Endangered and Threatened Wildlife and Plants; Threatened Status for Dakota Skipper and Endangered Status for Poweshiek Skipperling, 63573-63625 [2013-24175]
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Vol. 78
Thursday,
No. 206
October 24, 2013
Part II
Department of the Interior
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Fish and Wildlife Service
50 CFR Part 17
Endangered and Threatened Wildlife and Plants; Threatened Status for
Dakota Skipper and Endangered Status for Poweshiek Skipperling;
Endangered and Threatened Wildlife and Plants; Designation of Critical
Habitat for Dakota Skipper and Poweshiek Skipperling; Proposed Rules
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Federal Register / Vol. 78, No. 206 / Thursday, October 24, 2013 / Proposed Rules
DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[FWS–R3–ES–2013–0043; 4500030113]
RIN 1018–AY01
Endangered and Threatened Wildlife
and Plants; Threatened Status for
Dakota Skipper and Endangered
Status for Poweshiek Skipperling
Fish and Wildlife Service,
Interior.
ACTION: Proposed rule.
AGENCY:
We, the U.S. Fish and
Wildlife Service, propose to list the
Dakota skipper as a threatened species
and the Poweshiek skipperling as an
endangered species under the
Endangered Species Act of 1973, as
amended. If we finalize this rule as
proposed, it would extend the Act’s
protections to the Dakota skipper and
the Poweshiek skipperling. The effect of
this regulation is to add the Dakota
skipper and the Poweshiek skipperling
to the List of Endangered and
Threatened Wildlife. We also propose a
special rule under section 4(d) of the
Act that outlines the prohibitions
necessary and advisable for the
conservation of the Dakota skipper, if it
is listed as a threatened species.
DATES: Written Comments: We will
accept comments received or
postmarked on or before December 23,
2013. Comments submitted
electronically using the Federal
eRulemaking Portal (see ADDRESSES
section, below) must be received by
11:59 p.m. Eastern Time on the closing
date. We must receive requests for
public hearings, in writing, at the
address shown in the ADDRESSES section
by December 9, 2013.
Public Informational Meetings: To
better inform the public of the
implications of the proposed listing and
to answer any questions regarding this
proposed rule, we plan to hold five
public informational meetings. We have
scheduled informational meetings
regarding the proposed rule in the
following locations:
(1) Minot, North Dakota, on November
5, 2013, at the Souris Valley Suites, 800
37th Avenue SW;
(2) Milbank, South Dakota, on
November 6, 2013, at the Milbank
Chamber of Commerce, 1001 East 4th
Avenue;
(3) Milford, Iowa, on November 7,
2013, at the Iowa Lakeside Laboratory,
1838 Highway 86;
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SUMMARY:
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(4) Holly, Michigan, on November 13,
2013, at the Rose Pioneer Elementary
School, 7110 Milford Road; and
(5) Berlin, Wisconsin, on November
14, 2013, at the Berlin Public Library,
121 West Park Avenue.
Except for the meeting in Berlin,
Wisconsin, each informational meeting
will be from 5:30 p.m. to 8:00 p.m.; the
meeting in Berlin, Wisconsin will be
from 4:30 p.m. to 7:00 p.m.
ADDRESSES: You may submit comments
by one of the following methods:
(1) Electronically: Go to the Federal
eRulemaking Portal: https://
www.regulations.gov. In the Search box,
enter FWS–R3–ES–2013–0043, which is
the docket number for this rulemaking.
Then, in the Search panel on the left
side of the screen, under the Document
Type heading, click on the Proposed
Rules link to locate this document. You
may submit a comment by clicking on
‘‘Comment Now!’’
(2) By hard copy: Submit by U.S. mail
or hand-delivery to: Public Comments
Processing, Attn: FWS–R3–ES–2013–
0043; Division of Policy and Directives
Management; U.S. Fish and Wildlife
Service; 4401 N. Fairfax Drive, MS
2042–PDM; Arlington, VA 22203.
We request that you send comments
only by the methods described above.
We will post all comments on https://
www.regulations.gov. This generally
means that we will post any personal
information you provide us (see the
Public Comments section below for
more information).
FOR FURTHER INFORMATION CONTACT: Pete
Fasbender, Field Supervisor, U.S. Fish
and Wildlife Service, Twin Cities
Ecological Services Office, 4101
American Boulevard East, Bloomington,
Minnesota, 55425, by telephone (612)
725–3548 or by facsimile (612) 725–
3609. 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 (Act), if a
species is determined to be an
endangered or threatened species
throughout all or a significant portion of
its range, we are required to promptly
publish a proposal in the Federal
Register and make a determination on
our proposal within one year. Listing a
species as an endangered or threatened
species can only be completed by
issuing a rule. A species may warrant
protection through listing under the Act
if it meets the definition of an
endangered or threatened species
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throughout all or a significant portion of
its range.
This rule consists of:
• A proposed rule to list the
Poweshiek skipperling as an endangered
species;
• A proposed rule to list the Dakota
skipper as threatened species; and
• A proposed special rule under
section 4(d) of the Act that outlines the
prohibitions necessary and advisable for
the conservation of the Dakota skipper.
Elsewhere in today’s Federal Register,
we propose to designate critical habitat
for the Dakota skipper and Poweshiek
skipperling under the Act.
The basis for our action. Under the
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.
Furthermore, whenever a species is
listed as a threatened species, we may
issue regulations that are necessary and
advisable for the conservation of that
species under section 4(d) of the Act.
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, and other unknown stressors.
• Existing regulatory mechanisms are
inadequate to mitigate these threats to
both species.
We will seek peer review. We are
seeking comments from knowledgeable
individuals with scientific expertise to
review our analysis of the best available
science and application of that science
and to provide any additional scientific
information to improve this proposed
rule. Because we will consider all
comments and information received
during the comment period, our final
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determinations may differ from this
proposal.
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Information Requested
We intend that any final action
resulting from this proposed rule will be
based on the best scientific and
commercial data available and be as
accurate and as effective as possible.
Therefore, we request comments or
information from other concerned
government agencies, the scientific
community, industry, or any other
interested party concerning this
proposed rule. We particularly seek
comments concerning:
(1) The species’ biology, range, and
population trends, including:
(a) Habitat requirements for feeding,
breeding, and sheltering;
(b) Genetics and taxonomy;
(c) Historical and current range
including distribution patterns;
(d) Historical and current population
levels, and current and projected trends;
and
(e) Past and ongoing conservation
measures for the species, its habitat, or
both.
(2) The factors that are the basis for
making a listing determination for a
species under section 4(a) of the Act (16
U.S.C. 1531 et seq.), which are:
(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.
(3) Biological, commercial trade, or
other relevant data concerning any
threats (or lack thereof) to these species
and existing regulations that may be
addressing those threats;
(4) Additional information concerning
the historical and current status, range,
distribution, and population size of
these species, including the locations of
any additional populations;
(5) Any information on the biological
or ecological requirements of these
species and ongoing conservation
measures for these species and their
habitat;
(6) Specific information on the
amount and distribution of the Dakota
skipper and Poweshiek skipperling and
their habitat; and
(7) Our approach to determining the
status of each species at each site, and
our definitions of ‘‘present,’’
‘‘unknown,’’ ‘‘possibly extirpated,’’ and
‘‘extirpated’’ as described under Species
Status, below.
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(8) Suitability of the proposed 4(d)
rule for the conservation, recovery, and
management of the Dakota skipper.
(9) Whether it would be appropriate
to allow routine livestock grazing
activities on lands inhabited by Dakota
skipper in any additional counties. The
proposed 4(d) rule would allow routine
livestock grazing activities on lands
inhabited by the Dakota skipper in
counties where the species does not
primarily occur in relatively flat and
moist (wet-mesic or mesic) prairie
habitats. Wet-mesic or mesic habitats in
which the Dakota skipper occurs are
typically hayed after July 15 and not
grazed. We are seeking comments on
whether or not grazing may be
implemented in these habitats in a
manner that would allow for the
persistence of the Dakota skipper.
(10) Any information on Tribal
regulations or Tribal conservation
efforts that may affect either the Dakota
skipper or Poweshiek skipperling and
their habitat.
Please include sufficient information
with your submission (such as scientific
journal articles or other publications) to
allow us to verify any scientific or
commercial information you include.
Please note that submissions merely
stating support for or opposition to the
action under consideration without
providing supporting information,
although noted, will not be considered
in making a determination, as section
4(b)(1)(A) of the Act directs that
determinations as to whether any
species is a threatened or endangered
species must be made ‘‘solely on the
basis of the best scientific and
commercial data available.’’
You may submit your comments and
materials concerning this proposed rule
by one of the methods listed in the
ADDRESSES section. We request that you
send comments only by the methods
described in the ADDRESSES section.
If you submit information via https://
www.regulations.gov, your entire
submission—including any personal
identifying information—will be posted
on the Web site. If your submission is
made via a hardcopy that includes
personal identifying information, you
may request at the top of your document
that we withhold this information from
public review. However, we cannot
guarantee that we will be able to do so.
We will post all hardcopy submissions
on https://www.regulations.gov. Please
include sufficient information with your
comments (such as scientific journal
articles or other publications) to allow
us to verify any scientific or commercial
information you include.
Comments and materials we receive,
as well as supporting documentation we
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used in preparing this proposed rule,
will be available for public inspection
on https://www.regulations.gov, or by
appointment, during normal business
hours, at the U.S. Fish and Wildlife
Service, Twin Cities Ecological Services
Office (see FOR FURTHER INFORMATION
CONTACT).
Previous Federal Actions
The U.S. Fish and Wildlife Service
(Service) initiated proceedings to list the
Dakota skipper as a threatened species
in 1978 (43 FR 28938), but withdrew the
proposed rulemaking after Congress
amended the Endangered Species Act in
1979 (45 FR 58171). The Dakota skipper
was designated a category 2 candidate
species in the May 22, 1984, Notice of
Review (49 FR 21664) and remained a
category 2 species (January 6, 1989, 54
FR 572; November 21, 1991, 56 FR
58830; and November 15, 1994, 59 FR
59020). A category 2 candidate was
defined as a species for which
information in the Service’s possession
indicates that listing was possibly
appropriate, but for which sufficient
information on biological vulnerability
and threats was not currently available
to support a proposal for listing under
the Act.
