveys, the occupancy
status of the species at several sites has been updated in this final
listing rule.
(32) Comment: One peer reviewer stated that there is a DuPage
County, Illinois, record of a Poweshiek skipperling--the specimen was
collected in 1968 near the DuPage River, and was only recently
identified as a Poweshiek skipperling.
Our Response: We have added the DuPage County record to the
Illinois status and distribution section of this final listing rule.
(33) Comment: One peer reviewer stated that, because no Poweshiek
skipperlings were observed in 2013 at Scuppernong Scientific and
Natural Area (SNA) in Wisconsin, nor at the nearby Wilton Road site,
those populations may be extirpated. The peer reviewer also stated that
the apparent decline in numbers was also observed in Michigan.
Our Response: We have updated the Background section of this final
listing rule to include the 2013 data for those two locations. Because
there are just one or two years of negative data at the Scuppernong SNA
and Wilton Road sites, the occupancy status at both sites is unknown.
(34) Comment: A peer reviewer commented that the low numbers of
Poweshiek skipperling observed in 2012 at Scuppernong SNA were at least
partially due to the spring burns of 25-30 percent of their prime
breeding habitat at that location. The range of variation of the
maximum numbers observed in 2009-2012 may be skewed due to the low
numbers observed in 2010, when the peak flight may have been missed due
to an early flight and late survey effort. The anticipated increase in
the population in 2012 due to a mild winter and early spring phenology
was not observed, which may indicate that the burn killed a high number
of larvae.
Our Response: We clarified the statements regarding the uncertainty
of the effect that the 2012 spring burn had on the Poweshiek
skipperling population at that location. It is difficult to make cause-
and-effect statements without direct measures of larvae mortality
following a burn.
(35) Comment: A peer reviewer stated that the same protocol has
been used for Poweshiek skipperling surveys in Wisconsin since the
early 1990s--a modified Pollard transect count with a set transect
pattern covering 6 ha (15 ac) of area and 40 minutes to complete.
Our Response: We clarified the methodology used at the Scuppernong
SNA sites in the Background section of this final listing rule.
Factors Affecting the Species
(36) Comment: A peer reviewer suggested that it would be useful to
rank or evaluate risks to the butterfly populations as they relate to
management recommendations. For example, would haying carry a lower
risk of causing extirpations? The level of risk, however, would depend
on the type, duration, and timing of haying activities versus the type
of fire management applied to sites.
Our Response: Ranking management methods goes beyond the scope of
this final listing document and is more appropriate for recovery
planning. Furthermore, management recommendations may vary for each
location, based on the habitat type and condition; therefore, it may
not be possible to generalize the level of risk associated with various
management types.
(37) Comment: One peer reviewer commented on the level of private
landowner awareness of the species and its status on their lands.
Specifically, in Canada, most private landowners are unaware of the
presence of the Dakota
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skipper, and this may also be true for private landowners in the United
States. Even where current management on lands may be conducive to the
species, it is not typically due to a conscious effort to conserve the
species. Landowner apathy should be considered a threat of considerable
concern.
Our Response: We agree that some landowners may not be aware of the
presence of either butterfly on their lands and that land may not be
intentionally managed for the conservation of the species, but rather
used in ways that are inadvertently favorable to the species. We have
discussed this issue further in Factor E of this final listing rule. In
the United States, we have notified private landowners of most of the
sites where we believe the species is still present or its status is
unknown, and many of the sites where the species is extirpated or
possibly extirpated, but where the habitat may still be suitable for
the species. We will continue to focus on public awareness and work
cooperatively with landowners following listing.
(38) Comment: One peer reviewer asked for clarification on the
reduction of Dakota skipper range, specifically what was meant by our
statement of ``an approximately 690-km (430-mi) reduction of its
range''
Our Response: We have removed this phrase from this final listing
rule, because it was unclear. The Dakota skipper is considered to be
extirpated from Illinois and Iowa and no longer occurs in eastern
Minnesota.
Factor A
(39) Comment: One peer reviewer recommended that the date of first
allowable haying be after July 22, because some adult flight has been
documented after the date of July 16, which was our recommendation for
the earliest haying. Another peer reviewer noted that in Manitoba,
August 1 is the recommended earliest haying date at Dakota skipper and
Poweshiek skipperling sites, although little haying is occurring where
the Poweshiek skipperling is present. Sites should not be hayed within
3 to 4 weeks of the beginning of the adult flight period to prevent
destruction of nectar plants. While there may be situations in the
United States where sites undergo haying ``no more than every other
year,'' most sites in Manitoba are hayed for several years in a row,
but there are no studies on the impact of repeat annual haying.
Our Response: Our categorization of stressors as having high,
medium, or low impacts on the species, and the criteria we use to
define those categories, were developed specifically to guide our
analysis of the factors affecting the species, and are not intended as
guidelines for conservation efforts. Conservation guidelines for the
Dakota skipper are available (online at https://www.fws.gov/midwest/endangered/insects/dask/DASKconservationguidelines.html), and we are
developing similar guidelines for the Poweshiek skipperling. In those
guidelines, we recommend that haying activities occur after the adult
flight period.
(40) Comment: A peer reviewer asked whether, in the grazing section
of the proposed rule, did the Service mean that even when grazing is
hard enough to eliminate the skipper, the habitat potential isn't
completely destroyed, as it is by mining or plowing, and can be
restored?
Our Response: This is correct, and we clarified the language in
this rule to more clearly state that, unlike habitat destroyed by
mining or plowing, for example, intensely grazed habitat has potential
to recover or be restored. Attempts have been made to restore prairie
remnants that have been plowed or mined (where significant soil
disturbance has occurred), but such restorations have not been
successful for the Dakota skipper or Poweshiek skipperling, at least in
observable timeframes.
(41) Comment: A peer reviewer noted that the proposal asserts that
``grazing is one of the primary treatments for controlling smooth brome
and enhancing native plant diversity in prairies that have been invaded
by this nonnative grass species.'' The peer reviewer stated that the
assertion goes beyond anything in the cited document (Service 2006).
There is no supporting research for grazing reducing brome, while at
the same time maintaining or improving the native species composition.
There is, however, support for the opposite--that grazing can stimulate
brome and reduce native diversity. Smart et al. (2011) discuss grazing
as a promising possibility, based on inferential, circumstantial, and
anecdotal information, and the group agreed that experimental
investigation is a big need. More accurately, the citation would
support this statement: ``grazing may be a valuable tool for
controlling smooth brome invasion and maintaining native diversity in
prairies, especially where circumstances make the use of fire
difficult.''
Our Response: We clarified the statement regarding grazing as a
potential management tool for invasive species control to more
accurately reflect the proceedings of the Service workshop (Service
2006) and Smart et al. (2011). Smart et al. (2011) used repeated
clipping methods to simulate intensive early-season grazing and
discusses the potential for using grazing as a tool to improve native
prairie under certain conditions.
(42) Comment: One peer reviewer said that recent statistics related
to habitat conversion show that the statement, ``The economic benefit
of grazing to ranchers may also benefit the species at some sites by
deterring conversion of remnant prairies to row crop agriculture'' is
out-of-date, and said this sentence contributes little to the argument
that remaining habitat is secure.
Our Response: We clarified the statement on conversion in this
final rule to reflect the current economic conditions that row crop
agriculture is generally more economically profitable than light
grazing.
(43) Comment: A peer reviewer noted that the proposed rule includes
little discussion of soil compaction as a result of grazing. A field
demonstration by Natural Resources Conservation Service (NRCS) staff
showed that soil compaction on a heavily grazed pasture was almost as
hard as a brick, and very little of the water falling on it soaked in.
Soil of this character would be quite difficult for the larvae of
Dakota skipper to penetrate for shelter construction, causing them to
be more exposed to predators, parasitoids, and other environmental
stresses. The Poweshiek skipperling would not be affected by
compaction, as it doesn't burrow.
Our Response: We agree that soil compaction due to heavy grazing
may cause the Dakota skipper to be more exposed to predators,
parasites, and other environmental stresses, such as fire, than if they
were able to build underground shelters, and we have taken this into
consideration in our evaluation of the threats to the species.
(44) Comment: A peer reviewer commented that the effects of grazing
in Manitoba and Saskatchewan, as stated in Webster (2007), may not be
applicable under current population scenarios. Even light grazing may
be detrimental on dry short-grass prairie sites prior to and during the
adult flight period.
Our Response: We incorporated this information into the Factor A
threats analysis of this final listing rule, below.
(45) Comment: A peer reviewer stated that potash mining, gravel
mining, flooding, and associated flooding protection activities may be
significant threats to these species in Canada.
[[Page 63699]]
Our Response: We incorporated this information into the Factor A
threats analysis of this final listing rule, below.
(46) Comment: One peer reviewer recommended that we not include the
research from an unpublished paper by Schlicht (2001a), due to serious
flaws in the methodology.
Our Response: Because of serious concern over the methods used in
this unpublished paper, we removed the information from Schlicht
(2001a) from this final listing rule (under Factor A--Fire), below.
(47) Comment: A peer reviewer stated that the discussion on threats
from fire in the proposed rule focuses on controlled burns, but
wildfires are a serious problem in Manitoba and previously inhabited
sites in northwestern Minnesota. Due to the highly fragmented nature
and comparatively small size of sites, wildfire may be a greater threat
than either haying or grazing activities.
Our Response: We considered wildfires to have moderate to high
impacts to Dakota skipper and Poweshiek skipperling populations; the
impacts would depend on the timing, intensity, and extent of the burn.
We discuss wildfires in Manitoba in the Background (population
distribution and status) section and in Factor E of this final rule,
and considered that fragmentation due to stochastic events, such as
wildfires, may lead to extinction at isolated sites (Factor E).
(48) Comment: One peer reviewer provided a link to the Northern
Tallgrass Prairie Lepidoptera Conservation Conference Working Group
Reports Synthesis.
Our Response: We added the reference to the discussion regarding
conservation efforts under Factor A in this final listing rule, below.
(49) Comment: A peer reviewer noted that, in the Conservation
Efforts To Reduce Habitat Destruction, Modification, or Curtailment of
Its Range section of the proposed rule, there was reference to a 1995
expert panel and plan. The peer reviewer asked whether an actual plan
was developed.
Our Response: The group outlined a plan for surveying populations
and characterizing sites and habitats at priority areas, identifying
and recommending management needs, monitoring, and outreach and
education; however, this plan was not drafted or finalized.
(50) Comment: A peer reviewer noted that, in a number of incidences
within the last decade in Canada, sites have had general population
declines or sites have been lost to intense agricultural use.
Our Response: We are aware of four sites in Canada where the Dakota
skipper is now extirpated or possibly extirpated due to habitat
destruction. Only sites where we believed the species is currently
present or possibly present (unknown) were evaluated in our threats
assessment.
(51) Comment: One peer reviewer provided details on Poweshiek
skipperling populations following prescribed burns in Manitoba (based
on Dupont 2013). Specifically, Poweshiek skipperling populations were
most numerous in sites burned 5 to 8 years previously. The species was
absent in sites that were burned the previous year, in small numbers in
areas that were burned 2 to 4 years prior, and absent from areas that
were burned 10 or more years before the survey.
Our Response: We have incorporated this information under Factor A
of this final listing rule, below.
Factor C
(52) Comment: One peer reviewer provided additional information on
Wolbachia, a bacteria affecting many butterfly species.
Our Response: We incorporated the new information into our
discussion on Wolbachia under Factor C of this final listing rule,
below.
(53) Comment: A peer reviewer commented that parasitism, predation,
and disease may be significant stressors to Poweshiek skipperlings and
Dakota skippers. A hypothesis in the rapid decline of the Poweshiek
skipperling, and possibly the Dakota skipper, is that a newly virulent
pathogen or a new parasitoid has increased mortality above normal
levels. The small number of predation and parasitization events that
were observed is evidence only of the difficultly in documenting such
events. Dana (1991, pp. 26-27) reported observing predation on the
butterfly by arthropods and large robber flies (Asilidae), which are
common in upland prairie habitats. The peer reviewer also cited and
discussed several studies that pertain to predation on butterflies.
Our Response: We reviewed the McCabe (1981) and Dana (1991) reports
again and considered additional information on the normal population
dynamics of insects, how these factors may explain the rapid decline of
the Poweshiek skipperling, and perhaps the Dakota skipper, and how
these factors may affect small, isolated populations in the future. We
cannot conclude with certainty that parasitism and predation are
significant stressors, because these occurrences are extremely
difficult to observe, and only a few studies document these events.
Therefore, we conclude that the level of impact from disease,
parasitism, and predation is uncertain, but do not dismiss the
possibility that these factors may become significant in the future.
Factor D
(54) Comment: A peer reviewer commented that, in North Dakota, the
fundamental purpose of management of State School lands is economic,
not scientific or environmental. Consequently, if such land does not
produce income for the State, it may be subjected to deliberate change
in management strategy, including sale at auction. The Dakota skipper's
security at no fewer than two sites in North Dakota, therefore, depends
on the economic value of hay, because those sites are on North Dakota
Trustlands and are currently under haying management.
Our Response: We have incorporated this information into Factor D
of this final listing rule.
(55) Comment: A peer reviewer stated that the Poweshiek skipperling
was listed as State-endangered in Minnesota on August 19, 2013.
Our Response: We have updated the State status of the Poweshiek
skipperling in Minnesota in this final rule.
Factor E
(56) Comment: One peer reviewer stated that, although the Service
has not collected much direct evidence of threats to populations of the
Poweshiek skipperling in North Dakota compared to Dakota skippers in
the State, it is reasonable to assume that the same factors that affect
the Dakota skipper have similarly affected the Poweshiek skipperling,
because the two species share a preponderance of habitat
characteristics, and often are sympatric (have overlapping ranges).
Our Response: The Service agrees with the reviewer's statement. We
also think that the reverse is true: It is reasonable to assume that
Dakota skipper may be vulnerable to the factors that have caused
dramatic declines in the Poweshiek skipperling, but perhaps with a
delay in timing. We consider this possibility in our analysis.
(57) Comment: One peer reviewer provided detailed information on
the size and isolation of Dakota skipper sites in central Manitoba.
These sites are generally greater than 158 ac (64 ha), and all are
separated by 1 km (0.6 mi). Several sites are separated by many
kilometers (miles). The reviewer also suggested that the Service
consider the implications of the separation of the U.S. and Canada
sites.
[[Page 63700]]
Our Response: We have incorporated this information, supplemented
by information in two recently published Master's theses (Dupont 2013,
Rigney 2013a), to update our threats analysis for Canadian populations.
Although we were unsure of the size of many sites in Canada, most sites
were separated by more than 1 km (0.6 mi); therefore, approximately 25
of the sites evaluated in Canada were thought to be at least moderately
affected by small size and isolation. The Canada sites where Dakota
skippers are considered to be present are approximately 115 km (71 mi)
from the nearest U.S. sites, and the Manitoba site is approximately 166
km (103 mi) from the nearest Poweshiek skipperling site in Minnesota.
(58) Comment: A peer reviewer noted that South Dakota State
University conducted a climate change analysis, with an emphasis on
terrestrial habitats, in association with the revision of the South
Dakota Wildlife Action Plan.
Our Response: We reviewed that report and incorporated relevant
information into Factor E of this final listing rule. We will also
consider this report during recovery planning for the two species.
(59) Comment: One peer reviewer queried as to whether either
species has been evaluated using NatureServe's Climate Change
Vulnerability Index (https://connect.natureserve.org/science/climate-change/ccvi)?
Our Response: The Service has not evaluated either species using
NatureServe's Climate Change Vulnerability Index, but will consider
using this tool in the recovery phase. We used several studies specific
to the Dakota skipper and Poweshiek skipperling, as well as general
studies of climate-related changes in the Midwest and throughout North
America. See the Climate Change section of this final rule for more
details on the studies used.
(60) Comment: A peer reviewer suggested that the Service should
provide more detail on the need for future planning, potential
dispersal corridors, restoration of existing sites, and potential
reintroduction and augmentation sites. The high degree of habitat
fragmentation and isolation of sites combined with the limited
dispersal ability of these species have potential for long-term
implications, and management actions, even if effective in short-term
conservation of local populations, may not be enough to prevent the
species from extirpation.
Our Response: We agree with the peer reviewer that detailed
planning will be needed to recover the Dakota skipper and Poweshiek
skipperling. The Service will begin the recovery planning process once
the final listing becomes effective.
(61) Comment: One peer reviewer wanted to know how the species
would be treated for law enforcement purposes, in order to ensure that
private landowners and others that may have these species on their land
would comply with section 9 of the Act. The reviewer asked specifically
about unauthorized collection, handling, and possession that could
result in a violation of section 9 of the Act, as listed in the
``Available Conservation Measures'' section of the proposed listing
rule. The reviewer stated that it may be likely that private citizens
have specimens of these species in their possession.
Our Response: If private citizens hold specimens of either species
that have been collected in the past, they should report these
specimens to their local conservation officer or Service enforcement
official to receive the appropriate documentation that they were
collected prior to listing. Collecting either the Dakota skipper or
Poweshiek skipperling after they are listed would be a violation of
section 9 of the Act, unless the collector held an appropriate permit
from the Service.
(62) Comment: One peer reviewer noted that the list of nonnative
species in the ``Available Conservation Measures'' section of the
proposed listing rule are already well-established species. A more
meaningful list would include species that are not already established,
to prevent future invasive species issues that negatively impact these
and other native species, and that would inform land managers of plant
selection for grassland or wildlife-related plantings.
Our Response: We agree that glossy buckthorn, reed canary grass,
and leafy spurge are well established in many areas within the range of
the species. It is still important for landowners to know that these
nonnative species are detrimental to the butterflies and their habitat,
so they may avoid introducing them to additional areas or conduct
activities that would spread their growth. We added purple loosestrife
to the list of invasive plants as well. Purposeful introductions of any
of the above species would be detrimental to the butterflies and their
habitats. This list is not exhaustive, and other nonnative species may
be destructive to the butterflies or their habitats.
(63) Comment: A peer reviewer asked how the habitats in which the
Poweshiek skipperling or Dakota skipper is known to occur will be
defined, and whether that information will be available to the public,
such that landowners can comply with section 9 of the Act.
Our Response: The Service maintains a list of counties that are
within the current range of the species on publicly accessible Web
sites. We suggest that project proponents contact their State's U.S.
Fish and Wildlife Service Ecological Services Field Office for specific
information on their area. The species are likely to be present only in
areas with suitable native-prairie habitat, and may be present in
nearby grass-dominated areas suitable for dispersal during the adult
flight period. Suitable habitats are further described in the
Background section of this final listing rule.
4(d) Rule
(64) Comment: A peer reviewer suggested that the 4(d) rule should
exempt take caused by haying only after July 22, because the Dakota
skipper flight period extends until after July 15 at some sites in some
years.
Our Response: We acknowledge that extending the earliest date of
haying from July 15 to July 22 may further minimize the likelihood of
adverse effects to the Dakota skipper, but we will retain the July 15
date for the following reasons: First, factors other than the date in
the 4(d) rule will likely play a greater role in determining actual
haying dates, and those factors are likely to cause much of the haying
conducted in areas where the Dakota skipper occurs to be carried out
later than the July 22 date suggested by the commenter. Second, the
July 15 date has been used for many years in a variety of conservation
agreements as a date to ensure that the effects of haying on nesting
birds is minimized. It is typically included, for example, as a
required provision in grassland conservation easements purchased on
private lands by the Service. By retaining the July 15 date, we
minimize the likelihood of causing confusion, and encourage greater
cooperation with our conservation partners. Third, even if haying is
conducted immediately after July 15, it may be sufficient to minimize
adverse effects to Dakota skippers at most sites and in most years.
Moreover, in years when the flight period is ongoing past July 15, the
Service can work voluntarily with landowners and land managers to delay
haying until the flight period is over.
Comments From Federal Agencies
(65) Comment: The National Guard in North Dakota (NDARNG) commented
on their concern that training activities on the Camp Grafton South
(CGS) and Garrison Training Area (GTA) will be
[[Page 63701]]
restricted and that the NDARNG would be overwhelmed with new permitting
and reporting requirements due to the listing of the Dakota skipper.
The NDARNG requested that either State-owned or federally-owned land
that is operated and managed by the NDARNG be exempt from these
proposed rules per proposed Sec. 17.47(b)(3) for military training
conducted on lands covered under an Integrated Natural Resources
Management Plan (INRMP).
Our Response: Neither the CGS nor the GTA was included in the
proposed critical habitat designation. However, according to section
4(b)(B)(iii) of the Act, the Department of Defense must still comply
with section 9 of the Act, including the prohibition preventing
extinction and taking of endangered species and threatened species.
(66) Comment: The NDARNG provided additional reports by Fauske for
surveys conducted in the CGS and GTA in 2003 and 2004. The National
Guard also mentioned surveys that were conducted by Fauske in 2013 at
those locations. Dakota skipper was not observed at those sites in
those years.
Our Response: We incorporated the data from the 2003 and 2004
reports into this final listing rule. We have not been able to obtain
the data from Fauske's 2013 surveys, but did incorporate the National
Guard's claim of negative surveys in 2013 into this final listing rule.
(67) Comment: One commenter stated that two publications (Grant et
al. 2009, DeKeyser et al. 2009) that discuss management of prairies
show that sometimes prescriptions for long-term management of habitat
are at odds with short-term management of the species. For example, no
or light grazing or late-season haying may lead to invasion of cool-
season exotic grasses and loss of native forb and grasses. Thus no
management could sometimes be considered a threat, just as prairie
conversion may cause take.
Our Response: We agree that no management or lack of disturbance
may be a threat to Dakota skipper and Poweshiek skipperling habitat and
that haying, grazing, and fire may be an important management tool for
these butterflies, if carried out appropriately. These topics are
discussed further in Factor A in this final listing rule, below.
Adaptive management may be necessary at many locations to take into
account the underlying causes of habitat degradation and the long-term
and short-term consequences of management to the habitat and the
species. We will be addressing management at specific locations during
recovery planning for both species.
(68) Comment: A Federal agency commented that some native-prairie
plant species decrease without proper grazing management, and long-term
monitoring is needed to properly examine plant species declines.
Furthermore, plant species declines may be due to other factors, such
as landscape position, climatic factors, historical and current
management, and other ecological site conditions. Several papers cited
in the proposed rule incorrectly identify forb species that decrease
due to grazing, such as the purple coneflower.
Our Response: We acknowledge that long-term monitoring data would
be a valuable indicator of important plant species declines.
Unfortunately, we do not have long-term monitoring established at most
sites; therefore, we must rely on the best information available. Most
references to grazing impacts on prairie butterflies are based on
ancillary observations made during research focused on other management
impacts. Some of these may be observational data of changes in site
conditions at a particular site from one year to the next following
changes in management regimes. We cite a few studies that show that
certain levels of grazing remove nectar sources and are, therefore,
likely to adversely affect Dakota skipper populations (e.g., Rigney
2013a, pp. 143, 153). We discuss grazing, including the effects of
grazing management in different habitat types, further in Factor A of
this final listing rule, below.
(69) Comment: A Federal agency noted that the proposed listing rule
states that a large portion of the Dakota skipper habitat should remain
ungrazed or lightly grazed during the adult flight period. Management
focused on preserving every life stage of the butterflies will actually
lead to their demise by inadvertently destroying their habitat.
Our Response: Britten and Glasford (2002) recommend minimizing
disturbance of Dakota skipper habitat during the flight period (late
June to early July) to maximize genetically effective population sizes
(the number of adults reproducing), to offset the effects of genetic
drift of small populations (change in gene frequency over time due to
random sampling or chance, rather than natural selection). All life
stages are essential to the survival of the species, including the
adult flight stage, which is when breeding occurs. Removal of important
nectar sources during the short adult flight period can adversely
affect the Dakota skipper (e.g., Rigney 2013a, pp. 143, 153). Thus, it
is equally important to minimize disturbance of Poweshiek skipperling
habitat during their adult flight period for the same reasons.
(70) Comment: A Federal agency noted that Britten and Glasford
(2002, p. 373), cited in the proposed rule, does not identify grazing
as a disturbance, as the proposed rule indicates.
Our Response: Although Britten and Glasford (2002) did not
specifically identify grazing as a disturbance, other information
sources indicate that grazing can disturb adult Dakota skippers and
Poweshiek skipperlings, because it may remove important nectar sources
(e.g., Rigney 2013a, pp. 143, 153). Both the beneficial and negative
effects of grazing are further discussed in Factor A of this final
listing rule, below.
Comments From States
(71) Comment: A State commented that a comprehensive survey effort
throughout the range of the two species is prudent, if not necessary,
before any listing can occur.
Our Response: Under the Act, we are obligated to use the best
available scientific and commercial information in decisions on whether
to list a species. In this case, the best available information
included results from surveys, reports by scientists and biological
consultants, natural heritage data, and expert opinion from biologists
with extensive experience studying the Dakota skippers and Poweshiek
skipperling and their habitats, whether published or unpublished. We
are required to make a decision based on that available data. Also, see
response to comment 76.
(72) Comment: The Minnesota Department of Natural Resources (MN
DNR) agrees with the Service's conclusion that these species warrant
protection under the Act and fully supports the proposed threatened
status for the Dakota skipper and the proposed endangered status for
the Poweshiek skipperling. The MN DNR has a long history of commitment
to the conservation of these species and has been an active participant
in recent efforts to assess their status in Minnesota. The MN DNR
agrees with the Service's conclusions regarding factors affecting the
species and their resulting status. In light of recent findings, the MN
DNR has reclassified both species as endangered under Minnesota's
Endangered Species Statute, effective August 19, 2013.
Our Response: We appreciate our partnership with MN DNR and their
supporting comments, and have updated the information regarding the
reclassification of both species under
[[Page 63702]]
Minnesota's Endangered Species Statute in Factor D of this final
listing rule.
Habitat
(73) Comment: The North Dakota Game and Fish Department suggests
that the Service use NRCS Ecological Sites of North Dakota as a means
to describe specific potential habitat, rather than Type A and Type B
habitat as described in the proposed rule. The ecological site
descriptions and transition models would help direct the proper grazing
prescription to promote and achieve the plant species composition
appropriate for the given site and requisites for these two butterfly
species.
Our Response: We are considering using NRCS ecological site
descriptions as a tool for managers and others to narrow down potential
habitat for one or both species. However, NRCS ecological site
descriptions have not been developed for all areas where the species
may be present. For the purposes of this final listing, we found that
Type A and Type B habitat descriptions were descriptive of the habitat
and flowering forbs and grasses necessary for the two butterflies.
(74) Comment: North Dakota commented that, based on the specific
precipitation and evaporation rates of Dakota skipper habitat that
McCabe suggests, the western area of North Dakota should not be
considered as part of the range for the Dakota skipper, as those areas
do not meet those specific rates.
Our Response: We have determined that the Dakota skipper is
threatened throughout its range, which includes the 18 counties where
the species has been documented in North Dakota. The Dakota skipper is
historically known from several counties in western North Dakota (e.g.,
McKenzie, Burke, Montrail, and Dunn counties) and is considered to be
present in at least two locations in McKenzie County. The Dakota
skipper may still occur in areas of western North Dakota that may have
conditions that are different from what McCabe (1981) describes for
some of the eastern counties. See the Background section of this final
listing rule for a list of counties in each State.
(75) Comment: North Dakota commented that it appears that any
native grassland in North Dakota that has not been cultivated is
potential Dakota skipper habitat.
Our Response: To more clearly define what constitutes Dakota
Skipper habitat and where take of Dakota skippers may occur, the
Service developed tools to help determine whether the species may be
present in specific areas, which are available on the Internet at
https://www.fws.gov/midwest/Endangered/section7/s7process/s7guid_cons.html#dask. We will continue to refine these materials to
help reduce uncertainty as to where Dakota skippers may occur. Dakota
skippers are present on only a subset of native grassland and are
unlikely to be present in areas where key habitat features are lacking.
Those features are described in the Background section of this rule and
in the materials available on the Internet. As we work to conserve
Dakota skippers, we will provide landowners and land managers with
information that is as accurate and up-to-date as possible to describe
the areas where the species is likely to be present. In addition, we
will also work with these parties to ensure that they understand what
activities are likely to cause take of the species, whether or not the
take would be exempted under the 4(d) rule, and what actions may be
implemented to conserve the species.
Population Status and Distribution
(76) Comment: A State commented that surveys appear to be focused
on repeated visits to sites that were previously inventoried, and a
systematic search for additional sites has not been conducted.
Furthermore, a few new sites have been discovered since 1996 without
such a systematic search for new sites, which suggests that many new
sites may be found with a systematic search. Additionally, roadside
searches for habitat are not a scientifically valid method for
identifying potential habitat.
Our Response: The search for additional locations of both species
has been conducted using a variety of approaches over the years, and
potential sites have been narrowed down on the landscape using
topographic and aerial maps, State natural heritage habitat mapping
data, aerial surveys, roadside surveys, and other methods. Other sites
have been surveyed because of a proposed project and the known
potential for suitable habitat in the area or proximity to other known
locations of the butterflies. Many sites are repeatedly surveyed to
understand long-term trends in the presence of the species or to
quantify other population parameters. Although only a small fraction of
all grassland in North Dakota, South Dakota, and Minnesota has been
surveyed, a significant proportion of the un-surveyed area is likely
not suitable for the species. For example, the species was not detected
at approximately 108 additional locations in North Dakota that were
surveyed for the species in the period 1991-2013 (USFWS 2014, unpubl.
geodatabase). Similarly, in South Dakota and Minnesota, 79 and 148
additional locations, respectively, were surveyed for the species in
the period 1991-2013 (USFWS 2014, unpubl. geodatabase).
Many of these sites have been surveyed multiple times over several
years. Surveys for the Dakota skipper are typically conducted only in
areas that have the particular plant species the skipper requires. New
potential sites surveyed are generally focused on prairie habitat that
appears suitable for the species and has a good potential of hosting
the species. Therefore, researchers have a higher likelihood of
detecting the species at these sites than at sites randomly selected
across the landscape. Based on these surveys, the likelihood that
significant numbers of undiscovered Dakota skipper populations occur in
North Dakota, South Dakota, or Minnesota is low. We acknowledge that
there may be some undiscovered populations, however, and are exploring
using spatially explicit modeling to develop probability occurrence
maps of both species, to help direct future surveys and conservation
efforts.
(77) Comment: Since the Poweshiek skipperling has not been detected
in South Dakota since 2002, South Dakota should not be included in the
listing proposal. Further research needs to be conducted to determine
if this species is present in South Dakota before it is listed.
Our Response: According to our data and analysis, the species'
presence is unknown at 36 of the total 69 sites where the species has
been documented in South Dakota. The species was detected at least once
at all 36 of these sites in 1993 or later; 19 of these sites had
positive detections of the species in 2002 or later. The most recent
detection of the species in South Dakota was at two sites in 2008.
Surveys for the species were not conducted at any of the 36 sites with
unknown occupancy between the years 2007 and 2011, and we cannot
presume that the species is not persisting at a site only because there
have not been consistent annual surveys. At several sites, the species
has persisted for longer than 20 years; for example, the Dakota skipper
was first recorded at Scarlet Fawn Prairie in South Dakota in 1985 and
the species was detected during every survey since that date.
Similarly, the Poweshiek skipperling was first recorded at Waubay
National Wildlife Refuge in 1969 and was recorded during every year the
site was surveyed through 2003. South Dakota is in the range of the
Poweshiek skipperling, and the species is listed throughout its range.
See our
[[Page 63703]]
response to comment 76 regarding additional surveys or research.
Factor A
(78) Comment: A State commented that careful implementation of
grazing and prescribed fire can be an effective management tool in
prairie remnants. The Service should provide clear and practical HMGs/
BMPs (Habitat Management Guidelines/Best Management Practices) for
acceptable use of prescribed fire and grazing implementation.
Our Response: We developed Dakota skipper conservation guidelines
(https://www.fws.gov/midwest/endangered/insects/dask/DASKconservationguidelines.html) that address grazing, prescribed fire,
weed/invasive species control, and other topics, and are preparing
similar guidelines for the Poweshiek skipperling. While some detail is
provided in terms of timing, periods of rest, and number and size of
burn units, the Service stresses that effective implementation of the
conservation measures relies on a thorough and accurate understanding
of the distribution and status of the Dakota skipper and Poweshiek
skipperling and their habitat within a management area. These two
species are likely to be non-uniformly distributed within habitat areas
(e.g., Rigney 2013a, p. 140). Therefore, a species expert should
frequently assess and map habitat and distribution of the species
within management areas to ensure that managers may act based on
correct and up-to-date information.
(79) Comment: A State asked whether grazing of potential butterfly
habitat other than low mesic sites will constitute take.
Our Response: Such decisions will require site-specific
information. If a project occurring in potential butterfly habitat may
affect one or both species or its habitat, we suggest contacting the
Service's Ecological Service Office in your State.
(80) Comment: A State commented that habitat modification and
fragmentation may be a large threat to many grassland species. While
other factors may need to be addressed to protect the species,
conversion of grasslands is the largest single issue. Once land
conversions have occurred, the land cannot be restored to match the
specific requirements of these specialist species. Listing can be
viewed by private landowners as an encumbrance and a disincentive to
conserve grassland; hence privately owned grassland could be converted,
due to the current crop commodity environment and demand for additional
cropland.
Our Response: We agree that conversion of remnant prairies is a
significant concern. Conversion of land to agricultural and other uses
is discussed in Factor A of this final listing rule, below.
Factor E
(81) Comment: South Dakota commented that, as part of the South
Dakota Wildlife Action Plan Revision, experts at South Dakota State
University conducted a climate change analysis with an emphasis on
terrestrial habitats.
Our Response: The Service appreciates this information. We reviewed
the climate report and included information from it into Factor E of
this final listing rule. This report will also help inform recovery
planning and implementation.
Economic Concerns
(82) Comment: A State questioned how a private landowner would be
compensated if, during the course of the Service's activities for
monitoring the critical habitat areas, the private landowner's land or
property is damaged.
Our Response: Surveys for either species on private lands would
only be conducted with landowner permission. Surveys for the species
and its habitat are not destructive in nature and have little, if any,
impact on the land.
(83) Comment: North Dakota commented that listing these two species
will add a substantial workload relative to highway improvement project
development, construction, and maintenance, due to additional section 7
consultations with the Service. This increased workload could add
months to project timelines and would cause a major and unnecessary
disruption to the highway and road systems in North Dakota.
Our Response: Although an increased workload for section 7
consultations may be associated with listing these two species, section
4 of the Act requires species to be listed as endangered or threatened
solely on the basis of their biological status and threats to their
existence. Section 7 of the Act requires Federal agencies to use their
legal authorities to promote the conservation purposes of the Act and
to consult with the Service to ensure that effects of actions they
authorize, fund, or carry out are not likely to jeopardize the
continued existence of listed species. During consultation, the action
agency receives a biological opinion or concurrence letter addressing
the proposed action. In the relatively few cases in which the Service
makes a jeopardy determination, the agency offers reasonable and
prudent alternatives for how the proposed action could be modified to
avoid jeopardy. The Service will work with the consulting agency as
expeditiously as possible to complete the section 7 consulation process
in a timely manner.
(84) Comment: A State asked, what would happen should a private
landowner incidentally take either species during the course of routine
farming operations on private land.
Our Response: Under the Act, it is unlawful for a person to take a
listed animal without a permit. Take is defined as ``harass, harm,
pursue, hunt, shoot, wound, kill, trap, capture, or collect or attempt
to engage in any such conduct.'' Through regulations, the term ``harm''
is defined as ``an act which actually kills or injures wildlife. Such
an act may include significant habitat modification or degradation
where it actually kills or injures wildlife by significantly impairing
essential behavioral patterns, including breeding, feeding, or
sheltering.'' Section 10 of the Act may be used by landowners including
private citizens, corporations, Tribes, States, and counties who want
to develop property inhabited by listed species. Landowners may receive
a permit to take such species incidentally to otherwise legal
activities, provided they have developed an approved habitat
conservation plan (HCP). HCPs include an assessment of the likely
impacts on the species from the proposed action, the steps that the
permit holder will take to avoid, minimize, and mitigate the impacts,
and the funding available to carry out the steps. HCPs may benefit both
landowners and the species by securing and managing important habitat,
and by addressing economic development with a focus on species
conservation.
We recognize that the Dakota skipper and Poweshiek skipperling
remain only on lands where management has allowed them to survive. This
is due to good land-stewardship, and we want to encourage management
practices that support the butterflies. To minimize impacts to
landowners and promote continued cooperation with them while recovering
the Dakota skipper, the Service developed a 4(d) rule under the Act for
that species. This 4(d) rule exempts incidental take of Dakota skippers
caused by certain routine livestock operations and mowing recreational
trails. Any ``take'' that results from private landowner activities not
exempted under the 4(d) rule would require a permit from the Service.
Therefore, private landowners with
[[Page 63704]]
Dakota skippers on their property should become familiar with the
contents of the 4(d) rule and contact the Service if they have
questions. Actions that may cause ``take'' and require a permit from
the Service include prescribed burns, haying before the adult flight
period ends, broadcast herbicide treatments, some insecticide
treatments, and permanent conversion of the Dakota skipper's grassland
habitats. The 4(d) rule does not apply to take of the Poweshiek
skipperling because it is listed as endangered, and the Act does not
allow 4(d) rules for endangered species. Any activity that would result
in take of Poweshiek skipperlings would first require a permit from the
Service.
(85) Comment: A State commented that where section 7 consultations
will be required is unclear. What areas would have to be surveyed to
determine whether the species is present? A large amount of potential
habitat may need to be surveyed during the short adult flight period,
and there are a limited number of qualified entomologists to conduct
the surveys.
Our Response: The Dakota skipper and the Poweshiek skipperling are
both closely tied to native-prairie habitats and are unable to inhabit
areas such as nonnative grasslands, weedy roadsides, or tame haylands.
In addition, these butterflies are not likely to inhabit reconstructed
prairies (e.g., former cropland replanted to native-prairie species).
Therefore, the Service recommends that, to determine whether a section
7 consultation may be required or recommended, action agencies should
first coordinate with their local U.S. Fish and Wildlife Service
Ecological Services field office and provide a description of the area
that would be affected, directly or indirectly, by the proposed or
ongoing action. If survey data are unavailable or inconclusive for the
action area, and features of Dakota skipper or Poweshiek skipperling
habitat are predominant in at least part of the area, a survey by a
qualified individual may be recommended. The Service is developing a
list of qualified surveyors, which will be available through the field
offices in each State.
(86) Comment: North Dakota expressed concern that any impact to
native grasslands in North Dakota will be considered take and require
an incidental take permit. Adjusting the timing of construction
activities will not avoid take because of the species' biology.
Our Response: The Dakota skipper and Poweshiek skipperling
historically occurred in 18 and 7 counties in North Dakota,
respectively, and unless the species are discovered in additional
counties, section 7 consultation would be required only in those
counties and on a subset of lands within those counties where the
species may occur or where critical habitat has been designated. You
may obtain a list of counties in which the species may occur from the
U.S. Fish and Wildlife Service Ecological Services field office in your
State. Furthermore, these two species have specific habitat
requirements (native, unbroken prairies), and it is likely that many
action areas will not contain those types of prairie habitats.