On January 21, 1994, the Service
received a petition from the Biodiversity
Legal Foundation to list the Dakota
skipper as an endangered or threatened
species and to designate critical habitat.
We made a 90-day finding that the
petition presented substantial
information to indicate that the
requested action may be warranted; the
finding was published in the Federal
Register on July 28, 1994 (59 FR 38424).
On February 27, 1995, we announced a
12-month finding in which we
determined that the species should
remain as a category 2 candidate, that
timely appropriate prairie management
and protection may eliminate the need
to list the species, and that researchers
indicated that more surveys,
particularly in Minnesota, Iowa, and
North Dakota, were needed (60 FR
10535).
In a December 5, 1996 (61 FR 64481)
decision, the Service discontinued the
practice of maintaining a list of species
regarded as ‘‘category-2 candidates.’’
Instead, the Service would keep a single
list of candidate species—species for
which the Service has on file sufficient
information to support issuance of a
proposed listing rule.
In 2002, the Service reviewed the
status of the Dakota skipper and
determined that it met the definition of
a candidate species. The Dakota skipper
was assigned a listing priority number
of 11 on June 13, 2002 (67 FR 40657).
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The Dakota skipper remained a
candidate species with a listing priority
number of 11 in subsequent notices,
including May 4, 2004 (69 FR 24876),
May 11, 2005 (70 FR 24870), and
September 12, 2006 (71 FR 53756). The
Service changed the listing priority 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, including December
10, 2008 (73 FR 75176), November 9,
2009 (74 FR 57804), November 10, 2010
(75 FR 69222), and October 26, 2011 (76
FR 66370).
On May 12, 2003, the Service received
a petition from the Biodiversity
Conservation Alliance and five others to
list the Dakota skipper as endangered or
threatened and to designate critical
habitat. The Service agreed with the
petitioners, by virtue of having made it
a candidate in 2002, that the Dakota
skipper warranted listing as threatened
or endangered under the Act. The
petition did not contain evidence
supporting emergency listing or
changing the listing priority number;
therefore, the Service took no further
action on the petition.
On July 12, 2011, the Service filed a
proposed settlement agreement with the
Center for Biological Diversity in a
consolidated case in the U.S. District
Court for the District of Columbia. The
settlement agreement was approved by
the court on September 9, 2011. As part
of this settlement agreement, the Service
agreed to complete a proposed listing
rule or not warranted finding for the
Dakota skipper by September 30, 2013.
The Service identified the Poweshiek
skipperling (Oarisma poweshiek) as a
candidate species, with a listing priority
number of 2, in a notice of review
published in the Federal Register on
October 26, 2011 (76 FR 66370).
Status Assessments for Dakota Skipper
and Poweshiek Skipperling
Background
Dakota Skipper
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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 includes 3 other
subfamilies, and the genus Hesperia
contains 18 species (Miller and Brown
1981, p. 31; Ferris 1989 in Royer and
Marrone 1992a, p. 1). Dakota skipper is
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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).
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, depending on
weather patterns. Females emerge
slightly later than males (Dana 1991, p.
1), 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 two to four weeks, and
mating occurs throughout this period
(Braker 1985, p. 46; McCabe and Post
1977a, p. 38; McCabe and Post 1977b, p.
36; McCabe 1979, p. 6; McCabe 1981, p.
180; Dana 1991, p. 15; Swengel and
Swengel 1999, p. 282). 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).
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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. 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), bluebell bellflower
(Campanula rotundifolia), white prairie
clover (Dalea candida), upright prairie
coneflower (Ratibida columnifera),
fleabanes (Erigeron spp.), blanketflowers
(Gaillardia spp.), black-eyed Susan
(Rudbeckia hirta), groundplum
milkvetch (Astragalus crassicarpus),
and yellow sundrops (Calylophus
serrulatus) (McCabe and Post 1977b, p.
36; Royer and Marrone 1992a, p. 21).
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). Swengel and
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Swengel (1999, pp. 280–281) observed
nectaring at 25 plant species, but 85
percent of the nectaring was at the
following three plants, in declining
order of frequency: Purple coneflower,
blanketflower, and groundplum
milkvetch. 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. 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.).
Dakota skipper larvae feed only 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 Panicum spp., Poa spp., and
other native grasses (Royer and Marrone
1992a, p. 25). Seasonal senescence
patterns 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 (Dana 1991, p. 46).
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
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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 with roads and
crop fields compared with movements
in adjacent widespread prairie habitat.
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, 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) 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
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goldenrod (Solidago canadensis), strict
blue-eyed grass (Sisyrinchium
montanum), common goldstar (Hypoxis
hirsuta), and black-eyed Susan (Lenz
1999a, 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 1999a, 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 (Gaillardia aristata) (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 1999b, 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
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 (H.
comata), and prairie dropseed, and a
high diversity and abundance of forbs,
including purple coneflower, purple
prairie clover (Dalea purpurea), white
prairie clover, yellow sundrops, prairie
groundsel (Packera plattensis),
groundplum 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
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(Zizia aptera), blanket flower (Gaillardia
sp.), 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 inhabit
Type B habitats. 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
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 twelve
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
skippers inhabit Type A habitats,
occupy the slightly higher, drier areas of
wet-mesic prairie where nectar sources
are more abundant (Webster 2003, p. 7).
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 (Poa pratensis),
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
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dispersed (Swengel 1994, p. 6), although
invasion by smooth brome grass
(Bromus inermis) 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 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; Minnesota sites generally had
higher soil temperatures at all depths
than sites in North Dakota or South
Dakota (Royer et al. 2008, p. 11).
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 (Royer et al. 2008, pp. 2,
16). 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
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surface) within ‘‘larval nesting zones’’
(between the soil surface and 2 cm
deep) 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.
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
of the following five 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 species to be present at one
Dakota skipper site (Frenchman’s Bluff
Preserve in Minnesota) where the most
recent survey was from 1993. 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. 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) and
one site with a 1998 record (an
unnamed site in North Dakota).
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. Little information is known
about the one unnamed site in North
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Dakota; however, the best information
we have indicates that the habitat is still
suitable for the species, and the North
Dakota species expert supports that the
species is likely present.
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 is 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 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.
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 75 percent of known
Poweshiek skipperling sites and over 89
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 or under
unsuitable conditions (e.g., high wind
speeds).
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
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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 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.
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
every survey since that date—the most
recent detection was in 2012. The year
1993 was chosen based on habitatrelated 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
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63579
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. In several cases, species
experts provided input on occupancy
based on their familiarity 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 sites with a present
status have had a positive detection in
2002, 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 2012,
except one site where the species was
detected in 2011 and no further surveys
have occurred. Likewise, 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
1993, two sites with 1996 records, and
one site with a 1998 record. 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: 20 sites in Canada
that were surveyed only once 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;
2 sites with a 2006 detection; 25 sites in
Canada that were surveyed only once in
2007; 1 additional site with a 2007
detection; 7 sites with a positive
detection in 2008; 2 sites with a positive
detection in 2009; and 27 sites with
positive detections in 2012.
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 occurs east of
western Minnesota—an approximately
690-kilometer (km) (430-mile) reduction
of its range. Populations persist in
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western Minnesota, northeastern South
Dakota, North Dakota, southern
Manitoba, and southeastern
Saskatchewan. Royer and Marrone
(1992a, p. 5) stated 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 Royer (2002, pers. comm.)
no longer thinks that the species occurs
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 1999, 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
where we consider the Dakota skipper
to be present, 81 sites with unknown
status, 40 possibly extirpated sites, and
47 that are considered extirpated (Table
1). Approximately half (45 of 91) of the
sites where the species is considered to
be present are located in Canada, mostly
within three isolated complexes, and
were observed in either 2002 or 2007
with no subsequent surveys. The
remaining 46 sites where the species is
considered to be present are about
equally distributed among Minnesota
(14 sites), North Dakota (18 sites), and
South Dakota (14 sites). Researchers
made positive detections of the species
in 27 of these sites in 2012. Other sites
with a present status with relatively
older positive detections and no
subsequent surveys for the species
include 2 sites with positive detections
in 1996, one site with a positive
detection in 1998, one site with a
positive detection in 2002, one site with
a positive detection in 2003, one site
with a positive detection in 2005, 2 sites
with a positive detection in 2006, one
site with a positive detection in 2007, 7
sites with a positive detection in 2008,
and 2 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.
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 259 historically
documented sites, there are 91 sites
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
Percent of
total number
of historical
sites by
state
Present
Unknown
Illinois .......................................................................
Iowa ..........................................................................
Minnesota .................................................................
North Dakota ............................................................
South Dakota ...........................................................
Manitoba ..................................................................
Saskatchewan ..........................................................
....................
....................
14
18
14
31
14
....................
....................
22
13
46
0
0
........................
........................
18
10
10
2
0
1
3
12
13
15
3
0
1
3
66
54
85
36
14
0.4
1
26
21
33
14
5
Total Number of Historically Documented Sites
91
81
40
47
259
....................
Percent of the Total Number of Historical Sites
by Occupancy ...............................................
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State
Possibly
extirpated
35
31
16
18
....................
100
Illinois
Iowa
Dakota skippers are considered to be
extirpated from Illinois. The species was
last recorded near Chicago in 1888
(McCabe 1981, p. 191).
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
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Extirpated
Total
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).
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The species was not observed at eight
sites surveyed between 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
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Minnesota historically contained
about 26 percent of the sites where the
Dakota skipper has been recorded (Table
1) (Service 2013, 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 2013,
unpubl. geodatabase). Of the 66 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 22
others (Service 2013, unpubl.
geodatabase). Dakota skipper is
considered to be present at 14 sites in
Minnesota in 6 counties: Clay, Lincoln,
Murray, Norman, Pipestone, and Pope,
although 2 of those sites have not been
surveyed since 1996 and 1 site has not
been surveyed since 1993.
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McCabe (1981, p. 187) observed very
stable population numbers in Minnesota
prairies that he visited repeatedly from
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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63581
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, to 56 percent (10 of 18 sites) in
2008, to 6 percent (1 of 18 sites) in 2012
(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.). 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 2013, 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 2013,
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 2013,
unpubl. geodatabase). Of the 18 sites
where the species is possibly extirpated,
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10 have not been surveyed since the
species was last seen in 1988 or earlier.
Dakota skippers at two of the sites
where the species is possibly extirpated
have not been observed since 1991
(Service 2013, unpubl. geodatabase).
The remaining 6 sites had positive
observations prior to 1993, were
surveyed once more recently, and had a
negative observation (Service 2013,
unpubl. geodatabase).
The status of Dakota skipper is
unknown at 22 sites; Dakota skipper
have not been observed at 11 of these
sites since the mid- to late 1990s,
despite one or two years of survey effort
at several sites. The remaining 11 sites
with unknown status have had positive
observations in 2007 or more recently,
but are given this designation due to a
subsequent negative survey. 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 (Selby 2009a, p. Appendix 5 li,
xxxiii and Appendix 4 xlix).
In 2007 and 2008, the Minnesota DNR
carried out a broad survey effort to
assess the status of Dakota skipper and
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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-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 flight period (Runquist
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2012, pp. 13–14, 18–20; Runquist 2012a,
pers. comm.); therefore, we consider the
status of the species at the Hole-in-theMountain preserve to be unknown.
Relatively important populations of
Dakota skipper in Minnesota may still
occur at the Prairie Coteau, Felton
Prairie, and Glacial Lakes complexes,
but the 2012 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 flight period
(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 onehour 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 has
not been resurveyed since 2008 (Service
2013, 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 25
mi (40 km) 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. l and liv)
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
seven hours of surveys in and around
the park (Selby 2009a, p. 1 and liv).
Glacial Lakes State Park surveys
conducted in 2012 were outside of the
Dakota skipper flight period (Runquist
2012a, pers. comm.).
In summary, the Dakota skipper is
now considered to be extirpated or
possibly extirpated from at least 30 of
the 66 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 14 and 22 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. Similar surveys
of prairie remnants with no previous
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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 2013, unpubl.
geodatabase). The Dakota skipper is
currently present at 18 sites in 5 North
Dakota counties, of these, 13 occur
within the Towner-Karlsruhe complex
in McHenry County, 1 is within the
Sheyenne National Grasslands complex
in Ransom County, 2 in northern
McKenzie County, 1 site is in Wells
County, and 1 site in McLean County.
Of the 18 sites where we consider the
Dakota skipper to be present, 15 sites
had positive observations of the species
in 2012 and the remaining 3 sites had
positive observations between 1998 and
2003. The status of the species is
unknown at 13 sites; 10 of these sites
have not had positive records since the
mid- to late 1990s and the other 3 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 10
additional sites and 3 additional
counties. Researcher 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 =
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).
Of the Dakota skipper populations in
North Dakota, none may be secure,
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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, p. 21–22; Royer et al. 2008, pp.
14–16). Five sites within the TownerKarlsruhe complex are owned by the
North Dakota State Land Department,
and the remaining seven 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
1999b, 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
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
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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.
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 4 sites outside
of the Towner-Karsruhe Complex and
Sheyenne National Grasslands
complexes are thought to have extant
(present) Dakota skipper populations,
including Garrison Training Center in
McLean County. 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).
In summary, North Dakota contains
approximately 21 percent (N= 53) of all
known historical locations of the
species rangewide; however, the current
occupancy status of the Dakota skipper
is unknown at 12 sites, and it is
considered to be extirpated or possibly
extirpated from at least 23 of the 53
known sites in the state (Table 1). The
species is considered to be present at
only 18 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
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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
statewide surveys (ND state average =
17.4 encounters per hour).
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 135
additional locations in North Dakota
that were surveyed for the species from
1991–2012 (USFWS 2013, unpubl.
geodatabase). Many of these sites have
been surveyed multiple times over
multiple years (USFWS 2013, 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 appear
suitable for the species and have a good
potential of finding the species, in other
words, sites are not randomly selected
across the landscape. Therefore, these
sites have a higher likelihood of
detecting the species 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) of the
species in South Dakota, 85 sites have
been documented across 11 counties in
the State, but recent surveys indicate
that the species is declining in the State
(Service 2013, unpubl. geodatabase). Of
the 85 historical sites, Dakota skipper is
presumed extirpated from 15 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 46 sites. Twentysix sites in South Dakota with previous
Dakota skipper records were surveyed
in 2012; the species was detected at 9
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of those sites (Service 2013, 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 2013, unpubl. geodatabase;
Skadsen 2012a, pers. comm.). The
proportion of positive surveys at known
sites has fluctuated over time; however,
the 2012 surveys had the lowest positive
detection rate (35 percent) 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 2012,
pp. 4–5; Skadsen, 2012, pers. comm.;
Skadsen 2003, p. 10; Skadsen 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 2012, 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 2013, 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; 2 or 3 new sites have been
discovered each survey year since 2005
(3 sites in 2005, 2 sites in 2006, 2 sites
in 2007, zero sites in 2010, and 2 sites
in 2012). 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,
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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
2013, unpubl. geodatabase)), a
significant proportion of the unsurveyed area is likely not suitable for
the Dakota skipper. For example, there
is an estimated 1,620,549 acres (ac)
(655,813 hectares (ha)) of unbroken
(untilled) grasslands (excluding
Conservation Reserve Program (CRP)
grasslands, which generally do not
provide habitat for the Dakota skipper
(Larson 2013, pers. comm.)) in the 9
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, these unbroken grasslands
may not contain the specific native
prairie plants that the Dakota skipper
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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 73 additional locations
in South Dakota that were surveyed
from 1991 through 2012 (USFWS 2013,
unpubl. geodatabase). Several of these
sites have been surveyed multiple times
in one year or during multiple years
(USFWS 2013, 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. New potential sites surveyed
are generally focused on prairie habitat
that appear suitable for the species and
have a good potential of finding the
species, in other words, sites are not
randomly selected across the landscape.
Therefore, these sites have a higher
likelihood of detecting the species 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
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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, and 35 percent (9
of 26 sites) in 2012 (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 Eco-regions is
thought to be a stronghold for Dakota
skipper, since nearly 40 percent of the
total documented Dakota skipper sites
are within that subsection (83 of the 259
documented sites—Service 2013,
unpubl. geodatabase). Most of these
Outer Coteau des Prairie sites are in
South Dakota; 73 of the 85 Dakota
skipper sites in South Dakota are within
the Outer Coteau des Prairies subsection
(Service 2013, unpubl. geodatabase).
Dakota skipper is considered to be
present at only 10 of those 73 sites—the
species status is unknown at 41 of those
sites, possibly extirpated at 8 sites, and
extirpated at the remaining 13 sites
within that ecoregion subsection in
South Dakota (Service 2013, 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 46 sites and it is
considered to be extirpated or possibly
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extirpated from at least 25 of the 85
known sites in the State, although large
areas of grasslands remain in South
Dakota and substantial additional
populations of Dakota skipper would be
expected 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 85
documented sites in the State. Twentysix 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. The proportion of positive
surveys at known sites has fluctuated
over time; however, the 2012 surveys
had the lowest positive detection rate
(35 percent) for the last 16 years (since
1996)—much less than comparable
survey years in South Dakota.
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Manitoba
Manitoba historically contained
approximately 14 percent (N = 36) of the
known locations of the Dakota skipper
rangewide. The Dakota skipper is
considered present at 1 isolated site and
30 sites split between 2 distinct
complexes, 14 sites near Griswold and
16 sites along Lake Manitoba. The 14
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 presumed extirpated or
possibly extirpated from five sites in
Manitoba, including from the Tallgrass
Prairie Preserve, where it has not been
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). Population
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estimates and trends at these sites have
not been examined quantitatively;
however, the population appears to be
stable at 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).
Dakota skipper was first recorded near
Miniota in 1944 and then at two
additional sites in the early 1990s. In
2002, the species was observed at 19
sites near Lundar, within about 25 km
(16 mi) east of Lake Manitoba (Webster
2003, p. 4); however, most of these sites
have not been surveyed since. 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). 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). The areas
near Brandon and the high ground
within the wetland complexes near Oak
Lake may still contain 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
200 km (125 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
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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 one 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
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
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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
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
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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).
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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 2000a, p. 7). McAlpine (1972,
pp. 85–92) described the various lifehistory stages of Poweshiek skipperling.
McAlpine (1972, pp. 85–93) observed
hatching of larvae Poweshiek
skipperling after about nine 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). After hatching, Poweshiek
skipperling larvae crawl to the base of
grasses, but unlike Dakota skippers,
Poweshiek skipperling do not form
shelters underground (McAlpine 1972,
pp. 88–92; Borkin 1995a, p. 9; Borkin
2008, pers. comm.). Poweshiek
skipperling are not known to form
shelters, 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.
Food and Water
For the Poweshiek skipperling,
preferred nectar plants vary across its
geographic range. Smooth ox-eye
(Heliopsis helianthoides) and purple
coneflower were noted as the favored
nectar plants in Iowa, Minnesota, and
North Dakota (Swengel and Swengel
1999, p. 280). Other nectar species used,
in descending order of number of
observations, were stiff tickseed
(Coreopsis palmata), black-eyed Susan,
and palespike lobelia (Lobelia spicata)
(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
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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). 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 (Sporobolus
heterolepis) (Borkin 1995b, p. 6); larvae
have also been observed feeding on little
bluestem (Schizachyrium scoparium)
(Borkin 1995b, pp. 5–6) and sideoats
grama (Bouteloua curtipendula) (Dana
2005a, pers. comm.). Poweshiek
skipperling 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).