Therefore, project proponents should first provide the field office
with a description of the area that would be affected by the proposed
or ongoing action to determine whether a section 7 consultation may be
required or recommended. See our response to comment 85 and the
Background of this final listing rule for additional information
regarding the habitats these two species inhabit.
(87) Comment: A State asked whether reinitiation under section 7 of
the Act will need to occur, or will any new restrictions be recommended
when new projects begin or existing projects are renewed.
Our Response: Section 7(a)(2) of the Act requires Federal agencies
to consult with the Service to ensure that actions they fund,
authorize, permit, or otherwise carry out will not jeopardize the
continued existence of any listed species or adversely modify
designated critical habitat. Therefore, reinitiation of section 7
consultations may be required for ongoing, new, or revised actions that
may affect the Dakota skipper or Poweshiek skipperling or their
designated critical habitat. We recommend contacting the U.S. Fish and
Wildlife Service Ecological Services field office in your State to
determine the need for section 7 consultations on specific projects.
(88) Comment: A State asked what types of conservation or
mitigation measures would be needed to offset potential impacts to the
species or designated critical habitat, and how will the Service ensure
timely approval of mitigation measures.
Our Response: The Service developed conservation guidelines for the
Dakota skipper that are available online (https://www.fws.gov/midwest/endangered/insects/dask/DASKconservationguidelines.html) and is
developing similar guidelines for the Poweshiek skipperling. We suggest
that private landowners implement applicable guidelines to assist
species and habitat conservation efforts and contact their local
Service Ecological Services field office if they are planning an
activity that may affect one of these species. For actions with a
Federal nexus, action agencies should contact their local field office
to discuss the timeliness of our section 7 consultation process. For
example, from the date that formal consultation is initiated, the
Service is allowed 90 days to consult with the agency and applicant (if
any) and 45 days to prepare and submit a biological opinion. Biological
opinions may include reasonable and prudent measures and terms and
conditions, both intended to minimize the impact of incidental take.
(89) Comment: A State asked whether State natural resource agencies
be expected to restore the species to State-owned lands where they are
considered to be extirpated.
Our Response: The Service will work with the State agencies and
other stakeholders through recovery planning to identify areas that
would aid in recovery of these species, and determine appropriate
actions to take on those lands.
(90) Comment: A state commented that incentive-based voluntary
programs work well for other species and may be a better solution to
conserving the species than listing and critical habitat designations.
The State would like to provide potential voluntary methods and
programs to assist and incentivize landowners to implement conservation
measures and practices that enhance butterfly habitat.
Our Response: We appreciate any assistance to incentivize
landowners to conserve these species. Voluntary actions can have a
significant contribution to conservation. If such measures are in place
when we are evaluating a species for listing, we consider those
measures and how they affect the status of the species in our
determination. The Service's policy regarding voluntary prelisting
conservation actions (79 FR 42525, July 22, 2014), encourages voluntary
conservation actions for non-listed species. However, a species may
still warrant listing if such voluntary actions are not in place when
we are evaluating a species for listing, or if those actions are not
sufficient to affect the need to list a species. We suggest you contact
the Service's Ecological Services Field Office in your State to discuss
voluntary conservation programs in detail.
(91) Comment: A State suggested that the Service should develop
habitat management guidelines and best management practices (HMGs/BMPs)
in close collaboration with State agencies and others knowledgeable
about
[[Page 63705]]
effective prairie management. Many State-owned prairies are managed
with the support of Federal funding, and HMGs/BMPs are needed
immediately in order for the State agencies to comply with the Act.
Such HMGs/BMPs should include clear guidance on: Prescribed fire;
grazing; appropriate use of herbicides on occupied sites; pesticide
buffers around occupied sites and notice to landowners adjacent to
occupied sites; adherence to and enforcement of pesticide labels;
available tools and incentives, including incentives and management
practices for expanding prairie restoration to adjacent restorable
lands; distinct measures for occupied habitat and unoccupied habitat,
including lands targeted for restoration or enhancement; measures for
restored habitat, and the point at which habitat is considered
restored; and importance of effectiveness monitoring and adaptive
management practices in ensuring that HMGs/BMPs produce the desired
benefits to the species and their habitat.
Our Response: We appreciate this comment and look forward to
working with our State partners in implementing conservation and
providing assistance. The Service has developed conservation guidelines
for the Dakota skipper that are available online (https://www.fws.gov/midwest/endangered/insects/dask/DASKconservationguidelines.html) and is
developing similar guidelines for the Poweshiek skipperling. The Dakota
skipper conservation guidelines address: Prescribed fire management,
grazing, haying and native seed harvest, habitat preservation, habitat
restoration, weed/invasive species control, maintenance of genetic
diversity within populations, and coordinated management. The Service
looks forward to continued collaboration with State agencies and other
stakeholders to further develop and refine these conservation
guidelines. These guidelines will be used as a basis to begin a
discussion of HMGs/BMPs development.
(92) Comment: A State suggested that, if HMGs/BMPs cannot be
completed before the effective date of the listing, the final rule
should be delayed until the necessary guidance is available.
Our Response: Section 4(b)(6)(A) of the Act establishes that the
Service must make a final determination as to its proposed action
within 1 year of publishing the proposal, unless there is substantial
disagreement about the sufficiency or accuracy of the available data on
which that decision is based, for which the Service may seek up to a 6-
month extension.
4(d) Rule
(93) Comment: A state suggested that the 4(d) rule be expanded to
exempt take caused by prescribed burns, as it is a valuable habitat
management tool.
Our Response: Although we can establish general guidelines for
managers and landowners who are planning prescribed burns in Dakota
skipper habitats, we determined that it would not be advisable to
broadly exempt take caused by burning in the 4(d) rule. The impacts of
prescribed fires on Dakota skipper populations depend on numerous
factors that warrant site-specific evaluation, including the number,
proximity, and size of populations in nearby unburned areas; fuel
loads; timing of the fire; likelihood of escape from fire units; and
post-fire management of unburned units. If fires are proposed in areas
where they are likely to result in take of Dakota skippers, individual
reviews should be conducted to determine potential effects to the
species.
(94) Comment: A state suggested that the 4(d) rule should
specifically exempt mowing and haying of road rights-of-way under all
jurisdictions (State, county, or township). Exemptions should apply in
the area from the road surface to the right-of-way boundary.
Our Response: We modified the 4(d) rule to exempt take of Dakota
skippers caused by mowing native grassland for hay after July 15 within
transportation rights-of-way. Except for mowing of section line rights-
of-way and recreational trails, the 4(d) rule only exempts take of
Dakota skippers that occurs as a result of mowing or haying that is
part of routine livestock ranching activities. Except for the two
specific cases mentioned above--mowing section line rights-of-way and
recreational trails--the 4(d) rule does not exempt take of Dakota
skippers caused by mowing that does not produce hay for livestock
consumption. Regardless, the 4(d) rule exempts take of Dakota skippers
only if the haying is carried out after July 15. We also further
clarified that Dakota skippers do not inhabit tame hayland or grassland
(hayland or grassland planted to, and composed primarily of, nonnative
grass species, such as smooth brome).
(95) Comment: One commenting agency indicated its support for the
4(d) rule, but also stated that it does not support the exemption of
the listed activities for purposes other than ranching and trail
maintenance, and requested that the Service clarify that the listed
activities would not be permitted if used for other categories of
actions. These activities include haying and spot application of
herbicides to control noxious weeds.
Our Response: In the final 4(d) rule, the Service clarifies that
take would be exempted for certain activities listed in the 4(d) rule
when carried out in relation to routine livestock operations. We did,
however, also clarify that take that occurred as a result of mowing
native grassland for hay would be exempted if conducted after July 15
in transportation rights-of-way.
(96) Comment: A State commented that, in the 4(d) rule, only
exempting spot spraying of weeds is overly restrictive. Leafy spurge,
for example, cannot be effectively controlled at the seedling stage by
spot spraying.
Our Response: We understand that there may be cases where spot-
spraying is insufficient to control outbreaks of noxious weeds.
Frequent herbicide applications, however, have been associated with
reduced diversity of native flowering plants in native rangelands
(e.g., Smart et al. 2011, p. 184). Therefore, take caused by broadcast
herbicide applications is not exempted by the 4(d) rule. It many cases,
Dakota skippers may not be present in areas where broadcast
applications are necessary. The Service can provide technical
assistance to help determine whether Dakota skipper may be present. If
noxious weed control is needed where the Dakota skipper is likely to be
present, the Service will work with landowners or land managers to
identify techniques that avoid take.
(97) Comment: One commenter requested guidance on whether
prescribed fire and the activities described under the 4(d) rule could
be implemented ``on sites that might have historically supported''
Dakota skipper.
Our Response: Take of Dakota skipper is prohibited under the Act,
unless it is a specific action that is exempted under the 4(d) rule,
which applies to all State, private, or tribal lands. If an action is
implemented on a site where the Dakota skipper is no longer present,
then take is unlikely. An action could result in take of Dakota
skippers at sites where the species has been extirpated if key habitat
features are still present and an extant population inhabits a nearby
area. In those cases, Dakota skipper may have reoccupied the site, and
we recommend coordinating with the Service to ensure that a proposed
activity is not likely to result in take of Dakota skippers.
(98) Comment: One commenter stated that the list of counties in
which the proposed 4(d) rule did not exempt take caused by grazing
(Eddy, McHenry, Richland, Rolette, Sargent, and Stutsman) did not
directly correspond
[[Page 63706]]
to the list of counties in which critical habitat was proposed
(McHenry, McKenzie, Ransom, Richland, Rolette, and Wells).
Our Response: We revised the 4(d) rule to exempt take caused by
grazing throughout the range of the species, and not limited to certain
counties. Thus, the final 4(d) rule exempts take of Dakota skippers
caused by livestock grazing on all private, State, tribal, and other
non-Federal (e.g., county) lands.
Public Comments
General
(99) Comment: A number of public comments opposed the listing of
the Dakota skipper and Poweshiek skipperling as federally threatened or
endangered species, but provided no substantive scientific or
commercial evidence suggesting that listing is not warranted.
Our Response: While we appreciate the opinion of all interested
parties, the Service must base its decision of whether to list the
Dakota skipper and Poweshiek skipperling solely on the basis of the
best scientific and commercial data available.
(100) Comment: Several comments stated that listing these species
will interfere with private property rights and cause economic impacts,
such as reduction in land values, fines to citizens, prohibitions to
development, wasteful use of taxpayer money, and intrusion to grazing
and farming operations.
Our Response: For listing actions, the Act requires that we make
determinations ``solely on the basis of the best available scientific
and commercial data available'' (16 U.S.C. 1533(b)(1)(A)) regarding the
status of the species. Therefore, we do not consider any information
concerning potential economic or other possible impacts when making
listing determinations. We will work with entities to conserve the
butterflies and develop workable solutions. Furthermore, in this rule,
we have included a 4(d) rule for the Dakota skipper that exempts take
from certain routine grazing activities. The presence of a listed
species does not give government employees or representatives any
rights to access private property.
(101) Comment: A commenter stated that the Service did not use the
best available science in the proposal. There is a lack of evidence to
justify the proposed actions.
Our Response: The comment did not provide details on what
scientific information we failed to consider in our proposal. In
preparation of the proposal and this final rule, we used the best
available scientific and commercial information of which we are aware.
We sought comments from independent peer reviewers to ensure that our
determination is based on scientifically sound data, assumptions, and
analysis. The peer reviewers stated that our proposed rule was based on
the best available scientific information. Additionally, the results of
2013 surveys conducted throughout the range of both species in the
United States and information from recently published research
conducted in Saskatchewan and Manitoba were considered in our final
listing rule.
(102) Comment: A commenter stated that listing under the Act and
critical habitat designations are intertwined and cannot be separated,
as the Service has done with these proposals.
Our Response: When a species is proposed for listing as endangered
or threatened under the Endangered Species Act (Act), we must consider
whether there are areas of habitat we believe are essential to the
species' conservation. The listing determination and critical habitat
determination for the Dakota skipper and Poweshiek skipperling were
conducted at the same time and in coordination with each other. The
proposed rules for each action were published on the same date, but in
separate documents. We are currently working to finalize the critical
habitat determination for these two species, which will be published
shortly.
(103) Comment: A commenter requested that we clarify the status
that is proposed for each species, as it is confusing which is proposed
as threatened and which as endangered.
Our Response: The Dakota skipper is listed in this rule as a
threatened species, and the Poweshiek skipperling, as an endangered
species.
(104) Comment: A commenter requested that the listing and critical
habitat designations for these species will create an adversarial
atmosphere between the Service and the agricultural community, and
punish producers, who are the best stewards of habitat for a variety of
species.
Our Response: We based our listing decisions on the basis of
biological information and have determined that the Dakota skipper is
threatened and the Poweshiek skipperling is endangered under the Act.
The Service is committed to working with private landowners, public
land managers, conservation agencies, nongovernmental organizations,
and the scientific community to conserve the Dakota skipper and
Poweshiek skipperling and their habitats. For example, in recognition
of efforts that provide for conservation and management of the Dakota
skipper and its habitat in a manner consistent with the purposes of the
Act, we developed a 4(d) rule that outlines the prohibitions, and
exceptions to those prohibitions, necessary and advisable for the
conservation of the Dakota skipper. We believe that exempting
incidental take of Dakota skippers that may result from grazing in
certain geographic areas will afford us more time to protect the
species' habitats in these areas and will facilitate the coordination
and partnerships needed to recover the species.
(105) Comment: The North Dakota Stockman's Association commented
that they have policy supporting the use of sound science in
decisionmaking. Much of the science used to develop these proposals was
not peer-reviewed or published, and was largely based on internal
documents. The Service's own ``Information Standards Under the
Endangered Species Act'' policy calls for ``review of all scientific
and other information used by the Services to prepare biological
opinions, incidental take statements, and biological assessments to
ensure that any information used by the Services to implement the Act
is reliable, credible, and represents the best scientific and
commercial data available.'' Sound, peer-reviewed science needs to be
the foundation of any proposal, but particularly of those with such
serious implications for citizens.
Our Response: Under the Act, we are obligated to use the best
available scientific and commercial information, which in this cased
included results from surveys, reports by scientists and biological
consultants, natural heritage data, and expert opinion from biologists
with extensive experience studying the Dakota skipper and Poweshiek
skipperling and their habitats, whether published or unpublished. The
Service's databases were also referenced several times within the
document (e.g., Service 2014, unpublished geodatabase). These databases
were built using hundreds of sources, including unpublished reports,
published papers, and State heritage data. We referenced these
databases in the proposed and final listing document, in places where
we summarized data across many sources. All of the reports utilized in
these databases are publically available, upon request.
Additionally, we sought comments from independent peer reviewers to
ensure that our determinations are based on scientifically sound data,
[[Page 63707]]
assumptions, and analysis. We solicited information from the general
public, nongovernmental conservation organizations, State and Federal
agencies that are familiar with the species and their habitats,
academic institutions, and groups and individuals that might have
information that would contribute to an update of our knowledge of the
species, as well as the activities and natural processes that might be
contributing to the decline of either species. The existing body of
literature on the Dakota skipper and Poweshiek skipperling, including
results from surveys, reports by scientists and biological consultants,
natural heritage data, and expert opinion from biologists with
extensive experience studying the Dakota skipper and Poweshiek
skipperling and their habitats, whether published or unpublished, is
the best available information.
(106) Comment: A commenter noted that the Dakota skipper listing
priority number indicating threats of moderate to low magnitude.
Our Response: The Service believes that the Dakota skipper warrants
protection under the Act, as a threatened species, as discussed in
detail in this final listing rule. The listing priority number was
changed from 11 to 8 on December 6, 2007 (72 FR 69034), and the Dakota
skipper remained a candidate species with a listing priority number of
8 in subsequent notices through October 26, 2011 (76 FR 66370). The
listing priority numbers range from 1 to 12, indicating the relative
urgency for listing plants or animals as threatened or endangered. The
criteria used to assign this number reflect the magnitude and immediacy
of threat to the species, as well as the relative distinctiveness or
isolation of the genetic material they possess. This latter criterion
is applied by giving a higher priority number to species that are the
only remaining species in their genus, and a lower priority number to
subspecies and varieties. The listing priority number assigned to a
species, however, does not necessarily reflect the classification the
Service ultimately determines is appropriate for a species when making
a listing determination, as new information may become available that
affects that decision.
(107) Comment: A commenter questioned how this listing would
adversely affect other species.
Our Response: We are unaware of any adverse effects that these
listings would have on other native species of plants or animals.
Nonnative or invasive plant species and species of woody plants
encroaching into prairie habitats may be managed to maintain or
increase the quality of native-prairie habitats.
(108) Comment: Commenters asked whether those who are enrolled in
the Conservation Reserve Program, Environmental Quality Incentive
Program, or other U.S. Department of Agriculture programs would be
subject to special requirements. How will the listing affect those who
have Federal crop insurance, have received a Federal loan or Federal
disaster assistance, or own property that has a Federal easement? If a
landowner is required to seek consultation before requesting Federal
funding or authorization for an action that may affect a listed species
or critical habitat, what cost will be involved, both in terms of money
and time? Will this be reflected in the economic impact analysis the
Service is preparing?
Our Response: Proposed projects in areas where one or both species
may be present or on designated critical habitat that has a Federal
nexus (in other words, funded, authorized, or carried out by a Federal
agency) will be required to undergo consultation with the Service under
section 7 of the Act. In such cases, it is the responsibility of the
Federal agency involved to complete the consultation. In those
instances, the action agency should contact the Service's Ecological
Services Office in their State if they are planning an activity that
may affect the species or its critical habitat. For more information
about section 7 consultations, visit the Service's Web site (https://www.fws.gov/endangered/what-we-do/consultations-overview.html). In
accordance with the Act, we cannot consider possible economic impacts
in making a listing determination. However, section 4(b)(2) of the Act
states that the Secretary shall designate and make revisions to
critical habitat on the basis of the best available scientific data
after taking into consideration the economic impact, national security
impact, and any other relevant impact of specifying any particular area
as critical habitat.
(109) Comment: One commenter recommended that better documentation
is needed when Landowner Incentive Program grants or other government
funding is used.
Our Response: Government-funded grant accomplishment reports are
typically available online. Information on our grant programs available
to aid species recovery can be found at https://www.fws.gov/grants.
(110) Comment: Private landowners who are participating in the
Service's recovery program for the Karner blue butterfly commented that
private landowners are critical to the protection of endangered and
threatened species. Private landowners often provide suitable `stepping
stone' habitat otherwise unavailable to public agencies. The Federal
status of the Karner blue butterfly facilitated habitat improvements
and public awareness that may not have occurred but for the protection
of that species. The commenter believes that listing the Dakota skipper
and Poweshiek skipperling will similarly benefit these two species.
Our Response: We thank you for your comment and participation in
species recovery efforts. The Service understands the importance of
private landowner participation and support in recovery of the Dakota
skipper and Poweshiek skipperling and will continue to work with all
stakeholders to this end.
(111) Comment: One commenter expressed disappointment with the
Service stating that other Service projects that are of great benefit
to society, the commenter did not believe that listing the butterflies
was one of them. The commenter questioned why these two butterflies are
of such importance that they should be listed.
Our Response: In the preamble to the Endangered Species Act of
1973, Congress recognized that endangered and threatened species of
wildlife and plants ``are of esthetic, ecological, educational,
historical, recreational, and scientific value to the Nation and its
people.'' In this statement, Congress summarized convincing arguments
made by scientists, conservationists, and others who are concerned by
the disappearance of unique creatures. The Service is responsible for
implementing the Act, and as such, must determine whether any species
is an endangered or threatened species, based on the best scientific
and commercial data available regarding the status of that species, not
based on a certain benefit to society or importance.
Although the Service does not consider the value of a particular
species when making a listing determination, these butterflies are
important and do provide a societal benefit. Humans depend on the
variety of life for food, clothing and medicines. When we lose species
we lose their potential for the future and we lose their effect on
other species which, in turn, have ecosystem roles and future value.
Continued degradation of our lands and waters that reduces our
biological diversity--the variety of life--is important. Habitat and
water degradation, and maybe even climate change, can be reversed, but
the loss of a species and its genes are irreversible.
[[Page 63708]]
Further, the prairie ecosystem is not completely gone, yet, but it will
be if we do not take measures to save its plants and animals.
Protecting these small butterflies means protecting their habitats, so
that some of this ecosystem, with all its variety of life, remains.
Humans depend on the variety of life for food, clothing and medicines.
The variety of life that we have in this country, including functioning
ecosystems, is our natural heritage.
(112) Comment: One commenter stated that change, both desired and
undesired, is a natural part of the evolutionary cycle.
Our Response: Although extinctions occur naturally, scientific
evidence strongly indicates that the current rate of extinction is much
higher than the natural or background rate of the past. The main force
driving this higher rate of loss is habitat loss. Over-exploitation of
wildlife for commercial purposes, the introduction of harmful exotic
(nonnative) organisms, environmental pollution, and the spread of
diseases also pose serious threats to our world's biological heritage.
None of these creatures exists in a vacuum. All living things are part
of a complex, often delicately balanced, network called the biosphere.
The earth's biosphere, in turn, is composed of countless ecosystems,
which include plants and animals and their physical environments. No
one knows the myriad ways the extinction of organisms will affect the
other members of its ecosystem, but the removal of a single species can
set off a chain reaction affecting many others. Furthermore, many
individual species are uniquely important as indicators of
environmental quality. The rapid decline of the Poweshiek skipperling
and Dakota skipper may be an indicator of a greater environmental
problem. Regardless of the reason for the species' decline, it it meets
the definitions of a threatened or endangered species under the Act, we
are obligated list it under the Act.
(113) Comment: A commenter noted that prairie ecosystems are one of
the most endangered ecosystems of the world. Currently only 4 percent
of remnant tallgrass prairie remains in the United States, and the loss
in habitat has led to the declines in the Poweshiek skipperling and
Dakota skipper. Furthermore, these two species play an important role
in the prairie ecosystem, and by protecting them, we also protect other
prairie plants and animals.
Our Response: Native tallgrass and mixed-grass prairies have been
reduced by 85 to 99.9 percent of their former area throughout the
historical range of both species (Samson and Knopf 1994, pp. 418-419).
Even further destruction of remnant prairies has occurred since Samson
and Knopf's study. Conversion is discussed in Factor A of this final
listing rule, below.
(114) Comment: A commenter stated that the limits and prohibitions
on land uses like grazing and haying that are a result of this listing
will negatively affect livestock producers. For example, the areas in
North Dakota within the range of the butterflies are significant beef-
producing counties. Limiting grazing or haying on those lands will have
serious economic ramifications for the cattle-ranching landowners.
Because of the terrain, some of these lands are suited only for
livestock grazing. If those lands cannot be used for that purpose,
their value will largely be diminished. Under the Service proposals,
six North Dakota counties are deemed too sensitive for grazing, and it
appears that grazing will be prohibited there altogether.
Landowner concerns about compliance could influence those impacted
to convert their grass and haylands to other uses before a final rule
is in effect. This would be detrimental to both the livestock industry
and the butterflies the Service is aiming to protect.
Our Response: Through public meetings, meetings with private
landowners, and outreach efforts, the Service has attempted to reduce
the concerns of private individuals. It is important for private
individuals to know that only those projects or actions that occur in
areas where the butterflies may be present or on designated critical
habitat and that have a Federal nexus (in other words, funded,
authorized, or carried out by a Federal agency) must undergo
consultation with the Service under section 7 of the Act. In such
cases, it is the responsibility of the Federal agency involved to
complete the consultation. We suggest that private landowners contact
their local Service Ecological Services Office if they are planning an
activity with a Federal nexus that may affect the species or its
critical habitat. For more information about section 7 consultations,
visit the Service's Web site (https://www.fws.gov/endangered/what-we-do/consultations-overview.html). Under the 4(d) rule for the Dakota
skipper, take of Dakota skippers caused by certain routine livestock
operations on all non-Federal lands is exempt from the prohibitions
under section 9 of the Act. For more information on the 4(d) rule for
the Dakota skipper, refer to the Provisions of the 4(d) Rule for the
Dakota Skipper section of the preamble to this final rule.
(115) Comment: A commenter stated that livestock owners are the
original stewards of this land and other natural resources, and the
general management practices utilized by these owners are ecologically
sound and enhance the productive capabilities of the land. These
practices may even be enhancing the habitat for these two butterflies.
As private landowners and stewards of livestock, land, and other
natural resources, we look for policies that allow coexistence and do
not threaten our livelihood.
Our Response: We appreciate your comment. Landowners deserve great
credit for their land stewardship, and we want to continue to encourage
those management practices that support the butterflies. The Service
also strives to find ways to work with people while protecting
imperiled species. To this end, the Act allows for some flexibility for
species that are listed as threatened; the Service is able to tailor
the protections of the Act to what it deems as necessary and advisable
to provide for the conservation of such species. We have developed a
4(d) rule for the Dakota skipper that provides for the conservation of
the species while allowing some flexibilities for landowners. This 4(d)
rule exempts incidental take of Dakota skippers that is caused by
certain routine livestock operations and mowing of recreational trails.
For more information on the 4(d) rule for the Dakota skipper, refer to
the Provisions of the 4(d) Rule for the Dakota Skipper section of this
final rule, below.
Biology and Habitat
(116) Comment: A commenter stated that the Service is correct to
rely on Royer et al. (2008) for understanding and describing Dakota
skipper habitat. Dakota skipper data in Minnesota are overwhelmingly
attributable to Type B (upland prairie: Dry-mesic or dry). However,
type A and B habitats can blend into each other. As correctly described
by the Service here, upland and lowland prairie are often intermixed in
both habitat types (A and B).
Our Response: We describe prairie types as Type A or Type B
habitat, but realize that the two habitat types may be intermixed,
there may be smaller patches that may be better categorized, or
specific microhabitats that the species uses at various times to
fulfill their biological needs.
Occupancy
(117) Comment: A commenter stated that the definition of occupancy
is
[[Page 63709]]
difficult to understand and should be clarified.
Our Response: We clarified the definition of occupancy in this
final rule by adding language that clarifies that the three sequential
years of negative surveys necessary to consider the species extirpated
from a site could be from any survey year. We also clarified that the
occupancy status of an extirpated site would not change unless the
species was detected at that location during future surveys. We strove
to be as accurate as possible in defining occupancy for the purposes of
the listing and critical habitat determinations. If you are unsure
whether either species may occur on your property, we suggest you
contact the Service's Ecological Services Field Office in your state.
(118) Comment: A commenter stated that the Service's methodology
for classifying occupancy is well supported. Given the difficulties of
detecting these small butterflies most observable in the brief period
per year when it is in the adult life stage, a conservative approach is
justified. The timing of the adult flight period and the species'
abundance varies greatly among years, due to climatic variation. At
least 3 years of surveys are needed before an area should be considered
extirpated. Furthermore, those 3 years of surveys need to be detailed
efforts per survey, with multiple dates of surveys per year.
Our Response: We appreciate your comment in support of our
occupancy rationale. We agree that multiple dates of surveys per year
are desired to verify non-detection of the species in a given year. We
have added language to clarify that point in the Background section of
this final listing rule, above.
(119) Comment: A commenter stated that the determinations to list
these two butterflies are based on historical declines, although
significant documentation of butterfly fauna did not occur until 1960,
and it is, therefore, impossible to determine anything about the
historical range or any possible historical declines. How are past
declines relevant to the species now, and why is the Service listing
these species now, as opposed to when those declines were occurring? It
is not possible to characterize the magnitude of threats to these
species without knowing what has caused the historical decline and
understanding what constitutes natural levels of inter-annual
population fluctuation.
Our Response: We consider historical declines, and the ongoing
effects of those historical declines, as well as current and recent
declines, in our determinations. Significant population declines have
occurred in both species very recently and are still ongoing, and the
effects of historical declines continue to impact both species today.
Populations that were historically fragmented by habitat destruction
continue to be isolated from one another, which may have negative
genetic consequences or increased vulnerability to stochastic events,
for example.
Population Status and Distribution
(120) Comment: A commenter stated that the survey methods are
inadequate and poorly described. In particular, it appears that a high
percentage of survey sites are in close proximity to roads. These sites
may be disturbed sites, and some literature indicates Dakota skippers
do not occupy formerly disturbed and subsequently restored sites.
Our Response: As described in the Background section of this final
listing rule, above, Dakota skippers occupy native-prairie sites that
have never been plowed. During the adult flight period, it is possible
that Dakota skipper may use lesser quality grassland dominated areas to
travel (disperse) from one native-prairie site to another nearby
native-prairie site. Surveys were conducted using various protocols
(for example, Pollard walks (Pollard 1975), modified Pollard walks,
wandering transects, and timed transects) depending on the objective of
the survey, funding, or available resources and staff. Describing the
details of survey methods for each site is beyond the scope of this
rule, however, those details are described in the survey reports that
are cited within this final rule. We added some brief examples of
commonly used survey methodologies in the Background section of this
final listing rule.
(121) Comment: A few commenters suggested that there are multiple
approaches to interpreting data and conducting trend analyses. One such
suggested approach is to use the concepts of Schlicht et al. (2009,
Table 10, p. 439) and Swengel and Swengel (2012b, Table 2). The
observed timing of population declines may differ depending on the
approach used. As such, the commenter cautions that the information
included in Figures 1 and 2 of the proposed listing rule should be
interpreted carefully, and provides specific suggestions for an
alternate approach.
Our Response: We acknowledge that there are other ways to look at
the data and the approach suggested by the commenter would be a good
way to determine the apparent disappearance (either absence or
undetectable levels) of a species at each particular site. These types
of analyses may be an appropriate approach for recovery planning and
implementation, and we will consider their utility at that time. We
believe the way we interpreted the data in the listing rule is
appropriate for looking at the overall trends in detections and non-
detections of the species through the years across all of the known
sites, without relying on the numbers of individuals observed at each
site during each survey year, since we often do not have those data.
Although many of the skipper sites have been surveyed over multiple
years, the frequency and type of surveys varied among, and sometimes
within, sites and years. Surveys may have been conducted using various
protocols and with varied objectives and, therefore, had varying
results. For instance, some surveys focused simply on documenting
species presence while others documented the numbers observed in a
certain area, distance, or period of time. Whether or not the species
was detected in a given year is the only common result of all the
surveys, so that is the data we used to evaluate trends through time.
(122) Comment: One private citizen commented that he has never
observed the Dakota skipper and the Poweshiek skipperling on his
property or anywhere else.
Our Response: Dakota skippers and Poweshiek skipperlings have a
single adult flight period per year that typically occurs from the
middle of June through the end of July. The actual flight period varies
somewhat across the range of each species and can also vary
significantly from year-to-year, but typically lasts 2 to 4 weeks. Both
the Dakota skipper and Poweshiek skipperling are small and cryptic
species. Therefore, it is unlikely someone will observe these two
species unless they are actively searching for the species in suitable
habitat within their ranges during the short adult flight period. The
likelihood of observing these species recently is low, because these
two species have reached undetectable levels, even by experienced
observers, at most of their known locations.
(123) Comment: One commenter recommended that surveying and
monitoring protocols be developed for the two species.
Our Response: Because the objectives of surveys may vary across the
range of these species, we recommend contacting the Service's
Ecological Services Field Office in your State to discuss the
appropriate survey protocol to use for
[[Page 63710]]
particular projects, habitat types, and geographic areas. To facilitate
effective cooperation among agencies, organizations, and individuals
interested in the distribution of these species, the Service will
maintain a list of individuals who meet certain qualifications for
conducting reliable surveys for the target species.
(124) Comment: One commenter provided results from butterfly
surveys conducted for the past 19 years (1995-2013) in Clay and Polk
counties, Minnesota. Low numbers of Dakota skippers were observed in
1996, 2006, 2007, and 2010. The Poweshiek skipperling was observed in
1997-2002, 2004-2006, and two individual Poweshiek skipperlings were
observed in 2013.
Our Response: We appreciate receiving the new information on Dakota
skipper and Poweshiek skipperling occurrences in Minnesota. We verified
the information with Minnesota Department of Natural Resources staff (a
qualified surveyor), who confirmed the validity of the data. We
confirmed that the individual was capable of identifying the Poweshiek
skipperling and that the 2013 observations were valid. This information
was incorporated into this final listing rule. The Service has
prioritized the Polk County location for surveys in future years.
(125) Comment: A commenter noted that the Service included two
graphs indicating a decline in Dakota skipper sites in Minnesota and
South Dakota, but did not include a graph for North Dakota. The 2012
abstract by Royer indicates that ``essentially the same proportion of
count locations hosted detectable Dakota skipper populations . . .'' in
1996, 1997 and 2012, but that the encounters per hour had decreased.
The commenter contend that fewer ``encounters per hour'' could be the
result of many factors, including the very specific conditions
necessary to do an accurate sampling. The summary data does not provide
the necessary background to determine other factors that could have
influenced the ``encounters per hour'' count.
Our Response: The detection versus non-detection data for Dakota
skippers in North Dakota produced no clear trend. If we examine years
with more than 10 sites surveyed, for example, we find that in 1991,
the species was detected at 19 of the 31 sites surveyed (61 percent);
in 1995, the species was detected at 5 of the 10 sites surveyed (50
percent); in 1996, the species was detected at 13 of the 18 sites
surveyed (72 percent); in 1997, the species was detected at 10 of the
25 sites surveyed (40 percent); in 1998, the species was detected at 11
of the 17 sites surveyed (65 percent); and in 2012, the species was
detected at 15 of the 27 sites (56 percent) surveyed (where the species
had previously been observed). Royer (2012) was correct that the
proportion of sites with detections versus non-detections of Dakota
skippers were similar (e.g., statewide proportions in 1996 (72
percent), 1997 (40 percent), and 2012 (56 percent)). Therefore, we
examined the results of sites that Royer (2012) surveyed using methods
that quantified results such that they could be compared among years.
Royer used the same survey protocol, timed transect searches (where
the number of individuals observed per hour were recorded), for the
surveys conducted in 1996-1997, 1998, and 2012 (Royer 1997, Royer and
Royer 2012b). Furthermore, Royer's 1996, 1997, 1998, and 2012 surveys
(Royer 1997, Royer and Royer 2012b) adhered to our acceptable survey
standards (e.g., wind speeds, time of day). Therefore, the variation in
numbers observed attributable to survey error is expected to be
negligible. Average encounter frequencies observed across the State in
2012 (10.7 encounters per hour) were lower than during the 1996-1997
and 1998 statewide surveys (North Dakota State average = 16.94
encounters per hour and 22.67 encounters per hour, respectively). At
the site level, sites surveyed in 1996-1997 or 1998 generally had
higher numbers of Dakota skippers encountered per hour than in 2012.
(126) Comment: A commenter stated that the proposed listing of the
Dakota skipper as a threatened species is unwarranted at this time. In
North Dakota, surveys show that essentially the same proportion of
locations had detectable levels of Dakota skipper in 1996-1997 (46
percent) as in 2012 (46 percent). Additionally, new sites have been
discovered in North Dakota, even though a systematic survey has not
been conducted. A substantially lower encounter rate in 2012 compared
to historical surveys was reported, but one year of data does not
justify listing.
Our Response: Although the proportion of sites surveyed with
positive detections of the species is similar when comparing sites
surveyed in North Dakota in 1996-1997 with those surveyed in 2012, the
numbers of individuals observed recently were substantially lower than
in previous surveys; see our response to Comment 125. In addition to
the survey data and population trend information, the Service also
considers listing species based on an analysis of threats, described in
detail in this final listing rule. The results of that threat analysis
indicates that all of the Dakota skipper sites where the species is
considered to be present or unknown in North Dakota have one or more
documented threat of moderate to high levels. At least one moderate- to
high-level threat is documented in all Minnesota, North Dakota, South
Dakota, and Canada Dakota skipper sites with present or unknown
occupancy.
(127) Comment: A commenter stated that the Service rightly states
that most Poweshiek skipperling decline likely went unrecorded because
most prairie destruction occurred prior to 1960, but most prairie
butterfly surveys post-date those declines. Most decline during 1960-
2000 also went largely undocumented. This is evidenced by the large
number of sites in Minnesota that fall into an uncertain occupancy
category. Longer term Poweshiek skipperling decline has been masked by
data paucity and turnover in sites surveyed.
Our Response: We agree that there is a paucity of data at many
sites in recent years (1960-1993). However, most Poweshiek skipperling
sites and Dakota skipper sites have been surveyed at least once in 1993
or more recently. The lack of surveys at a given site since 1993 does
mean that we are uncertain of the occupancy at many sites. We used a
cautious approach; by assigning sites unknown status, we cannot say
that the species is truly absent or extirpated from a site, while
acknowledging that the species may still be present, possibly at
undetectable levels, if suitable habitat is still present. More surveys
are needed at these sites to determine if the species is present.
(128) Comment: A commenter stated that, at the time of Swengel's
(1992) review, Poweshiek skipperlings had fewer known populations, were
more highly concentrated in preserves (a single kind of ownership and
land use category), were in a narrower range, were more concentrated in
a highly destroyed ecosystem (tallgrass prairie), and had a worse
immediate response to typical preserve management (fire) than Karner
blue butterflies, which were federally listed in 1992. Poweshiek
skipperlings are capable of high local abundance in a few sites, but
these population numbers are highly volatile, and so extremely low
numbers also occur during these abundance fluctuations. Compared to
Dakota skipper incidence within Poweshiek skipperling range, Poweshiek
skipperlings occurred on relatively more preserves, but Dakota skippers
had a range further west, including mixed-
[[Page 63711]]
grass prairie, less of which has been destroyed. Also, the Dakota
skipper is more compatibile with agricultural uses on ranch land (e.g.,
Royer 1992; Marrone 1992). Thus, the Dakota skipper had relatively more
habitat, even if there were fewer known sites specifically in
Minnesota. Furthermore, there is a tendency to assume that habitat
protection (making a site a preserve) means the skippers in the
preserve are secure; thus, if few are found on a given survey, the
assumption is that this is due to the surveys being conducted at the
wrong time, or due to fluctuations in abundance resulting from climatic
variation. It is only through consistent long-term monitoring with the
sites held constant (as in Swengel and Swengel 2013) that trend can be
distinguished from those issues.
Our Response: Because of the number of historical sites and the
various ways that data were collected at those sites, we examined the
range-wide data using detections and non-detections. We agree that
there are few sites with consecutive years of data, and even fewer that
have data over the long term. We have examined the data at individual
sites where we had several consecutive years of data, and found that
Poweshiek skipperling numbers have appeared to decline, along with the
number of sites with positive detections (vs. non-detections) of the
species.