In southwestern Minnesota dry hill
prairies, Poweshiek skipperling
oviposition was observed on prairie
dropseed, little bluestem, big bluestem
(Andropogon gerardii), porcupine grass
(Hesperostipa spartea), 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 1995a, p. 6). Dana
(2005b, pers. comm.) noted that larvae
and ovipositing females prefer grasses
with ‘‘very fine, threadlike structures’’
and hypothesized that Poweshiek
skipperling lack a specific host and may
adapt to acceptable plant species at a
site.
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
maximum dispersal distance of 1.6 km
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(1.0 mi) is 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). 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 or 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
Poweshiek skipperling (mean mobility
of 2) (Burke et al. 2011, p. 2279;
Fitzsimmons 2012, pers. comm.), a more
conservative estimated dispersal
distance would be that of the Dakota
skipper, approximately 1 km (0.6 mi)
(Cochrane and Delphey 2002, p. 6).
In summary, 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, and
wet-mesic to dry tallgrass prairie.
McCabe and Post (McCabe and Post
1977a, p. 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 1977a, p. 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
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(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,
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-mesic, and dry-mesic
prairie habitats (Borkin 1995b, p. 6). The
dry-mesic habitats contain ‘‘extensive
patches of prairie dropseed and little
bluestem grasses’’ (Borkin 1995b, 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 1995b, p. 7).
Like Dakota skipper, 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
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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 microclimalogical (climate in
a small space, such as at or near the soil
surface) levels within ‘‘larval nesting
zones’’ (between the soil surface and 2
cm deep) 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
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).
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
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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 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 87
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 nearly 50
percent of all known Poweshiek
skipperling locations rangewide.
Numbers and distribution dropped
dramatically in subsequent years,
however, and the species has not been
seen in Minnesota since 2007. 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
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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 24 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. 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
about 6 percent of all known historical
Poweshiek skipperling records. There is
one population of Poweshiek
skipperling in Wisconsin with fairly
consistent numbers observed over the
last 5 years (17 to 63 individuals
counted, no consistent measure of
effort) and one population in Manitoba
with fairly consistent numbers
(typically hundreds of individuals
observed each year). To summarize, of
the 296 documented sites, there are 14
sites where we consider the Poweshiek
skipperling to be present, 131 sites with
unknown status, 98 possibly extirpated
sites, and 53 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.
counted at 1 site, and 0 were detected
at 6 other sites. Surveys conducted
during the 2012 flight season 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
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
Percent of
the total
number of
historical
sites by
state
State
Present
Unknown
Possibly extirpated
Extirpated
Illinois .......................................................................
Indiana .....................................................................
Iowa ..........................................................................
Michigan ...................................................................
Minnesota .................................................................
North Dakota ............................................................
South Dakota ...........................................................
Wisconsin .................................................................
Manitoba ..................................................................
....................
....................
....................
10
....................
....................
....................
3
1
....................
....................
4
1
67
10
48
1
....................
........................
........................
24
........................
68
6
........................
........................
........................
3
1
13
6
7
1
22
........................
........................
3
1
41
17
142
17
70
4
1
1
0.3
14
6
48
6
24
1
0.3
Total Number of Historically Documented Sites
14
131
98
53
296
....................
Percent of the Total Number of Historical Sites
by Occupancy ...............................................
5%
44%
33%
18%
....................
....................
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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
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
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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.). 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.
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Total
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,
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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.
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). Four Poweshiek
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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
Hoffman Prairie site because the species
had not been seen in the last two survey
years; however, Selby believes that the
species may be extirpated from this site
(Selby 2012a, pers. comm.), so we have
assigned a status of extirpated to this
site.
To summarize, 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 ten
sites (Table 2) in four counties in
Michigan: Jackson, Lenawee, Oakland,
and Washtenaw. The species has been
observed very recently (2007–2012) 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 one site; Bullard
Lake in Livingston County, where
Poweshiek skipperling were last seen in
2007, but not in subsequent surveys in
2008 and 2009 (Cuthrell 2012a, 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
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63591
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 ten extant
(present) Poweshiek skipperling
occurrences are considered to have at
least good viability (Michigan Natural
Features Inventory 2011, unpubl. data).
Three of these sites (Buckthorn 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.). The largest extant
(present) Poweshiek skipperling
population in Michigan is at Long Lake
Fen, where 225 individuals (1.3/hr.)
were counted during 2012 surveys,
down from 389 individuals (2.2/hr.)
observed in the previous survey year
with similar sampling effort. Long Lake
Fen is likely the largest population of
Poweshiek skipperling in the United
States, and is subjected to intense
development pressure. The fourth site,
Grand River Fen (also known as Liberty
Fen) in Jackson County, is
approximately 100 km (62 mi) from the
other three sites. 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
(Cuthrell, 2012a, pers. comm.; 2012b,
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
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in Michigan. In 2010, eight (0.1/hr.)
Poweshiek skipperling were recorded at
Park Lydon in Washtenaw County; 12
individuals were counted in 2011 (0.1/
hr.), and 22 were counted in 2012 (0.2/
hr.) (Cuthrell 2012a, 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, nine (0.07/hr.) were
seen in 2011 (Cuthrell 2012a, pers.
comm.; Cuthrell 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 2013b, pers. comm.). The
Eaton Road site is approximately 1 mi
(0.6 km) from the Long Lake Fen site
and is considered a sub-site within Long
Lake Fen (Cuthrell 2013b, 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 10 of the
sites. The occupancy is unknown at 1
site, and the species is considered to be
extirpated at 6 sites.
Minnesota
Minnesota historically contained
approximately 48 percent (N=142) 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 142 distinct historical
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site records in the State (Dana 2012d,
pers. comm; Service 2013, unpubl.
geodatabase). Poweshiek skipperling are
presumed extirpated or possibly
extirpated from at least 75 of these
known sites. The status of the species is
unknown at 67 sites, although 31 of
those locations have not been surveyed
since 2003, and the species has
undergone a sharp decline in the State
since then.
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). The 2008 surveys documented no
Poweshiek skipperling records on any of
the 58 sites surveyed (Selby 2009a, p. 1).
An extensive survey effort was also
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 it 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
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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
2007 survey despite good survey
conditions (Selby 2009a, p. xxxv).
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 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.).
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, or 2012) 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
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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).
To summarize, Poweshiek skipperling
was historically documented in
approximately 142 sites in Minnesota
(Table 2). The species is not considered
to be present at any of these sites (Table
2). The occupancy is unknown at 67
sites, and the species is considered to be
extirpated or possibly extirpated at 7
and 68 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 2013,
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 seven sites and four
counties (Cass, Dickey, LaMoure, and
Grand Forks) in North Dakota. The
status of the species is unknown at 10
sites, where the species was last
observed between 1996 and 2001, but
not during the most recent 1–2 year(s)
surveyed. The status of the species is
also unknown at one site where the
species was observed in 1996 with no
recent surveys for the species, but the
habitat was recently rated as poor
(Service 2013, unpubl. geodatabase).
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 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
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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 three years of survey
work (1995–1997) in southeast 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
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 six 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
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63593
unknown at 10 sites, and the species is
considered to be extirpated or possibly
extirpated at 1 and 6 sites, respectively
(Table 2).
South Dakota
South Dakota historically contained
approximately 24 percent (N=70) of all
known records of Poweshiek
skipperlings rangewide (Table 2). The
Poweshiek skipperling has been
historically documented at
approximately 70 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 48
sites and presumed extirpated at the
remaining 22 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 2012: 6 sites in 2009,
10 sites in 2010, 1 sites in 2011, and 10
sites in 2012 (Skadsen 2009, p. 12;
Skadsen 2011, p. 5; Skadsen 2010, pers.
comm.; Skadsen 2012a, pers. comm.;
Skadsen 2012, p. 3). The 2009 to 2012
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).
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 three sites in Wisconsin
(Table 2); two sites are within the
Southern Unit of the Kettle Moraine
State Forest in Waukesha County. The
third site, 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 another site within the
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Kettle Moraine State Forest. 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.). The larger of the
two populations at Kettle Moraine State
Forest inhabits a 6-ha (15-ac) prairie
remnant on Scuppernong Prairie SNA,
which had record counts exceeding 100
individuals in 1994, 1995, 1998, and
1999 (Borkin 1995a, p. 10; Borkin 1996,
p. 7; Borkin 2000b, 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.).
There was some concern that a
controlled burn in late March of 2012
may correlate with lower numbers
observed during the 2012 flight (Borkin
2012a, pers. comm.); however, this
difference is within the range of
variation observed over the previous
four years (Wisconsin DNR 2012, in
litt.).
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,
pers. comm.; Borkin 2012a, 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
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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
wild fire (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, there were no photographs or
voucher specimens to 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 three days.
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 2000b, 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 three sites
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and the occupancy is unknown one site
(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’s 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).
The preserve has detailed management
recommendations to facilitate recovery
of the Poweshiek skipperling
(Westwood 2010, p. 5).
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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 Tall Grass Prairie Preserve
(Environment Canada 2012, p. ii).
Summary of Factors Affecting the
Species
Section 4 of the Act (16 U.S.C. 1533),
and its implementing regulations at 50
CFR Part 424, set forth the procedures
for adding species to the Federal Lists
of Endangered and Threatened Wildlife
and Plants. Under section 4(a)(1) of the
Act, we may list a species based on any
of the following 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; and (E)
other natural or manmade factors
affecting its continued existence. Listing
actions may be warranted based on any
of the above threat factors, singly or in
combination. Each of these factors is
discussed below.
We evaluated the level of impact to
the population at each site of stressors
at 170 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 rule. These 170 sites are found
across the current range of the species
in Minnesota, North Dakota, and South
Dakota. Two Dakota skipper 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 2013, 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; therefore, the
number of sites evaluated varies with
each stressor.
We evaluated the level of impact to
the species from stressors at 68
Poweshiek skipperling sites where the
occupancy status of the site is
considered to be present or unknown, as
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defined in the Background section of
this proposed rule. Although we did not
evaluate every stressor at all 145
Poweshiek skipperling sites with
present or unknown occupancy, the 68
sites that were evaluated are
representative of all those sites in terms
of geography (sites in Iowa, Michigan,
Minnesota, North Dakota, South Dakota,
and Wisconsin were evaluated),
ownership, and management. To
determine the levels of impact to the
population at each site, we used the best
available and most recent information,
including reports, discussions with site
managers, and information from natural
heritage databases (Service 2012,
unpubl. data; Service 2013, unpubl.
geodatabase). We only evaluated a
particular stressor at any one site if we
had sufficient information to determine
if the level of impact was high, medium,
or low (as defined below); therefore, the
number of sites evaluated varies with
each stressor.
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
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63595
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
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 170 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 proposed
rule (Table 3). These 170 sites are found
across the current range of the species
in Minnesota, North Dakota, and South
Dakota. Two 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 2013, 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 68 Poweshiek skipperling
sites with present or unknown status
(Table 4). Although we did not evaluate
Factor A stressors at all 145 Poweshiek
skipperling sites with present or
unknown occupancy, the 68 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 (59 sites for Dakota skipper and
32 sites for Poweshiek skipperling)
experience at least two habitat-related
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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 170 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 2013, UNPUBL. DATA)
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
0
13
9
10
2
10
50
5
87
0
6
31
4
29
11
5
35
2
Low level of
impact
60
8
6
18
6
14
27
3
58
9
Total
number of
rated sites
150
9
12
62
19
53
40
18
143
16
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 68 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. DATA; SERVICE 2013, UNPUBL. DATA)
High level of
impact
Stressor
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
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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
threat of such conversion to extant
populations is not well known and may
now be secondary to other threats. 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
71.9 percent in North Dakota (Samson
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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 threat to Dakota skippers in the
important Towner-Karlsruhe complex
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Medium
level of
impact
1
0
2
9
7
7
0
5
25
3
13
0
4
30
3
14
3
6
24
1
Low level of
impact
40
6
14
12
14
2
7
2
19
6
Total
number of
rated sites
54
6
20
51
24
23
10
13
68
10
(Royer and Royer 1998, p. 22; Lenz
1999b, 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
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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 150 Dakota
skipper and 54 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 2013,
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 threat in at
least three of the five sites that comprise
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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 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.
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.). Much of the
Dakota skipper’s range and some of the
Poweshiek skipperling’s range overlaps
with major areas of oil and gas
development, which have been
increasing rapidly in parts of both
species’ ranges. North Dakota, for
example, is now one of the top two oilproducing 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, is a future stressor to Dakota
skipper populations in McKenzie
County (Royer and Royer 2012b, p. 16).
Oil company officials anticipate that
production will 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
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63597
(Westwood et al. 2012, p. 18). Oil and
gas development can double the density
of roads on range lands (Naugle et al.
2009, pp. 11, 46), increase pipelines,
and increase the number of gravel pits
to accommodate the increased road
construction (Mueller 2013, pers.
comm.). 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.
2009, p. 11). 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. 2009, p. 11).
The habitat fragmentation associated
with oil and gas development may
amplify other threats 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. No such
spills are known to have occurred in the
region, however, and the likelihood 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;
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Shaffer et al. 2012, p.). 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 threat 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
distribution 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 as a result of routine
maintenance (e.g., broadcast herbicide
applications, early mowing, and
cleaning out ditches), improvements
(e.g., widening roads or converting twolane highways to four-lane highways),
or new construction. Poweshiek
skipperling habitat was destroyed or
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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 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 150 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 87
sites, and 60 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
organization (e.g., The Nature
Conservancy), or educational institution
(e.g., South Dakota State University).
Similarly, 54 Poweshiek skipperling
sites with present or unknown status
were assessed that had sufficient
information: The level of threat was
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high at one site and moderate at 13 sites,
and 40 sites are protected from
destruction or conversion through a
conservation easement or fee title
ownership by a conservation agency
(Table 4). At least 5 of the 14 sites where
the Poweshiek skipperling is considered
to still be present have a medium 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 threat 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).
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 12 Dakota
skipper sites with present or unknown
status and 20 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
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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 10 of the
Michigan prairie fen Poweshiek
skipperling sites where the species is
present and one with unknown
occupancy (Service 2013, unpubl. data).
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
Inventory 2011, 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 2013, 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
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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
2013, unpubl. data). Similarly, we
assessed 20 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). Flooding is a stressor with
moderate impact to the populations at 3
Poweshiek skipperling sites (including a
site in Wisconsin—one of the 14
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 10 of 14
Poweshiek skipperling sites that have a
present status) and 1 site in North
Dakota (Service 2012 unpubl. data;
Service 2013, unpubl. data).
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 threat 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
(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). Leafy spurge
and Kentucky bluegrass have been cited
as one of the major threats 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.). 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
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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 not growing when Dakota
skipper and Poweshiek skipperling
larvae are feeding, 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 62
Dakota skipper sites and 51 Poweshiek
skipperling sites that had sufficient
information to evaluate the stressor
(Table 3 and Table 4; Service 2012
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unpubl. data; Service 2013, 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
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 13 of the 62 assessed
Dakota skipper sites, a moderate level of
impact to populations at 31 sites, and
low impact to populations at 18 sites.
Sites with high and moderate level of
impact occur throughout the species
range in Minnesota, North and South
Dakota (Service 2012 unpubl. data;
Service 2013, unpubl. data). Similarly,
invasive species are a stressor of high
level of impact to populations at 9 of the
51 evaluated Poweshiek skipperling
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sites, moderate of level impact to
populations at 30 sites, and low level of
impact to populations at 12 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 11 of the
14 sites where the species is still present
(Service 2013, 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 Manitoba’s
Tall Grass Prairie Preserve (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
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
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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. At Prairie Coteau
Preserve in Minnesota, Schlicht (2001a,
pp. 9–10) found greater flower
abundance on regularly burned than
rarely burned sites, but Dakota skipper
abundance showed the greatest decline
on the burned sites.
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 threat 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 threat 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). 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
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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 2000a, p. 2), where they are
exposed to fires during their larval
stages. 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 1995b, 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 increase 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 °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
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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 four years after burns (Swengel
1996, p. 83). Poweshiek skipperling had
the most negative initial response to fire
among six species of prairie-obligate
butterfly species (Swengel 1996, p. 83).
Numbers were still lower than expected
one year post-fire, exceeded
expectations after two years, and
declined slightly after three years
(Swengel 1996, p. 83). In habitats that
had not been burned for four or more
years, Poweshiek skipperling abundance
was about as low as in habitats sampled
less than one year after being burned
(Swengel 1996, p. 83).
Swengel’s (1996, p. 83) observations
are consistent with other findings. That
is, Poweshiek skipperling numbers
decline in burned areas for 1–2 years
after the burn then rebound, but may
decline again if management does not
maintain the habitat (Skadsen 2001, p.
37; Webster 2003, p. 12). In general,
recovery times of 1–5 years post burn
have been predicted (Swengel 1996, pp.
73, 79, 81; Panzer 2002, pp. 1302–1303);
however, Vogel et. al (2010, p. 671)
found that habitat-specialist butterfly
abundance recovery time was
approximately 50 months after
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prescribed fires. 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 the
typical post-fire rebound.
We assessed the stressor posed by fire
at 19 Dakota skipper sites with present
or unknown status and 24 Poweshiek
skipperling sites with present or
unknown site status where we had
sufficient information to evaluate the
stressor (Tables 3 and 4; Service 2012
unpubl. data; Service 2013, unpubl.
data). We considered fire a stressor of
high level of impact to populations at 9
of the 19 evaluated Dakota skipper sites
and 7 of the 24 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 three years;
or, habitat is divided into two or more
burn units, each unit is burned no more
frequently than once every three 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 threat of moderate
severity at 4 of the 19 evaluated Dakota
skipper sites and 3 of the 24 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 four 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 four 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
19 evaluated Dakota skipper sites and
14 of the 24 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
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conducted with conservation of prairie
invertebrates as a primary objective, it 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. Furthermore, in contrast
to the permanent habitat destruction
and larval mortality caused by plowing
or mining, for example, some habitats
can remain suitable for Dakota skipper
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 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
(Service 2006, p. 2; Smart et al. in
prep.).
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). Schlicht
(1997b, p. 5) found that the Dakota
skipper was relatively abundant on
prairies subjected to light grazing
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regimes, but absent on nearby idle
prairies that were no longer used for
grazing; moreover, he observed more
Dakota skippers 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.
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
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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.
The intensity at which grazing occurs
may dictate the level of impact to the
Dakota skipper and Poweshiek
skipperling. 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
two 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 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 2013,
unpubl. geodatabase). Spomer (2004, p.
4) found that larval host plants and
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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 1977b, p. 36; 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 threat to
Dakota skipper in the wet-mesic habitats
of Manitoba (Webster 2007, pp. i–ii, 6).
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 threat to
Dakota skippers and Poweshiek
skipperlings, but that occasional light
grazing is not a long-term threat 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
or be restored afterwards, if sufficient
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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 proposed 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).
Grazing also causes direct mortality of
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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). 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 threat 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 53 Dakota
skipper sites and 23 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 2013, 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
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(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
four 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 threat, 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 coolseason grasses and invasive species.
Cattle are often removed by July 1 to
minimize adverse impacts to warmseason 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 lead
to further management actions (see
Invasive Species and Secondary
Succession).
Of the 53 Dakota skipper sites
assessed, we found the level of impact
to Dakota skipper populations from
grazing to be high at 10 sites, moderate
at 29 sites, and low at 14 sites (Service
2012 unpubl. data; Service 2013,
unpubl. data). Moderate- to high-level
impacts to populations were primarily
at South Dakota sites (N=28)—other
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
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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 10 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 19 Poweshiek skipperling sites
for which we had sufficient information
to assess grazing, the level of impact to
populations from grazing is high at 7
sites, moderate at 14 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 14
sites where grazing is a moderate level
of impact to Poweshiek skipperling
populations, 10 have habitat rated as
fair to excellent. The habitat quality was
rated as poor at 3 of the 6 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.).
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
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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 are 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
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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).
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
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
1999b, 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).