(129) Comment: A commenter stated that the sudden recent decline in
Poweshiek skipperlings over the last 10 years is likely because there
are few new populations being discovered to replace the already
undetectable, previously known populations. Furthermore,
conservationists identified the best sites first; thus, more recently
discovered populations were not as large and robust as the earlier
discovered populations. Those more fragile populations would have less
favorable prospects for long-term persistence. This also contributes to
the sense that decline is now occurring everywhere. In addition, in
some places, such as North Dakota, the dramatic population declines of
the Poweshiek skipperling primarily occurred prior to 2000 (see Royer
and Marrone 1992a, b; and Orwig 1994; 1995; 1996; and 1997).
Our Response: We acknowledge that there are documented declines in
Poweshiek skipperling populations prior to 2000. However, in our
comprehensive review, it appears that many sites with known populations
of Poweshiek skipperlings have simultaneously declined to undetectable
levels across much of the species' range in the early 2000s.
Factors Affecting the Species--General
(130) Comment: A commenter stated that, throughout the proposed
listing rule, the Service attributes perceived threats to the Dakota
skipper as threats to the Poweshiek skipperling or vice versa. The
Service must independently evaluate threats to each species and may not
assume that a threat to one species is necessarily a threat to the
other.
Our Response: We have conducted the analysis of factors affecting
the species separately for the two species. Since these two species
have similar biology and are often found in the same locations, they
face similar or identical threats at many locations. Therefore, when
describing the factors, we discuss their effects to both species
together when they are the same or similar. For example, if a remnant
(untilled) native tallgrass prairie is being considered for a housing
development, the resulting habitat conversion would affect both species
by removing suitable habitat from the landscape.
(131) Comment: A commenter stated that listing these species will
impede the use of certain grassland management tools such as grazing,
haying, burning, and chemical spraying that are necessary to meet the
desired habitat for these butterflies.
Our Response: The listing of these two butterflies will not
necessarily impede the use of these grassland management tools. The
Service recognizes that management, including grazing, haying,
prescriptive fire or targeted herbicide treatments, may be needed to
benefit the species and their habitats, as discussed in Factor A and
Factor E of this final listing rule, below. The types, extent,
duration, and intensity of various management regimes that would
benefit the butterflies may depend on the specific past, present, or
future threats at that location. The success of management regimes will
need to be monitored and adjusted accordingly.
(132) Comment: A commenter noted that suggestions of ``light,''
``limited'' and ``no'' grazing and ``late-season haying'' are mentioned
in the proposed rule to support rebuilding the butterfly populations.
However, such practices have proven to have long-term implications that
will actually do the opposite. For instance, limiting or eliminating
grazing and haying is likely to promote invasion by exotic grasses,
such as smooth brome grass and Kentucky bluegrass, which will compete
with the very same native species that the butterflies require for
habitat. The Service should encourage and incentivize grazing and
haying approaches, such as rotational grazing, that would support both
the economic viability of livestock operations and butterfly population
growth.
Our Response: Conservation of Dakota skipper and Poweshiek
skipperling populations relies on careful implementation of management
practices that conserve its habitat while minimizing adverse effects to
reproduction and survival. Rotational late-season haying after the
adult flight period, for example, can be beneficial to the species'
habitat. We have developed Dakota skipper conservation guidelines
(https://www.fws.gov/midwest/endangered/insects/dask/DASKconservationguidelines.html), which describe those practices in
more detail, and are developing similar guidelines for the Poweshiek
skipperling. We discuss both the harm and the benefits that various
management practices may have on prairie habitats in Factors A and E of
this final listing rule (below).
(133) Comment: A commenter stated that grassland easements are a
broad-brush approach to conserve native prairies, but there is no
targeted program or recovery plan specific to the Dakota skipper that
would provide financial incentives and technical information for
ranchers and farmers to manage habitat in a way that would expand the
population of Dakota skippers.
Our Response: Service programs, including Partners for Fish and
Wildlife and State and tribal grant programs, are available to develop
projects and partnerships to conserve these and other species.
Following listing, the Service will develop a recovery plan for these
two species.
(134) Comment: A commenter stated that beaver dams can cause water
level fluctuations in some Poweshiek skipperling areas in Michigan. The
commenter asked whether these fluctuations, or the act of returning the
water level to its normal level, harm Poweshiek skipperling larvae or
habitat.
Our Response: It is possible that higher than normal water levels,
for an extended amount of time, may harm larvae. We discuss fluctuating
water levels in Factor E of this final listing rule, below.
Factor A
(135) Comment: A commenter stated that current Dakota skipper
population sites are already protected, and the imminent threat to the
species is deemed to be on ``remnant habitat.''
Our Response: While some Dakota skipper sites are on land that is
protected from some threats, such as
[[Page 63712]]
conversion of remnant prairies to other uses, the Dakota skipper
populations at these sites are still exposed to other stressors, as we
detailed in the Summary of the Factors Affecting the Species section of
this final listing rule, below.
(136) Comment: A commenter stated that the Dakota skipper and
Poweshiek skipperling do not warrant listing because the Service
improperly characterized oil and gas development as a threat to the
Dakota skipper and Poweshiek skipperling, overstated the amount of oil
and gas development occurring in the ranges of the Dakota skipper and
Poweshiek skipperling, incorrectly assumed that the level of oil and
gas development seen in western North Dakota will occur throughout the
species' ranges, and erred by concluding that impacts from oil
development in western North Dakota to the two butterflies are similar
to impacts from coal-bed natural gas in Wyoming on the greater sage-
grouse. Accordingly, the Service should withdraw the listing and
critical habitat rules.
Our Response: The Act directs us to determine whether a species is
an endangered species or a threatened species because of any factors
affecting its continued existence. Listing actions may be warranted
based on any of the five factors, singly or in combination. We
completed a comprehensive assessment of the biological status of the
Dakota skipper and Poweshiek skipperling, and all factors that might
affect its existence. The effects from oil and gas activities are just
one of the factors we considered. Our determinations that the Dakota
skipper is a threatened species and the Poweshiek skipperling is an
endangered species are based on numerous threats, acting individually
and synergistically, that are leading to substantial population
declines.
Specifically with regard to our evaluation of impacts from oil and
gas activities, much of this activity is currently occurring in areas
of native prairie overlying the Bakken and Three Forks formations, to
the west of known locations for both butterfly species. However,
current Bakken oil and gas development is occurring in two counties
that have records of Dakota skippers (McKenzie and McLean counties in
North Dakota). In those areas, oil and gas development is a stressor to
the populations that may be present. Because there are few locations
where the butterflies may still be extant, significant stressors to
these few populations can be threats to the species as a whole.
Furthermore, although oil and gas development is unlikely to occur
throughout the entire range of the two butterflies in the foreseeable
future, there may be future development or increases in current
activities associated with the shale-oil formations (such as the Bakken
formation in North Dakota) that may affect butterfly populations in
those areas. Finally, we used the Naugle et al. (2011) study and its
impacts to sage grouse as a surrogate to estimate the impacts of
similar energy development projects to the butterfly habitat. Because
the Powder River Basin development varies from the development in the
Bakken formation, we have corrected our estimations and analysis in
this final listing rule (see Destruction and Conversion of Prairies to
Nonagricultural Development, below).
(137) Comment: A commenter noted that wind energy is not a threat
to the species in North Dakota. The Service's conclusion that wind
energy development will expand into the ranges of the Dakota skipper
and Poweshiek skipperling, and thus is a threat to the species, is
based on outdated data and is poorly supported. The Service must
justify its assumptions that wind energy will expand into Dakota
skipper and Poweshiek skipperling range and consequently be a threat to
the species.
Our Response: We have evaluated the stressors to populations at
sites where we had sufficient information to do so. Generally, we
consider that wind development will have localized impacts in a few
sites. We know of at least one site where a proposed wind development
project poses a threat to the Dakota skipper and its habitat. Another
wind farm is proposed within 2 miles of areas we proposed as critical
habitat, with expansion phases that could overlap that critical
habitat. Both of these projects are in the draft Environmental Analysis
stage of development. See Destruction and Conversion of Prairies to
Agricultural Land, below, for a full discussion on impacts from wind
energy development.
(138) Comment: The proposed listing determination relies heavily on
the work of McCabe and Royer for North Dakota, who have both published
generalized statements about impacts of grazing on the Dakota skipper.
These authors do not discuss the types of animals, season of use,
intensity of grazing, or whether a grazing system is involved.
Our Response: The Service used butterfly surveys and habitat
reports written by Royer, McCabe, Spomer, and others to inform our
determination on the status of the species in North Dakota. These
authors also often reported stressors they observed at sites, such as
invasive species encroachment or intensive grazing practices. We also
used other reports and publications to inform the discussion regarding
grazing effects on the butterflies, which included a discussion
regarding types of animals, intensity of grazing, habitat type,
proximity of nearby populations, associated herbicide use, and timing.
In the conservation guidelines for the Dakota skipper (https://www.fws.gov/midwest/endangered/insects/dask/DASKconservationguidelines2013.html), we further discuss grazing in
terms of intensity, duration, season of use, and type of habitat.
(139) Comment: A commenter stated that invasive plant control needs
to be done very carefully and in small-scale treatments to ensure any
adverse effects on the Poweshiek skipperling, or the vegetative
conditions they specifically require, are minimized, as invasive plant
and brush control is not automatically beneficial to the butterfly.
Specifically, at the Puchyan Prairie site, there is greater risk of
unintended negative side effects of invasive plant control on Poweshiek
skipperlings themselves, or the specific types and structures of
vegetation they require, than risk of habitat deterioration in the next
several years, if a more cautious approach is used. More time should be
allowed to assess and describe the full extent of the kinds of
microhabitats used by the Poweshiek skipperling, which likely differ
among years due to climatic variation, and the extent of any change or
deterioration in the vegetation in their core habitat areas.
The commenter also stated that the Service is also correct that
fire management, without careful planning, may have significant adverse
effects on these skippers; however, the Service understates the risks
of fire. A number of areas of good Dakota skipper and Poweshiek
skipperling habitat have been converted by fire management over the
last several decades from light agricultural land uses to areas lacking
the features needed by the butterflies. These converted areas in Iowa,
Minnesota, and westward have few recent records of either species. Fen
wetland preserves in Michigan do have recent Poweshiek skipperling
records, but some of these sites have new, not long-term, fire
management. The Poweshiek skipperling has not fared well in the working
landscape; thus, deliberate conservation effort is needed.
Our Response: We agree that conservation of Poweshiek skipperling
populations relies on careful implementation of management practices
that conserve its habitat, while
[[Page 63713]]
minimizing adverse effects to reproduction and survival, including
invasive species control at the few sites where the Poweshiek
skipperling remains, such as Puchyan Prairie. As discussed in Factor A.
The Present or Threatened Destruction, Modification, or Curtailment of
Its Habitat or Range, below, encroaching invasive plants may replace or
reduce the coverage of native forbs and grasses used by adults and
larval butterflies and, therefore, need to be controlled. However, we
further discuss that control methods (such as fire and herbicide
spraying) may have their own unintended consequences, such as reduced
native forbs and grasses and direct mortality of the butterflies, if
not conducted carefully. Furthermore, various habitat types at these
sites may respond differently to various types of control treatments.
Therefore, when considering recovery planning for the species, it will
be important to continue to individually assess sites to determine the
need to control invasive species, exercise caution when implementing
treatments, monitor the response to any treatments over the long-term,
and refine or modify treatments as needed to get desired outcomes.
Similarly, assessment and long-term monitoring of the species' needs,
such as microhabitat use, will help inform conservation efforts at
specific locations.
(140) Comment: One commenter recommended that land managers be
advised as to the appropriateness of prescribed burns in Poweshiek
skipperling habitat.
Our Response: The Service contacted all of the landowners within
proposed critical habitat designations as part of this rulemaking
process. We have developed conservation guidelines for the Dakota
skipper (online at https://www.fws.gov/midwest/endangered/insects/dask/DASKconservationguidelines.html), and are developing similar guidelines
for Poweshiek skipperling. Contact the Service's Ecological Services
Field Office in your State to discuss prescribed burn practices on land
where one or both species may be present.
(141) Comment: One commenter recommended that sites with Dakota
skipper populations where fire management is not already occurring
should remain fire-free, and that fire management should cease in core
habitat for the Dakota skipper. Instead, cautious rotational haying or
grazing regimes should be used to rehabilitate grassland vegetation to
the shorter turf height that Dana (1991) recommends for the species.
Our Response: We have developed conservation guidelines for the
Dakota skipper (https://www.fws.gov/midwest/endangered/insects/dask/DASKconservationguidelines.html), and are developing similar guidelines
for Poweshiek skipperling. The recommendations will be reviewed for
possible incorporation as we continue to refine these guidelines.
(142) Comment: A commenter noted that the proposed rule states that
the negative effects of fire persist for 1 to 5 years, citing Swengel
(1996, pp. 73, 79, 81) and Panzer (2002, pp. 1302-3). These papers,
however, include a range of butterfly species found in prairies, not
just localized prairie specialists like the Dakota skipper and
Poweshiek skipperling. Panzer's study contains no data on the Poweshiek
skipperling or Dakota skipper. Swengel (1996) includes specific
analysis of both species, but no explicit predictions are made. Swengel
(1996, pp. 73, 79) describes that the negative effects of fire persist
for specialists for 3 to 5 or more years. Swengel (1996) does not
indicate an expectation of recovery 1-2 years post-burn for these
species. Thus, Swengel's analysis is better used to define when
recovery has certainly not occurred (within years 0-3), but not when
recovery actually has occurred.
Our Response: We corrected our interpretation of the Swengel (1996)
and the Panzer (2002) papers as discussed under Factor A. The Present
or Threatened Destruction, Modification, or Curtailment of Its Habitat
or Range, below, to better reflect the included data and information.
We also changed our use of the word ``recovery'' in this context to the
term ``rebound,'' which more accurately describes an upward trend, but
does not imply a stable recovered trend in populations.
(143) Comment: A commenter noted that Dana (1991, pp. 55-56)
discusses concern about grass growth structure and height, namely that
fire encourages taller grass growth, but that Dakota skippers prefer
shorter grass. Therefore, effectively controlling weeds and brush does
not necessarily mean that the management is creating suitable habitat
for skippers. In the long run, fire does not produce a suitable
vegetative structure for skippers. The long-term compounding indirect
effect of fire on the vegetation (increasing grass height and
thickness) may have a more lasting impact on the species and be more
difficult to manage.
Our Response: We will consider the longterm effect of fire on
native vegetation growth and structure when developing and refining
conservation guidelines for the Dakota skipper and Poweshiek
skipperling.
(144) Comment: The data used for North Dakota in the proposed
listing rule relies heavily on the work of McCabe and Royer, who have
both published generalized statements about grazing and its effects on
the Dakota skipper. These authors do not discuss the types of animals,
season of use, intensity of grazing or whether a grazing system is
involved.
Our Response: The Service relied on butterfly surveys and habitat
reports written by Royer, McCabe, Spomer, and others to inform species
and habitat data in North Dakota. These authors also often reported
stressors they observed at sites, such as invasive species encroachment
or intensive grazing practices. We used various other reports and
publications to inform the discussion regarding grazing in Factor A of
this final listing rule and included a discussion regarding types of
animals, intensity of grazing, habitat type, proximity of nearby
populations, associated herbicide use, and timing. In our conservation
guidelines for Dakota skipper, we further discuss grazing in terms of
intensity, duration, season of use, and type of habitat.
(145) Comment: A commenter noted that low-intensity grazing is
mentioned as a potential management tool to help maintain habitat and
abate other threats to these two species. In some cases, high-
intensity, short-duration grazing may have a role in providing the
disturbance that prairies require to prevent them from being overrun by
woody plants, and invasive species.
Our Response: We have developed conservation guidelines for the
Dakota skipper's specific needs. These guidelines include some grazing
recommendations; however, we are interested to learn more details about
the effects of grazing practices implemented in various areas as we
continue to refine our recommendations, and will take this information
into consideration.
(146) Comment: A commenter noted that data suggest Poweshiek
skipperling populations at sites that were hayed prior to preservation
did not recover to the same level following any subsequent fire.
Our Response: We acknowledge that fire management may be
detrimental to the Poweshiek skipperling, if not conducted properly. We
are developing conservation guidelines for the Poweshiek skipperling
that will address fire management and other actions, and are interested
to learn more about the implications of fire practices as we continue
to develop and refine our conservation recommendations.
[[Page 63714]]
(147) Comment: A commenter stated that the Service should provide
data to support that fire management, even if applied to most or all of
the patch occupied by the Dakota skipper or Poweshiek skipperling, has
a low effect on the long-term persistence of these populations. The
Service does not cite long-term studies of impacts from fire, but
instead provides a list of assumptions, such as the following: (1) Fire
happens in prairie (although the extent of that in a natural context is
open to great debate; see literature review in Swengel and Swengel
2007, p. 264); (2) these skippers live in prairie; (3) fire has various
effects on prairie plants (although it should not be assumed that fire
controls brush and weeds; see Swengel et al. 2011, p. 535); (4) those
floristic effects are assumed to be beneficial to these skippers
(although vigorous tall grass growth caused by fire may not be; see
Dana 1991, pp. 5-56). Based on these assumptions, the Service concludes
that fire should be fine for these skippers. The Service needs to
provide direct positive evidence indicating that the skippers,
especially the larvae, actually succeed in the long term following a
fire.
Our Response: We will consider all factors and data regarding the
effects of fire on the species during recovery planning and
implementation and in developing and refining the conservation
guidelines for these two species. We acknowledge that there are no
long-term (more than two decades) studies of fire management that
provided data showing long-term persistence of the populations. We
based our threats analysis and ranking of stressors as high, medium,
and low based on the studies cited in our discussion of impacts from
fire under the Summary of the Factors Affecting the Species section of
this final rule, below. The possibility that we may have underestimated
the stressors of fire management on the species further supports our
determinations that fire can be a significant stressor to populations
of Poweshiek skipperlings.
(148) Comment: A commenter stated that there are problems with some
reports that use McCabe's 1981 management recommendations, because
McCabe's paper reflects a point-in-time. Prairie ecology requires long-
term observations and knowledge of how past and current management
activities impact plant community dynamics. Further, prairie management
conclusions based upon observations made in 1981 are no longer valid,
due to changes in ecological drivers caused by broad-scale invasion of
exotic cool-season grasses and forbs.
Our Response: McCabe's 1981 report is used as a reference to
prairie conditions prior to much habitat degradation or exotic species
invasions that are common in many locations today. We acknowledge that
an understanding of prairie ecology requires long-term observations, as
well as knowledge of how past and current management activities have
impacted and continue to impact plant community dynamics.
(149) Comment: One commenter agreed that annual haying on or after
August 1 presents little or no stress to Dakota skippers. However, the
commenter went on to point out that Swengel (1998b) found that
Poweshiek skipperling abundance was strongly correlated with increasing
number of years since the last management action, of any management
type, including haying. Thus, annual haying of the entire habitat patch
should be considered a high stressor for the Poweshiek skipperling. The
Service is correct that alternate-year haying is better than annual
haying, but it's even better when the haying is done rotationally (half
per year, instead of all every other year). Additionally, the moderate
stressor category for haying is confusing. As it currently reads, a
site could fall in the moderate category because you do not know the
timing of the haying, but if you did know the timing, you would place
it in the high category.
Our Response: We developed the stressor categories for the purposes
of the threats analysis to inform our listing determinations; these
categories are not intended to be prescriptive conservation measures or
guidelines. We acknowledge that there is some uncertainty in the
`moderate' stressor category for haying, but we wanted to fairly
capture sites where we were unsure of the timing of haying activities,
but that showed signs indicative of reduced nectar sources. It is true
that these sites could be moved into the low or high category if we
received more specifics on the timing of haying in those locations, and
those details will be more important during the recovery planning
stages for these species.
Factor B
(150) Comment: A commenter noted that recent publications report
that nonlethal sampling of genetic material adds an immeasurable or
minor effect on survival or reproductive success of butterflies
compared to handled individuals that were not also genetically sampled
(Marschalek et al. 2013; Crawford et al. 2013). However, there is
abundant literature on how handling has adverse effects on butterflies,
documented for a wide range of species (e.g., Benson and Emmel 1973;
Singer and Wedlake 1981; Lederhouse 1982; Morton 1984). It is possible
that some types of nonlethal sampling do not significantly increase the
harm to the butterfly from capture and handling, but the handling for
such sampling still causes harm compared to the butterfly not being
handled. Thus, the benefits of such sampling should be weighed against
the harm caused to individuals.
Our Response: As stated under Factor B of this final rule, handling
stress during scientific study may affect individuals of both species.
Adverse effects on butterflies have been documented for a wide range of
species (e.g., Benson and Emmel 1973, p. 329; Singer and Wedlake 1981,
pp. 215-216; Lederhouse 1982, pp. 381-382; Morton 1984, pp. 56-57;
Mallet et al. 1987, pp. 380-383). The Service will consider stress and
other impacts to the butterflies from handling when issuing scientific
permits for genetic sampling and other sampling efforts.
(151) Comment: A commenter noted that reliably effective captive
propagation has not been demonstrated for either of these species.
However, the Service should consider and assess the effect on wild
populations of either species before attempting to develop captive
propagation.
Our Response: The Service will consider incidental take for
otherwise legal activities in our permitting (e.g., section 10 recovery
permits) process.
Factor D
(152) Comment: A commenter stated that as of August 2013, the
Minnesota Department of Natural Resources listed both the Dakota
skipper and the Poweshiek skipperling as endangered. The Dakota skipper
is also an ``endangered'' species under Iowa law.
Our Response: We have updated the State-level protections for
Dakota skipper and Poweshiek skipperling in Factor D of this final
listing rule.
Factor E
(153) Comment: A commenter stated that herbicides applied in
skipper habitat can negatively affect nectar resources for the species.
However, herbicide use can have benefits if carefully targeted to
treating brush and weeds, so long as bare ground does not subsequently
result from the treatment, as bare ground greatly facilitates
recruitment of new weed and brush growth.
Our Response: We acknowledge that carefully targeted herbicide
treatments
[[Page 63715]]
may result in the beneficial control of nonnative or invasive plants
and brush, and have clarified our statements in Factor E of this final
listing rule, below.
(154) Comment: A commenter noted that results of a preliminary
analysis of the genetic diversity of the Poweshiek skipperling show
limited levels of genetic diversity in the Wisconsin, Michigan, and
Manitoba populations. Demographic factors are of greater concern,
specifically, small population sizes and numbers of populations are
more likely to lead to extinction than loss of genetic diversity. The
widespread and intensive survey effort showing continual extirpation of
populations and reduced population sizes supports the listing of
Poweshiek skipperling as endangered.
Our Response: We have incorporated information from the preliminary
results of Saarinen (2013, pers. comm.) under Factor E. Other Natural
or Manmade Factors Affecting Its Continued Existence, in the discussion
on Habitat Fragmentation and Population Isolation, below, and look
forward to receiving final results from this research to inform future
conservation efforts for this species.
(155) Comment: A commenter stated that weather and climate events,
such as the persistent drought in the Midwest, and their effects on the
Dakota skipper and Poweshiek skipperling require further study. Funding
and staff are needed to accomplish these efforts.
Our Response: In this rule, we used the best available information
on climate and climate change, however we agree that more study of
weather and climate events will help us with recovery planning and
implementation for these two species, and will consider new information
when developing the recovery plan.
(156) Comment: A commenter stated that, in its assessment of
impacts to the butterflies from climate change, the Service ignores
model uncertainty that the Intergovernmental Panel on Climate Change
(IPCC) acknowledges.
Our Response: We appreciate your comment and understand that there
are uncertainties in the climate modeling. We consider climate change
to be a potential threat to the species, while acknowledging
uncertainty of how changes may specifically impact these species or
their habitats.
(157) Comment: A commenter stated that, while it is possible that
unknown threats to the species exist, it is inappropriate to focus too
much effort on the search for unknown stressors. This distracts from
addressing the challenges of dealing with the stressors that have been
known for decades (isolated populations in fragmented habitats that are
under pressure from habitat degradation and land management practices).
Our Response: We acknowledge that multiple stressors are acting on
populations of both species, and have been so for many years. In our
review, however, it appears that many sites with known populations of
the Poweshiek skipperling appear to have simultaneously declined to
undetectable levels. A similar, but perhaps delayed, decline is being
observed in Dakota skipper populations. We did not want to rule out the
possibility that this decline may be due to some unknown cause.
However, we will focus on all potential factors affecting the species
in recovery planning and implementation, not simply on any single
factor.
Determinations
(158) Comment: A commenter stated that the Dakota skipper and
Poweshiek skipperling are both threatened by loss of native prairie
vegetation to agriculture, development, altered fire patterns, and
groundwater depletion. The Dakota skipper and Poweshiek skipperling are
also threatened by pesticides, drought, and climate change. In light of
the population declines and ongoing threats, both butterflies should be
protected as endangered rather than as threatened.
Our Response: The Dakota skipper is experiencing population
declines and facing multiple threats. A few populations in the United
States are doing relatively well, however, and are in habitats that
have low or non-immediate threats. Furthermore, Canada has an estimated
15 populations on lands that are being utilized in a manner conducive
to the conservation of Dakota skipper, and the threats at those sites
are not imminent. Based on our review of the best available scientific
and commercial information, we conclude that the Dakota skipper is
likely to become in danger of extinction in the foreseeable future
throughout all of its range and, therefore, meets the definition of a
threatened species. For a detailed discussion, see the Determination
section of this final rule, below.
(159) Comment: A commenter stated that the Service should list the
Dakota skipper as endangered, as it is ``in danger of extinction
throughout all or a significant portion of its range.'' The species is
present at 91 sites, at least 83 ``are subject to one or more threats
that have a moderate to high impact on those populations.'' The Service
does not explain why 8 sites that are presumably secure outweigh 83
sites that are experiencing moderate to high threat levels, especially
since ``Dakota skipper . . . habitat is highly fragmented and because
the species are subject to local extinction . . . and approximately 84
percent of Dakota skipper sites with present or unknown status are
effectively isolated.''
Our Response: We agree that the Dakota skipper is imperiled, which
is why we determined that the species warrants listing under the Act.
However, we believe that the Dakota skipper is not in immediate danger
of going extinct at this point in time. Instead, we believe that, if
trends continue as they currently are, the species is likely to get to
that point in the foreseeable future. Because there are stable
populations of the Dakota skipper that do not appear to be currently
suffering from high-magnitude threats, and the declining trends are
happening at a slower pace, we determined that threatened species
status is appropriate for the Dakota skipper (see Determination, below,
for a full discussion).
(160) Comment: A commenter stated that the Service determines that
the Dakota skipper is a threatened species because ``Canada has a fair
number of populations that are being managed in a manner conducive to
the conservation of Dakota skipper, and the threats at those sites are
not imminent.'' A ``fair number'' is not a biologically meaningful
measure. The Service needs to explain this contention in a measurable
manner.
Our Response: We are aware of 14 sites in Canada where the species
is considered to be present and one site where the occupancy is
unknown. Those sites are managed by late-season haying (after August 1)
that is conducted at least every other year, and there is no indication
that native plant diversity is declining due to timing or frequency of
mowing.
(161) Comment: A commenter stated that the Canadian populations are
functionally isolated from each other and from U.S. populations. The
distance between all these metapopulations makes interaction or
recolonization unlikely, as Dakota skippers may be incapable of moving
greater than 1 km (0.6 mi) between patches of prairie habitat separated
by structurally similar habitats. The Service did not conduct an
adequate analysis of ``significant portion of range,'' to determine if
the three metapopulations (U.S., Manitoba, and Saskatchewan) should
each be considered ``significant,'' and if one is ``in danger of
extinction,'' then the species as a whole should be listed as
endangered. The Service must
[[Page 63716]]
separately analyze threats to each isolated metapopulation because
population isolation and accompanying loss of genetic diversity are
acknowledged to have significant impacts on the species.
Our Response: Under the Act and our implementing regulations, a
species may warrant listing if it is endangered or threatened
throughout all or a significant portion of its range. Because we have
determined that the Dakota skipper is a threatened species throughout
all of its range, no portion of its range can be ``significant'' for
purposes of the definitions of ``endangered species'' and ``threatened
species.'' See the Final Policy on Interpretation of the Phrase
``Significant Portion of Its Range'' in the Endangered Species Act's
Definitions of ``Endangered Species'' and ``Threatened Species'' (79 FR
37577, July 1, 2014).
(162) Comment: A commenter stated that the Service has an
obligation to make available the studies that form the basis of its
action. The Service failed to provide any materials other than its own
draft species assessment and textual descriptions of proposed critical
habit for either the proposed listing or critical habitat designation
in the regulations.gov docket or on its Web sites. The Service did
provide a bibliography; however, many references cited were unpublished
reports or internal documents.
Our Response: One element of the transparency and open government
directive encourages executive departments and agencies to make
information about operations and decisions readily available to the
public. Supporting documentation used to prepare the proposed and final
rules is available for public inspection, by appointment, during normal
business hours, at the U.S. Fish and Wildlife Service, Twin Cities
Ecological Services Field Office, 4101 American Boulevard East,
Bloomington, Minnesota 55425.
4(d) Rule
(163) Comment: One commenter said that the 4(d) rule proposed for
the Dakota skipper should be extended to remove prohibitions for take
incidental to lawfully conducted oil and gas operations and that this
would not undermine the goal of promoting the healthy growth of these
populations throughout their entire range. The commenter indicated that
the activities that were addressed by the proposed 4(d) rule--a variety
of routine livestock ranching activities and mowing of recreational
trails--were far more widespread in the region and contribute more
directly to the threats listed in the proposed rule than were oil and
gas related activities.
Our Response: Although livestock ranching activities and mowing of
recreational trails may be more widespread throughout the species
range, livestock grazing also can be a key factor in the conservation
of Dakota skipper habitat, by helping to ensure that the species'
habitats are not subjected to activities that result in their permanent
destruction. That is, lands are likely to remain unplowed as long as
the landowner chooses to continue to use them for grazing. In addition,
grazing may also be implemented in a manner that provides significant
benefits to the species. In these ways oil and gas production and
grazing are fundamentally different with respect to Dakota skipper
conservation. Regardless, the Service recognizes that a variety of
interests, including oil and gas activities, may hold the potential to
contribute to Dakota skipper conservation.
(164) Comment: One commenter stated that the 4(d) rule would
provide an important incentive to continue late-summer haying where
that practice is currently being implemented.
Our Response: We agree that the 4(d) rule will provide this
incentive, as intended. Late-summer haying is currently the primary
management on numerous sites inhabited by Dakota skipper that are
important for the species' conservation.
(165) Comment: One commenter requested that we also exempt take
caused by ``construction with minimal disturbance, such as that for
transmission lines, that occurs after July 15th'' in the 4(d) rule. The
same commenter requested that the Service ``give consideration to
exempting transmission line maintenance activities and existing right-
of-way maintenance in the same way that section line maintenance is
exempted in the proposed 4(d) rule.''
Our Response: It is unclear which populations could be affected by
these activities, what the effects might be, and how the effects might
be minimized. Therefore, we have not included these activities in the
4(d) rule.
(166) Comment: One commenter stated that ``the proposed 4(d) rule
will undermine, not advance, conservation of the species'' and that the
4(d) rule was not needed to prevent habitat destruction because it
would already be illegal under section 9 of the Act and uninhabited
areas at risk for conversion would be protected by designating them as
critical habitat.
Our Response: It is true that take of Dakota skippers that results
from destruction of its habitat would be prohibited under section 9 of
the Act, but there are other reasons to promulgate the 4(d) rule. As we
stated in the proposed rule, the 4(d) rule will facilitate cooperation
with private landowners that will be needed to recover the species.
About 47 percent of the sites where the Dakota skipper has been
recorded in the United States and that may still harbor the species are
on private land. Almost all of these sites are working lands managed
with grazing or haying. Conservation of the Dakota skipper on these
sites, and in general, will require the Service and other conservation
agencies and groups to develop and maintain cooperative partnerships
with private landowners. Without that cooperation, we are unlikely to
realize the substantial improvements in habitat conditions and public-
private partnerships necessary to conserve the species.
(167) Comment: A commenter stated that the proposed 4(d) rule does
not provide details as to how the Service intends to ensure that
infrastructure, such as corrals, loading chutes, and other livestock
working facilities, are carefully sited so that impacts to the species
are minimized.
Our Response: These types of facilities are unlikely to have
significant impacts to Dakota skipper populations, except where the
species has been reduced to only very small areas. In grazed lands that
are typically inhabited by Dakota skipper, these facilities affect only
small proportions of the available habitat. Therefore, we do not think
that the small degree of impact posed by placement of livestock working
facilities would merit site-specific approval and review by the
Service. Instead, by foregoing any requirement for landowners to seek
Service approval for siting these facilities, we are likely to further
facilitate continued development of positive working relationships that
will be essential for recovering the species. In addition, we can work
with landowners on voluntary methods to minimize any impacts that might
result from installation of facilities associated with grazing.
(168) Comment: One commenter stated that the protections afforded
the Dakota skipper through the 4(d) rule are not sufficient to reverse
the trend toward extinction because they do not ensure that the grazing
practices exempted under the rule will benefit the Dakota skipper.
Our Response: It may not be practicable to expect broad
implementation of specific mandated grazing practices on private land
to conserve the Dakota skipper without the
[[Page 63717]]
willingness of the landowner to implement those practices. Conservation
of Dakota skippers on grazed lands will require several steps that
include the development of site-specific grazing recommendations,
monitoring the effects of the recommend practices on the Dakota skipper
and its habitat, and science-based adaptive management. Each step will
require access to private and other non-Federal lands by persons with
expertise in identifying and describing the Dakota skipper and its key
habitat components and, in at least some cases, by grazing experts and
conservation partners. Landowners and land managers may be less likely
to grant access for these activities if we broadly mandate specific
grazing practices. Furthermore, although the incidental take permitting
process would also provide an avenue by which to work with private
landowners and is often the best available option for some species,
there is no clear avenue that is immediately available by which to
engage the large and geographically widespread group of landowners in
such a process for Dakota skippers. A permitting process that would
involve more than a few landowners is likely to take years and would
have significant potential to become contentious and unwieldy.
(169) Comment: One commenter suggested that, instead of listing
counties in which take caused by grazing would not be exempted under
the 4(d) rule, the Service should base this on habitat.
Our Response: We decided that it is more appropriate to exempt take
of Dakota skippers caused by grazing on all non-Federal lands in the
United States, regardless of geographic area, and have made this change
in the final 4(d) rule. We recommend, however, that lands where native
prairie is currently maintained by haying continue to be hayed, and
that any change to grazing on these lands only be done with the prior
input from experts in Dakota skippers and range conservation. We
suggest contacting the Service's Ecological Services Office in your
State for more information.
(170) Comment: A commenter asked what areas can be treated for
weeds or pests and still be exempted by the 4(d) rule.
Our Response: The 4(d) rule does not address control of animal
pests; therefore, it does not exempt take that may result from
treatments that are applied to control animal pests. The 4(d) rule also
does not exempt take of Dakota skippers that would result from the
broadcast application of herbicides--that is, application of herbicides
evenly across all or a portion of an area. Take of Dakota skippers that
is caused by applications of herbicide that do not meet this definition
of broadcast spraying would be exempted by the 4(d) rule.
Take of Dakota skippers is unlikely if they do not inhabit an area
where broadcast application of herbicides is proposed. If the presence
of Dakota skippers is suspected in an area where broadcast application
of herbicides is proposed, we recommend that the Service be contacted
to determine whether the action may be likely to cause take of the
species, and if reasonable measures may be adopted that would avoid
take.
Summary of Changes From the Proposed Rule
Based on our review of the public comments, comments from other
Federal and State agencies, peer review comments, issues addressed at
the public hearing, and any new relevant information that may have
become available since the publication of the proposal, we reevaluated
our proposed rule and made changes as appropriate.
During the comment periods, the Service received additional survey
information, minor clarifications, and additional information on the
species biology. New survey information has changed the occupancy
status at several sites, for example a site that we considered to be
``unknown'' in the proposed rule may now be considered ``extirpated''
due to three sequential years of negative survey data. Consequently,
some sites were dropped from our analysis of factors affecting the
species because we no longer consider the species to be present or
possibly present (unknown) at a particular location. In addition, we
included new information into our analysis of the factors affecting the
species. Neither the new information nor the updated occupancy at some
sites has significantly changed our analyses such that it changed our
determinations of status under the Act for either species.
The 4(d) rule now exempts take of Dakota skippers caused by grazing
on all non-federal lands in the United States; the proposed 4(d) rule
did not apply to certain lands in Minnesota and North Dakota. The final
4(d) rule no longer exclude some counties from the part of the rule
that exempts take caused by grazing. Other minor changes to the 4(d)
rule include: Clarifying broadcast versus spot-spraying of herbicides;
defining ``recreational trail''; and, that take of Dakota skipper
caused by haying in transportation rights-of-ways and corridors after
July 15 is exempt under the 4(d) rule, as long as it is associated with
livestock ranching activities. The 4(d) rule exempts take of Dakota
skippers caused by mowing recreational trails, a term that is defined
in the rule, even when it is not associated with livestock grazing.
Summary of the Factors Affecting the Species
Factor A. The Present or Threatened Destruction, Modification, or
Curtailment of Its Habitat or Range
Habitat quality is a powerful determinant of extinction probability
in butterflies such as the Dakota skipper and Poweshiek skipperling
(Thomas et al. 2001, p. 1795). Among butterfly species in the United
Kingdom, for example, equilibrium density of butterflies at sites with
optimum habitat are from 25 to more than 200 times greater than those
for occupied sites with suboptimal, yet suitable, habitat (Thomas 1984,
cited in Thomas et al. 2001, p. 1794). Consistently good habitat
quality is especially important for Dakota skipper and Poweshiek
skipperling isolated populations, which would not be naturally
recolonized if they were extirpated. Protection or restoration of
habitat quality at these isolated sites is critical to the survival of
both species, although stochastic events still pose some risk,
especially for smaller populations and at small sites.
The Poweshiek skipperling and Dakota skipper depend on a diversity
of native plants endemic to tallgrass prairies and, for the Poweshiek
skipperling in Michigan, prairie fens. When nonnative or woody plant
species become dominant, Poweshiek skipperlings and Dakota skippers
decline due to insufficient sources of larval food and nectar for
adults. For example, at Wike Waterfowl Production Area in Roberts
County, South Dakota, the extirpation of Poweshiek skipperling is
attributed to the deterioration of native vegetation, in particular,
the loss of nectar sources for adult butterflies due to invasive
species encroachment (Skadsen 2009, p. 9).
Destruction of native tallgrass and mixed-grass prairie began in
1830 (Samson and Knopf 1994, pp. 418-419). Extant populations of Dakota
skipper and Poweshiek skipperling are restricted to native-prairie
remnants and prairie fens; native prairies have been reduced by 85 to
99.9 percent of their former area throughout the historical range of
both species (Samson and Knopf 1994, pp. 418-419). Degradation and
destruction of habitat occurs in many ways, including but not limited
[[Page 63718]]
to: Conversion of native prairie to cropland or development; ecological
succession to woody vegetation; encroachment of invasive species; past
and present fire, haying, or grazing management that degraded or
destroyed the species' habitats; flooding; and groundwater depletion,
alteration, and contamination, which are discussed in further detail
below.
We evaluated the level of impact to the population at each site of
several habitat-related stressors at 163 Dakota skipper sites where the
occupancy status of the site is considered to be present or unknown, as
defined in the Background section of this final rule (Table 3, above).
These 163 sites are found across the current range of the species in
Minnesota, North Dakota, and South Dakota. Eight sites with an unknown
or present occupancy were not evaluated. To determine the levels of
impact to the population at each site, we used the best available and
most recent information for each site, including reports, discussions
with site managers, information from natural heritage databases, etc.
(Service 2012, unpubl. data; Service 2014, unpubl. geodatabase). We
only evaluated a stressor to the population at any one site if we had
sufficient information to determine if the level of impact was high,
medium, or low as defined for each stressor below. Similarly, the level
of impact to the population was evaluated at 60 Poweshiek skipperling
sites with present or unknown status (Table 4). Although we did not
evaluate Factor A stressors at all 87 Poweshiek skipperling sites with
present or unknown occupancy, the 60 sites that were evaluated are
representative of all the present or unknown Poweshiek skipperling
sites in terms of geography (range of the species, i.e., sites in Iowa,
Michigan, Minnesota, North Dakota, South Dakota, and Wisconsin were
evaluated), ownership, and management. Many sites for both species (58
sites for Dakota skipper and 26 sites for Poweshiek skipperling)
experience at least two habitat-related stressors at a medium or high
level of impact (Tables 3 and 4).
Table 3--Number of Dakota Skipper Sites With Each Level of Impact and the Total Number of Sites That Were Rated
for Each Type of Stressor. A Total of 163 Dakota Skipper Sites With Either Present or Unknown Status Were
Examined; Only Sites With Sufficient Data for a Particular Stressor Were Rated as High, Medium, or Low
[Service 2012 Unpubl. data; Service 2014, unpubl. geodatabase]
----------------------------------------------------------------------------------------------------------------
High level of Medium level Low level of Total number
Stressor impact of impact impact of rated sites
----------------------------------------------------------------------------------------------------------------
Destruction & Conversion (Agricultural & 3 83 58 144
Nonagricultural Development)...................
Wind Development................................ 1 0 8 9
Flooding........................................ 2 6 6 14
Invasive Species................................ 12 33 20 65
Fire............................................ 10 4 6 20
Grazing......................................... 9 29 14 52
Haying & Mowing................................. 1 11 29 41
Lack of Management.............................. 9 5 3 17
Size/Isolation.................................. 50 50 63 163
Herbicide and/or Pesticide Use.................. 5 2 8 15
----------------------------------------------------------------------------------------------------------------
Table 4--Number of Poweshiek Skipperling Sites With Each Level of Impact and the Total Number of Sites That Were
Rated for Each Type of Stressor. A Total of 60 Poweshiek Skipperling Sites With Either Present or Unknown Status
Were Examined; Only Sites With Sufficient Data for a Particular Stressor Were Rated as High, Medium, or Low
[Service 2012 unpubl.; Service 2014, unpubl. data]
----------------------------------------------------------------------------------------------------------------
High level of Medium level Low level of Total number
Stressor impact of impact impact of rated sites
----------------------------------------------------------------------------------------------------------------
Destruction & Conversion (Agricultural & 2 11 28 41
Nonagricultural Development)...................
Wind Development................................ 0 0 5 5
Flooding/Hydrology.............................. 2 3 14 19
Invasive Species................................ 6 29 11 46
Fire............................................ 4 2 10 16
Grazing......................................... 4 10 2 16
Haying & Mowing................................. 0 3 3 6
Lack of Management.............................. 4 6 2 12
Size/Isolation.................................. 21 22 11 54
Herbicide and/or Pesticide Use.................. 3 1 5 9
----------------------------------------------------------------------------------------------------------------
Destruction and Conversion of Prairies
Destruction and Conversion of Prairies to Agricultural Land
Conversion of prairie for agriculture may have been the most
influential factor in the decline of the Poweshiek skipperling and
Dakota skipper since Euro-American settlement, but the impacts of such
conversion on extant populations is not well known. By 1994, tallgrass
prairie had declined by 99.9 percent in Illinois, Iowa, Indiana, North
Dakota, Wisconsin, and Manitoba; and by 99.6 percent in Minnesota; and
85 percent in South Dakota (Samson and Knof 1994, p. 419). Samson and
Knof (1994, p. 419) did not provide a figure for the decline of
tallgrass prairie in Saskatchewan, but mention an 81.3 percent decline
in mixed grasses from historical levels. By 1994, mixed-grass prairie
had declined from historical levels by 99.9 percent in Manitoba and
[[Page 63719]]
71.9 percent in North Dakota (Samson and Knof 1994, p. 419).
Destruction of tallgrass and mixed-grass prairie began in 1830, but
significant documentation of the ecosystem's butterfly fauna did not
begin until about 1960. Therefore, most of the decline of the Dakota
skipper and Poweshiek skipperling probably went unrecorded.
Since about 1980, observers have documented the extinction of
several populations of the Dakota skipper and Poweshiek skipperling due
to habitat conversion to agricultural use in the United States and
Canada. For example, four Dakota skipper sites in North Dakota were
converted to irrigated potato fields, and one in South Dakota was
converted for crop production (Royer and Marrone 1992a, p. 17). The
Fannystelle site in Manitoba, where the Dakota skipper was last
recorded in 1991, was subsequently converted for row-crop agriculture
(Webster 2003, p. 7). In North Dakota, further conversion is a stressor
to Dakota skippers in the important Towner-Karlsruhe complex (Royer and
Royer 1998, p. 22; Lenz 1999, p. 13), where the flat topography and
high water table facilitate conversion to irrigated crop production.
Populations of Dakota skipper in Manitoba typically occupy flat terrain
that may be vulnerable to conversion to cropland, although soil
conditions may be unsuitable for row crops at some of these sites
(Webster 2003, p. 10). Similarly, conversion of native prairie to
cropland continues to be a threat to Poweshiek skipperling habitat
throughout its range (Royer and Marrone 1992b, p. 17).
The Dakota skipper, and until recently, the Poweshiek skipperling,
have largely persisted in areas that are relatively unsuitable for row
crop agriculture because of their steep terrain (e.g., in the Prairie
Coteau of South Dakota) or where soils are too wet or rocky for row-
crop agriculture (McCabe 1981, pp. 189-190, Webster 2003, p. 10).
Densely spaced, large glacial rocks, for example, may have deterred
cultivation at the Chippewa Prairie in Minnesota and ``spared Chippewa
Prairie in Minnesota from the plow'' (Dana 2012, pers. comm.). In areas
where Poweshiek skipperling and Dakota skipper habitat persists but is
adjacent to agriculture, added nutrients from agricultural runoff
affects groundwater and additional nutrients in the system contribute
to the dominance of invasive plants (Fiedler and Landis 2012, p. 51:
Michigan Natural Features Inventory 2012, p. 4).
In summary, conversion for agriculture on lands suitable for such
purposes is a current, ongoing stressor of high level of impact to the
Poweshiek skipperling and Dakota skipper populations in areas where
such lands still remain. Advances in technology may also increase the
potential of conversions in areas that are currently unsuitable for
agriculture.
We rated the level of impact to the populations of the stressor
posed by habitat destruction or conversion for both agriculture and
nonagricultural purposes (except for conversion for wind energy
development, which was analyzed separately) at 144 Dakota skipper and
41 Poweshiek skipperling sites with present or unknown status (see
Tables 3 and 4) where we had sufficient information to evaluate the
stressor. In our evaluation of this stressor, we combined agricultural
and nonagricultural impacts--our analyses are discussed below (see
Destruction and Conversion of Prairies due to Nonagricultural
Development).
Destruction and Conversion of Prairies to Nonagricultural Development
Conversion of prairie for nonagricultural land uses, such as energy
development, gravel mining, transportation, and housing are stressors
to both Poweshiek skipperling and Dakota skipper populations. For
example, a site where the Dakota skipper and Poweshiek skipperling were
recorded in 1997 (Skadsen 1997, pp. 15-16, B-1) in the Bitter Lake area
of Day County, South Dakota, is now a gravel pit, and the species'
habitat no longer exists there (Skadsen 2003, pp. 47-48).
Almost all prairie remnants with Poweshiek skipperling and Dakota
skipper populations are associated with gravelly glacial till soils
(Service 2014, unpubl. geodatabase); therefore, gravel mining is a
potential stressor to populations at a large number of sites. Gravel
mining is a stressor to Poweshiek skipperling and Dakota skipper
populations at several sites in Minnesota (Dana 1997, p. 15). For
example, gravel mining is a stressor in at least three of the five
sites that comprise the Felton Prairie complex (Cochrane and Delphey
2002, pp. 16-17); however, the Clay County Stewardship Plan (Felton
Prairie Stewardship Committee 2002) may have reduced the likelihood of
the gravel mining stressor to populations at this complex. On at least
seven sites in Minnesota, Dakota skippers inhabit northern dry prairie
plant communities, which are generally impacted by gravel mining due to
the predominance of gravel soils (Minnesota DNR 2006, p. 221). Gravel
mining is a stressor to populations of Dakota skipper in central
Manitoba (Rigney 2013a, p. 28). Gravel mines are considered a stressor
with a high level of impact to populations of both species because,
where it occurs, the habitat is completely destroyed.
Potash (salt that contains potassium) mining is a stressor to
Dakota skipper populations in some Saskatchewan sites (Westwood 2013,
pers. comm.), although the exact number of sites that are being
considered for potash mining is unknown and were not included in our
stressor evaluation.
Energy development (oil, gas, and wind) and associated roads and
facilities result in the loss or fragmentation of suitable prairie
habitat (Reuber 2011, pers. comm.). Major areas of recent oil and gas
development, such as that occurring in the Bakken formation, overlaps
with parts of the Dakota skipper's range in North Dakota. North Dakota,
for example, is now one of the top two oil-producing states in the
United States, and new development is occurring rapidly (MacPherson
2012, p. 1; North Dakota Petroleum Council 2012, p. 1). The number of
drilling permits in North Dakota nearly doubled between 2007 and 2008,
from 494 permits issued in 2007 to 946 in 2008 (North Dakota Petroleum
Council 2009, p. 2). Permits dropped to 627 in 2009 (North Dakota
Petroleum Council 2010, p. 2), but increased dramatically to 1,676 in
2010 (Ogden 2011, p. 1). While much of the oil activity is currently
occurring in areas of native prairie overlaying the Bakken and Three
Forks formations to the west of known locations for both species,
mineral exploration has occurred in all but one county in North Dakota
(North Dakota Petroleum Council 2012, p. 1). McKenzie County falls in
the center of this development and McHenry County is also within these
formations (Mueller 2013, pers. comm.). The oil development on the
Bakken formation in North Dakota, for example, may be a future stressor
to Dakota skipper populations in McKenzie County (Royer and Royer
2012b, p. 16). Oil production is anticipated to continue to expand at
record levels (MacPherson 2012, p. 1; MacPherson 2010, entire).
Native-prairie habitat would be destroyed in the footprint of an
oil and gas well pad, but the pads are relatively small. However, each
oil and gas well pad requires new road construction, and evidence
suggests that Poweshiek skipperlings may avoid crossing roads (Westwood
et al. 2012, p. 18). Energy development can double the density of roads
on range lands (e.g., Naugle et al. 2011, pp. 493-494), increase
pipelines, and increase the number of gravel pits to accommodate the
increased road construction (Mueller 2013, pers.
[[Page 63720]]
comm.). Development for coal-bed natural gas (as described in Naugle
2011), for example, in areas with ranching, tillage agriculture, and
oil and gas development, 70 percent of the developed land was within
100 m (109 yards (yd)), and 85 percent of the developed land was within
200 m (218 yd), of a human structure (Naugle et al. 2011, p. 493).
Researchers estimated that, in those areas, every square km (0.39
square miles) of land may be both bounded by a road and bisected by a
power line (Naugle et al. 2011, p. 493). These coal-bed natural gas
developments can be densely located (e.g., 8 wells per 640 acres) and
are drilled vertically, whereas shale-oil wells in the Bakken formation
are drilled horizontally and ``relatively far apart'' (Conoco Phillips
2013, in litt.). The habitat fragmentation associated with oil and gas
development may amplify other stressors to both species, such as the
effects of population isolation and the impacts of stochastic events.
Energy development has additional undesirable and potentially
significant cumulative impacts on wildlife. Catastrophic events, such
as oil and brine spills, could cause direct mortality of Dakota skipper
or Poweshiek skipperling larvae that are in shelters at or below the
soil surface. Such spills may also cause the loss of larval host and
nectar plants in the spill path. Additional plants may be lost during
spill response, particularly if the response involves burning. The
likelihood, however, of spills occurring on the small fraction of land
that remains native tallgrass prairie in North Dakota (less than one
percent according to Samsom and Knoff 1994, p. 419) is low.
Wind energy turbines and associated infrastructure (e.g.,
maintenance roads) are likely stressors to Dakota skipper and Poweshiek
skipperling populations, particularly on private land in South Dakota
(Skadsen 2002, p. 39; Skadsen 2003, p. 47; Skadsen 2012d, pers. comm.).
Similar to oil and gas development, wind development would destroy
native-prairie habitat in the footprint of the structure, add access
roads and other infrastructure that may further fragment prairies, and
could be catalysts for the spread of invasive species. Further, it is
unknown if the noise and flicker effects associated with wind turbines
may impact Dakota skipper or Poweshiek skipperling populations beyond
direct impacts from the turbines and/or infrastructure. Other wildlife
species, such as birds, have shown significant avoidance of grasslands
where wind development has occurred (Pruett et al. 2009, p. 1256;
Shaffer et al. 2012,unpaginated). Wind development was assessed at nine
Dakota skipper sites and six Poweshiek skipperling sites where we had
sufficient information. The level of threat was considered to be low at
most sites because, although the site may be in an area with the
potential for wind development, there are no specific plans or
proposals to develop wind power on the site.
Wind development is considered a stressor of high level of impact
to populations at sites where development is proposed and there are no
actions or plans to mitigate impacts to the species. For example, a
wind facility was recently proposed at a Dakota skipper site in South
Dakota (Skadsen 2012d, pers. comm.), which poses a high-level threat
for the species at that site because there are no plans to mitigate
impacts of habitat destruction. Although wind power development
currently poses a high level of impact to the population at only one
site, the extent of this stressor will likely increase in the future,
due to the high demand for wind energy and the number of Dakota skipper
and Poweshiek skipperling sites that are conducive to wind development
(e.g., Skadsen 2003, pp. 47-48). Furthermore, power transmission lines
may be developed in order to accommodate the added power of wind farms,
for instance, a new power line is currently being planned in the
Prairie Coteau in South Dakota for that purpose (Mueller 2013, pers.
comm.).
Housing construction has likely contributed to the loss of at least
two Poweshiek skipperling populations in Michigan, and the largest
extant population in Michigan is located in an area under intense
development pressure (Michigan Natural Features Inventory 2011, unpubl.
data). Residential wells and drainage disrupt prairie fen hydrology by
reducing water levels and, thus, facilitating rapid growth of woody
vegetation. In addition, nutrients added to the groundwater from
leaking septic tanks contribute to the dominance of invasive plants,
such as narrow-leaved cattail (Typha angustifolia) and red canary grass
(Phalaris arundinacea) (Michigan Natural Features Inventory 2012, p.
4).
Road construction impacts Poweshiek skipperling and Dakota skipper
habitat because it increases the demand for gravel, and impacts also
result from routine maintenance (e.g., broadcast herbicide
applications, early mowing, and cleaning out ditches), improvements
(e.g., widening roads or converting two-lane highways to four-lane
highways), or new construction. Poweshiek skipperling habitat was
destroyed or degraded on at least two private properties in Roberts
County, South Dakota, for example, in association with the widening of
U.S. Highway 12 (Skadsen 2003, p. 47). Roadside prairie remnants can
help support populations of both species and serve as dispersal
corridors between larger remnants; therefore, loss of these areas to
road expansion or construction further reduces and fragments remaining
habitat. In Michigan, at least one Poweshiek skipperling site and its
habitat has been negatively affected by recreational `mud bogging',
which destroys vegetation and creates conditions conducive to invasive
species (Hicks 2014, pers. comm.).
In summary, nonagricultural development, such as gravel mining,
activities associated with energy development, or housing and road
development, poses a current stressor of moderate to high impact to
populations on those lands that are not protected from destruction or
conversion through a conservation easement or fee title ownership by a
conservation agency. This type of development may become more
widespread as such practices increase in the future.
As discussed above in Destruction and Conversion of Prairies to
Agricultural Land, we rated the level of impact to the populations of
the stressor posed by habitat destruction or conversion for both
agriculture and nonagricultural purposes combined (except for
conversion for wind energy development, which was analyzed separately)
at 144 Dakota skipper sites with present or unknown status (see Table
3) where we had sufficient information to evaluate the stressor. The
level of impact of each stressor to the population at each site is high
at three of those sites, due to ongoing destruction of the native
prairie, or there was a high likelihood of conversion because it is
located close to other converted areas and the land is conducive for
agriculture. The level of threat is high at 3 sites, moderate at 83
sites, and 58 sites are protected from destruction or conversion
through a conservation easement or fee title ownership by a
conservation agency (Table 3). This stressor occurs across the range of
the Dakota skipper; the stressor has a medium to high level of impact
to Dakota skipper populations in Minnesota, North Dakota, South Dakota,
Manitoba, and Saskatchewan. The level of impact was considered to be
low if the site is protected from destruction or conversion by fee
title ownership by a governmental conservation agency, nongovernmental
conservation
[[Page 63721]]
organization (e.g., The Nature Conservancy), or educational institution
(e.g., South Dakota State University). Similarly, 41 Poweshiek
skipperling sites with present or unknown status were assessed that had
sufficient information: The level of threat was high at 2 sites and
moderate at 11 sites, and 28 sites are protected from destruction or
conversion through a conservation easement or fee title ownership by a
conservation agency (Table 4). At least 6 of the 12 sites where the
Poweshiek skipperling is considered to still be present have a medium
or high risk of conversion. This stressor occurs across most of the
Poweshiek skipperling range; the stressor has a medium to high level of
impact to Poweshiek skipperling populations in Iowa, Michigan,
Minnesota, and South Dakota; the level of impact is low for the species
at the Manitoba location.
Fluctuating Water Levels
Flooding is a stressor to Poweshiek skipperlings and Dakota
skippers at sites where too much of the species' habitat is flooded or
where patches are flooded too frequently. Poweshiek skipperlings and
Dakota skippers must either survive flooding events in numbers
sufficient to rebuild populations after the flood or recolonize the
area from nearby areas that had not flooded. In addition, the return
interval of floods must be infrequent enough to allow for recovery of
the populations between floods. Changes in hydrology resulting from
wetland draining and development may permanently alter the plant
community and, therefore, pose a threat to Poweshiek skipperling and
Dakota skipper due to loss of larval food and nectar sources.
The Dakota skipper and Poweshiek skipperling are presumed
extirpated from several sites due to flooding or draining. For example,
one Dakota skipper site was lost to flooding due to rising water levels
at Bitter Lake, South Dakota (Skadsen 1997, p. 15). At Whalen Lake Fen
in Michigan, dredging and channelization disrupted the hydrology of the
site and the fen has since been invaded by glossy buckthorn and narrow
leaf cattail; Poweshiek skipperlings are presumed to be extirpated from
the site (Michigan Natural Features Inventory 2011, unpubl. data). The
loss of a large area of habitat at two sites in Manitoba, which were
previously suitable for Dakota skipper, was caused by prolonged
inundation of water that likely caused larval mortality and mortality
of suitable nectar and larval food plants (Rigney 2013a, pp. 28, 153).
In addition, flood protection activities and associated alteration of
the landscape (e.g., road work that causes changes to overland
drainage) is a stressor to the species at some sites in Manitoba
(Rigney 2013a, p. 28).
Fluctuating water levels are a current stressor to populations
across both species' ranges. Loss of habitat or direct mortality due to
fluctuating water levels, such as permanent flooding or wetland
draining, is a current stressor to populations in at least 14 Dakota
skipper sites with present or unknown status and 19 Poweshiek
skipperling sites with present or unknown status. For example, one of
the three sites with present or unknown status of Poweshiek skipperling
in Wisconsin, Puchyan Prairie, is subject to flooding--the entire
prairie portion of the site was submerged in 1993 (Hoffman 2011, pers.
comm.; Wisconsin DNR 2012, in litt). The number of Poweshiek
skipperling observed at that site is consistently low. Flooding is a
likely factor that has contributed to the low numbers observed in at
least part of this site (Borkin 2012c, pers. comm.).
Conversely, groundwater disruption and draining is a stressor at
all 9 of the Michigan prairie fen Poweshiek skipperling sites where the
species is present and high at one site with unknown occupancy.
Interrupted groundwater flow-through fens can reduce water levels and
facilitate woody vegetation establishment and growth (Michigan Natural
Features Inventory 2012, p. 4). Agricultural and residential drains and
wells can lower the groundwater table, thereby reducing the supply of
calcareous seepage, which is an essential underlying component of
prairie fen hydrology (Michigan Natural Features Inventory 2012, p. 4).
Furthermore, nutrient additions associated with drain fields can
contribute to invasive species encroachment. For instance, if
groundwater flow to prairie wetlands is severed, fen habitats may
convert from native grasses and flowering forbs to habitats dominated
by invasive species or woody vegetation (Fiedler and Landis 2012, p.
51, Michigan Natural Features Inventory 2012, p. 4). The site with the
highest number of Poweshiek skipperlings in Michigan, for instance, is
partially bordered by residential areas and is under intense
development pressure (Michigan Natural Features Inventory2011, unpubl.
data). At least 8 of the 11 fen sites with present or unknown status
are at least partially unprotected from development, and at least 7 of
those are closely bordered by roads, agriculture, or residential
developments (Michigan Natural Features Inventory 2011, unpubl. data;
Service 2014, unpubl. geodatabase). The status of Poweshiek skipperling
is unknown at one fen site where the hydrology was likely disrupted by
roads and extensive residential development in close proximity to the
fen (Michigan Natural Features Inventory 2011, unpubl. data).
The level of impact to populations due to flooding was assessed at
12 Dakota skipper sites with present or unknown status that had
sufficient information to evaluate the stressor (Table 3); this
evaluation only included sites in North and South Dakota. Flooding is a
stressor of moderate-level impact to populations at 6 of the sites,
where there is evidence of recent or pending decrease in the quality or
extent of suitable habitat at the site due to a change in wetland
vegetation, wetland hydrology, or flooding--all of these sites occur in
North Dakota (Service 2012 unpubl. data; Service 2014, unpubl. data).
Similarly, we assessed 19 Poweshiek skipperling sites with present or
unknown occupancy for the level of impact to populations due to water
fluctuations (e.g., flooding or draining) where we had sufficient
information to evaluate the stressor (Table 4). Water fluctuations is a
stressor with moderate impact to the populations at 3 Poweshiek
skipperling sites (including a site in Wisconsin--one of the 12
Poweshiek skipperling sites with a present status), and changes to
hydrology is a stressor of moderate- to high-level impact to
populations at all 11 Michigan sites (including 9 of 12 Poweshiek
skipperling sites that have a present status) and 1 site in North
Dakota (Service 2012 unpubl. data; Service 2014, unpubl. geodatabase).
In summary, fluctuating water levels is a current and ongoing
stressor of moderate level of impact to populations where the habitat
may be temporarily lost due to intermittent flooding and is a stressor
of high severity where a change in hydrology may completely degrade the
habitat quality of a site, particularly prairie fens.
Invasive Species and Secondary Succession
Poweshiek skipperlings and Dakota skippers typically occur at sites
embedded in agricultural or developed landscapes, which make them more
susceptible to nonnative or woody plant invasion. Nonnative species
including leafy spurge, Kentucky bluegrass, alfalfa, glossy buckthorn,
smooth brome, purple loosestrife (Lythrum salicaria), Canada thistle
(Cirsium arvense), reed canary grass, and others, have invaded
Poweshiek skipperling and Dakota skipper habitat throughout their
ranges
[[Page 63722]]
(Orwig 1997, pp. 4, 8; Michigan Natural Features Inventory 2011,
unpubl. data; Skadsen 2002, p. 52; Royer and Royer 2012b, pp. 15-16,
22-23). Kentucky bluegrass and leafy spurge (and the persistent efforts
for chemical control of leafy spurge) have been cited as one of the
major stressors to native-prairie habitat at several public and
privately owned Dakota skipper sites in North Dakota (Royer and Royer
2012b, pp. 15-16, 22-23; Royer 2012, pers. comm.; Royer 2013, pers.
comm.). Once these plants invade a site, they replace or reduce the
coverage of native forbs and grasses used by adults and larvae of both
butterflies. Leafy spurge displaces native plant species, and its
invasion is facilitated by actions that remove native plant cover and
expose mineral soil (Belcher and Wilson 1989, p. 172). The seasonal
senescence patterns (timing of growth) of grass species as they relate
to the larval period of Dakota skippers determine which grass species
are suitable larval host plants. Exotic cool-season grasses, such as
Kentucky bluegrass and smooth brome, are available when Dakota skipper
and Poweshiek skipperling larvae begin feeding; however, the morphology
and growth habit of these grasses are likely major determinants of
their unsuitability to support Dakota skippers (Dana 1991, pp. 46-47).
Thus, a prevalence of these grasses reduces food availability for the
larvae.
The stressor from nonnative invasive herbaceous species is
compounded by the encroachment of woody species into native-prairie
habitat. Glossy buckthorn and gray dogwood encroachment, for example,
is a major stressor to Poweshiek skipperling populations at the Brandt
Road Fen in Michigan, which supports the second largest population of
Poweshiek skipperlings in the State (Michigan Natural Features
Inventory 2011, unpubl. data). Invasion of tallgrass prairie and
prairie fens by woody vegetation such as glossy buckthorn reduces light
availability, total plant cover, and the coverage of grasses and sedges
(Fiedler and Landis 2012, pp. 44, 50-51). This in turn reduces the
availability of both nectar and larval host plants for Poweshiek
skipperlings and Dakota skippers. If groundwater flow to prairie
wetlands is disrupted (e.g., by development) or intercepted (e.g.,
digging a pond in adjacent uplands or installing wells for irrigation
or drinking water), it can quickly convert to shrubs or other invasive
species (Fiedler and Landis 2012, p. 51; Michigan Natural Features
Inventory 2012, p. 4). For example, roads and residential development
likely disrupted the hydrology of a prairie fen where the Poweshiek
skipperling was last observed in 2007 and where 2008 and 2009 surveys
for Poweshiek skipperlings were negative (Michigan Natural Features
Inventory 2011, unpubl. data). Furthermore, on some sites, land
managers intentionally facilitated succession of native-prairie
communities to woody vegetation or trees, such as Ponderosa pine (Pinus
ponderosa) or spruce (e.g., Dana 1997, p. 5). This converts prairie to
shrubland, forest, or semi-forested habitat types and facilitates
invasion of adjacent native prairie by exotic, cool-season grasses,
such as smooth brome. Moreover, the trees and shrubs provide perches
for birds that may prey on the butterflies (Royer and Marrone 1992b, p.
15; 1992a, p. 25).
We rated the level of impact to populations of invasive species at
65 Dakota skipper sites and 46 Poweshiek skipperling sites that had
sufficient information to evaluate the stressor (Table 3 and Table 4;
Service 2012 unpubl. data; Service 2014, unpubl. data). This stressor
is considered to have a low level of impact to the populations if there
was either no information to indicate a stressor or management was
ongoing to control invasive species using methods that are unlikely to
cause adverse effects to Dakota skippers or Poweshiek skipperlings
(e.g., spot-spraying or hand-pulling). Sites were assigned a moderate
level of impact to populations if invasive species are typically a
primary driver of management actions and make it difficult for managers
to specifically tailor management to conserve Dakota skipper or
Poweshiek skipperling habitat. The site was assigned a high level of
impact to populations if one or more nonnative invasive plant species
are abundant or increasing and management activities are not being
implemented to control their expansion; or if necessary management
actions cannot be implemented without themselves causing an additional
stressor to the Dakota skipper or Poweshiek skipperling populations at
the site.
Invasive species are a current and ongoing stressor with high
levels of impact to Dakota skipper and Poweshiek skipperling
populations on sites where land management is conducive to their
invasion or expansion or where they have become so pervasive that even
favorable management may not be quickly effective. Succession is a
current and ongoing stressor of moderate-level impact to populations at
sites where management is insufficient. The stressor of invasive
species to populations on small and isolated sites (e.g., Big Stone
NWR) is a current and ongoing stressor of high level of impact to
populations, because Dakota skipper and Poweshiek skipperling
populations have little resilience to the resulting habitat degradation
and to the often aggressive management needed to control the invasive
plants. Loss of habitat or degradation of the native plant community
due to encroachment of invasive species or woody vegetation is
considered a high level of impact to populations at 12 of the 65
assessed Dakota skipper sites, a moderate level of impact to
populations at 33 sites, and low impact to populations at 20 sites.
Sites with high and moderate level of impact occur throughout the
species range in Minnesota, and North and South Dakota (Service 2012
unpubl. data; Service 2014, unpubl. data). Similarly, invasive species
are a stressor of high level of impact to populations at 6 of the 46
evaluated Poweshiek skipperling sites, moderate level of impact to
populations at 29 sites, and low level of impact to populations at 11
sites--sites with high and moderate levels of impact are throughout the
range of the species in Iowa, Minnesota, Michigan, North Dakota, South
Dakota, Wisconsin, and Manitoba and include at least 9 of the 12 sites
where the species is still present (Service 2014, unpubl. data).
Fire
Dakota skipper and Poweshiek skipperling populations existed
historically in a vast ecosystem maintained in part by fire. Due to the
great extent of tallgrass prairie in the past, fire and other intense
disturbances (e.g., locally intensive bison grazing) likely affected
only a small proportion of the habitat each year, allowing for
recolonization from unaffected areas during the subsequent flight
period (Swengel 1998, p. 83). Fire can improve Poweshiek skipperling
(Cuthrell 2009, pers. comm.) and Dakota skipper habitat (e.g., by
helping to control woody vegetation encroachment), but it may also kill
most or all of the individuals in the burned units and alter entire
remnant prairie patches, if not properly managed (e.g., depends on the
timing, intensity, etc.). Accidental wildfires also may burn entire
prairie tracts (Dana 1997, p. 15) and may hamper plans to carefully
manage Dakota skipper and Poweshiek skipperling habitat. A human-set
wildfire in late fall 2009 and another extensive fire in 2011, for
example, burned considerable amounts of good prairie habitat in The
Nature Conservancy of Canada's Tall Grass
[[Page 63723]]
Prairie Preserve in Manitoba (Hamel et al. 2013, p. 1; Westwood 2010,
pers. comm.), which is the only location in Canada where Poweshiek
skipperlings are present; Dakota skippers are extirpated from the site.
The fires at The Nature Conservancy of Canada's Tall Grass Prairie
Preserve may have killed overwintering larvae, and the population of
Poweshiek skipperling in Canada ``may have been greatly reduced as a
result of these fires'' (Hamel et al. 2013, p. 1).
Intentional fires, without careful planning, may also have
significant adverse effects on populations of Dakota skippers and
Poweshiek skipperlings, especially after repeated events (McCabe 1981,
pp. 190-191; Dana 1991, pp. 41-45, 54-55; Swengel 1998, p. 83; Orwig
and Schlicht 1999, pp. 6, 8). In systematic surveys of Minnesota
tallgrass prairies, for example, Dakota skippers were less abundant on
sites that had been burned, compared with otherwise similar hayed sites
(Swengel 1998, p. 80; Swengel and Swengel 1999, pp. 278-279).
Similarly, Schlicht (1997b, p. 5) counted fewer Dakota skippers per
hour in burned than on grazed sites in Minnesota. Orwig and Schlicht
(1999, p. 8) speculated that inappropriate use of prescribed burning
eliminated Dakota skippers from the last known occupied site in Iowa, a
65-ha (160-ac) preserve. The effects of fire on prairie butterfly
populations are difficult to ascertain (Dana 2008, p. 18), but the
apparent hypersensitivity of Poweshiek skipperlings and Dakota skippers
indicates that it is a stressor to both species in habitats burned too
frequently or too broadly. The Poweshiek skipperling and Dakota skipper
are not known to disperse widely (Swengel 1996, p. 81; Burke et al.
2011, p. 2279); therefore, in order to reap the benefits of fire to
habitat quality, Poweshiek skipperlings and Dakota skippers must either
survive in numbers sufficient to rebuild populations after the fire or
recolonize the area from a nearby unburned area. In addition, the
return interval of fires needs to be infrequent enough to allow for
recovery of the populations between burns. Therefore, fire is a
stressor to Poweshiek skipperlings and Dakota skippers at any site
where too little of the species' habitat is left unburned or where
patches are burned too frequently.
Panzer (2002, p. 1306) identified four life-history traits of duff-
dwelling insects (such as the Dakota skipper and Poweshiek skipperling)
that were good predictors of a negative response to fire: (1) Remnant
dependence (occurring as small, isolated populations); (2) upland
inhabitance (dry uplands burn more thoroughly than wetter habitats);
(3) nonvagility (low recolonization rate); and (4) univoltine (slower
recovery rates for species with only one generation per year). Species
exhibiting all four traits should be considered ``hypersensitive'' to
fire (Panzer 2002, p. 1306). While not specifically included in his
study, the Poweshiek skipperling and Dakota skipper meet all of
Panzer's criteria for hypersensitivity (Panzer 2002, p. 1306) and have
additional life-history traits that further suggest hypersensitivity to
fire. Panzer (2002) observed mean declines of 67 percent among fire-
negative species, although actual mortality was likely higher due to
some immigration into experimental areas after the burn. When all or
large portions of prairie remnants are burned, many or all prairie
butterflies may be eliminated at once. Complete extirpation of a
population, however, may not occur after a single burn event (Panzer
2002, p. 1306), and the extent of effects would vary depending on time
of year and fuel load.
Poweshiek skipperlings lay their eggs near the tips of leaf blades,
and they overwinter as larvae on the host plants (Borkin 2000, p. 2),
where they are exposed to fires during their larval stages. Poweshiek
skipperlings have also been documented laying eggs on the entire length
of grass leaf blades and on low-growing deciduous foliage (Dupont 2013,
p. 133). If larvae are on prairie dropseed or little bluestem, which
occur in dry prairie, rather than spike-rush or sedges, which typically
occur in wet prairie, then the larvae are even more vulnerable to fire
(Selby 2005, p. 36). Unlike Dakota skippers, Poweshiek skipperlings do
not burrow into the soil surface (McAlpine 1972, pp. 88-92; Borkin
1995, p. 9), which makes them more vulnerable to fire (and likely more
vulnerable to chemicals such as herbicides and pesticides) throughout
their larval stages. Species whose larvae spend more time above ground,
such as Poweshiek skipperlings, are likely more vulnerable to fire than
species that form underground shelters. As the spring progresses,
however, the vulnerability of Dakota skippers to fire increases as
larvae shift from buried shelters to horizontal shelters at the soil
surface (Dana 1991, p. 16).
Studies of all life-stages may be necessary to fully evaluate these
species' response to fire. Early spring burns may be less likely to
harm Dakota skipper populations than late spring burns, due to larval
phenology and differences in subsurface soil temperatures during the
fire; however, studies have not conclusively linked the relationship of
mortality risk to the timing of spring burns. Experiments to evaluate
the effects of early spring versus late spring fires and of different
fuel levels on Dakota skipper mortality found that, despite higher
ambient temperatures during the early spring burn, temperatures at the
average depth of buried Dakota skipper shelters (Dana 1991, p. 11) were
10 [deg]C (50 [deg]F) higher during the late-spring burn (Dana 1991, p.
41). Fuel load was positively related to subsurface soil temperature
(Dana 1991, pp. 41-43). Fuel loads that were clearly associated with
lethal subsoil temperatures, however, were more typical of mesic
tallgrass prairie, which had about twice the fuel loads of the dry-
mesic habitats inhabited by Dakota skippers on the site (Dana 1991, pp.
41, 54). Although Dana's study was inconclusive in quantifying the risk
of mortality in relation to the timing of spring burns, he was able to
conclude that a late-spring burn in ``moderate'' fuels (430-440 g/m\2\)
would have a devastating effect on Dakota skipper populations, and that
early spring burning would afford some amelioration (Dana 1991, p. 55).
Rotational burning may benefit prairie butterflies by increasing
nectar plant density and by positively affecting soil temperature and
near-surface humidity levels due to reductions in litter (Dana 1991,
pp. 53-55; Murphy et al. 2005, p. 208; Dana 2008, p. 20). Purple
coneflower and little bluestem, for example, occurred more frequently
on burned areas than on unburned areas in mixed-grass prairie at
Lostwood National Wildlife Refuge in northwestern North Dakota (Murphy
et al. 2005, pp. 208-209). An increase in purple coneflower, an
important nectar source for Dakota skippers and Poweshiek skipperlings,
may last for 1-2 years after early spring fires, and females may
preferentially oviposit near concentrations of this nectar source (Dana
2008, p. 20).
Although fire tends to increase native plant diversity in prairies
(Murphy et al. 2005, pp. 208-209), several years may be necessary for
Dakota skipper and Poweshiek skipperling populations to recover after a
burn. Few studies have documented recovery times for prairie
butterflies after a burn, and even fewer have measured the
relationships between species abundance in tallgrass prairies and time
since burn. One such study, however, found lower relative abundances of
Dakota skippers and Poweshiek skipperlings in burned units than in
otherwise similar hayed units even 4 years after burns (Swengel 1996,
p. 83). Poweshiek skipperling had the most negative initial response to
fire
[[Page 63724]]
among six species of prairie-obligate butterfly species (Swengel 1996,
p. 83). Numbers were still lower than expected 1 year post-fire,
exceeded expectations after 2 years, and declined slightly after 3
years (Swengel 1996, p. 83). In habitats that had not been burned for 4
or more years, Poweshiek skipperling abundance was about as low as in
habitats sampled less than 1 year after being burned (Swengel 1996, p.
83). The 2012 spring burn that comprised approximately 25-30 percent of
the breeding habitat at Scuppernong SNA may have contributed to the
apparent absence of the species in 2013--the relatively small
population that was also affected by the 2012 summer drought and the
cold wet spring of 2013 (Borkin 2014, pers. comm.)