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We assessed the level of impact of
haying to populations at 40 Dakota
skipper sites and 10 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 2013, 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 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
threats, 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 three
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 27 of the 40 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 13 of the 40 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 2 of the 40 Dakota
skipper sites assessed and a stressor of
moderate-level impacts to the
populations at 11 of the 40 Dakota
skipper sites assessed. Of the 10
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 10 sites.
In summary, haying is a current and
ongoing threat of moderate to high level
of impacts to Dakota skippers and
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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
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.
We assessed the stressor posed by
lack of management for populations at
18 Dakota skipper sites and 13
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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 2013,
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
secondary succession and invasive
species (e.g., smooth brome). Ten of the
18 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. Five of the 13
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 threats 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
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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 170 Dakota skipper sites for
which we evaluated for one or more
habitat stressors, at least 136 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
2013, unpubl. data). Fifty-eight sites
have 2 or more documented stressors of
moderate to high levels of impact to
populations, and 23 sites have three 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 2013, unpubl. data).
Twenty-three of these sites had 3 or
more documented stressors at moderate
or high levels of impact. Sites with three
or more stressors are found across the
current range of the species in the
United States; these sites occur in
Minnesota, North Dakota, and South
Dakota. 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 68 Poweshiek
skipperling sites with present or
unknown status that we analyzed for
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one or more habitat stressors, 55 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 2013, unpubl. data). Fifty-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 2013, unpubl. data). Thirtyseven 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,
North Dakota, South Dakota, Wisconsin,
and Manitoba (Service 2013, unpubl.
data). Thirty-seven of these sites had 3
or more documented stressors at
moderate or high levels of impact to the
population for both species. These sites
are found across most of the current
range of the species and occur in Iowa,
Michigan, Minnesota, North Dakota,
South Dakota, and Manitoba (Service
2013, 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 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 mitchellii), 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 lifehistory, 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
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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. 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 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.
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 1979 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
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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
2003a, entire; Selby 2003b, entire; Selby
2004b, entire, Selby 2006, entire);
however, skipper numbers were too low
to collect sufficient data to test
hypotheses (Selby 2006, 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 2013, 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 2013, 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 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 threat of
conversion and may provide dispersal
corridors or buffer sites from external
threats (e.g., pesticide drift).
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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 U.S. Department of
Agriculture Natural Resources
Conservation Service 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 (Larson 2013, pers. comm.).
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
(Table 5; 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 (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
172) 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
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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
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
2012, 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 2012, 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
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able to produce seed (Royer and Royer
2012, 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 seven 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 14 Dakota skipper
sites in Day County: 2 sites where the
species is considered to be present, and
12 sites that have an unknown
occupancy. 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
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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 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.
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.
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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 this and other species in
the future. If this program is successful,
the conservation benefit could be
possible if it could facilitate
reintroduction and augmentation efforts
into areas where the species has
declined or disappeared. Furthermore,
this propagation effort may lead to
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; 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). No
collection threats are known or likely
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for the Poweshiek skipperling (Royer
and Marrone 1992b, p. 16). Collection is
not currently a threat 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.
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. 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
1995b, 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 and ant species and
predation by various insects. 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. The University
of Michigan (at Dearborn) has plans to
study Wolbachia bacteria on one or both
of the species.
Predation by birds or insects is not
considered a major component of
Dakota skipper or Poweshiek
skipperling population dynamics and
does not likely impact the species.
McCabe (1981, p. 187), however, noted
three kinds of predators to Dakota
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skippers, including Ambush bugs
(Hemiptera: Phymata sp.), flower
spiders (Aranaea: Misumena spp.), and
orb weavers (various Araneldae).
Although flower spiders and ambush
bugs are effective predators of nectarfeeding insects (McCabe 1981, pp. 187–
188) and may cause mortality to some
individuals, no evidence indicates that
these predators have population level
impacts to either the Dakota skipper or
Poweshiek skipperling. Similarly, Orb
weaver spiders appear to be successful
predators of ‘‘old, warn individuals’’
(McCabe 1981, p. 188), but no evidence
indicates that these predators have
population-level impacts to the Dakota
skipper and Poweshiek skipperling.
Therefore, we do not consider either
disease or predation to be a significant
stressor to the Dakota skipper or
Poweshiek skipperling populations at
this time, nor do we expect these
stressors to become threats in the future.
Factor D. The Inadequacy of Existing
Regulatory Mechanisms
Existing regulatory mechanisms vary
by location, but generally do not
mitigate for the numerous threats that
the Dakota skipper and Poweshiek
skipperling face.
State Regulations
The Dakota skipper is listed as
threatened 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 is listed as a
species of special concern in Minnesota,
which conveys no prohibitions against
take of the species. The Minnesota DNR
has proposed to list Poweshiek
skipperling as endangered and to
change the status of Dakota skipper from
threatened to endangered (Minnesota
DNR 2012), but it is unclear when this
may go into effect. The Poweshiek
skipperling is listed as threatened under
state endangered species statutes in
Iowa and Michigan and as endangered
in Wisconsin. 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
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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), 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 noncollection threats. While some threats
may result in direct mortality of both
species, such as ill-timed fires, most
threats to the species are indirect and
state laws that regulate direct harm to
the species do not address these threats.
In Iowa, for example, Poweshiek
skipperling populations are likely now
extirpated due to habitat destruction
and conversion and other undetermined
threats, despite its presence on the
State’s list of threatened species since
1994. In Wisconsin, where threats 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 threats to the State’s small and
isolated populations.
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
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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 February 8, 2012).
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 this has not been done
for either of these species. 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/
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.
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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.
Although there are no genetic studies
on the Poweshiek skipperling,
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 172
separate sites where the species is
known to be or may still be present
(sites with present (91) or unknown (81)
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).
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
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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, 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 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
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effectively isolated, and would not be
recolonized if extirpated (Service 2012
unpubl. data; Service 2013, unpubl.
data). Using a more conservative
maximum dispersal of 1.0 km (0.6 mi),
approximately 56 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 2013, unpubl. data). For Dakota
skipper, if we use a maximum dispersal
distance of 1 km (0.6 miles),
approximately 84 percent of Dakota
skipper sites with present or unknown
status are effectively isolated.
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)
from the Wilton Road population; fewer
than 100 individuals have been counted
at this site each year (See Population
Distribution and Status). Numbers at
Wilton Road are currently too small
(less 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 100 km (62 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. Only 2
of the 11 Poweshiek skipperling sites
with present status in Michigan are
located within 1 mi (1.6 km) 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
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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) 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, 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 143 Dakota
skipper sites and 68 Poweshiek
skipperling sites with present or
unknown status—many of the sites with
where the species is present in Canada
were not evaluated because we had little
or no information on the size of sites
(Service 2012 unpubl. data; Service
2013, 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
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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 threat 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 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.
Dakota skipper populations on about
35 percent of the evaluated sites (50 of
143 sites) face a high level of impact to
populations due to a combination of
size and isolation (Service 2012, 2013,
unpubl. data). Approximately 24
percent of evaluated sites (35 sites) face
a moderate level of impact to
populations due to small size and
isolation. About 40 percent of Dakota
skipper sites (50 of the 143 evaluated
sites) in the United States inhabit sites
that 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 37
percent of rated sites (25 of 68 sites), on
24 sites (35 percent) the threat is
considered to have a moderate level of
impact to populations, and on 28
percent (19 of the 68 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 2 sites are
within 1 km (0.6 mi) of another site
where the species is present (Service
2013, unpubl geodatabase).
In summary, small, isolated
populations face a current and ongoing
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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 two percent of Poweshiek
sites with present or unknown status are
within the estimated maximum
dispersal distance from one another as
are about 16 percent of Dakota skipper
sites with present or unknown
occupancy. The small populations are
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 and all but one site surveyed in
2012.
Climate Change
Our analyses under the Act include
consideration of ongoing and projected
changes in climate. The terms ‘‘climate’’
and ‘‘climate change’’ are defined by the
Intergovernmental Panel on Climate
Change (IPCC). The term ‘‘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 2007a, p. 78). 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 2007a, p. 78).
Scientific measurements spanning
several decades demonstrate that
changes in climate are occurring, and
that the rate of change has been faster
since the 1950s. Examples include
warming of the global climate system,
and substantial increases in
precipitation in some regions of the
world and decreases in other regions.
(For these and other examples, see IPCC
2007a, p. 30; and Solomon et al. 2007,
pp. 35–54, 82–85). Results of scientific
analyses presented by the IPCC show
that most of the observed increase in
global average temperature since the
mid-20th century cannot be explained
by natural variability in climate, and is
‘‘very likely’’ (defined by the IPCC as 90
percent or higher probability) due to the
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observed increase in greenhouse gas
(GHG) concentrations in the atmosphere
as a result of human activities,
particularly carbon dioxide emissions
from use of fossil fuels (IPCC 2007a, pp.
5–6 and figures SPM.3 and SPM.4;
Solomon et al. 2007, pp. 21–35). Further
confirmation of the role of GHGs comes
from analyses by Huber and Knutti
(2011, p. 4), who concluded it is
extremely likely that approximately 75
percent of global warming since 1950
has been caused by human activities.
Scientists use a variety of climate
models, which include consideration of
natural processes and variability, as
well as various scenarios of potential
levels and timing of GHG emissions, to
evaluate the causes of changes already
observed and to project future changes
in temperature and other climate
conditions (Meehl et al. 2007, entire;
Ganguly et al. 2009, pp. 11555, 15558;
Prinn et al. 2011, pp. 527, 529). All
combinations of models and emissions
scenarios yield very similar projections
of increases in the most common
measure of climate change, average
global surface temperature (commonly
known as global warming), until about
2030. Although projections of the
magnitude and rate of warming differ
after about 2030, the overall trajectory of
all the projections is one of increased
global warming through the end of this
century, even for the projections based
on scenarios that assume that GHG
emissions will stabilize or decline.
Thus, there is strong scientific support
for projections that warming will
continue through the 21st century, and
that the magnitude and rate of change
will be influenced substantially by the
extent of GHG emissions (IPCC 2007a,
pp. 44–45; Meehl et al. 2007, pp. 760–
764 and 797–811; Ganguly et al. 2009,
pp. 15555–15558; Prinn et al. 2011, pp.