Poweshiek skipperling numbers decline in burned areas for at least
1-2 years after the burn, and may take several years to rebound, but
may decline again if management does not maintain the habitat (Skadsen
2001, p. 37; Webster 2003, p. 12). In general, rebound times of 1-5
years postburn have been predicted (Panzer 2002, pp. 1302-1303);
however, Vogel et. al (2010, p. 671) found that habitat-specialist
butterfly abundance rebound time was approximately 50 months after
prescribed fires. Swengel (1996, pp. 73, 78-79) describes that the
negative effects of fire persist for prairie specialists for 3 to 5
plus years, and these species were collectively the most abundant after
5 or more years since the last fire. In Manitoba, Poweshiek skipperling
populations were most numerous in sites burned 5-8 years previously--
the species was absent in sites that were burned the previous year, in
small numbers in areas that were burned 2-4 years prior, and absent
from areas that were burned 10 or more years previous to the survey
(Dupont 2013, pp. 4, 86-87). Recent survey results in some areas, most
notably, Iowa and Minnesota, indicate that other factors are acting
independently (Dana 2008, p. 18) or in concert with fire to forestall
post-fire rebound.
We assessed the stressor posed by fire at 20 Dakota skipper sites
with present or unknown status and 16 Poweshiek skipperling sites with
present or unknown status where we had sufficient information to
evaluate the stressor (Tables 3 and 4; Service 2012, unpubl. data;
Service 2014, unpubl. data). We considered fire a stressor of high
level of impact to populations at 10 of the 20 evaluated Dakota skipper
sites and 4 of the 16 Poweshiek skipperling sites. Sites that face a
high level of impact to populations were primarily those with a high
proportion of Dakota skipper or Poweshiek skipperling habitat that may
be burned in a single year or where all of the species' habitat is
burned with no likely source of immigrants to sustain the population.
This type of fire management is a documented cause of extirpation
(Selby 2000, p. 19). Sites with a moderate level of impact to
populations from fire management were those where the habitat is
divided into at least three burn units and no unit is burned more
frequently than once every 3 years; or, habitat is divided into two or
more burn units, each unit is burned no more frequently than once every
3 years, but the entirety of the species' habitat is never burned in
the same year and the species is present at another site that is less
than 1 km (1.6 mi) away.
Fire is considered to be a stressor of moderate severity at 4 of
the 20 evaluated Dakota skipper sites and 2 of the 16 Poweshiek
skipperling sites. Fire presents a low level of impact to populations
at sites where the species' habitat is divided into at least four burn
units and no unit is burned more frequently than once every 4 years;
or, the species' habitat is divided into three or more burn units, at
least three units are burned no more frequently than once every 4
years, and the site contains more than 140 ha (346 ac) of native
prairie or where the site is separated from another occupied site by
less than 1 km (1.6 mi). Fire is considered to be a stressor with a low
level of impact to populations at 6 of the 20 evaluated Dakota skipper
sites and 10 of the 16 Poweshiek skipperling sites.
In summary, fire may be an important management tool for these
butterflies, if carried out appropriately. However, where managers burn
without ensuring a sufficient amount of contiguous or nearby habitat
from which immigrants can re-inhabit burned areas or if not conducted
with conservation of prairie invertebrates as a primary objective, fire
is a current stressor that can have moderate impacts on populations.
Uncontrolled wildfires may also have high or moderate levels of impacts
to populations, and would also depend on the timing, intensity, and
extent of the burn. Poweshiek skipperlings may be among the most
sensitive of prairie butterflies to fire, and thus, coordination
between habitat managers and butterfly experts is necessary to ensure
that it is not implemented in a manner that degrades population
viability. Fire is a current and ongoing stressor of high level of
impact where burns occur without ensuring there is a sufficient amount
of contiguous or nearby habitat from which immigrants can re-inhabit
burned areas. Fire is an ongoing stressor rangewide for both species
and has been documented at a high or moderate level of impact to
populations at several sites in North Dakota, South Dakota, Minnesota,
Wisconsin, and the Tallgrass Prairie Preserve in Manitoba.
Grazing
As with fire management, grazing may maintain habitat for the
Poweshiek skipperling and Dakota skipper, but as with any management
practice, appropriate timing, frequency, and intensity are important.
The level of impact of grazing on Dakota skipper and Poweshiek
skipperling populations also depends on the type of habitat that is
being grazed. In contrast to the permanent habitat destruction and
larval mortality caused by plowing or mining, for example, some
habitats can remain suitable for the Dakota skipper and Poweshiek
skipperling when grazed (Dana 1991, p. 54, Schlicht 1997, p. 5, Skadsen
1997, pp. 24-29), and native plant diversity in tallgrass prairie may
recover from overgrazing if it has not been too severe or prolonged. In
addition, grazing may be a valuable tool for controlling smooth brome
invasion and maintaining native diversity in prairies, especially where
circumstances make the use of fire difficult or undesirable (Service
2006, p. 2; Smart et al. 2013, pp. 685-686). Conversely, grazing may
stimulate brome growth and reduce native plant diversity.
Grazing may benefit the Dakota skipper and Poweshiek skipperling
under some management scenarios (e.g., adaptive management to adjust
grazing prescriptions according to their effects on essential features
of the prairie ecosystem). In some habitats, Dakota skippers benefit
from light grazing that minimizes the area dominated by tall grasses
(e.g., big bluestem and indiangrass) (Dana 1991, p. 54). Dakota
skippers were relatively abundant on prairies subjected to light
grazing regimes, but absent on nearby idle prairies that were no longer
used for grazing; moreover, more Dakota skippers were observed per hour
on the lightly grazed prairies than on nearby habitat managed with fire
(Schlicht 1997b, p. 5). Similarly, in eastern South Dakota, Dakota
skipper populations were deemed secure at some sites managed with
rotational grazing light enough to maintain plant species diversity
(Skadsen 1997, pp. 24-29), but the species was since extirpated at one
site where a change in ownership resulted in significant overgrazing
(Skadsen 2006b, p. 5). The economic benefit of grazing to ranchers may
also benefit the species at some sites by deterring conversion of
remnant prairies to row crop agriculture; however, recent
[[Page 63725]]
evidence indicates that conversion is more economically viable (Dowd
2013, pers. comm.).
Bison (Bison bison) grazed at least some Dakota skipper and
Poweshiek skipperling habitats historically (McCabe 1981, p. 190; Bragg
1995, p. 68; Schlicht and Orwig 1998, pp. 4, 8; Trager et al. 2004, pp.
237-238), but cattle (Bos taurus) are now the principal grazing
ungulate in both species' ranges. Bison and cattle both feed primarily
on grass, but have some dissimilar effects on prairie habitats
(Damhoureyeh and Hartnett 1997, pp. 1721-1725; Matlack et al. 2001, pp.
366-367). Cattle consume proportionally more grass and grasslike plants
than bison, whereas bison consume more browse and forbs (flowering
herbaceous plants) (Damhoureyeh and Hartnett 1997, p. 1719). Grasslands
grazed by bison may also have greater plant species richness and
spatial heterogeneity than those grazed by cattle (Towne et al. 2005,
pp. 1553-1555). Both species remove forage for larvae (palatable grass
tissue) and adults (nectar-bearing plant parts), change vegetation
structure, trample larvae, and alter larval microhabitats. Livestock
grazing was identified as a stressor to populations on most of the
privately owned sites and some public sites on which Dakota skippers
occurred in 2002 (Cochrane and Delphey 2002, pp. 62-69). Swengel and
Swengel (1999, p. 286), for example, noted that at the Sheyenne
National Grassland in North Dakota, grazing appeared to be unfavorable
for the Poweshiek skipperling and Dakota skipper.
Reduced availability of nectar resources and larval food plants is
likely the primary factor leading to declines in Poweshiek skipperling
and Dakota skipper populations on heavily grazed sites. In South
Dakota, for example, Higgins (1999, p. 15) found lower plant diversity
on privately owned prairies, which were mostly grazed, than on publicly
owned prairies, which were almost all idle (no grazing or fire
management). McCabe (1981, p. 189) observed that grazing eliminated
Dakota skippers on North Dakota wet-mesic prairies; nectar plants such
as yellow sundrops and bluebell bellflower rapidly diminished with
light grazing, and heavy grazing eliminated upright prairie coneflower
and purple coneflower. In Manitoba, certain levels of grazing are
likely to adversely affect Dakota skipper populations in proportion to
its intensity because it removes nectar sources (e.g., Rigney 2013a,
pp. 143 and 153).
The intensity at which grazing occurs may dictate the level of
impact to the Dakota skipper and Poweshiek skipperling, and grazing may
have a larger impact on the Poweshiek skipperling than the Dakota
skipper (Westwood 2013, pers. comm.). Grazing reduces Dakota skipper
numbers in direct proportion to its intensity, due to the reduction in
flowers that provide nectar and perhaps by influencing adult behavior
(Dana 1997, p. 4). Dana (1997, p. 5) predicted that privately owned
pastures in Minnesota's Hole-in-the-Mountain complex, for example, will
likely only support low densities of skippers if they continued to be
heavily grazed and sprayed with herbicides. Surveys at this habitat
complex in 2007, 2008, and 2012 failed to record any Poweshiek
skipperlings (Dana 2008, p. 8; Selby 2009a, pp. xxxi-xxxii; Runquist
2012a, pers. comm.; Runquist 2012, pp. 13-14, 18-20), and Dakota
skippers were not detected in 2012 surveys (Runquist 2012, pp. 13-14,
18-20; Runquist 2012a, pers. comm.).
While most references to grazing impacts on prairie butterflies are
based on ancillary observations made during research focused on other
management impacts, one Minnesota study (Selby 2006b) focused on the
effects of grazing on all life stages of the Dakota skipper, and also
included data for the adult stage of the Poweshiek skipperling. Both
species were too scarce to collect data adequate to test the hypotheses
(Selby 2006b, p. 2), but observations based on 2 years (2003 and 2004)
of surveys suggested that numbers in the lightly to moderately grazed
pasture were similar to those in the best portions of nearby ungrazed
habitats (Selby 2006b, p. 30). Poweshiek skipperlings were almost
absent from the study sites (Selby 2006b, pp. iii-xxiii). Within the
grazed study area, the number of Dakota skippers declined with
increasing grazing intensity; Dakota skippers were absent from the most
heavily grazed areas (Selby 2006b, p. 16). Skadsen (2001, p. 55) found
that native forb diversity was poor on the grazed lands and predicted
the extirpation of both species unless management practices were
changed. The Dakota skipper is now extirpated at one of these sites,
and its status is unknown at the other; Poweshiek skipperling status is
unknown at both sites (Service 2014, unpubl. geodatabase). Spomer
(2004, p. 4) found that larval host plants and nectar sources were
missing from heavily grazed pastures at Sheyenne National Grassland,
North Dakota.
Grazing intensity combined with varying habitat type may also
affect the level of grazing impacts. On wet-mesic habitat in North
Dakota, for example, Dakota skippers and Poweshiek skipperlings
tolerate little to no grazing (McCabe and Post 1977, pp. 36-38; Royer
and Marrone 1992a, pp. 10, 17, 28; Royer and Marrone 1992b, pp. 17-18;
Royer and Royer 1998, p. 22). Webster (2003, pp. 7-8) described very
similar Dakota skipper habitats in Manitoba and, although grazing
generally does not occur in these habitats that are occupied by Dakota
skipper, they may be as sensitive to grazing as similar habitats in
North Dakota; in a later report, he described the conversion of lands
from haying to grazing as a major stressor to Dakota skipper in the
wet-mesic habitats of Manitoba (Webster 2007, pp. i-ii, 6). More
recently, it is thought that the effects of grazing in Manitoba and
Saskatchewan, as stated in Webster (2007, entire), may not be
applicable under current population sizes, and that even light grazing
may be detrimental on dry short grass prairie sites prior to and during
the Dakota skipper flight period (Westwood 2013, pers. comm.).
In the drier and hillier habitats that the species inhabits,
grazing may benefit Dakota skipper depending on its intensity. For
example, in eastern South Dakota, Dakota skipper populations were
deemed secure at some sites managed with rotational grazing that was
sufficiently light to maintain native plant species diversity (Skadsen
1997, pp. 24-29), and grazing may also benefit Dakota skippers by
reducing the area dominated by tall native grasses, such as big
bluestem and Indiangrass (Dana 1991). Proximity of nearby populations
or contiguous habitat may alleviate some of the negative impacts of
grazing. Royer and Marrone (1992b, p. 29; 1992a, p. 18) stated that
heavy grazing was a stressor to Dakota skippers and Poweshiek
skipperlings, but that occasional light grazing is not a long-term
stressor in some habitats as long as there are areas of contiguous
habitat that remain ungrazed. At Chekapa Creek Ridge and Knapp Pasture
in South Dakota, heavy grazing apparently extirpated both the Poweshiek
skipperling and Dakota skipper (Skadsen 2002, p. 38; 2004, p. 7; 2006a,
p. 11). Due to its proximity to other Poweshiek skipperling populations
and a return to fall haying in 2005, the Poweshiek skipperling
recolonized Chekapa Creek Ridge in 2006 (Skadsen 2006a, p. 12), but
more recent surveys indicate that the Poweshiek skipperling has again
been extirpated from this site due to habitat degradation because of a
change from haying to grazing (Skadsen 2012a, pers. comm., Skadsen
2012c, pers. comm.).
As with fire, Dakota skipper and Poweshiek skipperling populations
may persist through intense grazing episodes
[[Page 63726]]
or be restored afterwards, if sufficient numbers survive and reproduce
in lightly grazed patches or if nearby habitats provide sufficient
numbers of immigrants to reestablish the population after habitat
quality is restored. Years of grazing without rest, however, may
preclude recovery from the effects of intense grazing, although the
capacity for restoration of suitable plant community and other habitat
features may be highly variable among sites. On some sites, plant
diversity may not be restored when grazing pressure declines (Dana
1997, p. 30; Jackson 1999, pp. 134-135; Spomer 2004, p. 4). Grazing
intensely (where a high proportion of plant biomass is removed) or for
long duration leads to native plants being replaced with exotic, cool-
season European forage grasses and legumes that are tolerant of
continuous grazing (Jackson 1999, p. 128, Minnesota DNR 2006, p. 232).
In overgrazed native prairie in Minnesota, for example, the prairie is
dominated by exotic grasses with a low native forb species diversity
and abundance, and foliage height is less than 10 cm (4 in) (Dana 1997,
p. 3); these prairies lack the native plants necessary to sustain adult
and larval prairie butterflies. In comparison, sites less disturbed by
grazing have a high native forb (nectar) species diversity and
abundance foliage height is generally more conducive to perching and
reproductive activities (between 25 and 40 cm (10 and 16 in)) (Dana
1997, p. 2).
Land managers also frequently use herbicides, often through
broadcast application, to control weeds and brush on grazed remnant
prairies, which further reduces native forb diversity and abundance
(Dana 1997, p. 3; Stark et al. 2012, pp. 25, 27) necessary for adult
nectar sources. Skadsen (2006, p. 11), for example, documented the
likely extirpation of Dakota skippers at Knapp Ranch in South Dakota
after a July 2006 application of broadleaf herbicide in concert with
heavy grazing. Herbicide and pesticide use is discussed further under
Factor E of this final rule.
While reduced availability of nectar resources and larval food
plants may be the primary factors leading to declines in Poweshiek
skipperling and Dakota skipper populations on heavily grazed sites,
changes in vegetation structure may also be important. For example,
grazing prairie each year during mid-summer eliminates nectar plants,
such as purple coneflower, and native warm-season grasses that function
as larval host plants (Skadsen 2007, pers. comm.). In South Dakota,
vegetation height and litter depth were lower on prairie remnants that
were mostly grazed (Higgins 1999, pp. 27-29). Grazing also causes
direct mortality of larvae due to trampling and altering larval
microhabitats (Royer et al. 2008, pp. 10-15). In North Dakota, grazing
can compact soils in wet-mesic prairie inhabited by Dakota skippers and
Poweshiek skipperlings, altering vertical water movement in the soil,
which may lead to larval desiccation (Royer et al. 2008, p. 16) and may
inhibit subsurface shelter construction, potentially increasing larval
vulnerability to predators, parasites, and other environmental
stressors (Dana 2013, pers. comm.). Cattle may also kill larvae by
trampling them, particularly in wet-mesic prairies (McCabe 1981, p.
189).
Livestock grazing is the predominant use of privately owned
tallgrass prairie remnants in South Dakota (Higgins 1999, p. 15) and
was identified by the Service as a stressor on most of the privately
owned sites on which Dakota skipper occurred when the species was
identified as a candidate species in 2002 (Cochrane and Delphey 2002,
pp. 62-69). The presence and density of purple coneflower may serve as
an indicator of grazing impacts to Dakota skippers and Poweshiek
skipperlings where the species occur in dry-mesic prairie (Skadsen
2006a, p. 2); grazing from mid-June through July may reduce purple
coneflower abundance (Skadsen 2007, pers. comm.)--as discussed in the
Background section of this rule, purple coneflower has been identified
as a primary source of nectar for both species, particularly in dry
prairie habitats.
Britten and Glasford (2002, p. 373) recommended minimizing
disturbance of Dakota skipper habitat during the flight period (late
June to early July) to maximize genetically effective population sizes
(the number of adults reproducing) to offset the effects of genetic
drift of small populations (change in gene frequency over time due to
random sampling or chance, rather than natural selection). Therefore, a
large portion of the habitat of any Dakota skipper population should
remain ungrazed or only lightly grazed during the flight period, and
similar precautions should be taken for the Poweshiek skipperling.
We assessed the level of impact to populations from grazing at 52
Dakota skipper sites and 16 sites currently occupied by Poweshiek
skipperling with present or unknown status that had sufficient
information to evaluate the stressor (Tables 3 and 4; Service 2012
unpubl. data; Service 2014, unpubl. data). This analysis was conducted
differently for different habitat types. For Type A habitat (Royer et
al. 2008, pp. 14-16) where stocking rates (number of cattle or bison
over a given area) have little or no evidence of grazing effects on
Dakota skipper or Poweshiek skipper habitat quality, we found the level
of impact to populations of grazing to be low. For Type B habitat
(Royer et al. 2008, p. 14), we assumed that the level of impact of
grazing to populations would be low if the dry-mesic slopes were grazed
only before June 1 with at least one year of rest between rotations and
if the pasture were only spot-sprayed with herbicides when and where
necessary, or, the best available information does not indicate that
grazing practices are degrading habitat quality for the species (i.e.,
no apparent diminishment of nectar plant density and diversity and
habitat is good or excellent for Dakota skipper).
At grazed sites where extirpation of the local population is not
imminent, but habitat quality is fair to poor and the relative
abundance of Dakota skippers or Poweshiek skipperlings is often low, we
found the level of impact of grazing to populations to be moderate.
Sites with a moderate level of impact to populations due to grazing may
be lightly grazed for less than 4 months or less than 25 percent of the
above-ground biomass of native grasses and forbs is consumed (Smart et
al. 2011, pp. 182-183), are grazed after June 1, or are not given a
year of rest between grazed years. At sites where grazing is conducted
season-long, or for more than 4 months during the year, or more than 50
percent of the above-ground biomass of native grasses and forbs is
consumed and herbicide use is frequent, we found the level of impact of
grazing to populations to be high. At sites where grazing is a high-
level stressor, extirpation of the population is likely imminent and
habitat quality is poor. On public lands inhabited by the species,
grazing is typically used to control nonnative cool-season grasses and
invasive species. Cattle are often removed by July 1 to minimize
adverse impacts to warm-season grasses, but this type of management
minimizes the density of nectar species that are important to the
Dakota skipper and Poweshiek skipperling. Invasive species are often
present at grazed sites, which often leads to further management
actions (see Invasive Species and Secondary Succession).
Of the 52 Dakota skipper sites assessed, we found the level of
impact to Dakota skipper populations from grazing to be high at 9
sites, moderate at 29 sites, and low at 14 sites (Service 2012 unpubl.
data; Service 2014, unpubl. data). Moderate- to high-level impacts to
populations were primarily at South Dakota sites (N=27)--other
[[Page 63727]]
sites with moderate- to high-level impacts were in Minnesota (N=7),
North Dakota (N=3), and Manitoba (N=1). As described above as part of
our assessment of grazing, we examined the habitat quality ratings that
were primarily assigned by researchers during surveys for the species,
during separate habitat assessments, or that were available from State
heritage databases or other sources of scientific data. The habitat
quality was rated as poor at 7 of the 9 sites where grazing poses a
high level of impact to Dakota skipper populations. At each of the 14
sites where grazing pressure is low, habitat quality was good or
excellent, with two exceptions where habitat was rated as fair to good.
Among the 29 sites where grazing is a moderate level of impact to
Dakota skipper populations, 6 had habitat rated good or excellent.
Of the 16 Poweshiek skipperling sites for which we had sufficient
information to assess grazing, the level of impact to populations from
grazing is high at 4 sites, moderate at 10 sites, and low at 2 sites--
all but 2 of these sites were in South Dakota. No sites in Wisconsin or
Michigan were assessed for grazing impacts to populations, where the
grazing does not occur. Among the 10 sites where grazing is a moderate
level of impact to Poweshiek skipperling populations, 8 have habitat
rated as fair to excellent. The habitat quality was rated as poor at 2
of the 4 sites where grazing is having a high level of impact to
Poweshiek skipperling populations.
In summary, grazing may benefit Dakota skippers and Poweshiek
skipperlings in native tallgrass prairie by increasing native plant
diversity and patchiness of fires (Minnesota DNR 2006, p. 232). The
economic benefit of grazing to ranchers may also be a benefit to the
species by deterring conversion of remnant prairies to row crop
agriculture. Grazing is a stressor to these species, however, if it is
not managed with the goal of conserving native-prairie vegetation that
comprises suitable habitat for Dakota skipper and Poweshiek
skipperling. Dakota skippers and Poweshiek skipperlings may benefit
when prairie habitat is rested from grazing for at least a part of each
growing season, if livestock are precluded from removing too much plant
material (e.g., are moved when stubble heights are 6-8 in (15-20 cm)
(Skadsen 2007, pers. comm.), and if the timing of grazing for each
field varies from year to year (Skadsen 2007, pers. comm.). Grazing
management recommendations may not be universally applicable to all
locations, and may depend on the habitat type and other ecological and
physical conditions of the site. For instance, stubble heights of 6-8
inches may be difficult to attain in certain dry-mesic sites (ND NRCS
2013, pers. comm.).
Conversely, Dakota skipper and Poweshiek skipperling populations
may be reduced or extirpated when too much plant material is removed,
when fields are not rested for some portion of the growing season, or
fields are grazed during the same period each year. Grazing poses a
current and ongoing stressor of moderate to high level of impact to
populations where its intensity is such that Dakota skippers and
Poweshiek skipperlings are unlikely to thrive or even persist. Grazing
poses a likely future stressor where current management is conducive to
Dakota skipper or Poweshiek skipperling conservation, but where
landowners may allow excessive grazing in the future, for example,
where management may change as a result of the changing market prices
of agricultural products. Unsuitable grazing is an ongoing stressor
throughout much of the range of the Dakota skipper and Poweshiek
skipperling (primarily in flat wet prairies of Minnesota, North Dakota,
and South Dakota); grazing is not a documented stressor at the
Poweshiek skipperling sites with present or unknown status in
Wisconsin, Michigan, and Iowa or at most Dakota skipper sites in
Canada.
Haying
As with grazing and fire, haying (mowing grasslands and removing
the cuttings) may maintain habitat for the Poweshiek skipperling and
Dakota skipper, but as with any management practice, appropriate
timing, frequency, and intensity are important. Poweshiek skipperling
habitat at Scuppernong Prairie in Wisconsin, for example, would have
succeeded to shrubby or forested habitat if it had not been hayed each
fall (Borkin 2011, in litt.)--it is now one of the few sites in
Wisconsin that is occupied by the Poweshiek skipperling. Nearly all of
the Dakota skipper sites in Canada where the species is present are
privately owned, fall-hayed prairies (Westwood 2013, pers. comm.).
Haying generally maintains prairie vegetation structure, but it may
favor expansion of invasive species such as Kentucky bluegrass. If done
during the adult flight period, haying may kill the adult butterflies
or cause them to emigrate, and if done before or during the adult
flight period, it may reduce nectar availability (McCabe 1979, pp. 19-
20; McCabe 1981, p. 190; Dana 1983, p. 33; Royer and Marrone 1992a, p.
28; Royer and Marrone 1992b. p. 14; Swengel 1996, p. 79; Webster 2003,
p. 10). Royer and Marrone (1992b, p. 14), for example, ascribed the
loss of a North Dakota Poweshiek skipperling population to June and
July haying. Several years of July haying may have led to the Poweshiek
skipperling's extirpation at Wakidmanwin Prairie in South Dakota
(Skadsen 2006b, p. 13). The Dakota skipper was observed at the
Wakidmanwin Prairie in 2010 (Skadsen 2010, p. 6); however, it is not
clear if the management has changed since the observation. Early June
haying may have eliminated Dakota skippers from at least one site in
North Dakota (Royer and Royer 2012a, p. 72).
Hayed prairies are important reservoirs of native-prairie plant
diversity; however, long-term annual haying negatively impacts prairie
plant diversity (Jog et al. 2006, pp. 164-165). Jog et al. (2006, pp.
164-165) recommended diversifying management to include, for example,
periodic fire and to forego annual haying to increase plant species
diversity. In a long-term study of a prairie in southeastern Wisconsin,
a switch from late-season haying to fire management led to increased
native plant diversity and coverage of warm-season grasses, although
woody plant species also increased (Rooney and Leach 2010, p, 319)--
this increased plant diversity was likely an expression of plants that
were already at that location.
Late-season haying may benefit Dakota skipper populations (McCabe
1981, p. 190), and Dakota skipper populations might be more common on
hayed prairies than on idle (not hayed) prairies (Webster 2003, p. 10).
Swengel and Swengel (1999, p. 279) observed significantly greater
relative abundance of Dakota skippers on hayed tracts compared with
either idle or burned tracts in Minnesota, and Skadsen (2004, p. 7)
documented the extirpation of Dakota skippers from a site after its
management switched from haying to intensive grazing. Some remnant
Dakota skipper populations in the eastern Dakotas are found on fall-
hayed prairies (Skadsen 1997, pp. 10-23; Royer and Royer 2012b) as are
many of the sites in Manitoba (Webster 2003, p. 10). Webster (2003, p.
8) found ``healthy populations'' of Dakota skippers in Manitoba on
sites used as hay fields, as described by the absence of standing dead
grass, low numbers of shrubs, shorter bluestem grasses, and abundant
and readily observable nectar flowers, as compared to un-hayed sites.
Scarlet Fawn Prairie in South Dakota, which is hayed in the fall, is
considered one of the highest quality prairies in that State (Skadsen
2012, pers. comm.). In the
[[Page 63728]]
Dakotas, late-season (mid-August to October) haying appears to minimize
impacts to the prairie butterflies, although annual haying may diminish
the vigor of native, warm-season grasses and reduce forb density in
north-central North Dakota (wet-mesic) habitats (Lenz 1999, p. 14;
Skadsen 2009, p. 8). Consistent late-season haying of Poweshiek
skipperling habitat in South Dakota, appears to have facilitated the
expansion of green needlegrass (Stipa viridula), a cool-season grass,
and prevented seed development in warm-season plants (Skadsen 2009, p.
8).
We assessed the level of impact of haying to populations at 41
Dakota skipper sites and 6 Poweshiek skipperling sites with present or
unknown status where we had sufficient information to assess the
stressor (Tables 3 and 4; Service 2012 unpubl. data; Service 2014,
unpubl. data). Haying was considered to be a stressor with a low or no
negative impact on populations where it is implemented after the flight
period (after approximately August 1) and when there is no reduction in
the availability of native plant species. Haying was considered to be a
stressor with a moderate level of impact on populations, where the
exact timing or extent of haying was unknown, but there are: (1) One or
more indications that haying is resulting in a reduction in nectar or
larval food sources important to the species due to timing or frequency
of mowing; (2) part of the Dakota skipper or Poweshiek skipperling
habitat on the site is hayed before August 1, but a substantial
proportion of habitat is not hayed and not clearly subject to other
stressors, such as frequent fire or grazing (e.g., Smokey Lake site,
North Dakota); or (3) where haying occurs before or after August 1, but
the site is hayed no more frequently than once every 3 years (e.g., Roy
West Game Production Area, South Dakota).
We considered haying to be a stressor with a high level of impact
on populations where the site was hayed prior to August 1 (e.g., Oaks
Prairie, North Dakota). At 29 of the 41 evaluated Dakota skipper sites,
current haying practices are conducive (beneficial) to Dakota skipper
conservation, because it is conducted after August 1 and is not
reducing native plant species diversity. One or more indications that
current haying practices are slowly degrading habitat quality for
Dakota skippers has been documented at 11 of the 41 sites. At several
sites in North Dakota, for example, Royer and Royer (2012b, pp. 15, 21,
24, 45) noted a decrease in the diversity and density of forbs at sites
hayed annually. Haying is a stressor with a high level of impact on
populations at 1 of the 41 Dakota skipper sites assessed and a stressor
of moderate-level impacts to the populations at 11 of the 41 Dakota
skipper sites assessed. Of the 6 Poweshiek skipperling sites evaluated,
haying was a stressor with moderate-level impacts on populations at 3
sites and was not considered to have high-level impacts to the
populations at any of the 6 sites.
In summary, haying is a current and ongoing stressor of moderate to
high level of impacts to Dakota skippers and Poweshiek skipperlings at
the few sites where the site is normally hayed before August and where
annual haying is reducing availability of larval food and adult nectar
plants. However, fall haying is beneficial to both species,
specifically if it is conducted after the flight period (after August
1), no more than every other year, and there is no indication that
native plant species diversity is declining due to timing or frequency
of haying. Haying is a current stressor at a small number of sites for
both species; these sites occur primarily in North Dakota and South
Dakota.
Lack of Disturbance
While inappropriate or excessive grazing, haying, and burning are
stressors to some Poweshiek skipperling and Dakota skipper populations
and have led to the extirpation of others, both species are also
subject to the stress of no management practices being implemented.
Prairies that lack periodic disturbance become unsuitable for Poweshiek
skipperlings and Dakota skippers due to expansion of woody plant
species (secondary succession), litter accumulation, reduced densities
of adult nectar and larval food plants, or invasion by nonnative plant
species (e.g., smooth brome) (McCabe 1981, p. 191; Dana 1983, p. 33;
Dana 1997, p. 5; Higgins et al. 2000, p. 21; Skadsen 2003, p. 52). For
example, Dakota skipper numbers were reduced at Felton Prairie,
Minnesota, in tracts that had not been hayed or burned for several
years (Braker 1985, p. 47). Another study also observed significantly
lower Dakota skipper abundance on unmanaged or idle sites, compared
with hayed sites; however, Poweshiek skipperlings were significantly
denser with idling (Swengel and Swengel 1999, p. 285). Skadsen (1997,
pp. 10-23; 2003, pp. 8, 35, 42) reported deterioration of several
unburned and unhayed South Dakota prairies in just a few years due to
encroachment of woody plants and invasive species and found lower
species richness of prairie-dependent butterflies and lower floristic
quality at sites with no disturbance versus sites managed by grazing or
fall haying (Skadsen 2006a, p. 3). For example, Dakota skippers
returned to an idle site, Pickerel Lake State Park, after a burn
conducted in 2007 resulted in a significant increase in forbs,
particularly purple coneflower (Skadsen 2008, p. 2). In a separate
study, Higgins et al. (2000, p. 24) found that prairie habitats left
idle had lower plant diversity and quality than prairies managed with
fire.
Populations of Dakota skippers and Poweshiek skipperlings may also
be at risk at sites where a private landowner is not aware of the
presence or potential presence of the species, but would conserve the
land if they were made aware. The land use in some areas in Canada, for
example, are currently inadvertently used in ways that are favorable to
the species (for example, fall haying), but the land use may change in
the future (Westwood 2014, pers. comm.). In the United States, the
Service has notified private landowners of the presence or potential
presence of one or both species on their land at most sites with
present or unknown occupancy and many sites that are considered
extirpated or possibly extirpated but still may have suitable habitat.
We assessed the stressor posed by lack of management for
populations at 17 Dakota skipper sites and 12 Poweshiek skipperling
sites with present or unknown status where we had sufficient
information to evaluate the stressor (Tables 3 and 4; Service 2012
unpubl. data; Service 2014, unpubl. data). Lack of management was
considered to be a stressor of moderate-level impacts to the population
where the species' habitat is degraded or likely to become degraded due
to secondary succession, invasive species, or both, but actions to
restore habitat quality are planned or ongoing, or where the site is
idle with no evident plans to initiate management (e.g., fire, grazing,
haying), and there are signs of ongoing or imminent secondary
succession. Lack of management was considered to be a stressor with a
high level of impact to the population where the habitat quality at a
site is degraded or likely to become degraded due to secondary
succession or invasive species, and there are no ongoing or planned
actions to maintain or restore habitat quality. Lack of management was
considered to be a stressor of low-level impacts to Dakota skipper or
Poweshiek skipper populations at sites that are managed by grazing,
haying/mowing, or fire that precludes loss of Dakota skipper or
Poweshiek skipperling habitat to
[[Page 63729]]
secondary succession and invasive species (e.g., smooth brome).
Nine of the 17 Dakota skipper sites assessed are under high level
of impact to population due to lack of management and 5 sites are under
moderate level of impact to the population. Four of the 12 Poweshiek
skipperling sites assessed are under high level of impact to the
population due to lack of management, and 6 sites are under moderate
level of impact to the population. The Dakota skipper and Poweshiek
skipperling are unlikely to persist at those sites where the level of
impact to the population due to lack of management is high. Sites
currently under stress by lack of management occur throughout the range
of both species; however, most of the present or unknown sites that
lack appropriate management are in North Dakota, South Dakota,
Minnesota, and Michigan. In summary, lack of disturbance is a current
and ongoing stressor to Dakota skipper and Poweshiek skipperling
populations where woody vegetation or invasive species expansion will
reduce native-prairie grasses and flowering forbs.
Summary of Factor A
We identified a number of stressors to the habitat of the Dakota
skipper and Poweshiek skipperling that operated in the past, are
impacting both species now, and will continue to impact the species in
the future. The decline of both species is the result of the long-
lasting effects of habitat loss, fragmentation, degradation, and
modification from agriculture, development, invasive species, secondary
succession, grazing, and haying. Although efforts have been made to
effectively manage habitat in some areas, the long-term effects of
large-scale and wide-ranging habitat modification, destruction, and
curtailment will last into the future. Invasion of the species' habitat
by exotic species and woody vegetation, overgrazing, long-lasting or
permanent alterations in water levels or hydrology, and too frequent or
improperly timed haying remove or significantly reduce the availability
of plants that provide nectar for adults and food for larvae. Fire and
flooding cause direct mortality or destroy nectar and food plants if
the intensity, extent, or timing is not conducive to the species'
biology.
Of the 160 Dakota skipper sites we evaluated for one or more
habitat stressors, at least 131 sites have at least one documented
stressor with moderate to high levels of impact to populations--these
sites are found across the current range of the species in Minnesota,
North Dakota, South Dakota, Manitoba, and Saskatchewan (Service 2012
unpubl. data; Service 2014, unpubl. data). Fifty-eight sites have 2 or
more documented stressors of moderate to high levels of impact to
populations, and 24 sites have 3 or more documented stressors of
moderate to high level of impact to populations. Sites with three or
more stressors are found across most of the current range of the
species; these sites occur in Minnesota, North Dakota, South Dakota,
and Manitoba (Service 2012 unpubl. data; Service 2014, unpubl. data).
Furthermore, concurrently acting stressors may have more intense
effects than any one stressor acting independently. Therefore, based on
our analysis of the best available information, present and future loss
and modification of Dakota skipper habitat is a stressor that has
significant impacts on populations of the species throughout all of its
range. Habitat-related stressors occur at sites with Dakota skipper
populations within every State and province of occurrence.
Similarly, of the 60 Poweshiek skipperling sites with present or
unknown status that we analyzed for one or more habitat stressors, 46
of them have at least one stressor at moderate to high levels of impact
to the population. These sites are found across the current range of
the species and occur in Iowa, Michigan, Minnesota, North Dakota, South
Dakota, Wisconsin, and Manitoba (Service 2014, unpubl. data). Twenty-
five sites have 2 or more documented stressors that have moderate to
high levels of impact to the population. These sites are found across
the current range of the species and occur in Iowa, Michigan,
Minnesota, North Dakota, South Dakota, Wisconsin, and Manitoba (Service
2014, unpubl. data). Eleven of them have at least three documented
stressors that have moderate to high levels of impact to the
population. These sites are found across the current range of the
species and occur in Iowa, Michigan, Minnesota, South Dakota, and
Manitoba (Service 2014, unpubl. data). Furthermore, concurrently acting
stressors may have more intense effects than any one stressor acting
independently. Therefore, based on our analysis of the best available
information, present and future loss and modification of Poweshiek
skipperling habitat is a stressor that has significant impacts on the
species throughout its range.
Conservation Efforts To Reduce Habitat Destruction, Modification, or
Curtailment of Its Range
In the past, funding for conservation of rare species was primarily
directed toward federally listed or candidate species, so while the
Poweshiek skipperling may have benefited indirectly from conservation
activities focused on species such as the Dakota skipper and Mitchell's
satyr (Neonympha mitchellii mitchelli), it has not generally been the
primary focus of those activities. As a result, survey data and
incidental life-history observations have been accumulated as a part of
projects focused on other species, but surveys were not necessarily
focused on Poweshiek skipperling sites and detailed life-history,
population, and demographic data have generally not been collected for
the species. Various conservation activities directed at the Dakota
skipper also indirectly benefit the Poweshiek skipperling; these
activities are summarized below.
Conservation agencies have recognized the need to address the
status of prairie butterflies for more than 30 years beginning with a
1980 workshop held to initiate studies of Dakota skippers and other
prairie butterflies. In June 1995, the U.S. Fish and Wildlife Service
convened Dakota skipper experts to outline tasks needed to preserve
enough viable populations to ensure long-term security for the species.
The group outlined a plan for surveying populations and characterizing
sites and habitats at priority areas, identifying and recommending
management needs, monitoring, and outreach and education; however, this
plan was not drafted or finalized. In 1999, a Dakota skipper recovery
strategy meeting was held in South Dakota with State, Federal, and
nongovernmental biologists attending (Skadsen 1999b, entire). In 2011,
researchers in Canada organized a Poweshiek Skipperling Workshop and
followup conference call that brought together researchers and managers
from across the range of the Poweshiek skipperling to provide updates
on survey data, discuss ongoing activities, and plan future work. The
workshop resulted in specific conservation action plans for the
species. The Minnesota Zoo organized a followup conference during March
2013 to assess progress of the 2011 Poweshiek Skipperling Workshop
Action Plans, facilitate discussion on the potential effects of
management activities on prairie butterflies, identify needed
information and data gaps, establish new priorities for research and a
draft
[[Page 63730]]
action plan for 2013, and facilitate networking and collaborations
focused on the conservation of the Dakota skipper and Poweshiek
skipperling, as well as other tallgrass prairie butterflies in the
Midwest--the Northern Tallgrass Prairie Lepidoptera Conservation
Conference Working Group Report Synthesis is posted at https://www.mnzoo.org/PrairieLepidopteraConference/Northern%20Tallgrass%20Prairie%20Lepidoptera%20Conservation%20Conference%20Working%20Group%20Reports%20-%20Synthesis.pdf.
Research and survey work has occurred throughout the range of both
species to document populations, to study the life history of both
species, and to examine the effects of various management practices,
such as fire and grazing, on the species and their habitat. For
example, research and survey work on Dakota skippers began with Dana's
(1991, entire) doctoral study on fire effects at Hole-in-the-Mountain,
Minnesota, beginning in 1978 and McCabe's (1981, entire) 1979 surveys
for the Garrison Diversion project in North Dakota. Additional work has
been completed on characterizing habitat at important Dakota skipper
sites in Minnesota (Dana 1997, entire) and North Dakota (Lenz 1999,
entire, Royer and Royer 1998, entire, Royer and Royer 2012a, entire).
Royer (2008, entire) assessed abiotic habitat parameters of soil in
relation to management and conservation of Dakota skippers to
complement prior floristic characterization of these habitats. The
Minnesota DNR and the Service planned to cooperatively study the
effects of grazing on the Dakota skipper and Poweshiek skipperling
(Selby 2003, entire; Selby 2006b, entire); however, skipper numbers
were too low to collect sufficient data to test hypotheses (Selby
2006b, p. 30).
In the past, the Service funded some management activities intended
to benefit the Dakota skipper, including habitat management at Big
Stone National Wildlife Refuge, Minnesota (Olson 2000, entire),
landowner contacts and education on conservation practices in South
Dakota (Skadsen 1999b, entire), and prairie vegetation restoration at
Chippewa Prairie in 2000 and at Twin Valley Prairie SNA, Minnesota, in
2001. The results of these efforts are varied; for instance, the
prairie habitat at Twin Valley Prairie SNA was recently rated as
excellent quality (Service 2014, unpubl. geodatabase), but the status
of both species at that site is unknown; the last positive observation
of Dakota skippers and Poweshiek skipperlings was 1993 and 1994,
respectively. The Dakota skipper is extirpated from Chippewa Prairie,
and the status of the Poweshiek skipperling is unknown at the site; the
last positive observations of the species were in 1995 and 1994,
respectively (Service 2014, unpubl. geodatabase).
The Service purchases easements to prevent prairie conversion for
agriculture and provide cost-share to support rotational grazing and
other practices that may benefit Dakota skippers and Poweshiek
skipperlings. For example, in 12 counties in South Dakota within the
range of the species, the Service's grassland easement program has
protected 365,193 ac (147,788 ha) of grassland that are primarily
native prairie (Larson 2013, pers. comm.; HAPET 2012, unpubl. data),
although it is not clear whether these lands are suitable habitat for
either species. Other Service fee title lands, State lands, and Natural
Resources Conservation Service (NRCS) easement lands may also protect
areas from conversion, depending on the protections in those areas
(Larson 2013, pers. comm.). If easements are near prairie butterfly
habitat they can minimize the impacts of conversion and may provide
dispersal corridors or buffer sites from external stressors (e.g.,
pesticide drift).
Prairie easements generally prevent grasslands from being plowed or
destroyed and prevent haying before July 16, but may not restrict
grazing, pesticide use, or other practices that can degrade the status
of Dakota skipper or Poweshiek skipperling populations. For example,
one property with a Service easement was recently overgrazed to the
extent that Dakota skipper was extirpated from the site (Skadsen 2006b,
p. 5). Cost-share partnerships on easements and other areas, however,
may further enable landowners to manage grasslands to benefit Dakota
skippers and other prairie endemic species. The Service may implement
such actions through the Partners for Fish and Wildlife program or in
collaboration with NRCS or other agencies. Since 1990, the Service has
purchased easements to prevent grassland conversion on millions of
acres in Minnesota, North Dakota, and South Dakota (HAPET 2012, unpubl.
data). Only some of these areas include Dakota skipper or Poweshiek
skipperling sites, are within the range of either species, or include
suitable habitat for either species.
Conservation-interested agencies, individuals, and Tribes in South
Dakota have made concerted efforts for decades to conserve native
prairie within the Dakota skipper range. For example, there are
approximately 54,000 ac (21,853 ha) of fee title lands in grassland
that are managed by the Service in 12 of the counties within the
historical or current range of the Dakota skipper and 365,000 ac
(147,710 ha) protected by the Services' grassland easement program
(HAPET 2012, unpubl. data; Larson 2013, pers. comm.). These acreages do
not include an additional 4,000 ac (1,619 ha) of grass protected by
acquisitions that have occurred in 2012 (HAPET 2012, unpubl. data;
Larson 2013, pers. comm.). Not all of these lands, however, may be
managed in such a manner that is conducive to Dakota skipper
populations.
About one-half of the present or unknown Dakota skipper sites
(total number of present/unknown sites is 171) in the United States are
privately owned (excluding populations on land owned by The Nature
Conservancy). Twelve of these populations are on private land on which
the Service has purchased conservation easements that preclude plowing
and haying before July 16. Manitoba Habitat Heritage Corporation has an
easement that overlaps with one Dakota skipper site in Canada (Friesen
2013, pers. comm.). Similarly, of the 70 privately owned sites where
Poweshiek skipperling has been recorded since 1985, 8 sites (all in
Minnesota) have conservation easements. These easements do not
prescribe grazing practices but are intended to prevent grassland
conversion to cropland, which is detrimental to Dakota skippers or
Poweshiek skipperlings. Additional measures on some easement properties
could ensure grazing practices do not inadvertently impact either
species.
The Nature Conservancy's Minnesota and Dakotas offices initiated a
Prairie Coteau Coordinated Conservation Planning Effort and Plan in
1998 to facilitate conservation actions by various landowners,
including private, county, state, tribal and Federal, on high
biodiversity prairie sites (Skadsen 1999b, entire). Additional partners
include conservation organizations, local conservation districts, and
universities. The Nature Conservancy acquired a reserve in the Sheyenne
Grassland area, Brown Ranch, which is a Dakota skipper site with an
unknown status, and manages some of the most significant habitats for
the two species in Minnesota, including the Hole-in-the-Mountain
Prairie preserve. Based on intensive surveys in 2007, Dana (2008, p.
19) found ``considerable reassurance'' that the rotational burning
approach used at Prairie Coteau SNA and Hole-in-the-Mountain Preserve
is compatible with long-term persistence of the Dakota
[[Page 63731]]
skipper, for example, by controlling woody vegetation encroachment. The
Minnesota DNR also manages the Prairie Coteau SNA with rotational
burning (Dana 2008, p. 19), which may control woody vegetation
encroachment. The Clay County Stewardship Plan (Felton Prairie
Stewardship Committee 2002) may have reduced the likelihood and
severity of gravel mining within the Felton Prairie complex in
Minnesota.
Many of the best sites for Dakota skipper and Poweshiek skipperling
in South Dakota are on tribal lands managed by the Sisseton-Wahpeton
Sioux Tribe (e.g., Scarlet Fawn and Oak Island Prairies) (Skadsen 1997,
Skadsen 2012b, p. 3), with late-season haying. According to Skadsen
(2012, p. 3) ``. . . as in prior years, the fall hayed prairies held in
trust by the Sisseton Wahpeton Oyate had the most diverse native flora
and thus the largest numbers of Dakota skippers.'' Although these lands
generally contain high-quality habitat for prairie butterflies in
eastern South Dakota (Skadsen 2012b, p. 3), a change to alternate year
haying--instead of annual haying--may further improve habitat quality
by ensuring that plants that flower during the Dakota skipper and
Poweshiek skipperling flight periods are able to produce seed (Royer
and Royer 2012b, p. 15).
The Day County Conservation District, South Dakota, places a high
priority on implementing prescribed grazing on rangelands known to
support Dakota skippers and bordering sites in the Upper Waubay Basin
Watershed (Skadsen 1999b, p. 3). Their efforts include soliciting
grants and providing education on grazing management, controlled
burning, and integrated pest management to control leafy spurge,
through workshops and a demonstration site. There are five Poweshiek
skipperling sites in Day County with unknown occupancy and no sites
where the species is considered to be present. There are a total of 24
Dakota skipper sites in Day County: 3 sites where the species is
considered to be present, 11 sites that have an unknown occupancy, and
the remaining are extirpated or possibly extirpated. It is not known
how many of these sites are benefiting from these efforts and to what
degree.
In South Dakota, completed management plans guide habitat
restoration at Hartford Beach State Park and Pickerel Lake State
Recreation Area (Skadsen 2008, pp. 4-7; Skadsen 2011, pp. 1-4). At each
site, the lack of haying, grazing, or fire had allowed plant succession
to degrade and reduce the extent of Dakota skipper habitat. Dakota
skipper habitat at these sites is divided into 3-4 management units. A
controlled burn was conducted in one unit at Hartford Beach State Park
in 2008, and shrubs were removed from two of the units (Skadsen 2008,
p. 4). At Pickerel Lake State Recreation Area, a controlled burn was
conducted in 2007, and in 2008 the site was hayed and shrubs were
removed. The Dakota skipper was present in the burned unit for the
first time since 2002 after ``a dramatic increase in forbs, especially
purple coneflower, occurred after the burn'' and ``apparently attracted
Dakota skippers from a nearby site'' (Skadsen 2008, p. 2). The
Poweshiek skipperling is extirpated from both sites, but the reasons
for its disappearance are not known (Service 2012, unpubl. data). At
each site, prescribed fire and brush control are implemented on a
rotational basis (Skadsen 2011, pp. 1-4); at Pickerel Lake State
Recreation Area, forbs were planted in 2011 to diversify nectar
resources for prairie butterflies (Skadsen 2011, pp. 2-4).
A privately owned ranch with Dakota skippers in Day County, South
Dakota, is managed with a patch-burn grazing system in which each
grazing unit is rested for a full year (Skadsen 2008, p. 10), which may
be beneficial to the species. The effects of patch-burn grazing at this
site are being studied jointly by The Nature Conservancy and South
Dakota State University (Skadsen 2008, p. 10).
In 2005, the Service's National Wildlife Refuge System in North
Dakota and South Dakota adopted the Conservation Strategy and
Guidelines for Dakota Skippers on Service Lands in the Dakotas, which
are based on the Service's Dakota Skipper Conservation Strategy and
Guidelines and on versions of the Service's conservation guidelines for
Dakota skipper. The guidelines were revised in March 2013 (https://www.fws.gov/midwest/endangered/insects/dask/DASKconservationguidelines2013.html). In the Dakotas, the Service plans
to implement the conservation guidelines on all of its lands where the
Dakota skipper is known to occur--the Service owns 12 Dakota skipper
sites in the Dakotas where the species is considered present or has
unknown occupancy. The guidelines also suggest that the Service examine
other lands under its ownership to determine whether unrecorded
populations of Dakota skippers may be present and to conduct surveys in
those areas or manage the site in accordance with the Dakota Skipper
Conservation Strategy and Guidelines. These guidelines will be reviewed
and updated to reflect new information as it is developed.
In Manitoba, August 1st is the recommended earliest haying and
grazing date at Dakota skipper sites. The recommended intensity of
grazing is to be as low as economically feasible to prevent permanent
damage to sites (e.g., destruction of nectar plants). In Manitoba, it
is recommended that sites that have burned or have been impacted by
other factors such as extensive flooding, should not be grazed for at
least one year following these events.
Poweshiek Skipperling
Most of the conservation initiatives discussed above were put in
place to benefit the Dakota skipper, but may also benefit the Poweshiek
skipperling. Conservation initiatives are also in place at several
Poweshiek skipperling sites in Wisconsin and one or two sites in
Michigan.
At least two sites occupied by Poweshiek skipperling in Michigan
are at least partially owned and managed by the Michigan Nature
Association (MNA); however, the MNA does not specifically manage for
Poweshiek skipperling conservation. The State of Michigan owns part or
all of four occupied Poweshiek skipperling sites; however, most of
those lands are managed as State recreational areas, not for prairie
butterfly conservation. Landowners at one fen site are participating in
a Michigan DNR Land Incentive Program, and a portion of another
occupied site is part of the Burr Memorial Prairie Plant Preserve
(Michigan Natural Features Inventory 2011, unpubl. data). The Poweshiek
skipperling may benefit from conservation activities in place for the
federally endangered Mitchell's satyr at one Michigan site.
Poweshiek skipperling sites in Wisconsin are owned and managed by
the Wisconsin DNR, who manage the land to maintain and improve prairie
habitat. The Wisconsin DNR recently received a Sustain Our Great Lakes
(SOGL) grant to conduct invasive species management on several SNAs,
including Puchyan Prairie (Wisconsin DNR 2012, in litt.). The
Scuppernong Prairie SNA, Wilton Road, and Kettle Moraine Low Prairie
SNA are managed primarily through fire and invasive species control.
Furthermore, the Minnesota Zoo recently initiated a propagation
research program for the Poweshiek skipperling and Dakota skipper to
develop methods to propagate these and other species in the future. If
this program is successful, a conservation benefit could be possible if
the program could facilitate reintroduction and augmentation efforts
into areas where the species has
[[Page 63732]]
declined or disappeared. Furthermore, this propagation effort may lead
to increased knowledge of basic biology and life history of both
species.
To summarize, the conservation initiatives discussed above may
ameliorate one or more stressors on populations of Dakota skipper and
Poweshiek skipperling at a relatively small number of sites.
Approximately 12 Dakota skipper sites and 8 Poweshiek skipperling sites
benefit from conservation easements; an additional 12 Dakota skipper
sites are owned by the Service and may benefit from implementation of
Dakota skipper conservation guidelines; 2 sites in State parks are
undergoing prairie restoration and management; approximately 5
additional Dakota skipper sites and 4 Poweshiek skipperling sites are
managed to benefit prairie butterflies, such as rotational fire
management. Since numerous sites have two or more stressors of moderate
to high-level impacts to one or both species, all stressors are likely
not completely ameliorated at many sites. Initiatives such as captive
propagation and studies of the effects of various management techniques
may be applied broadly and may be beneficial to each species as a
whole--the timeframe for these benefits to be realized, however, will
not be immediate.
Factor B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
Although its biology could make the Dakota skipper sensitive to
collection at some locations, the present level of scientific
collection is minimal and recreational collecting is unlikely (Royer
and Marrone 1992a, p. 27). Collection is not known to be a stressor for
the Poweshiek skipperling (Royer and Marrone 1992b, p. 16). Collection
is not currently a stressor to either species in Canada (COSEWIC 2003,
p. 18). Scientific Collectors Permits are required in states where both
species have legal protection, and permission is often required to
collect specimens on protected areas. Furthermore, these species are
not collected for commercial purposes; the drab coloration likely makes
both species less desirable for collectors and the remoteness of
occupied habitat and limited flight period would make recreational
collections difficult (Borkin 2012, pers. comm.). Therefore,
overutilization for commercial, recreational, scientific, or
educational purposes is not currently a threat to Dakota skipper and
Poweshiek skipperling.
Handling stress during scientific study may be stressors to
individuals of both species. Adverse effects on butterflies have been
documented for a wide range of species (e.g., Benson and Emmel 1973, p.
329; Singer and Wedlake 1981, pp. 215-216; Lederhouse 1982, pp. 381-
382; Morton 1984, pp. 56-57; Mallet et al. 1987, pp. 380-383).
Although recreational collection is not a threat to these species
at this time, due to the few populations, small population size, and
restricted range, if any recreational collecting did occur in the
future, even limited collection from the remaining small and isolated
populations could have deleterious effects on these species'
reproductive and genetic viability.
Factor C. Disease or Predation
Diseases or parasites that are specific to the Dakota skipper or
Poweshiek skipperling are not known, but some parasitism or predation
likely occurs during each of the life stages. Disease and predation are
part of the natural population dynamics of any insect, including the
Dakota skipper and Poweshiek skipperling--without high rates of
mortality before reproduction, populations would increase
exponentially. The small amount of observations of predation and
parasitism makes documenting those phenomenons difficult (Dana 2013,
pers. comm.). Only a few studies have attempted to document parasitism
and predation. For example, 10 of 130 eggs tagged for field observation
in a 1994 study of a Wisconsin Poweshiek skipperling population
appeared to have suffered from predation or parasitism (Borkin 1995, p.
5); some were punctured and had the contents extracted, and others
turned black and dried up. Dana (1991, pp. 19-21) documented some
parasitism of Dakota skipper and Ottoe skipper (Hesperia ottoe) eggs
and larvae by various wasp species and predation by various insects,
such as ants, but escaping his observation would have been predation by
birds and small mammals on these immature stages (Dana 2013, pers.
comm.).
Wolbachia, ubiquitous intercellular bacteria estimated to affect
20-70 percent of all insect species, including many butterfly species,
affects the reproductive ecology of its host (Kodandaramaiah 2011, pp.
343-350). It is uncertain if Wolbachia are affecting the Dakota skipper
or Poweshiek skipperling. An infection of Wolbachia may reduce already
small population sizes and increase the probability of extirpation
(Nice et al. 2009, pp. 3137-3138), particularly if the population is
infected with a novel strain (Runquist 2013, pers. comm.). The
Minnesota Zoo plans to conduct Wolbachia screening and strain
identification of genomic DNA samples that the University of Michigan
(at Dearborn) extracted from both species. The effects of predation by
birds or insects on Dakota skipper or Poweshiek skipperling population
dynamics are not known and may impact the species.
McCabe (1981, p. 187), noted three kinds of predators to Dakota
skippers, including Ambush bugs (Hemiptera: Phymata sp.), flower
spiders (Aranaea: Misumena spp.), and orb weavers (various Araneldae).
Flower spiders and ambush bugs are effective predators of nectar-
feeding insects (McCabe 1981, pp. 187-188) and may cause mortality to
some individuals, but it is difficult to quantify the population-level
impacts of predators to either the Dakota skipper or Poweshiek
skipperling. Dana documented predation on adult skippers by robber
flies (Asilidae), which are common in upland prairie habitats, and
noted the incidence of wing damage indicative of an unsuccessful attack
by a bird or similar predator (Dana 1991, pp. 26-27; Dana 2013, pers.
comm.). Several incidences of predation by crab spiders and robber
flies on both the Dakota skipper and Poweshiek skipperling have been
documented in Canada, although it is not thought to be a common
occurrence (Westwood 2013, pers. comm.). McCabe (1981) failed to
observe bird or dragonfly predation; however these events are difficult
to observe (Dana 2013, pers. comm.). Orb weaver spiders appear to be
successful predators of ``old, worn individuals'' (McCabe 1981, p.
188), but bird and other animal predation on young and old adults
likely occurs when the butterflies are roosting or torpid and unable to
escape (Dana 1991, p. 27).
Disease, parasitism, and predation are important parts of
population dynamics of normal populations of insects, but may have an
amplified effect on small populations. Furthermore, as we discuss in
the possibility of unknown factors that may be affecting the species
(in Factor E of this final rule), it is possible that a new virulent
pathogen or parasitoid may have increased mortality above normal levels
and may be causing the rapid decline in the Poweshiek skipperling and
possibly also the Dakota skipper (Dana 2013, pers. comm.).
Disease and parasitism are a serious hypothesis that may explain
the rapid decline of the Poweshiek skipperling, and perhaps the Dakota
skipper, and these factors, along with predation, are extremely
difficult to observe. Therefore, we are unsure if either disease,
parasitism, or predation are
[[Page 63733]]
significant stressors to the Dakota skipper or Poweshiek skipperling
populations at this time, and we are not certain if these stressors
will contribute to significant population-level impacts in the future.
However, in the future, disease, parasitism, and predation may have an
amplified effect on these small and isolated populations.
Factor D. The Inadequacy of Existing Regulatory Mechanisms
Existing regulatory mechanisms vary by location, but generally do
not mitigate for the numerous stressors that the Dakota skipper and
Poweshiek skipperling face.
State Regulations
The Dakota skipper is listed as endangered under Minnesota's
endangered species statute. Under the Minnesota statute, a person may
not take, import, transport, or sell any portion of an endangered
species of wild animal or plant, or sell or possess with intent to sell
an article made with any part of . . . an endangered species of wild
animal or plant'' except as permitted by the Minnesota DNR (Minnesota
Statutes 2012, 84.0895). The Poweshiek skipperling was listed as State-
endangered in Minnesota, and the status of Dakota skipper was changed
from threatened to endangered on August 19, 2013 (Minnesota DNR 2013).
The Poweshiek skipperling is listed as threatened under State
endangered species statutes in Iowa and Michigan and as endangered in
Wisconsin. The Dakota skipper is listed as endangered under State
endangered species statutes in Iowa. South Dakota has an endangered
species act, but no invertebrates are currently listed. South Dakota
put forth a proposal to add the Dakota skipper to the State endangered
species act list, but it was not finalized. Although the Dakota skipper
is not listed as threatened or endangered under South Dakota's
endangered species statute, the State natural heritage program
considers the species to be imperiled because of rarity due to very
restricted range and very few populations. North Dakota does not have a
mechanism for conferring protection to threatened or endangered species
at the State level.
State endangered species statutes provide State natural resource or
conservation agencies with the authority to regulate collection of
individuals and related activities (for Poweshiek skipperling in Iowa,
Michigan, and Wisconsin and Dakota skipper in Minnesota and Iowa), but
we have no information to suggest that collection is a stressor that
impacts populations of the species. With the exception of the
regulation of some incidental take in Wisconsin and Minnesota, the
statutory protections afforded by these State statutes may do little to
protect or mitigate Poweshiek skipperling or Dakota skipper from non-
collection threats. While some stressors may result in direct mortality
of both species, such as ill-timed fires, most stressors to the species
are indirect and State laws that regulate direct harm to the species do
not address these factors. In Iowa, for example, Poweshiek skipperling
populations are likely now extirpated due to habitat destruction and
conversion and other undetermined stressors, despite the species'
presence on the State's list of threatened species since 1994. In
Wisconsin, where stressors from actions that may incidentally take
Poweshiek skipperlings may be addressed in conservation plans, State
endangered species protections do not protect the species from
stochastic events and habitat fragmentation that are stressors to the
State's small and isolated populations.
In North Dakota, the fundamental purpose of the North Dakota
Trustlands (e.g., State school lands) management is to obtain a ``fair
market'' return from the lands while maintaining or improving their
condition and value (ND Department of Trustlands Web site https://www.land.nd.gov/surface/About.aspx). Consequently, if such land does
not produce income for the State, it may be subjected to deliberate
change in management strategy or ownership (e.g., sale at auction). The
major source of income on the North Dakota Trustlands is from grazing
and agricultural leases, with additional revenue generated from rights-
of-way, salt water disposal, and gravel and scoria mining (ND
Department of Trustlands Web site https://www.land.nd.gov/surface/About.aspx). At least two Dakota skipper sites are under North Dakota
State School management and are managed as hay lands.
Federal Regulations
The U.S. Forest Service (Forest Service or USFS) has designated the
Poweshiek skipperling and the Dakota skipper as sensitive species (a
species identified by a Regional Forester for which population
viability is a concern) in North Dakota (Forest Service 2011). The
Forest Service's objectives for sensitive species benefit Dakota
skipper and Poweshiek skipperling where they occur (or could occur) on
USFS lands; however, the majority of populations of both species do not
occur within USFS lands. The Poweshiek skipperling has been documented
at two sites on the Sheyenne National Grasslands; however, it has not
been observed since 2001 at one site and 1996 at the other. Therefore,
these Forest Service objectives, although promising, have little
ability to affect the rangewide status of the species. If Forest
Service lands were to be occupied by either species in the future,
these objectives may benefit the species at a local scale.
Canadian Regulations
Dakota skipper and Poweshiek skipperling are listed as threatened
under Canada's Species at Risk Act (SARA) (Environment Canada 2012.
Species at Risk Act Public Registry. <https://www.registrelep-sararegistry.gc.ca/sar/index/default_e.cfm>. Accessed September 19,
2014). Under SARA, take of both species is prohibited on Canadian
Federal lands, but the Poweshiek skipperling occurs only on non-Federal
lands in Canada, and only four or five Dakota skipper sites are on
Federal lands (Coalfields Community Pasture) in Canada. The Federal
Cabinet may create an order extending SARA's powers (e.g., to private
lands) if a species is insufficiently protected by provincial laws;
however, such action has not been taken for either of these species. In
May 2014, the COSEWIC status designation of Dakota skipper was changed
from threatened to endangered (https://www.cosewic.gc.ca/rpts/detailed_species_assessments_e.html accessed September 19, 2014). The
Dakota skipper is listed as threatened under the Manitoba Endangered
Species Act, and it is, therefore, unlawful to kill, injure, possess,
disturb, or interfere with the Dakota skipper; destroy, disturb, or
interfere with its habitat; or damage, destroy, obstruct, or remove a
natural resource on which the species depends for its life and
propagation (Manitoba Endangered Species Act https://www.gov.mb.ca/conservation/wildlife/legislation/endang_act.html, accessed February 7,
2012). The Poweshiek skipperling was recently listed as endangered in
Manitoba (https://www.gov.mb.ca/conservation/wildlife/sar/sarlist.html,
accessed December 28, 2012). There is no legal basis for protecting
threatened or endangered invertebrates in Saskatchewan, but since both
species are listed under SARA, the national government could step in to
protect the species in the province if the province does not act to
protect the species (Environment Canada. 2012. Species at Risk Act: A
Guide. https://www.sararegistry.gc.ca/approach/act/
[[Page 63734]]
Guide_e.cfm, accessed February 7, 2012).
To summarize, some of the regulatory mechanisms discussed above are
beneficial to populations of Dakota skipper and Poweshiek skipperling
at a local scale; however, most do not ameliorate stressors except for
harm to individuals in certain States. With the exception of the
regulation of some incidental take in Wisconsin, Minnesota, and Canada,
the statutory protections afforded by these statutes may do little to
protect Poweshiek skipperling or Dakota skipper from non-collection
stressors.
Factor E. Other Natural or Manmade Factors Affecting Its Continued
Existence
Habitat Fragmentation and Population Isolation
As habitat specialists, habitat fragmentation has a strong negative
effect on the distribution and abundance of the Dakota skipper and
Poweshiek skipperling because both are dependent on remnant native
tallgrass prairie or native mixed-grass prairie, and, in Michigan,
Poweshiek skipperling depends on native prairie fens. Habitat
fragmentation reduced once-extensive areas of these habitats to a
collection of patches of varying quality and isolation. The probability
of extinction within patches can be determined primarily by degradation
of habitat quality, management techniques (e.g., haying, prescribed
burns), and likelihood of stochastic events, such as wildfire or
floods.
Fragmentation of tallgrass prairie has degraded the genetic
diversity of remaining Dakota skipper populations (Britten and Glasford
2002, pp. 371-372). What may have once been a single population of
Dakota skippers spread across formerly extensive tallgrass and mixed-
grass prairie (McCabe 1981, p. 184) is now fragmented into about 171
separate sites where the species is known to be or may still be present
(sites with present (83) or unknown (88) status). The small genetic
differences among seven Dakota skipper populations in the southern
portion of the species' range suggest that they were formerly connected
(Britten and Glasford 2002, pp. 371-372). Each Dakota skipper
population is now subject to genetic drift that may erode its genetic
variability over time and possesses genetic qualities indicative of
inbreeding (Britten and Glasford 2002, pp. 371-372). Inbreeding lowers
the capacity of local populations to adapt to environmental changes and
may magnify the effect of deleterious alleles (genes with undesirable
effects on individuals or populations) (Nieminen et al. 2001, pp. 242-
243).
Preliminary results of genetic studies on the Poweshiek skipperling
show that there appears to be limited levels of genetic diversity in
the 32 tissue samples that were collected from the Scuppernong Prairie
site in Wisconsin, 7 samples from Manitoba, and 93 from 6 Michigan
populations in 2012 (Saarinen 2013, pers. comm.). Of greater concern
than loss of genetic diversity, however, may be demographics,
specifically the limited number of populations and population sizes
that may be too small to persist (Saarinen 2013, pers. comm.)
compounded by other stressors.
Poweshiek skipperlings are not wide dispersers (Burke et al. 2011,
p. 2279; Fitzsimmons 2012, pers. comm.); species experts have estimated
maximum dispersal distance to be less than 1.6 km (1.0 mi) (Westwood
2012b, pers. comm; Dana 2012b, pers. comm.). Its mobility, however, has
been ranked as less than that of Dakota skipper (Burke et al. 2011, p.
2279; Fitzsimmons 2012, pers. comm.); therefore, a more conservative
maximum dispersal distance may be more similar to that of the Dakota
skipper (less than 1 km (0.6 mi)). Most individuals may remain within a
single habitat patch during their 5-7 day adult life span; therefore,
local extinctions of the Poweshiek skipperling on isolated habitat
fragments are likely permanent unless one or more populations located
within 1.0-1.6 km (0.6-1.0 mi) are large enough to produce immigrants
to reestablish populations. Furthermore, fragmentation of tallgrass
prairie began in about 1830, and at least 85 to 99 percent of the
original prairie is now gone across the species' ranges (Samson and
Knopf 1994, p. 419). As a result, Poweshiek skipperling and Dakota
skipper populations are now scattered in fragments of this once-vast
ecosystem. The Poweshiek skipperling may not move across barriers; for
instance, in Manitoba, Poweshiek skipperlings have been observed
avoiding dispersal over short distances, even to suitable habitat, if a
barrier such as a road exists between suitable prairie habitat or
nectar sources (Westwood et al. 2012, p.18). Repopulation of Poweshiek
skipperling sites after extirpation has been observed (e.g., after a
flood) (Saunders 1995, p. 15), but source populations need to be
adjacent or very close.
Similarly, adult Dakota skippers have a short (5- to 7-day) life
span (Dana 1991, p. 32) and an estimated maximum dispersal distance to
be no greater than 1 km (0.6 mi) between patches of prairie habitat
separated by structurally similar habitats (Cochrane and Delphey 2002,
pp. 6, 32). Therefore, Dakota skipper and Poweshiek skipperling habitat
patches separated by more than 1 km (0.6 mi) are effectively isolated
from one another (McCabe 1981, p. 190; Swengel 1998). Extirpation of
small, isolated populations may occur over many years in some cases,
but may be inevitable where immigration from nearby populations is not
possible (Hanski et al. 1996, p. 535).
Because Dakota skipper and Poweshiek skipperling habitat is highly
fragmented and because the species are subject to local extinction,
their ability to disperse to reoccupy vacant habitat patches may be
crucial for their long-term persistence. Patch isolation and decreased
permeability of surrounding habitat acts as a dispersal barrier between
patches, ultimately decreasing genetic diversity within the patch
through genetic drift and inbreeding. If we assume isolation occurs
when a patch is more than 1.6 km (1.0 mi) from another patch, then
about 45 percent of Poweshiek skipperling locations with present or
unknown status are effectively isolated, and would not be recolonized
if extirpated (Service 2012 unpubl. data; Service 2014, unpubl. data).
Using a more conservative maximum dispersal of 1.0 km (0.6 mi),
approximately 55 percent of Poweshiek skipperling locations with
present or unknown status are effectively isolated. Isolation was a
factor in loss of a site at Hartford Beach State Park, South Dakota,
where the Poweshiek skipperling was extirpated due to habitat
succession and exotic plant invasion (Skadsen 2009, p. 4; Skadsen 2010,
pers. comm.), but was located too far from a source population for
natural recolonization to occur. Improved prairie management has since
markedly improved habitat quality, but the species has not been
detected since 2006 at Hartford Beach State Park (Skadsen 2009, p. 4;
Skadsen 2012, p. 4; Service 2014, unpubl. geodatabase). For Dakota
skipper, if we use a maximum dispersal distance of 1 km (0.6 miles),
approximately 63 percent of Dakota skipper sites with present or
unknown status are effectively isolated (Service 2014, unpubl.
geodatabase).
This simple analysis, however, probably underestimates the impacts
of habitat fragmentation on the species. Populations of both species
may only be near others that are too small to produce sufficient
numbers of immigrants. This is true for the Poweshiek skipperling in
Scuppernong Prairie in Wisconsin, for example, which is about 0.3 km
(0.2 mi)
[[Page 63735]]
from the Wilton Road population; fewer than 100 individuals have been
counted at this site each year, and the species was not observed in
2013 (See Population Distribution and Status). Numbers at Wilton Road
are currently too small (fewer than 12 individuals counted each year)
to produce sufficient numbers of emigrants to Scuppernong Prairie to
reestablish a viable population in the event of the latter's
extirpation. There is no population of Poweshiek skipperlings near the
Puchyan Prairie site (which is about 115 km (71 mi) from the nearest
site in Wisconsin); additionally, only a few individuals have been
observed at this site each year. In North Dakota, Orwig (1997, p. 3)
found that a 6-ha (15-ac) patch of Poweshiek skipperling habitat at
Hartleben Prairie was connected by grassland to another Poweshiek
skipperling population, but neither was considered a robust population
at the time and the species was not observed at either location in
2013. Only 2 of the 9 Poweshiek skipperling sites with present status
in Michigan are located within 1.6 km (1 mi) of another site; the rest
are completely isolated from other populations. Furthermore, most of
these populations consist of few individuals (see Population
Distribution and Status). Poweshiek skipperlings at Little Goose Lake
Fen, for example, are separated from other populations by at least 8 km
(5 mi)--too far for immigrants to repopulate the site. Furthermore,
Little Goose Lake Fen may contain too few Poweshiek skipperlings
(Michigan Natural Features Inventory 2011, unpubl. data; Cuthrell 2013,
pers. comm.) to generate sufficient numbers of immigrants. In addition,
poor habitat quality negatively influences the number and quality of
emigrants (Thomas et al. 2001, p. 1795; Matter et al. 2009, p. 1467).
Isolation is not likely alleviated by connections to low-quality
habitats that are not capable of producing emigrants at the numbers or
frequency sufficient to reliably repopulate nearby patches.
Even with proper prairie management at individual sites, extreme
weather patterns or severe weather events may significantly impact
Poweshiek skipperling and Dakota skipper populations, because they can
occur across a large geographic area. These events include extremely
harsh winters, late hard frosts following a spring thaw, severe storms,
flooding, fire, or cool damp conditions. Habitats isolated as a result
of fragmentation will not be recolonized naturally after local
extirpations, as described above. Dakota skipper and Poweshiek
skipperling numbers may decline due to the extirpation of isolated
local populations where recolonization is no longer possible, even
without further habitat destruction (Schweitzer 1989, unpaginated). The
likelihood of population extirpation may be directly related to the
size of habitat fragments. For example, in systematic surveys on
Minnesota prairies, Swengel and Swengel (1997, pp. 134-137; 1999, p.
284) found no Dakota skippers on the smallest remnants (less than 20 ha
(49 ac)), and significantly lower abundance on intermediate size (30-
130 ha (74-321 ac)) than on larger tracts (greater than 140 ha (346
ac)). These differences were unrelated to vegetation characteristics;
habitat area did not correlate significantly with vegetation type,
quality, or topographic diversity (Swengel and Swengel 1999, p. 284).
We assessed the stressor of small size and isolation of habitat for
163 Dakota skipper sites and 54 Poweshiek skipperling sites with
present or unknown status (Service 2012 unpubl. data; Service 2014,
unpubl. data). We considered small size and isolation of habitat to be
a stressor with a low-level impact on populations at sites that contain
more than 140 ha (346 ac) of native prairie or the species' habitat
onsite is located less than 1 km (0.6 mi) from habitat occupied by the
species on another site. If the sum of native prairie on the site under
review plus that on the nearby site(s) is less than 140 ha (346 ac),
then this stressor was considered to have a moderate or high impact on
populations. We considered small size and isolation of habitat to be a
stressor with moderate impacts on populations at sites where the
species' habitat is greater than 1 km (0.6 mi) from any other area
where the species is present, but contains more than 30 ha (74 ac) of
habitat for the species; or where the species' habitat is less than 1
km (0.6 mi) from occupied Dakota skipper and Poweshiek skipperling
habitat on another site, but the sum of native prairie on the site
under review plus that on the nearby site(s) is less than 140 ha (346
ac) and greater than 30 ha (74 ac). Sites that contain a small area of
Dakota skipper and Poweshiek skipperling habitat--no more than 30 ha
(74 ac)--and that are not within the 1-km (0.6-mi) estimated maximum
dispersal distance of occupied Dakota skipper habitat are considered to
have a stressor of high magnitude to those populations due to a
combination of their small size and isolation.
Although we were unsure of the size of many sites in Canada, most
sites were separated by more than 1 km (0.6 mi). Dakota skipper sites
in central Manitoba are generally greater than 158 ac (64 ha), but all
of the sites are separated by more than 1 km (0.6 mi), and many sites
are separated by many kilometers (Westwood 2013 pers. comm.).
Therefore, about 25 of the sites evaluated in Canada were thought to
have at least a moderate level of stressor from size and isolation. The
Canada sites where Dakota skippers are considered to be present are
approximately 200 km (125 mi) from the nearest North Dakota site, and
the Manitoba site is 166 km (103 mi) from the nearest Poweshiek
skipperling site in Minnesota.
Dakota skipper populations on about 31 percent of the evaluated
sites (50 of 163 sites) face a high level of impact due to a
combination of size and isolation (Service 2012 unpubl. data, 2014
unpubl. data). Approximately 31 percent of evaluated sites (50 sites)
face a moderate level of impact to populations due to small size and
isolation. About 39 percent of Dakota skipper sites (63 of the 163
evaluated sites) in the United States are either sufficiently large
(greater than 130 ha (346 ac)) or are close enough to other Dakota
skipper populations that small size and isolation is not a stressor.
Similarly, the stressor of small size and isolation has a high level of
impact on Poweshiek skipperling populations on about 39 percent of
rated sites (25 of 54 sites), on 22 sites (41 percent) the stressor is
considered to have a moderate level of impact to populations, and on 20
percent (11 of the 54 evaluated sites) of the sites, we do not consider
a small size and isolation to be a stressor. In a separate analysis
strictly looking at distances between Poweshiek skipperling sites where
the species is present, we found that only 4 sites are within 1 km (0.6
mi) of another site where the species is present (Service 2014, unpubl
geodatabase).
In summary, small, isolated populations face a current and ongoing
stressor of moderate to high severity to both the Dakota skipper and
Poweshiek skipperling. The stressor has a high impact to populations
when isolation is combined with small habitat fragments or small
populations; for example, where the population is too small to
supplement nearby populations without adverse genetic consequences to
the source population. Isolated populations occur throughout both
species' entire ranges; only 4 of the 12 Poweshiek sites with present
status are within the estimated maximum dispersal distance from one
another as are about 40 percent (64-69 of 171 sites) of Dakota skipper
sites with present or unknown occupancy. The small populations are
[[Page 63736]]
subject to erosion of genetic variability leading to inbreeding, which
lowers the ability of the species to adapt to environmental change.