527, 529). (See IPCC 2007b, p. 8, for a
summary of other global projections of
climate-related changes, such as
frequency of heat waves and changes in
precipitation. Also see IPCC
2011(entire) for a summary of
observations and projections of extreme
climate events.)
Various changes in climate may 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
interactions of climate with other
variables (e.g., habitat fragmentation)
(IPCC 2007, pp. 8–14, 18–19).
Identifying likely effects often involves
aspects of climate change vulnerability
analysis. Vulnerability refers to the
degree to which a species (or system) is
susceptible to, and unable to cope with,
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adverse effects of climate change,
including climate variability and
extremes. Vulnerability is a function of
the type, magnitude, and rate of climate
change and variation to which a species
is exposed, its sensitivity, and its
adaptive capacity (IPCC 2007a, p. 89;
see also Glick et al. 2011, pp. 19–22).
There is no single method for
conducting such analyses that applies to
all situations (Glick et al. 2011, p. 3). 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 threat
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
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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), 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
threat 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 could
experience the effects of climate change.
Prairie Plant Harvesting
A potential, future threat to the
Dakota skipper and Poweshiek
skipperling is collection of purple
coneflower (blacksamson 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.
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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,
including intensive 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. In
southwest 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
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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.).
Broadcast chemical control of exotic
plants such as aerial spraying of leafy
spurge and application of broadspectrum 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 threats 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 threat to the Hole-in-theMountain complex in Minnesota, where
both butterfly species have been
documented. Furthermore, herbicide or
pesticide use in concert with other
management types may amplify other
threats 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 threat posed by
broadcast application of herbicides or
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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
threat 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 spread of nonnative gypsy moths
(Lymantria dispar dispar) has increased
efforts to control this damaging species
and may also pose a threat, 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/
GypsyMothPesticides.html, accessed
May 24, 2012).
Herbicide and pesticide use was
assessed at 16 present and unknown
Dakota skipper sites and 10 Poweshiek
skipperling sites occupied with present
or unknown occupancy where we had
sufficient information to evaluate the
stressor (Service 2012, 2013, unpubl.
data). We considered the level of impact
to populations posed by herbicide and
pesticide use to be low if herbicides or
pesticides are used, if the site is only
spot sprayed when and where necessary
(Smart et al. 2011, p. 182) and their use
is not expected to change in the future.
The level of threat 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
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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 four 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—one in North
Dakota and one in South Dakota. The
level of impact to populations posed by
herbicide and pesticide use was
considered to be high at 3 of the 10
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 threat 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.
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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
threats described throughout Factors A,
C and E of this proposed 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 or more unidentified stressors
have strongly impacted Poweshiek
skipperling populations in the western
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portion of its range, which contains
more than 80 percent of the species’ site
records. Unknown stressors may be the
current threat 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. 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. 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 surveys had the lowest positive
detection rate (35 percent) 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). 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.
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In summary, the results of extensive
surveys in the western portion of the
Poweshiek skipperling’s range have
documented the species’ response to
unknown stressors and indicate that
they are a current threat 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 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 threats 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 threat with the
most significant impacts to the
Poweshiek skipperling are one or more
unknown stressors 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
insecticides, herbicide and pesticide
use, and prairie plant harvest are also
threats to both species. Collectively,
these threats 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
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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. 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
2012, p. 7).
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 threats described in this
finding may cumulatively or
synergistically impact the Dakota
skipper and Poweshiek skipperling
beyond the scope of each individual
threat. 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
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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 threats are likely acting
cumulatively to further increase impacts
on the already vulnerable, small and
isolated populations of Poweshiek
skipperling and Dakota skipper.
Proposed Determinations
Section 4 of the Act (16 U.S.C. 1533),
and its implementing regulations at 50
CFR part 424, set forth the procedures
for adding species to the Federal Lists
of Endangered and Threatened Wildlife
and Plants. Under section 4(a)(1) of the
Act, we may list a species based on (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. Listing
actions may be warranted based on any
of the above threat factors, singly or in
combination.
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
2 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
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to undetectable levels in approximately
50 percent of sites where it had been
recorded rangewide. It is presumed
extirpated from Illinois and Iowa and no
longer occurs east of western
Minnesota—an approximately 430-mi
(690-km) reduction of its range. Much of
the rangewide decline in the species has
been observed in the last few years.
Since 1985, researchers have surveyed
10 or more sites in 27 years; the average
positive detection rate for those years is
69 percent rangewide. Since 2010, the
percent of surveyed sites with positive
detections of the species has dropped
from 80 percent in 2010, to 42 percent
in 2011, and to 35 percent in 2012.
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
2012 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 259 historical locations, the
species is presumed extirpated or
possibly extirpated from at least 87 (34
percent) of those sites, and the
occupancy of the species is unknown at
approximately 81 (31 percent) sites. Of
the 81 sites where the occupancy is
unknown, at least 72 sites are subject to
one or more threats that have a
moderate to high impact on those
populations—these sites are distributed
across Minnesota, North Dakota, and
South Dakota. The 9 sites with
unknown occupancy without moderateto high-level threats are scattered in
various counties in Minnesota and
South Dakota, and the skipper is
thought to still be present at
approximately 91 (35 percent) of the 259
historical locations, although 23 of these
sites have not been surveyed since 2002.
Of those 91 sites, at least 83 sites are
subject to one or more threats that have
a moderate to high impact on those
populations, such as conversion to
agriculture, lack of management, and
small size and isolation. The remaining
8 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 (45 of 91) of the
locations where the species is
considered to be present are located on
privately owned fall hayed prairies in
Canada, mostly within 3 isolated
complexes, and have not been surveyed
since 2007. All 45 of those Canadian
sites have one or more stressors of
moderate to high level of impact to
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populations. A fair number of
populations in Canada are being
managed in a manner conducive to the
conservation of the Dakota skipper and
the threats at those sites are not
immediate. However, few (4–5 sites) of
these Canadian populations are
protected (on Federal land). The
remaining sites where the species is
considered to be present are about
equally distributed among Minnesota
(14 sites), North Dakota (18 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
major threats, acting individually or
synergistically, continue today (see
Summary of Factors Affecting the
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
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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
stressors 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 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 stressors, and may only be
a few years behind those declines
experienced by 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
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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 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. However,
few of these populations are protected,
many are vulnerable to changes in 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 North
Dakota and South Dakota, is likely to
continue. Therefore, on the basis of the
best available scientific and commercial
information, we propose listing the
Dakota skipper as threatened in
accordance with sections 3(6) 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—primarily in North
Dakota, South Dakota, Manitoba, and
Saskatchewan. 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.
Furthermore, we believe the species to
be present in at least 8 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. Threats to the survival of the
Dakota skipper occur throughout the
species range and are not restricted to
any particular significant portion of that
range. Accordingly, our assessment and
proposed determination applies to the
Dakota skipper throughout its range.
Significant Portion of the Range
In determining whether a species is
threatened or endangered in a
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significant portion of its range, we first
identify any portions of the range of the
species that warrant further
consideration. The range of a species
can theoretically be divided into
portions an infinite number of ways.
However, there is no purpose to
analyzing portions of the range that are
not reasonably likely to be both (1)
Significant and (2) threatened or
endangered. To identify only those
portions that warrant further
consideration, we determine whether
substantial information indicates that:
(1) The portions may be significant, and
(2) the species may be in danger of
extinction there or likely to become so
within the foreseeable future. In
practice, a key part of this analysis is
whether the threats are geographically
concentrated in some way. If the threats
to the species are essentially uniform
throughout its range, no portion is likely
to warrant further consideration.
Moreover, if any concentration of
threats applies only to portions of the
species’ range that are not significant,
such portions will not warrant further
consideration.
If we identify portions that warrant
further consideration, we then
determine whether the species is
threatened or endangered in these
portions of its range. Depending on the
biology of the species, its range, and the
threats it faces, the Service may address
either the significance question or the
status question first. Thus, if the Service
considers significance first and
determines that a portion of the range is
not significant, the Service need not
determine whether the species is
threatened or endangered there.
Likewise, if the Service considers status
first and determines that the species is
not threatened or endangered in a
portion of its range, the Service need not
determine if that portion is significant.
However, if the Service determines that
both a portion of the range of a species
is significant and the species is
threatened or endangered there, the
Service will specify that portion of the
range as threatened or endangered
under section 4(c)(1) of the ESA.
We evaluated the current range of the
Dakota skipper to determine if potential
threats for the species have any
apparent geographic concentration. We
examined potential habitat threats from
effects of habitat loss, fragmentation,
degradation, and modification from
agriculture, development, invasive
species, secondary succession, grazing,
and haying (Factor A); overutilization
for scientific or recreational collection
(Factor B); disease and predation (Factor
C); the inadequacy of existing regulatory
mechanisms (Factor D); and the effects
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of habitat fragmentation and small
population size and isolation, climate
change, pharmaceuticals, insecticides,
pesticides, prairie plant harvest, and
unknown stressors (Factor E). As
discussed above, although the specific
threats affecting the species may be
different at individual sites or in
different parts of the Dakota skipper’s
range, on the whole threats are
occurring throughout the species’ range.
The Dakota skipper is thought to still be
present at approximately 91 sites, at
least 83 of which are subject to one or
more threats that have a moderate to
high impact on those populations. On
no portions of its range are threats
significantly concentrated or
substantially greater than in other
portions of its range; therefore, we find
that impacts to the Dakota skipper are
essentially uniform throughout its
range, indicating that the entire range
warrants a threatened status under the
Act. As discussed above, our review of
the best available scientific and
commercial information indicates that
the Dakota skipper is not in danger of
extinction (endangered) but is likely to
become endangered within the
foreseeable future (threatened)
throughout all of its range. Therefore,
we find that listing the Dakota skipper
as a threatened species under the Act
throughout its entire range is warranted
at this time.