Small populations occur rangewide for both species; for example,
surveyors have counted fewer than 100 individuals in all but 4
Poweshiek skipperling sites in 2011, all but one site surveyed in 2012,
and all sites surveyed in 2013.
Climate Change
Our analyses under the Act include consideration of the likely
effects of ongoing and projected changes in climate. The terms
``climate'' and ``climate change'' are defined by the Intergovernmental
Panel on Climate Change (IPCC). ``Climate'' refers to the mean and
variability of different types of weather conditions over time, with 30
years being a typical period for such measurements, although shorter or
longer periods also may be used (IPCC 2013, p. 1450). The term
``climate change'' thus refers to a change in the mean or variability
of one or more measures of climate (e.g., temperature or precipitation)
that persists for an extended period, typically decades or longer,
whether the change is due to natural variability, human activity, or
both (IPCC 2013, p. 1450). Various types of changes in climate can have
direct or indirect effects on species. These effects may be positive,
neutral, or negative and they may change over time, depending on the
species and other relevant considerations, such as the effects of
interactions of climate with other variables (e.g., habitat
fragmentation) (IPCC 2007, pp. 8-14, 18-19). We use our expert judgment
and appropriate analytical approaches to weigh relevant information,
including uncertainty, in our consideration of various aspects of
climate change.
As is the case with all stressors that we assess, even if we
conclude that a species is currently affected or is likely to be
affected in a negative way by one or more climate-related impacts, it
does not necessarily follow that the species meets the definition of an
``endangered species'' or a ``threatened species'' under the Act. If a
species is listed as endangered or threatened, knowledge regarding the
vulnerability of the species to, and known or anticipated impacts from,
climate-associated changes in environmental conditions can be used to
help devise appropriate strategies for its recovery.
Global climate change, with projections of increased variability in
weather patterns and greater frequency of severe weather events, as
well as warmer average temperatures, would affect remnant prairie
habitats and prairie fen habitats and may be a stressor that has
significant impacts on prairie butterflies such as Dakota skippers and
Poweshiek skipperling (Royer and Marrone 1992b, p. 12; Royer and
Marrone 1992a, pp. 22-23; Swengel et al. 2011, p. 336; Landis et al.
2012, p. 140). For example, climatic factors, particularly
precipitation and evaporation, play an important role in defining
suitable Dakota skipper habitat (McCabe 1981, pp. 189-192). Larval
Dakota skipper have ``hydrofuge glands'' that suggest an historical or
present need of the species for protection from flooding (McCabe 1981,
p. 181). Royer et al. (2008, p. 2) hypothesize that temperature and
relative humidity at or near the soil surface may be important factors
dictating larval survival, particularly since early stages live in a
silken nest within a few centimeters (2-3) (0.8-1.2 in) of the soil
surface during most of the summer (McCabe 1981, pp. 180-181, 189; Dana
1991, p. 16). Furthermore, both species and their habitats may
experience the effects of gradual shifts in plant communities and an
increase in catastrophic events (such as severe storms, flooding, and
fire) due to climate change, which are exacerbated by habitat
fragmentation. Isolated populations, specifically, Dakota skipper
populations and Poweshiek skipperling populations that are separated by
more than about 1 km (0.6 miles), are unlikely to recover from local
catastrophes unless sufficient numbers are successfully reintroduced,
for instance, through artificial propagation efforts.
Documentation of climate-related changes that have already occurred
throughout the range of the Dakota skipper and Poweshiek skipperling
(Johnson et al. 2005, pp. 863-871) and predictions of changes in annual
temperature and precipitation in the Midwest region of the United
States, such as Minnesota prairies (Galatowitsch et al. 2009, pp.
2017), Michigan fens (Landis et al. 2012, p. 140), South Dakota
(Cochrane and Moran 2011, entire), and throughout North America (IPCC
2007, p. 9) indicate that increased severity and frequency of droughts,
floods, fires, and other climate-related changes will continue in the
future. Recent studies have linked climate change to observed or
predicted changes in distribution or population size of insects,
particularly Lepidoptera (Wilson and Maclean 2011, p. 262). Native
remnant prairies have been reduced by 85 to 99.9 percent across the
range of both species (Samson and Knof 1994, p. 419)--this fact,
coupled with the low dispersal ability of both species, makes it
unlikely that populations may expand to new areas, for example, in a
northward direction, to adapt to changing climate. Climate change is a
stressor that has the potential to have severe impacts on the species;
however, at this time our knowledge of how these impacts may play out
is limited. All of the sites within the range of both species are in an
area that will experience the effects of climate change, but how those
effects will be manifested is uncertain.
Prairie Plant Harvesting
A potential, future stressor to the Dakota skipper and Poweshiek
skipperling is collection of purple coneflower (also known as black
samson echinacea), a predominate nectar source for both species, for
the commercial herbal remedy market (Skadsen 1997, p. 30). Biologists
surveying skipper habitats have not reported signs of plant collecting,
but illegal or unregulated harvest could become a problem in Dakota
skipper and Poweshiek skipperling habitats due to economic demand
(Skadsen 1997, p. 30). Currently, prairie plant harvesting is not
considered a threat that impacts the species; however, this situation
may change if the demand for echinacea increases.
Management for Invasive Species and Succession
Native prairie and native prairie fens must be managed to prevent
the indirect effects of invasive species and succession (processes of
change in species structure to an ecological community over time;
secondary succession is a disruption to succession that occurs due to
an event such as fire) to Dakota skippers and Poweshiek skipperlings.
If succession progresses too far, established shrubs or trees must be
removed in a way that avoids or minimizes damage to the native prairie.
When succession is well advanced, managers must use intensive methods,
such as fire management, to restore prairie plant communities. If not
done carefully, these actions may themselves harm local populations of
the butterflies (for example, see Factor A. The Present or Threatened
Destruction, Modification, or Curtailment of Its Habitat or Range). For
example, once smooth brome has invaded Poweshiek skipperling or Dakota
skipper habitat, it is challenging to eradicate it while minimizing
harm to the butterflies. Willson and Stubbendiecks (2000, p. 36)
recommended burning prairie habitats, annually in some cases, to
control smooth brome at the stage when the lateral shoots are
elongating.
[[Page 63737]]
In southwestern Minnesota and in other parts of Dakota skipper's
range, the optimum time to burn to control smooth brome may occur
during the time that the adult butterflies are active. Cutting or
grazing to remove smooth brome may have less intensive effects on
Poweshiek skipperling and Dakota skipper larvae and could be used as an
alternative to fire, although these techniques also pose a risk to both
species if carried out annually at isolated sites. Puchyan Prairie is
another example of a small and isolated population that is susceptible
to invasive species control efforts, if they are not conducted properly
(Swengel and Swengel 2012, p. 6), although the Wisconsin DNR proposed
control efforts that may improve habitat by removing reed canary grass,
Canada thistle, and glossy buckthorn (Wisconsin DNR 2012 in litt.;
Carnes 2012, in litt.).
If not appropriately managed with fire, grazing, or haying,
Poweshiek skipperling and Dakota skipper habitat is degraded due to
reduced diversity of native-prairie plants and eventually succeeds to
shrubby or forested habitats that are not suitable for either species.
At Hartford Beach State Park in South Dakota, for example, the
Poweshiek skipperling was extirpated (Skadsen 2009, p. 4) after lack of
management led to invasion by smooth sumac (Rhus glabra) and quaking
aspen (Populus tremuloides) (Skadsen 2006a, p. 5). Lack of management
may also increase the likelihood of invasion of exotic cool-season
grasses, such as Kentucky bluegrass and smooth brome (Mueller 2013,
pers. comm.), which do not grow when Dakota skipper and Poweshiek
skipperling larvae are feeding; thus a prevalence of these grasses
reduces food availability for the larvae.
As with invasive species, actions intended to reverse secondary
succession may be intensive and can themselves affect Poweshiek
skipperling and Dakota skipper populations. For example, Poweshiek
skipperling populations failed to recover after prescribed burns were
carried out at Kettle Moraine Low Prairie SNA after it had become
overgrown (Borkin 2011, in litt.).
Although carefully targeted herbicide treatments result in
beneficial control of undesired plants, broadcast chemical control of
exotic plants such as aerial spraying of leafy spurge and application
of broad-spectrum herbicides to control weeds in pastures also
eliminates native forbs that are important nectar sources for both
species (Royer and Marrone 1992a, pp. 10, 16, 28, 29, 33, 1992b, p. 17,
Orwig 1997, p. 7). For example, invasion of native prairie by exotic
species, primarily leafy spurge and Kentucky bluegrass, as well as
chemical control of exotic species, are documented stressors to Dakota
skippers at about 12 sites in North Dakota (Royer and Royer 2012b, pp.
15-16, 22-23). In repeated surveys, Royer and Marrone (1992a, p. 33)
observed a correlation between the disappearance of the Dakota skipper
and the advent of chemical weed control methods in North Dakota,
including the Sheyenne National Grasslands. Royer and Marrone (1992b,
p. 17) cited the combination of drought and grasshopper control
programs along the Red River Valley as having serious impacts on the
Poweshiek skipperling. Dana (1997, p. 5) concluded that herbicide use
for weed and brush control on private lands is the principal stressor
to the Hole-in-the-Mountain complex in Minnesota, where both butterfly
species have been documented.
Furthermore, herbicide or pesticide use in concert with other
management types may amplify other stressors to the butterflies.
Skadsen (2006b, p. 11), for example, documented the likely extirpation
of the Poweshiek skipperling at Knapp Ranch in South Dakota after a
July 2006 application of broadleaf herbicide associated with heavy
grazing. The degree and immediacy of the impact posed by broadcast
application of herbicides or pesticides is not precisely understood,
but may be mostly tied to the use of herbicides to control invasive
species on rangelands. If broad applications of herbicides are used in
ways that remove plants from rangelands that are important for
Poweshiek skipperling or Dakota skipper, then this is a potential
stressor on all privately owned sites where broadcast applications may
occur.
Indiscriminant use of insecticides for pest control on rangeland,
adjacent cropland, or forests is a stressor to populations of Poweshiek
skipperling and Dakota skipper. Insecticides used in agriculture, urban
gardens, and forests are a suspected cause of Colony Collapse Disorder
in bees by reducing resistance to parasites and pathogens and may have
similar effects on other insects (Beyers 2012, p. 1). Neonicotinyl
pesticides, such as the imidacloprid compound, for example, are a
commonly used seed dressing that spreads to nectar and pollen of
flowering crops (Whitehorn 2012, p. 1). The use of neonicotinoids on
agricultural crops has dramatically increased in the last ten years and
they are now the most widely used group of insecticides in the world
(Jeschke et al. 2011, pp. 2897-2898; Main et al. 2014, p. 2; Goulson
2013, pp. 1-2). Neonicotinoids persist in the environment (Goulson
2013, p. 1) and are thought to accumulate in the soil from repeated
applications over time (Hopwood et al. 2013, p. 4). Insects can be
exposed through multiple routes--neonicotinoids are used in seed
dressings, foliar spray, soil irrigation water, soil drench, granular
in pastures, tree injections, and topical applications to pets.
In the United States, six neonicotinoids are approved for use--
imidacloprid, thiamethoxam, clothianidin, dinotefuran, thiacloprid, and
acetamiprid (EPA 2014 Web site)--and it is estimated that more than 3.5
million pounds (56 million ounces) of neonicotinoids were applied to
nearly 127 million acres (51 million hectares) of agricultural crops
each year from 2009 to 2011. The presence and concentrations of
neonicotinoids at Dakota skipper and Poweshiek skipperling sites or
nearby agricultural fields that use neonicotinoid seed treatments or
other such treatments has not been assessed, however, in general,
nearly 100 percent of corn is known to be treated, and about 75 percent
of soybean seeds are known to be treated with neonicotinoids, for
example. Similarly, soybean aphid spraying occurs during the adult
flight period, is widespread, and applied aerially--this spray can
drift to nearby Dakota skipper or Poweshiek skipperling habitat. The
presence and concentrations of insecticides at Dakota skipper and
Poweshiek skipperling sites or nearby agricultural fields that utilize
soybean aphid spraying has not been assessed. The Minnesota Zoo has
proposed a study to investigate the levels of neonicotinoids, aphid
pesticides, and other insecticides that may be present at several
skipper sites in Minnesota and South Dakota.
The spread of nonnative gypsy moths (Lymantria dispar dispar) has
increased efforts to control this damaging species and may also be a
stressor, especially in the range of Poweshiek skipperling.
Insecticides used in the gypsy moth suppression programs typically
include Foray, a formulation of the bacterial insecticide Bacillus
thuringiensis kurstakii (Btk), or Gypchek, a viral insecticide specific
to gypsy moth caterpillars. Btk is known to be lethal to butterfly
larvae (e.g., Karner blue butterfly) (Carnes 2011, p. 1). In Wisconsin,
the gypsy moth suppression program is managed under State Statute 26.30
and Natural Resources Board Rule number 47, and Gypchek is used when
endangered or threatened moths or butterflies are present (Wisconsin
DNR, https://dnr.wi.gov/topic/ForestHealth/
[[Page 63738]]
GypsyMothPesticides.html, accessed May 24, 2012).
Herbicide and pesticide use was assessed at 15 present and unknown
Dakota skipper sites and 9 Poweshiek skipperling sites occupied with
present or unknown occupancy where we had sufficient information to
evaluate the stressor (Service 2012 unpubl.; 2014, unpubl. data). We
considered the level of impact to populations posed by herbicide and
pesticide use to be low if the site is only spot sprayed with
herbicides or pesticides when and where necessary (Smart et al. 2011,
p. 182) and their use is not expected to change in the future. The
level of stressor was considered to be moderate if the use of
herbicides is likely to increase at a site (e.g., in response to new or
expanding invasive species), but Dakota skipper and Poweshiek
skipperling habitat is unlikely to be exposed to broadcast
applications. The level of impact to populations posed by herbicide and
pesticide use was considered to be high at sites where herbicides are
likely to be broadcast over the entire site at least once every 4
years, or herbicide use has significantly reduced forb or nectar plant
density and diversity or is likely to in the future. The level of
impact to populations posed by herbicide and pesticide use was high at
5 of the 16 assessed Dakota skipper sites (2 in North Dakota and 3 in
South Dakota) and moderate at 2 sites--1 in North Dakota and 1 in South
Dakota. The level of impact to populations posed by herbicide and
pesticide use was considered to be high at 3 of the 9 assessed
Poweshiek skipperling sites (all 3 in South Dakota), and 1 site in
North Dakota had a moderate level of impact to populations.
In summary, some efforts to manage woody encroachment and invasive
species, such as herbicide use, can be a stressor to both Dakota
skipper and Poweshiek skipperling populations. Invasive species
management is a current and ongoing stressor of low to high impact to
populations, depending on the intensity and extent of the use, types of
techniques, and the compounding effects that may occur from varying
management. Medium- to high-level impacts of herbicide or pesticide use
to Dakota skipper and Poweshiek skipperling populations have been
documented in North and South Dakota. This stressor has a high impact
to populations when it is combined with other stressors, such as
management, that reduces or eliminates nectar food sources, or small
habitat fragments that are isolated from other source populations that
may replenish individuals killed by pesticides. Herbicide and pesticide
use may have direct or indirect effects on Dakota skipper and Poweshiek
skipperling. Although such activities occur, there is no evidence that
these activities alone have significant impacts on either species,
since their effects are often localized. However, these factors may
have a cumulative effect on the Dakota skipper and Poweshiek
skipperling when added to habitat curtailment and destruction because
dramatic population declines have occurred in both species (discussed
in Factor A). Invasive species and woody vegetation management helps to
maintain prairie habitats and can also be beneficial to populations of
both species, for example, when concentrated on affected areas through
spot spraying.
Pharmaceuticals
The effect of pharmaceutical residues in the environment on
nontarget animals is an emerging concern (Lange et al. 2009).
Ivermectin, a widely used and persistent veterinary pharmaceutical used
to treat cattle, is a chemical of emerging concern to the Dakota
skipper and Poweshiek skipperling. Ivermectin is an anthelmintic (drugs
that are used to treat infections with parasitic worms) that is spread
to prairie environments via the dung of grazing cattle (Lange et al.
2009, p. 2238). Lange et al. (2009, pp. 2234, 2238) found that skipper
butterflies are particularly vulnerable to ivermectin, due to their low
dispersive capacities and habitat preferences for soil. The extirpation
of the Dakota skipper in at least one South Dakota site (Sica Hollow
West) is possibly due to ivermectin that has leached into the
environment (Skadsen 2010, pers. comm.).
Pharmaceutical use is a stressor that has the potential to have
high-level impacts on populations of the Dakota skipper and Poweshiek
skipperling; however, at this time our knowledge of these impacts is
limited. Sites within the range of both species could experience the
effects of pharmaceuticals. Sites that experience grazing, however, are
particularly vulnerable to ivermectin use; these sites are primarily in
South Dakota, North Dakota, and Minnesota. The use of pharmaceuticals
such as ivermectin may have a cumulative effect on the Dakota skipper
and Poweshiek skipperling when added to habitat curtailment or
destruction, because habitat destruction leads to population declines
in populations of both species (discussed in Factor A).
Unknown Stressors Causing Population Declines
The sharp and broad declines of Poweshiek skipperling documented in
Iowa, Minnesota, North Dakota, and South Dakota are indicative of a
response to one or more stressors that have yet to be ascertained.
These unknown factors may consist of a combination of one or more of
the stressors described throughout Factors A, C, and E of this final
rule, or may be something that has not yet been identified. These
declines are reminiscent of the widely publicized decline of honey bees
(Apis mellifera) in that they seem sudden and mysterious (Spivak et al.
2011, p. 34). One hypothesis to explain the rapid decline of the
Poweshiek skipperling, and possibly the Dakota skipper, is that a newly
virulent pathogen or a new parasitoid has increased mortality above
normal levels (Dana 2013, pers. comm.).
One or more unidentified stressors have strongly impacted Poweshiek
skipperling populations in the western portion of its range, which
contains more than 80 percent of the species' site records. Unknown
stressors may be the current factor with the most significant impacts
to Poweshiek skipperling in Minnesota, North Dakota, and South Dakota,
where populations experienced a sudden decline to undetectable numbers
after about 2003. Until about 2003, Poweshiek skipperling was regarded
as the most frequently and reliably encountered prairie-obligate
skipper in Minnesota, which contains nearly 50 percent of all known
Poweshiek skipperling locations. Numbers and distribution dropped
dramatically in subsequent years, however, and the species has not been
seen in Minnesota since 2007, with the exception of 2 individuals
observed at one location in 2013 (Weber 2014, in litt.; Dana 2014,
pers. comm.). Similar recent dramatic declines were observed in North
Dakota, South Dakota, and Iowa (See Background of this rule).
Recent declines of Dakota skippers indicate that this species may
also be impacted by unknown stressors. The Dakota skipper was last
detected at one site in Iowa in 1992. Only one individual was detected
in Minnesota during 2012 surveys, which included 18 sites with previous
records; surveys for undiscovered populations were also carried out on
23 prairie remnants without previous records for the species. Only six
individual Dakota skippers were detected at one site in Minnesota
during 2013 surveys, which included 15 sites with previous records and
12 prairie remnants without
[[Page 63739]]
previous records for the species (Service 2014, unpubl. geodatabase.).
Based on similar conditions in other parts of the species' range,
similar trends are anticipated outside of Minnesota.
Indications of recent declining trends have been observed in South
Dakota and North Dakota. In South Dakota, for example, the proportion
of positive surveys at known sites has fluctuated over time; however,
the 2012 and 2013 surveys had the lowest positive detection rate (38
percent and 32 percent, respectively) for the last 15 years (since
1996)--much less than comparable survey years in South Dakota (for
years with more than 20 surveys). The Dakota skipper was detected at 12
of the 23 sites surveyed during 2012 in North Dakota (and 2 additional
sites with no previous Dakota skipper records); average encounter
frequencies observed across the State in 2012 (9.4 encounters per
hour), however, were about half of those observed during the 1996-1997
State-wide surveys (ND State average = 17.4 encounters per hour). The
Dakota skipper was not detected at the three sites that were surveyed
in 2013 in North Dakota with previous records of the species. Recent
survey results and similar life histories suggest that the Dakota
skipper can be reasonably compared to the Poweshiek skipperling in
their potential rate of decline--that is, it is reasonable to assume
that Dakota skipper may be vulnerable to the same unidentified factors
that have caused dramatic declines in the Poweshiek skipperling, with a
slight delay in timing.
In summary, the results of extensive surveys in the western portion
of the Poweshiek skipperling's range have documented the species'
response to unknown factors and indicate that they are a current
stressor of high severity. Although to date the Dakota skipper has not
experienced such dramatic declines as the Poweshiek skipperling,
similar unknown stressors on Dakota skipper populations likely have
affected the species in Minnesota and Iowa, where recent surveys
indicate that the species may be largely absent or at undetectable
levels.
Summary of Factor E
Based on our analysis of the best available information, we have
identified several natural and manmade factors affecting the continued
existence of the Dakota skipper and Poweshiek skipperling. Effects of
small population size, population isolation, and loss of genetic
diversity are likely stressors that have significant impacts on both
species. Environmental effects resulting from climatic change,
including increased flooding and drought, are expected to become severe
in the future and result in additional habitat losses; however, we have
limited information on how this stressor may affect either species.
Possibly the stressor with the most significant impacts to the
Poweshiek skipperling are one or more unknown factors that have led to
widespread and sharp population declines in the western portion of the
species' range. These unknown stressors may also be the cause of the
recent declines observed in Dakota skipper populations over much of its
range. Anthropogenic factors such as insecticide, herbicide, and
pesticide use are also stressors to both species, and unregulated
prairie plant harvest has the potential to become a stressor in the
future (See Factor E). Collectively, these stressors have operated in
the past, are impacting both species now, and will continue to impact
the Dakota skipper and Poweshiek skipperling in the future.
Conservation Efforts To Reduce Other Natural or Manmade Factors
Affecting Its Continued Existence
Several of the conservation activities discussed under Factor A. in
this rule may address some factors discussed under Factor E, for
example, life-history studies of both species, studies to examine the
effects of various management strategies on the species and its
habitat, and habitat restoration techniques such as controlled burns on
sites divided into several management units.
The Minnesota Zoo has initiated a new program to research Poweshiek
skipperling and Dakota skipper propagation. If this program is
successful, it could facilitate reintroduction and augmentation into
areas where the species has declined or disappeared, to bolster the
small genetic pool and small numbers. In 2012, researchers at the
Minnesota Zoo and the University of Michigan initiated a genetics study
of Dakota skipper and Poweshiek skipperling using specimens at some of
the few sites where either species was observed in 2012, specifically a
few sites in Michigan, Wisconsin, and Manitoba for the Poweshiek
skipperling and sites in North Dakota, South Dakota, and Manitoba for
Dakota skipper. Too few (one adult male) Dakota skipper were observed
in Minnesota to obtain samples from that State in 2012. Similarly, only
six individuals were observed at one Minnesota site in 2013. The
genetics studies will help inform captive propagation and
reintroduction efforts, which may help alleviate stressors associated
with small and isolated populations.
In 2011, researchers collected 32 adult Dakota skippers from a
combination of 4 sites in South Dakota and translocated them to
Pickerel Lake State Park, where the species was last detected in 2008
(Skadsen 2011, pp. 7-9). The phenology of the adult flight period and
purple coneflower blooms did not coincide, and no Dakota skippers were
observed at the release site during subsequent visits in 2011 or 2012
(Skadsen 2011, pp. 8-9, Skadsen 2012, p. 4). Researchers and managers
continue to develop prairie restoration and management goals for this
and the Hartford Beach State Park site in South Dakota (Skadsen 2011,
p. 9; Skadsen 2012b, p. 7).
The Minnesota Zoo has also begun a study to investigate the levels
of neonicotinoids, aphid pesticides, and other insecticides present at
several skipper sites in Minnesota and at least one site in South
Dakota.
We are unaware of any conservation efforts that directly address
the impacts of climate change to Dakota skippers or Poweshiek
skipperlings. We are unaware of any conservation efforts that address
the possible effects of pharmaceuticals on the Poweshiek skipperling
and Dakota skipper.
Cumulative Effects From Factors A Through E
Many of the stressors described in this final rule may cumulatively
or synergistically impact the Dakota skipper and Poweshiek skipperling
beyond the scope of each individual stressor. For example, improper
grazing management alone may only affect portions of Dakota skipper or
Poweshiek skipperling habitat; however, improper grazing combined with
invasive plants, herbicide use, and drought may collectively result in
substantial habitat loss, degradation, or fragmentation across large
portions of the species' ranges. In turn, climate change may exacerbate
those effects, further diminishing habitat and increasing the isolation
of already declining and isolated populations, making them more
susceptible to genetic drift or catastrophic events such as fire,
flooding, and drought. Further, nonagricultural development such as
gravel mining or housing development not only can directly destroy
habitat, but also can increase fragmentation of habitat by increasing
associated road development. Additionally, draining prairie fens will
increase invasive plant and woody vegetation encroachment. Numerous
stressors are likely acting
[[Page 63740]]
cumulatively to further increase impacts on the already vulnerable,
small, and isolated populations of Poweshiek skipperling and Dakota
skipper.
Determination
Dakota Skipper
We carefully assessed the best scientific and commercial
information available regarding the past, present, and future threats
to the Dakota skipper. Dakota skippers are obligate residents of
undisturbed (remnant, untilled) high-quality prairie, ranging from wet-
mesic tallgrass prairie to dry-mesic mixed-grass prairie. Native
tallgrass prairies have been reduced by 85 to 99.9 percent of their
former area, and native mixed-grass prairies have been reduced by 71.9
to 99 percent of their former area in North Dakota, Manitoba, and
Saskatchewan. The Dakota skipper was once a common prairie butterfly
widely dispersed in five States, extending from Illinois to North
Dakota, and portions of two Canadian provinces. However, its range is
now substantially reduced such that the Dakota skipper is restricted to
small patches of fragmented native-prairie remnants in portions of
three States and two Canadian provinces. Recent survey data indicate
that the Dakota skipper has declined to zero or to undetectable levels
in approximately 77 percent of sites where it had been recorded
rangewide. It is presumed extirpated from Illinois and Iowa and no
longer occurs in eastern Minnesota.
Much of the rangewide decline in the species has been observed in
the last few years. Since 1988, researchers have surveyed 10 or more
sites in 25 years; the average positive detection rate for those years
is 63 percent rangewide. Since 2009, the percent of surveyed sites with
positive detections of the species has dropped from 63 percent in 2009,
to 41 percent in 2010, 36 percent in 2011, 37 percent in 2012, and 22
percent in 2013. While these types of lows in detections have been
observed in past years, for example, in the early 1990s, the numbers of
individuals observed in 2013 were the lowest ever recorded, despite
extensive survey effort. Dakota skippers currently occupy sites in
northeastern South Dakota, North Dakota, western Minnesota, southern
Manitoba, and southeastern Saskatchewan.
Of the 264 historical locations, the species is presumed extirpated
or possibly extirpated from at least 93 (35 percent) of those sites,
and the occupancy of the species is unknown at approximately 88 (33
percent) sites. Of the 88 sites where the occupancy is unknown, at
least 78 sites are subject to one or more stressors that have a
moderate to high impact on those populations--these sites are
distributed across Minnesota, North Dakota, and South Dakota. Three
sites with unknown occupancy were not evaluated for stressors, due to
lack of information. The 7 sites with unknown occupancy without
moderate- to high-level stressors are scattered in various counties in
Minnesota and South Dakota, and the skipper is thought to still be
present at approximately 83 (31 percent) of the 264 historical
locations, although 22 of these sites have not been surveyed since
2002. Of those 83 sites, at least 73 sites are subject to one or more
stressors that have a moderate to high impact on those populations,
such as conversion to agriculture, lack of management, and small size
and isolation. Four sites were not evaluated due to lack of
information, and the remaining six sites that do not have stressors
with moderate- to high-level impacts to populations occur in scattered
counties in Minnesota and South Dakota.
Approximately half (40 of 83) of the locations where the species is
considered to be present are primarily located on privately owned fall-
hayed prairies in Canada, mostly within 2 isolated complexes, and have
not been surveyed since 2007. All 40 of those Canadian sites have one
or more stressors of moderate to high level of impact to populations.
Approximately 15 populations in Canada are on lands that are being used
in ways that are favorable to the Dakota skipper (i.e., late-season
haying conducted at least every other year and there is no indication
that native plant species diversity is declining due to timing or
frequency of mowing), and the stressors at those sites are not
immediate. However, we are aware of only one of these Canadian
populations that is protected (on Federal land). The remaining sites
where the species is considered to be present are about equally
distributed among Minnesota (11 sites), North Dakota (16 sites), and
South Dakota (14 sites). Sites with stressors with moderate to high
level of impacts to populations occur in all three States.
Many factors likely contributed to the Dakota skipper's decline,
and numerous factors, acting individually or synergistically, continue
today (see Summary of Factors Affecting the Species). We identified
many stressors to the species, some of which rise to the level of
threats that contribute to the listing status for each species. Habitat
loss and degradation have impacted the Dakota skipper, curtailing the
ranges of the species (see Factor A). Extensive historical conversion
of prairie and associated habitats, nearly complete in some areas, has
isolated many Dakota skipper populations. These small and isolated
populations are subject to loss of genetic diversity through genetic
drift (see Factor E) and are susceptible to a variety of stochastic
(e.g., wildfires, droughts, and floods) and deterministic (e.g.,
overgrazing, invasive species) factors (see Factor A) that may kill all
or a substantial proportion of a population.
Although much of the habitat conversion occurred in the past, the
effects of the dramatic reduction and fragmentation of habitat have
persistent and ongoing effects on the viability of populations;
furthermore, conversion of native prairies to agriculture or other uses
is still occurring today. The life history of the species exacerbates
the threats caused by the fragmentation and degradation of the species'
habitat (see Factors A and E) as the Dakota skipper is not likely to
recolonize distant sites due to its short adult life span, single
annual flight, and limited dispersal ability. Therefore, the species'
extirpation from a site is likely permanent unless it is near another
site from which it can emigrate. Furthermore, because the larvae are
located at or near the soil surface, they are more vulnerable to fire
(Factor A); herbicides, pesticides, and other chemicals (see Factor E);
desiccation due to changing climate (see Factor E); or flooding (see
Factor A).
Within the remaining native-prairie patches, degradation of habitat
quality is now the primary threat to the Dakota skipper (see Factor A).
Of the various threats to Dakota skipper habitat, conversion, invasive
species, secondary succession, and reduction in the diversity of
native-prairie plant communities have moderate- to high-level impacts
to populations throughout the range of the Dakota skipper. An array of
other factors including nonagricultural development, chemical
contaminants, pesticides, and intensive grazing are also current and
ongoing threats to the Dakota skipper and its habitat (see Factors A
and E). Current and ongoing prairie management practices, such as
indiscriminate use of herbicides or intensive grazing that reduces or
eliminates food sources, contribute to the species' imperilment at
sites throughout the range of the species (see Factors A and E).
Unknown factors may be the current threat that has the most
significant impacts to the Dakota skipper in Iowa and Minnesota, where
populations experienced a sudden decline to
[[Page 63741]]
undetectable numbers in the most recent years (see Factor E). Based on
recent data, similar conditions in other parts of the Dakota skipper's
range, and the similarities in life histories between Poweshiek
skipperling and Dakota skipper, similar declining trends are
anticipated in other parts of the Dakota skipper's range due to unknown
factors, and may only be a few years behind those declines experienced
by other species, such as the Poweshiek skipperling (see Factor E).
Existing regulatory mechanisms vary across the species' ranges, and
although mechanisms do exist that protect the species from direct take
in Iowa and Minnesota, these mechanisms do not sufficiently mitigate
threats to the species (see Factor D). Climate change may affect Dakota
skipper, especially increased frequency of extreme climatic conditions
such as flooding and drought, but there is limited information on the
exact nature of impacts that these species may experience. Recent
temperature and precipitation trends indicate that certain aspects of
climate change may be occurring in Dakota skipper range now (see Factor
E).
The Act defines an endangered species as any species that is ``in
danger of extinction throughout all or a significant portion of its
range'' and a threatened species as any species ``that is likely to
become endangered throughout all or a significant portion of its range
within the foreseeable future.'' We find that the Dakota skipper is
likely to become endangered throughout all of its range within the
foreseeable future, based on the immediacy, severity, and scope of the
threats described above. These threats are exacerbated by small
population sizes, the loss of redundancy and resiliency of these
species, and the continued inadequacy of existing protective
regulations. A few scattered populations of Dakota skipper are doing
relatively well, however, and are in habitats that have low or non-
immediate threats.
Canada has approximately 15 populations on lands that are being
utilized in a manner conducive to the conservation of Dakota skipper,
and the threats at those sites are not imminent. However, few of these
populations are protected, many are vulnerable to changes in land use,
landowners may not be aware of the species presence and may change land
use, and the sites have not been surveyed in the last 5 years. While a
few new locations of Dakota skipper populations continue to be
discovered in North and South Dakota, the numbers of individuals
observed at those sites is generally low, and extirpation at previously
known sites seems to be occurring at a faster rate than new
discoveries. The decreasing numbers of sites with positive detections
and the decreasing numbers of individuals observed at each site
throughout its range, including known sites in Minnesota, North Dakota,
and South Dakota, is likely to continue. Therefore, on the basis of the
best available scientific and commercial information, we are listing
the Dakota skipper as a threatened species in accordance with sections
3(20) and 4(a)(1) of the Act.
We find that an endangered species status is not appropriate for
the Dakota skipper because some Dakota skipper populations still appear
to be doing relatively well (populations detected during the last
survey year, numbers appear stable, lower levels of threats and
stressors)--primarily in North Dakota, South Dakota, Manitoba, and
Saskatchewan. About 14 to 15 sites in Manitoba are used in a manner
conducive to the conservation of Dakota skipper (haying after the adult
flight period), and the threats at those sites are not imminent.
Furthermore, we believe the species to be present in at least 6 sites
that do not have documented stressors of a moderate- to high-level
impact to populations, primarily in scattered counties in Minnesota and
South Dakota. Additionally, a few new Dakota skipper sites continue to
be discovered in suitable prairie habitat in North Dakota and South
Dakota.
Under the Act and our implementing regulations, a species may
warrant listing if it is endangered or threatened throughout all or a
significant portion of its range. Because we have determined that the
Dakota skipper is a threatened species throughout all of its range, no
portion of its range can be ``significant'' for purposes of the
definitions of ``endangered species'' and ``threatened species.'' See
the Final Policy on Interpretation of the Phrase ``Significant Portion
of Its Range'' in the Endangered Species Act's Definitions of
``Endangered Species'' and ``Threatened Species'' (79 FR 37577).
Poweshiek Skipperling
We carefully assessed the best scientific and commercial
information available regarding the past, present, and future threats
to the Poweshiek skipperling. Poweshiek skipperling are obligate
residents of undisturbed (remnant, untilled) high-quality prairie,
ranging from wet-mesic tallgrass prairie to dry-mesic mixed-grass
prairie. Native tallgrass prairies have been reduced by 85 to 99.9
percent of their former area, and native mixed-grass prairies have been
reduced by 72 to 99 percent of their former area in North Dakota,
Manitoba, and Saskatchewan. The Poweshiek skipperling was once a common
prairie butterfly widely dispersed in eight States, extended from
Michigan to North Dakota, and portions of Manitoba, Canada. However,
its range is now substantially reduced such that the Poweshiek
skipperling is restricted to small patches of fragmented native-prairie
remnants in portions of two States and one Canadian province. The
species is presumed extirpated from Illinois and Indiana, and the
status of the species is unknown in four of the six States with
relatively recent records (within the last 20 years). Recent survey
data indicate that the Poweshiek skipperling has declined to zero or to
undetectable levels in approximately 96 percent of sites where it has
ever been recorded.
A drastic decline in this species has been observed rangewide very
recently. Between 1985 and 2003, researchers surveyed 10 or more sites
in 7 different years (excluding new sites in the first year); the
average positive detection rate for those years is 71 percent
rangewide. Since 2003, the percent of surveyed sites with positive
detections of the species has dropped to an average of 31 percent each
year (2004-2013), with a low of 12 percent at sites surveyed in 2012
and 2013. Despite recent substantial survey efforts in those States,
the Poweshiek skipperling has not been recorded in Iowa since 2007,
when it was observed at 1 site; in North Dakota since 2001, when it was
observed at 1 site, nor in South Dakota since 2008, when it was
observed at 3 sites. The species was not observed in North Dakota,
South Dakota, or Minnesota during 2012 surveys, for example. The
Poweshiek skipperling was observed at one site in Minnesota in 2007 and
there was a sighting of a Poweshiek skipperling at one site in 2013,
although no photographs or specimens were taken to confirm the
sighting. Iowa sites were not surveyed in 2012, and the species was not
detected in 2013. Poweshiek skipperling have historically been
documented at approximately 296 sites; now we consider the species to
be present at only 12 of those sites--one of these is considered a sub-
site of a larger site.
The only confirmed extant (present) populations of Poweshiek
skipperling are currently restricted to 1 small and isolated native-
prairie remnant in Wisconsin, 9 small and isolated prairie fen remnants
in Michigan, and a prairie complex in Manitoba. The species may also be
present at one site in Minnesota. These sites represent less than 5
percent of the total number of sites ever
[[Page 63742]]
documented for the species. The numbers observed at these sites are
relatively small (fewer than 100 individuals at all sites surveyed in
2013), and all of these sites have at least one documented threat that
has moderate to high impacts on those populations. The strongest
population in the United States, a prairie fen in Michigan with
relatively high and fairly consistent numbers observed each year
(numbers observed per minute ranged from 0.2 to 2.2 during the last 6
survey years), for instance, is under threat from intense development
pressure. The Tallgrass Prairie Preserve site in Manitoba also has
relatively high numbers observed each year; however, this site is
impacted by several immediate, moderate- to high-level threats,
including the encroachment of invasive plants and woody vegetation,
flooding, and isolation from the nearest site by hundreds of
kilometers. In addition, recent unplanned fires in 2009 and 2011
affected large portions of the site. Poweshiek skipperling is
considered to have unknown occupancy at 75 sites--throughout the range
of the species (Iowa, Michigan, Minnesota, North Dakota, and South
Dakota), 49 of these sites were included in the threats assessment. Of
the 49 sites where the occupancy is unknown that had sufficient
information to assess, at least 42 sites are subject to one or more
threats that have a moderate to high impact on those populations. These
sites are throughout the range of the species in Iowa, Michigan,
Minnesota, North Dakota, and South Dakota.
Many factors likely contributed to the Poweshiek skipperling's
decline, and numerous major threats, acting individually or
synergistically, continue today (see Summary of Factors Affecting the
Species). Habitat loss and degradation have impacted the Poweshiek
skipperling, curtailing the ranges of both species (see Factor A).
Extensive historical conversion of prairie and associated habitats,
nearly complete in some areas, has isolated many Poweshiek skipperling
populations. These small and isolated populations are subject to loss
of genetic diversity through genetic drift (see Factor E) and are
susceptible to a variety of stochastic (e.g., wildfires, droughts, and
floods) and deterministic (e.g., overgrazing, invasive species) factors
(see Factor A) that may kill all or a substantial proportion of a
population. Although much of the habitat conversion occurred in the
past, the effects of the dramatic reduction and fragmentation of
habitat have persistent and ongoing effects on the viability of
populations; furthermore, conversion of native prairies to agriculture
or other uses is still occurring today. The life history of the species
exacerbates the threats caused by the fragmentation and degradation of
its habitat (see Factors A and E) as Poweshiek skipperlings are not
likely to recolonize distant sites due to their short adult life span,
single annual flight, and limited dispersal ability. Therefore, the
Poweshiek skipperling's extirpation from a site is likely permanent
unless it is near another site from which it can emigrate. Furthermore,
because the larvae are located at or near the soil surface, they are
more vulnerable to fire (Factor A), herbicides, pesticides, and other
chemicals (see Factor E); desiccation due to changing climate (see
Factor E); or changes in hydrology (see Factor A).
Within the remaining native-prairie patches, degradation of habitat
quality is now the primary threat to the Poweshiek skipperling (see
Factor A). Of the various threats to Poweshiek skipperling habitat,
conversion, invasive species, secondary succession, and reduction in
the diversity of native-prairie plant communities have moderate- to
high-level impacts to populations throughout the range of the Poweshiek
skipperling. An array of other factors including nonagricultural
development, chemical contaminants, pesticides, and intensive grazing
are also current and ongoing threats to the Poweshiek skipperling and
its habitat (see Factors A and E). Current and ongoing prairie
management practices, such as indiscriminate use of herbicides or
intensive grazing that reduces or eliminates food sources, contribute
to the species' imperilment, particularly in North Dakota, South
Dakota, and Minnesota (see Factors A and E). Unknown factors may be the
current threat that has the most significant impacts to the Poweshiek
skipperling species in Iowa, Minnesota, North Dakota, and South Dakota,
where populations experienced a sudden decline to undetectable numbers
in the most recent years (see Factor E). Existing regulatory mechanisms
vary across the species' ranges, and although mechanisms do exist in
Iowa, Michigan, Minnesota, and Wisconsin that protect the species from
direct take, these mechanisms do not sufficiently mitigate threats to
the Poweshiek skipperling (see Factor D). Climate change may affect the
Poweshiek skipperling, especially increased frequency of extreme
climatic conditions such as flooding and drought, but there is limited
information on the exact nature of impacts that the species may
experience. Recent temperature and precipitation trends indicate that
certain aspects of climate change may be occurring in Poweshiek
skipperling range now (see Factor E).
The Act defines an endangered species as any species that is ``in
danger of extinction throughout all or a significant portion of its
range'' and a threatened species as any species ``that is likely to
become endangered throughout all or a significant portion of its range
within the foreseeable future.'' We find that the Poweshiek skipperling
is presently in danger of extinction throughout its entire range, based
on the immediacy, severity, and scope of the threats described above.
These threats are exacerbated by small population sizes, the loss of
redundancy and resiliency of these species, and the continued
inadequacy of existing protective regulations. There are only 12
locations where we believe the species to be present, and all of those
sites are subject to at least one or more ongoing and immediate threats
that have moderate- to high-level effects on those populations.
Therefore, on the basis of the best available scientific and commercial
information, we are listing the Poweshiek skipperling as endangered in
accordance with sections 3(6) and 4(a)(1) of the Act.
We find that a threatened species status is not appropriate for the
Poweshiek skipperling because the unknown factors have significant
impacts to the species throughout most of its range and have occurred
in a short timeframe. Sharp population declines have not been detected
at the few remaining sites where the species is still present, but all
of these sites are currently experiencing one or more threats that have
moderate- to high-level impacts to populations. Based on recent data
and similar conditions in other parts of Poweshiek skipperling range,
similar declining trends are anticipated in other parts of the range of
the species, and may only be a few years behind those declines
experienced by the species in Iowa, Minnesota, North Dakota, and South
Dakota (see Factor E). The impacts of the unknown factors on
populations are exacerbated by habitat curtailment and destruction and
other factors such as the effects of small and isolated populations due
to habitat fragmentation.
Under the Act and our implementing regulations, a species may
warrant listing if it is endangered or threatened throughout all or a
significant portion of its range. Because we have determined that the
Poweshiek skipperling is an endangered species throughout all of its
range, no portion of its range can be
[[Page 63743]]
``significant'' for purposes of the definitions of ``endangered
species'' and ``threatened species.'' See the Final Policy on
Interpretation of the Phrase ``Significant Portion of Its Range'' in
the Endangered Species Act's Definitions of ``Endangered Species'' and
``Threatened Species'' (79 FR 37577).
Available Conservation Measures
Conservation measures provided to species listed as endangered or
threatened under the Act include recognition, recovery actions,
requirements for Federal protection, and prohibitions against certain
practices. Recognition through listing results in public awareness and
conservation by Federal, State, Tribal, and local agencies, private
organizations, and individuals. The Act encourages cooperation with the
States and requires that recovery actions be carried out for all listed
species. The protection required by Federal agencies and the
prohibitions against certain activities are discussed, in part, below.
The primary purpose of the Act is the conservation of endangered
and threatened species and the ecosystems upon which they depend. The
ultimate goal of such conservation efforts is the recovery of these
listed species, so that they no longer need the protective measures of
the Act. Subsection 4(f) of the Act requires the Service to develop and
implement recovery plans for the conservation of endangered and
threatened species. The recovery planning process involves the
identification of actions that are necessary to halt or reverse the
species' decline by addressing the threats to its survival and
recovery. The goal of this process is to restore listed species to a
point where they are secure, self-sustaining, and functioning
components of their ecosystems.
Recovery planning includes the development of a recovery outline
shortly after a species is listed, preparation of a draft and final
recovery plan, and revisions to the plan as significant new information
becomes available. The recovery outline guides the immediate
implementation of urgent recovery actions and describes the process to
be used to develop a recovery plan. The recovery plan identifies site-
specific management actions that will achieve recovery of the species,
measurable criteria that determine when a species may be downlisted or
delisted, and methods for monitoring recovery progress. Recovery plans
also establish a framework for agencies to coordinate their recovery
efforts and provide estimates of the cost of implementing recovery
tasks. Recovery teams (comprising species experts, Federal and State
agencies, nongovernmental organizations, and stakeholders) are often
established to develop recovery plans. When completed, the recovery
outlines, draft recovery plans, and the final recovery plans will be
available on our Web site (https://www.fws.gov/endangered), or from our
Twin Cities Ecological Services Fish and Wildlife Office (see FOR
FURTHER INFORMATION CONTACT).
Implementation of recovery actions generally requires the
participation of a broad range of partners, including other Federal
agencies, States, Tribes, nongovernmental organizations, businesses,
and private landowners. Examples of recovery actions include habitat
restoration (e.g., restoration of native vegetation), research, captive
propagation and reintroduction, and outreach and education. The
recovery of many listed species cannot be accomplished solely on
Federal lands because their range may occur primarily or solely on non-
Federal lands. To achieve recovery of these species requires
cooperative conservation efforts on private, State, and Tribal lands.
When species are listed, funding for recovery actions will be
available from a variety of sources, including Federal budgets, State
programs, and cost-share grants for non-Federal landowners, the
academic community, and nongovernmental organizations. In addition,
pursuant to section 6 of the Act, the States of Iowa, Michigan,
Minnesota, North Dakota, South Dakota, and Wisconsin would be eligible
for Federal funds to implement management actions that promote the
protection and recovery of the Poweshiek skipperling and Dakota
skipper. Information on our grant programs that are available to aid
species recovery can be found at: https://www.fws.gov/grants.
Please let us know if you are interested in participating in
recovery efforts for the Dakota skipper or Poweshiek skipperling.
Additionally, we invite you to submit any new information on these
species whenever it becomes available and any information you may have
for recovery planning purposes (see FOR FURTHER INFORMATION CONTACT).
Section 7(a) of the Act requires Federal agencies to evaluate their
actions with respect to any species that is proposed or listed as
endangered or threatened and with respect to its critical habitat, if
any is designated. Regulations implementing this interagency
cooperation provision of the Act are codified at 50 CFR part 402. If a
species is listed subsequently, section 7(a)(2) of the Act requires
Federal agencies to ensure that activities they authorize, fund, or
carry out are not likely to jeopardize the continued existence of the
species or destroy or adversely modify its critical habitat. If a
Federal action may adversely affect a listed species or its critical
habitat, the responsible Federal agency must enter into formal
consultation with the Service.
Federal agency actions within the species habitat that may require
conference or consultation or both as described in the preceding
paragraph include, but are not limited to, management and any other
landscape-altering activities on Federal lands such as actions within
the jurisdiction of the NRCS; land management by the U.S. Forest
Service; issuance of section 404 Clean Water Act permits by the U.S.
Army Corps of Engineers; land management by the U.S. Fish and Wildlife
Service; construction and management of gas pipeline, wind facilities
and associated infrastructure, and power line rights-of-way by the
Federal Energy Regulatory Commission; construction and maintenance of
roads or highways by the Federal Highway Administration; and land
management within branches of the Department of Defense (DOD). Examples
of these types of actions include activities funded or authorized under
the Farm Bill Program, Environmental Quality Incentives Program, Clean
Water Act (33 U.S.C. 1251 et seq.), Partners for Fish and Wildlife
Program, and DOD construction activities related to training or other
military missions.
Poweshiek Skipperling
The Act and its implementing regulations set forth a series of
general prohibitions and exceptions that apply to all endangered
wildlife. The prohibitions of section 9(a)(2) of the Act, codified at
50 CFR 17.21 for endangered wildlife, in part, make it illegal for any
person subject to the jurisdiction of the United States to take
(includes harass, harm, pursue, hunt, shoot, wound, kill, trap,
capture, or collect; or to attempt any of these), import, export, ship
in interstate commerce in the course of commercial activity, or sell or
offer for sale in interstate or foreign commerce any listed species.
Under the Lacey Act (18 U.S.C. 42-43; 16 U.S.C. 3371-3378), it is also
illegal to possess, sell, deliver, carry, transport, or ship any such
wildlife that has been taken illegally. Certain exceptions apply to
agents of the Service and State conservation agencies.
[[Page 63744]]
Dakota Skipper
Under section 4(d) of the Act, the Service has discretion to issue
regulations that we find necessary and advisable to provide for the
conservation of threatened wildlife. We may also prohibit by regulation
with respect to threatened wildlife any act prohibited by section
9(a)(1) of the Act for endangered wildlife. Exercising this discretion,
the Service has developed a 4(d) rule containing all the general
prohibitions and exceptions to those prohibitions; these are found at
50 CFR 17.31 and 50 CFR 17.32. For the Dakota skipper, the Service has
developed a 4(d) rule that is tailored to the specific threats and
conservation needs of this species. As a means to promote conservation
efforts on behalf of the Dakota skipper, we are finalizing a 4(d) rule
for this species that modifies the standard protections for threatened
wildlife found at 50 CFR 17.31. In the case of a 4(d) rule, the general
regulations (50 CFR 17.31 and 17.71) applying most prohibitions under
section 9 of the Act to threatened species do not apply to that
species, and the 4(d) rule contains the prohibitions necessary and
advisable to conserve that species.
As discussed above, the primary factors supporting the
determination of threatened species status for the Dakota skipper are
habitat loss and degradation of native prairies, including conversion
of native prairie for agriculture or other development; ecological
succession and encroachment of invasive species and woody vegetation;
certain fire, haying, and grazing management that reduces the
availability of certain native-prairie grasses and flowering herbaceous
plants to the Dakota skipper; some fire management; flooding; existing
regulatory mechanisms that are inadequate to mitigate threats to the
species; loss of genetic diversity; small size and isolation of remnant
patches of native prairie; indiscriminate use of herbicides that
reduces or eliminates nectar sources; climate conditions such as
drought; and other unknown factors.
The Act does not specify particular prohibitions, or exceptions to
those prohibitions, for threatened species. Instead, under section 4(d)
of the Act, the Secretary of the Interior has the discretion to issue
such regulations as she deems necessary and advisable to provide for
the conservation of such species. The Secretary also has the discretion
to prohibit by regulation with respect to any threatened species, any
act prohibited under section 9(a)(1) of the Act. Exercising this
discretion, the Service has developed general prohibitions (50 CFR
17.31) and exceptions to those prohibitions (50 CFR 17.32) under the
Act that apply to most threatened species. Alternately, for other
threatened species, the Service develops specific prohibitions and
exceptions that are tailored to the specific conservation needs of the
species. In such cases, some of the prohibitions and authorizations
under 50 CFR 17.31 and 17.32 may be appropriate for the species and
incorporated into a rule under section 4(d) of the Act, but the section
4(d) rule will also include provisions that are tailored to the
specific conservation needs of the threatened species and may be more
or less restrictive than the general provisions at 50 CFR 17.31.
In recognition of efforts that provide for conservation and
management of the Dakota skipper and its habitat in a manner consistent
with the purposes of the Act, this 4(d) rule outlines the prohibitions,
and exceptions to those prohibitions, necessary and advisable for the
conservation of the Dakota skipper.
Conversion of grasslands for the production of agricultural crops
poses a threat to the Dakota skipper because it may directly destroy
the species' habitat, increase isolation of populations by impeding
dispersal, and increase the risk posed by drift of herbicides and
pesticides. A wide variety of peer-reviewed publications and government
reports have documented recent conversion of native grassland. In
addition, economic and policy incentives are likely to continue to
place pressure on landowners to convert native grassland from ranching
to agricultural cropland (Doherty et al. 2013, p. 14); Sylvester et al.
2013, p. 13; Rashford et al. 2011, p. 282; Stephens et al. 2008, p. 6;
(Congressional Research Service (CRS) 2007, p. 5, United States
Government Accountability Office (USGAO) 2007, p. 15, Stephens et al.
2008, p. 6, Rashford et al. 2011, p. 282, Sylvester et al. 2013, p.
13). Grassland loss in the western corn belt may be occurring at the
fastest rate observed since the 1920s and 1930s and at a rate
comparable to that of deforestation in Brazil, Malaysia, and Indonesia
(Wright and Wimberly 2013, p. 5). Between 2006 and 2011, destruction of
native grassland was mostly concentrated in North Dakota and South
Dakota, east of the Missouri River, an area corresponding closely to
the range of the Dakota skipper (Wright and Wimberly 2013, p. 2). In
northeastern South Dakota, one of the few remaining strongholds for the
Dakota skipper, about 269,000 acres (108,907 ha) of grassland was
lost--primarily to cropland--between 2006 and 2012 (Reitsma et al.
2014, p. 3).
As with agricultural policies (Doherty et al. 2013, p. 15),
prohibitions against take of Dakota skippers could interact with other
factors to affect the rates at which native grassland is converted in
the range of the species. Less than 20 percent of the grassland in the
Prairie Pothole Region of the United States is permanently protected
(Doherty et al. 2013, p. 7), and the vast majority of remaining
grassland is privately owned. The conservation of ``working
landscapes'' based on ranching and livestock operations (`grass-based
farming') is frequently a priority of programs to conserve native
grassland ecosystems in the northern Great Plains (e.g., U.S. Fish and
Wildlife Service 2011, p. 5). Exempting incidental take of Dakota
skippers that may result from grazing and other routine livestock
ranching activities will afford us more time to protect the species'
habitats in these areas and will facilitate the cooperation and
partnerships with livestock producers necessary to recover the species.
Three primary factors have led us to determine that it is necessary
and advisable to exempt take of Dakota skippers caused by certain
ranching activities, including grazing. First, a variety of
socioeconomic and policy factors are leading to the conversion of
native grasslands for the production of agricultural crops, as
summarized above. Whereas conversion of native grassland for crop
production would result in a permanent loss of Dakota skipper habitat
and may also exacerbate other threats (e.g., pesticide drift) to the
species, grasslands can remain suitable for Dakota skippers when grazed
(see below and Dana 1991, p. 54; Schlicht 1997, p. 5; Skadsen 1997, pp.
24-29). By exempting take of Dakota skippers caused by grazing, we
acknowledge the positive role that some ranchers have already played in
conserving Dakota skippers and the importance of preventing any
additional loss and fragmentation of native grasslands as the result of
activities in areas that could support the species.
Second, although some grazing practices pose a threat to Dakota
skipper, grazing may also be an effective tool to improve Dakota
skipper habitat when carefully applied in cooperation and consultation
with private landowners, public land managers, and grazing experts. In
eastern South Dakota, Dakota skipper populations were deemed secure at
some sites managed with rotational grazing that was sufficiently light
to maintain native plant species diversity (Skadsen 1997,
[[Page 63745]]
pp. 24-29), and grazing may also benefit Dakota skippers by increasing
coverage of mid-height grasses, such as little bluestem, relative to
tallgrasses, such as big bluestem and Indiangrass (Dana 1991, p. 54).
Intensive early-season grazing can reduce the extent of Kentucky
bluegrass, a nonnative species that invades prairie habitats and
competes with native plant species (DeKeyser et al. 2013, p. 86). In
addition, grazing may also inhibit the establishment of smooth brome
and help to enhance coverage and diversity of native plants in prairies
that have been invaded by nonnative cool-season grasses (U.S. Fish and
Wildlife Service 2006, p. 2; DeKeyser et al. 2009, p. 18; Smart et al.
2013, p. 686). Because grazing can lead to adverse conditions for the
Dakota skipper, however, the Service encourages collaboration with
private landowners, public land managers (e.g., Skadsen 2006, p. 5),
State and Federal conservation agencies, and nongovernmental
organizations to identify, implement, monitor, and refine grazing
practices that are conducive to the species' conservation.
Third, recovery of the Dakota skipper will depend on the protection
and restoration of high-quality habitats for the species on private
lands and on public lands that are grazed or hayed by private
individuals under lease or other agreements. Conservation of Dakota
skippers on these lands will require the development and implementation
of complex, individualized, and long-term management agreements that
rely on robust monitoring of Dakota skipper populations and habitat
features. All of these agreements will require a willingness on the
part of the private ranchers to collaborate with the Service and our
partners to implement, monitor, and adapt conservation grazing
practices in a manner that allows for stable or growing Dakota skipper
populations. This type of cooperative approach is more likely to take
place and to be successful if we exempt take caused by grazing and the
other activities that we specify in the 4(d) rule.
In some geographic areas, such as McHenry County, North Dakota, the
Dakota skipper almost exclusively inhabits relatively flat and moist
prairie habitats that are mowed for hay. In these areas we do not
encourage a switch to grazing without careful consideration of the
potential consequences to the Dakota skipper. These habitats, referred
to as calcareous or ``alkaline prairies'' by McCabe (1979, p. 17; 1981,
p. 179); ``wet mesic'' by Royer and Marrone (1992, p. 21); and ``Type
A'' by Royer et al. (2008, p. 14), are distinguished from other Dakota
skipper habitats by relatively flat topography and certain plant
community and soil characteristics (Lenz 1999, pp. 5-7; Royer et al.
2008, pp. 14-15). Dakota skippers appear to be generally absent from
this type of habitat in North Dakota where it is grazed, due to a shift
away from a plant community that is suitable for the species (McCabe
1979, p. 17; 1981, p. 179). The shift in plant community composition
and adverse effects to Dakota skipper populations may occur rapidly
(McCabe 1981, p. 179; Royer and Royer 1998, p. 23). The conversion of
similar habitats in Manitoba from haying to grazing may be a major
threat to the Dakota skipper there as well (Webster 2007, pp. i-ii, 6).
In contrast, limited or ``light rotational grazing'' of habitats on
steep dry-mesic slopes in Saskatchewan may not conflict with Dakota
skipper conservation (Webster 2007, p. ii).
The reduced vulnerability of habitats on dry-mesic slopes to the
effects of grazing may be due, in part, to the tendency for grazing
pressure to be lighter in sloped areas. The steepness of habitats
occupied by Dakota skippers in Saskatchewan, for example, limits their
use for grazing (Webster 2007, p. ii). Steep slopes may also play a
role in reducing the adverse effects of grazing at some sites in South
Dakota--at one grazed site inhabited by the Dakota skipper, for
example, habitat on steep slopes was ``in good condition,'' whereas
``lesser slopes'' were ``moderately grazed'' and some areas were
``overgrazed'' (Skadsen 1999a, p. 29).
In the proposed rule, we cited the lack of any examples of strong
populations of Dakota skippers where the relatively moist and flat
(`Type A') habitats are grazed as evidence that it would not be
necessary and advisable to exempt take caused by grazing in certain
counties where `Type A' habitats are found. As stated above, we still
do not recommend a change to grazing on `Type A' habitats occupied by
the Dakota skipper unless a cooperative plan is developed to ensure
that it will be done in a manner that conserves the species in the
affected habitats. Nevertheless, in light of the great importance that
cooperative relationships with certain public land management agencies
and private livestock producers will play in conserving the Dakota
skipper, we find that it is necessary and advisable to exempt take that
may be caused by grazing on non-Federal lands regardless of geographic
area. We do not expect this to result in a significant change in
management from haying to grazing because other factors, such as the
costs of building fences and developing livestock watering facilities,
are more important factors that will influence this land management
decision.
Provisions of the 4(d) Rule for the Dakota Skipper
Section 4(d) of the Act states that ``the Secretary shall issue
such regulations as [s]he deems necessary and advisable to provide for
the conservation'' of species listed as a threatened species.
Conservation is defined in the Act to mean ``to use and the use of all
methods and procedures which are necessary to bring any endangered
species or threatened species to the point at which the measures
provided pursuant to [the Act] are no longer necessary.'' Additionally,
section 4(d) states that the Secretary ``may by regulation prohibit
with respect to any threatened species any act prohibited under section
9(a)(1).''
The courts have recognized the extent of the Secretary's discretion
under this standard to develop rules that are appropriate for the
conservation of a species. For example, the Secretary may find that it
is necessary and advisable not to include a taking prohibition, or to
include a limited taking prohibition. See Alsea Valley Alliance v.
Lautenbacher, 2007 U.S. Dist. Lexis 60203 (D. Or. 2007); Washington
Environmental Council v. National Marine Fisheries Service, and 2002
U.S. Dist. Lexis 5432 (W.D. Wash. 2002). In addition, as affirmed in
State of Louisiana v. Verity, 853 F.2d 322 (5th Cir. 1988), the rule
need not address all the threats to the species. As noted by Congress
when the Act was initially enacted, ``once an animal is on the
threatened list, the Secretary has an almost infinite number of options
available to him with regard to the permitted activities for those
species. [S]he may, for example, permit taking, but not importation of
such species,'' or [s]he may choose to forbid both taking and
importation but allow the transportation of such species, as long as
the measures will ``serve to conserve, protect, or restore the species
concerned in accordance with the purposes of the Act'' (H.R. Rep. No.
412, 93rd Cong., 1st Sess. 1973).
Section 9 prohibitions make it illegal for any person subject to
the jurisdiction of the United States to take (including harass, harm,
pursue, shoot, wound, kill, trap, capture, or collect; or attempt any
of these), import or export, ship in interstate commerce in the course
of commercial activity, or sell or offer for sale in interstate or
foreign commerce any wildlife species listed as an endangered species,
without written authorization. It also is illegal under
[[Page 63746]]
section 9(a)(1) of the Act to possess, sell, deliver, carry, transport,
or ship any such wildlife that is taken illegally. Prohibited actions
consistent with section 9 of the Act are outlined for threatened
species in 50 CFR 17.31(a) and (b). Through this 4(d) rule, all
prohibitions in 50 CFR 17.31(a) and (b) apply to the Dakota skipper
except in the specific instances as outlined below. The 4(d) rule will
not remove or alter in any way the consultation requirements under
section 7 of the Act.
Routine Livestock Operations and Maintenance of Recreational Trails and
Rights-of-Way
Incidental take that is caused by the routine livestock ranching
and other specified trail and rights-of-way maintenance activities
described below and that are implemented on private, State, and tribal
lands and on other lands not under Federal jurisdiction (e.g. lands
owned by county governments or local governments) will not be
prohibited, as long as those activities are otherwise legal and
conducted in accordance with applicable State, Federal, tribal, and
local laws and regulations. For the purposes of this 4(d) rule, routine
livestock ranching and recreational trail and rights-of-way maintenance
activities include the items listed below. Except as explicitly stated
below, these activities must be associated with livestock ranching for
this 4(d) rule to apply.
(1) Fence Construction and Maintenance: Fences are an essential
tool for livestock and ranch management. In addition, the strategic
distribution of fencing is also necessary to implement multi-cell
rotational grazing systems, which may be necessary to improve grazing
management and provide a conservation benefit to Dakota skipper
habitat.
(2) Livestock Gathering and Management: The installation and
maintenance of corrals, loading chutes, and other livestock working
facilities are critical to ranch operations. These activities may be
carried out with only minimal impacts to Dakota skipper if carefully
sited with respect to the location and distribution of important Dakota
skipper habitat.
(3) Development and Maintenance of Livestock Watering Facilities:
Without a suitable water source in a pasture, livestock ranching is
impossible. The proper distribution of livestock watering sources is
also a prerequisite to implementing improved grazing management via the
use of multi-cell rotational grazing systems that may be necessary to
conserve Dakota skipper habitat and to provide a conservation benefit
to the species on grazed sites. This activity includes both the initial
development of water sources and their maintenance. Dugout ponds, for
example, typically require a cleanout after 15 to 20 years.
(4) Noxious Weed Control: State and county laws require landowners
to control noxious weeds on their property, and the timing of control
actions is usually dependent on the growth stage of the weed species.
Control of noxious weeds may also be important to protect Dakota
skipper habitat because native plant diversity declines when nonnative
plant species invade and become established in prairies (Boettcher et
al. 1993, p. 35). Broadcast application of herbicides, however, may
result in significant deterioration of native plant diversity in
prairies (Smart et al. 2011, p. 184). Therefore, incidental take of
Dakota skipper that may result from spraying of herbicides would be
exempt except as a result of broadcast spraying, which we define as the
application of herbicides evenly across the entire application area.
Note that herbicide applications would not affect the Dakota skipper if
they do not affect the limited areas where the species is present.
Broadcast applications of herbicides that do not affect habitats
occupied by the Dakota skipper would not result in take of the species,
and thus would not result in violation of section 9 of the Act. Take
that may occur as a result of mowing that is carried out for the
purpose of controlling one or more noxious weed species is also
exempted from the take prohibitions under section 9 of the Act by
issuance of this 4(d) rule.
(5) Haying: Stock cows need to be maintained through the non-
growing season though supplemental feeding with hay; thus, haying
(cutting grass and other vegetation for drying and use as livestock
feed) is a critical component of ranch activity. Dakota skippers occur
on several native hayland sites--sites where the native-prairie
vegetation is mowed for hay. For the purposes of this rule, native
hayland does not include lands that had previously been plowed and were
then replanted to native or nonnative vegetation. Native hayland may
include, however, areas within transportation (e.g., road, highway,
railroad) rights-of-ways and corridors where native grassland is mowed
for hay. Native haylands are typically cut in August, after the
needlegrass (Hesperostipa spp. or Nassella viridula, or both) awns
drop. Incidental take of Dakota skippers that occurs as a result of
haying no earlier than July 16 (after July 15) is exempted from the
take prohibitions under section 9 of the Act by issuance of this 4(d)
rule. Dakota skippers are unlikely to occur in replanted grasslands
(grasslands replanted on formerly plowed or cultivated lands) or in
tame hayland or grassland (hayland or grassland planted to and
comprising primarily nonnative grass species, such as smooth brome
(Bromus inermis inermis)). Therefore, mowing replanted and tame
grasslands before July 16 would not result in take of Dakota skippers
and would thus not result in a violation of section 9 of the Act.
(6) Mowing Section Line Rights-of-Way and Recreational Trails:
Section line rights-of-way and some recreational trails need to be
mowed several times during the growing season to ensure that snow will
not catch and block vehicle access and that they are suitable for
hiking and other intended recreational activities, respectively.
Section line rights-of-way typically comprise disturbed soil that has
been contoured for a roadway and are likely to contain only small
proportions of Dakota skipper habitat at any affected site. Therefore,
impacts to Dakota skipper populations are likely to be minimal, and any
incidental take that is a result of mowing of section line rights-of-
way and recreational trails will be exempt from the take prohibitions
of section 9 of the Act. Recreational trails are travel ways
established either through construction or use that are intended for
and passable by at least one or more of the following: foot traffic,
bicycles, in-line skates, wheelchairs, or cross-country skis.
Incidental take that may be caused by mowing recreational trails does
not need to be associated with livestock ranching for the 4(d) rule to
apply.
(7) Livestock (Cattle, Bison, or Horse) Grazing: Incidental take of
Dakota skippers that may result from grazing on private, State, or
tribal land is exempt from the take prohibitions of section 9 of the
Act.
We may issue permits to carry out otherwise prohibited activities
involving endangered and threatened wildlife species under certain
circumstances. Regulations governing permits are codified at 50 CFR
17.22 for endangered species, and at 17.32 for threatened species. With
regard to endangered wildlife, a permit must be issued for the
following purposes: For scientific purposes, to enhance the propagation
or survival of the species, and for incidental take in connection with
otherwise lawful activities.
It is our policy, as published in the Federal Register on July 1,
1994 (59 FR 34272), to identify to the maximum
[[Page 63747]]
extent practicable at the time a species is listed, those activities
that would or would not constitute a violation of section 9 of the Act.
The intent of this policy is to increase public awareness of the effect
of a final listing on proposed and ongoing activities within the range
of a listed species. Based on the best available information, the
following actions are unlikely to result in a violation of section 9,
if these activities are carried out in accordance with existing
regulations and permit requirements; this list is not comprehensive:
(1) Unauthorized collecting, handling, possessing, selling,
delivering, carrying, or transporting of the species, including import
or export across State lines and international boundaries, except for
properly documented antique specimens of these taxa at least 100 years
old, as defined by section 10(h)(1) of the Act;
(2) Unauthorized modification, removal, or destruction of the
prairie vegetation, soils, or hydrology in which the Dakota skipper and
Poweshiek skipperling are known to occur;
(3) The unauthorized release of biological control agents that
attack any life stage of these species, including the unauthorized use
of herbicides, pesticides, or other chemicals in habitats in which the
Poweshiek skipperling or Dakota skipper is known to occur;
(4) Introduction of nonnative species that compete with or prey
upon the Dakota skipper and Poweshiek skipperling or their food
sources, such as the introduction of nonnative leafy spurge, reed
canary grass, or glossy buckthorn, to the State of Iowa, Michigan,
Minnesota, North Dakota, South Dakota, and Wisconsin; and
(5) Unauthorized discharge of chemicals or fill material into any
wetlands in which the Poweshiek skipperling or Dakota skipper are known
to occur.
Questions regarding whether specific activities would constitute a
violation of section 9 of the Act should be directed to the Twin Cities
Ecological Services Fish and Wildlife Office (see FOR FURTHER
INFORMATION CONTACT). Requests for copies of the regulations concerning
listed animals and general inquiries regarding prohibitions and permits
may be addressed to the U.S. Fish and Wildlife Service, Endangered
Species Permits, 5600 American Blvd., West, Suite 990, Bloomington, MN
(telephone 612-713-5350; facsimile 612-713-5292).
Required Determinations
National Environmental Policy Act (42 U.S.C. 4321 et seq.)
We have determined that environmental assessments and environmental
impact statements, as defined under the authority of the National
Environmental Policy Act (NEPA; 42 U.S.C. 4321 et seq.), need not be
prepared in connection with listing a species as an endangered or
threatened species under the Endangered Species Act. We published a
notice outlining our reasons for this determination in the Federal
Register on October 25, 1983 (48 FR 49244).
Government-to-Government Relationship With Tribes
In accordance with the President's memorandum of April 29, 1994
(Government-to-Government Relations with Native American Tribal
Governments; 59 FR 22951), Executive Order 13175 (Consultation and
Coordination With Indian Tribal Governments), and the Department of the
Interior's manual at 512 DM 2, we readily acknowledge our
responsibility to communicate meaningfully with recognized Federal
Tribes on a government-to-government basis. In accordance with
Secretarial Order 3206 of June 5, 1997 (American Indian Tribal Rights,
Federal-Tribal Trust Responsibilities, and the Endangered Species Act),
we readily acknowledge our responsibilities to work directly with
tribes in developing programs for healthy ecosystems, to acknowledge
that tribal lands are not subject to the same controls as Federal
public lands, to remain sensitive to Indian culture, and to make
information available to tribes.
The Sisseton-Wahpeton Oyate, Flandreau Santee Sioux Tribe, Turtle
Mountain Band of Chippewa, Three Affiliated Tribes, Spirit Lake Sioux
Tribe, and Standing Rock Sioux Tribe are the main Tribes affected by
this final rule. We began government-to-government consultation with
these tribes prior to the publication of the proposed rule, through the
public comment period, and during the development of the final listing
determination.
We sent letters in September 2012 to each Tribe seeking early input
regarding the species status review and to offer government-to-
government consultation. We sent notification letters in October and
November of 2013 to each Tribe describing the critical habitat
exclusion process under section 4(b)(2) of the Act, and we engaged in
conversation with the Tribes about the proposed listing and critical
habitat rules to the extent possible. We have maintained contact with
Flandreau Santee Sioux Tribe, Turtle Mountain Chippewa, Three
Affiliated Tribes, Spirit Lake Sioux Tribe, and Standing Rock Sioux
Tribe through letters, phone calls, and emails, and we notified each
tribe when documents pertaining to the listing and critical habitat
rules were made available.
We have coordinated several survey efforts with Sisseton-Wahpeton
Oyate since 1995 and held an informational meeting for the Tribe in
April 2014, to better explain the proposed listing and designation of
critical habitat. We met with representatives from the Turtle Mountain
Chippewa in May 2014, and conducted a site visit at that time to
evaluate areas proposed for designation as critical habitat. We did not
receive comments from the Sisseton-Wahpeton Oyate, Three Affiliated
Tribes, Standing Rock Sioux Tribe, Flandreau Santee Sioux Tribe, Turtle
Mountain Chippewa, or the Spirit Lake Nation. However, notification of
the available economic analysis screening memorandum for the critical
habitat proposal was provided to all Tribes in the species' ranges at
the time it was made available to the public.
References Cited
A complete list of references cited in this rulemaking is available
on the Internet at https://www.regulations.gov and upon request from the
Twin Cities Ecological Services Field Office (see FOR FURTHER
INFORMATION CONTACT).
Authors
The primary authors of this final rule are the staff members of the
Twin Cities Ecological Services Field Office.
List of Subjects in 50 CFR Part 17
Endangered and threatened species, Exports, Imports, Reporting and
recordkeeping requirements, Transportation.
Regulation Promulgation
Accordingly, we amend part 17, subchapter B of chapter I, title 50
of the Code of Federal Regulations, as follows:
PART 17--[AMENDED]
0
1. The authority citation for part 17 continues to read as follows:
Authority: 16 U.S.C. 1361-1407; 1531-1544; 4201-4245; unless
otherwise noted.
0
2. Amend Sec. 17.11(h) by adding entries for ``Skipper, Dakota'' and
``Skipperling, Poweshiek'' to the List of Endangered and Threatened
Wildlife in alphabetical order under ``Insects'' to read as follows:
[[Page 63748]]
Sec. 17.11 Endangered and threatened wildlife.
* * * * *
(h) * * *
--------------------------------------------------------------------------------------------------------------------------------------------------------
Species Vertebrate
-------------------------------------------------- population where Critical Special
Historic range endangered or Status When listed habitat rules
Common name Scientific name threatened
--------------------------------------------------------------------------------------------------------------------------------------------------------
* * * * * * *
Insects
* * * * * * *
Skipper, Dakota............... Hesperia dacotae. U.S.A. (IA, IL, NA............... T 851 NA 17.47(b)
MN, ND, SD);
Canada
(Manitoba,
Saskatchewan).
* * * * * * *
Skipperling, Poweshiek........ Oarisma poweshiek U.S.A. (IA, IL, NA............... E 851 NA NA
IN, MI, MN, ND,
SD, WI,); Canada
(Manitoba).
* * * * * * *
--------------------------------------------------------------------------------------------------------------------------------------------------------
* * * * *
0
3. Amend Sec. 17.47 by adding paragraph (b) to read as follows:
Sec. 17.47 Special rules--insects.
* * * * *
(b) Dakota skipper (Hesperia dacotae).
(1) Which populations of the Dakota skipper are covered by this
special rule? This rule covers the distribution of Dakota skipper in
the United States.
(2) Prohibitions. Except as noted in paragraph (b)(3) of this
section, all prohibitions and provisions of Sec. Sec. 17.31 and 17.32
apply to the Dakota skipper.
(3) Exemptions from prohibitions. Incidental take of Dakota skipper
will not be a violation of section 9 of the Act if it occurs as a
result of the following activities (except where explicitly stated
otherwise, these activities must be associated with livestock
ranching):
(i) Fence construction and maintenance.
(ii) Livestock gathering and management. The installation and
maintenance of corrals, loading chutes, and other livestock working
facilities must be carefully sited with respect to the location and
distribution of important Dakota skipper habitat.
(iii) Development and maintenance of livestock watering facilities.
(iv) Noxious weed control. Incidental take of Dakota skipper that
results from spraying of herbicides is not a violation of section 9 of
the Act, except such take that results from broadcast spraying, which
is the application of herbicides evenly across the entire application
area. Incidental take that results from mowing to control one or more
noxious weed species would also not be a violation of section 9 of the
Act.
(v) Haying. For the purposes of this rule, native haylands do not
include lands that had previously been plowed and were then replanted
to native or nonnative vegetation, but native haylands do include areas
within transportation (e.g., road, highway, railroad) rights-of-ways
and corridors where native grasses are mowed for hay. Haying of native
haylands no earlier than July 16 (after July 15) would not be a
violation of section 9 of the Act. Mowing of replanted grasslands
(grasslands replanted on formerly plowed or cultivated lands) or tame
haylands or grasslands (planted hayland or grassland comprising
primarily nonnative grass species, such as smooth brome (Bromus inermis
inermis)) would also not be a violation of section 9 of the Act at any
time of the year.
(vi) Mowing section line rights-of-way and recreational trails.
Mowing of section line rights-of-way (typically disturbed soil that has
been contoured for a roadway) would not be a violation of section 9 of
the Act. Mowing of recreational trails (travelways established either
through construction or use that are intended for and passable by foot
traffic, bicycles, in-line skates, wheelchairs, or cross-country skis)
would not be a violation of section 9 of the Act, regardless of whether
the trails are associated with livestock ranching.
(vii) Livestock (cattle, bison, or horse) grazing on private,
State, or tribal land.
Dated: October 15, 2014.
Stephen Guertin,
Acting Director, U.S. Fish and Wildlife Service.
[FR Doc. 2014-25190 Filed 10-23-14; 8:45 am]
BILLING CODE 4310-55-P