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
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skipperling has declined to zero or to
undetectable levels in approximately 87
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 29
percent each year (2004–2012), with a
low of 13 percent at sites surveyed in
2012. 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 Minnesota 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. Iowa sites were not surveyed
in 2012. Poweshiek skipperling have
historically been documented at
approximately 296 sites; now we
consider the species to be present at
only 14 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 2 small and
isolated native-prairie remnants in
Wisconsin, 10 small and isolated prairie
fen remnants in Michigan, and a prairie
complex in Manitoba. These sites
represent only 5 percent of the total
number of sites ever documented for the
species. The numbers observed at these
sites are relatively small (less than 100
at all but 2 sites), and all of these sites
have at least one documented threat that
have 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 1.2 to 2.2 during the last 4 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
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considered to have unknown occupancy
at 131 sites—throughout the range of the
species (Iowa, Michigan, Minnesota,
North Dakota, and South Dakota), 54 of
these sites were included in the threats
assessment. Of the 54 sites where the
occupancy is unknown that had
sufficient information to assess, at least
43 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.
Summary
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
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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 stressors 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 14
locations where we believe the species
to be present, and all of those sites are
subject to at least one or more ongoing
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and immediate moderate- to high-level
threats that have moderate- to high-level
effects on those populations that is
ongoing and immediate. Therefore, on
the basis of the best available scientific
and commercial information, we
propose 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 stressors 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
stressors that has moderate- to highlevel 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 stressors
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. The Poweshiek skipperling
proposed for listing in this rule is highly
restricted in its range, and the threats
occur throughout its range. Therefore,
we assessed the status of the species
throughout its entire range. The threats
to the survival of the Poweshiek
skipperling occur throughout the
species’ range and are not restricted to
any particular significant portion of that
range. Accordingly, our assessment and
proposed determination applies to the
Poweshiek skipperling throughout its
entire range.
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
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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
(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, Tribal,
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
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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.
If these 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.
Although the Dakota skipper and
Poweshiek skipperling are only
proposed for listing under the Act at
this time, please let us know if you are
interested in participating in recovery
efforts for these species. Additionally,
we invite you to submit any new
information on this 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.
Section 7(a)(4) of the Act requires
Federal agencies to confer with the
Service on any action that is likely to
jeopardize the continued existence of a
species proposed for listing or result in
destruction or adverse modification of
proposed critical habitat. 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
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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
Natural Resources Conservation Service;
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-ofway 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.
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.
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.
Our policy, as published in the
Federal Register on July 1, 1994 (59 FR
34272), is 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 proposed listing on
proposed and ongoing activities within
the range of species proposed for listing.
The following activities could
potentially result in a violation of
section 9 of the Act; 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) 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;
(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) Unauthorized modification,
removal, or destruction of the prairie
vegetation, soils, or hydrology in which
the Dakota skipper and Poweshiek
skipperling are known to occur; 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).
Special Rule
Under section 4(d) of the Act, the
Secretary may publish a special rule
that modifies the standard protections
for threatened species in the Service’s
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regulations at 50 CFR 17.31, which
implement section 9 of the Act, with
special measures that are determined to
be necessary and advisable to provide
for the conservation of the species. As
a means to promote conservation efforts
on behalf of the Dakota skipper, we are
proposing a special rule for this species
under section 4(d) of the Act. In the case
of a special 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 special rule
contains the prohibitions necessary and
appropriate to conserve that species.
As discussed above, the primary
factors supporting the proposed
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 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
stressors.
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 special rule under
section 4(d) of the Act, but the section
4(d) special rule will also include
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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, we are proposing a 4(d) special
rule that outlines the prohibitions, and
exceptions to those prohibitions,
necessary and advisable for the
conservation of the Dakota skipper.
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) and a wide
variety of peer-reviewed publications
and government reports have
documented recent loss of native
grassland (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 Dakota skipper
(Wright and Wimberly 2013, p. 2).
As with agricultural policies (Doherty
et al. 2013, p. 15), the prohibitions
against take of Dakota skipper that
would become effective if the species is
listed 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 is
frequently a priority of programs to
conserve native grassland ecosystems in
the northern Great Plains (e.g., Service
2011, p. 5). We believe that allowing
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 would facilitate the
coordination and partnerships needed
to recover the species.
In light of the socioeconomic and
policy factors that are leading to the
conversion of native prairie to
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agricultural cropland and because there
is evidence that some grazing practices
are conducive to conservation of Dakota
skipper in parts of its range, we
determine that it is necessary and
advisable to allow take of the species
caused by certain ranching activities.
Whereas conversion to cropland would
kill any Dakota skipper larvae present
and destroy any habitat value for the
species into the foreseeable future, some
habitats can remain suitable for Dakota
skipper when grazed (Dana 1991, p. 54;
Schlicht 1997, p. 5; Skadsen 1997, pp.
24–29). In addition, 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
(Service 2006, p. 2; Smart et al. in
prep.). However, some grazing practices
are adverse for Dakota skipper;
therefore, we will work with private
landowners, public land managers, state
and Federal conservation agencies, and
nongovernmental organizations to
identify, refine, and implement grazing
practices that are conducive to the
species’ conservation.
Provisions of the Proposed Special Rule
for 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
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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
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). This proposed 4(d) special rule
proposes that all prohibitions in 50 CFR
17.31(a) and (b) will apply to the Dakota
skipper except in the specific instances
as outlined below. The proposed 4(d)
special 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
First, the Service proposes that
incidental take that is caused by the
routine livestock ranching and
recreational trail maintenance activities
described below and that are
implemented on private, state, and
tribal lands 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 rule, routine livestock
ranching and recreational trail
maintenance activities include:
(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 conserve Dakota
skipper habitat.
(2) Livestock Gathering and
Management: The installation and
maintenance of corrals, loading chutes,
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and other livestock working facilities
that 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 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
phenology (growth stage) of the weed
species. Control of noxious weeds may
also be important to protect Dakota
skipper habitat because native plant
diversity may decline when nonnative
plant species invade tallgrass prairie
(Boettcher et al. 1993, p. 35). Broadcast
application of herbicides, however, may
result in significant deterioration of
habitat quality for Dakota skippers
(Smart et al. 2011, p. 184). Therefore,
incidental take of Dakota skipper that
may result from spot-spraying of
herbicides would be allowed.
(5) Haying: Stock cows need to be
maintained through the non-growing
season; thus, haying is a critical
component of ranch activity. Dakota
skippers occur on several native
hayland sites—sites where the nativeprairie 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 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 allowed.
Dakota skippers are unlikely to occur in
replanted grasslands (grasslands
replanted on formerly plowed or
cultivated lands) or in tame hayland
(grassland comprised primarily of
nonnative grass species, such as smooth
brome (Bromus inermis inermis)).
Therefore, mowing before July 16 is
allowed on replanted and tame
grasslands.
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(6) Mowing 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 winter
snow will not catch and block vehicle
access and that they are suitable for
hiking and other intended recreational
activities, respectively. These areas
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 caused by mowing of section line
rights of way and recreational trails is
allowed.
(7) Livestock (e.g., cattle or bison)
grazing, except on lands where Dakota
skipper occurs in the following states
and counties: Minnesota—Kittson;
North Dakota—Eddy, McHenry,
Richland, Rolette, Sargent, and
Stutsman. In those counties Dakota
skippers inhabit relatively flat and moist
habitats where they may be especially
sensitive to effects of grazing (Royer et
al. 2008, pp. 11, 16), including
trampling, soil compaction, and loss of
important nectar sources; haying
conducted after the Dakota skipper
flight period is the predominant
management on sites inhabited by the
species in these counties. In all other
states and counties, incidental take of
Dakota skippers that may result from
grazing is allowed under this rule.
In the drier and hillier habitats that
the species inhabits outside of the
counties listed above, grazing may
benefit Dakota skipper depending on its
intensity. Moreover, in contrast to the
permanent habitat destruction caused
by plowing, mining, and certain other
activities, native plant diversity in
tallgrass prairie may recover from
overgrazing if it has not been too severe
or prolonged. 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). Nevertheless, grazing can also
have significant deleterious effects on
Dakota skipper; for example, a strong
population of the species at a grazed site
in South Dakota was extirpated after a
change in ownership resulted in
significant overgrazing (Skadsen 2006,
p. 5). Therefore, we intend to cooperate
with ranchers and our state and tribal
conservation partners to identify, test,
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and implement grazing practices that
effectively conserve Dakota skipper
populations. By allowing grazing in the
geographic areas where the Dakota
skipper primarily inhabits dry-mesic
prairie, we may slow the loss of native
prairie conversion for crop production
and also maintain partnerships that are
critical for conserving the species.
In the counties where this rule would
not allow take caused by livestock
grazing, Dakota skipper almost
exclusively inhabits relatively flat and
moist prairie habitats that are mowed
for hay. 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
when 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 (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 skipper 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 Dakota skipper,
for example, habitat on steep slopes was
‘‘in good condition’’, whereas ‘‘lesser
slopes’’ were ‘‘moderately grazed’’ and
some areas were ‘‘overgrazed’’ (Skadsen
1999, p. 29).
The best available information
indicates that in the counties where this
rule would not allow take caused by
livestock grazing the species may be
extant at 19 sites and only 1 of those is
currently grazed. The single grazed site
is in McHenry County, North Dakota,
and is owned by the State of North
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Dakota. The habitat at the site is
described as ‘‘marginal’’ for Dakota
skipper and there ‘‘has never been a
strong’’ presence of the species, based
on surveys of the site conducted since
about 1991 (Royer 2013, pers. comm.).
Since Dakota skipper was recorded
there in 1998, only one survey has been
conducted—in 2012 (Royer and Royer
1998, p. 9; Royer and Royer 2012, p. 3).
No Dakota skippers were found there
during two surveys in 2012, although
they were present at a hayed site across
the road (Royer and Royer 2012, p. 42).
At three other sites in the counties
where this rule would not allow take
caused by grazing, grazing was likely
the primary factor that led to the
species’ extirpation. At each of these
sites grazing was described as ‘‘heavy’’
or ‘‘substantial’’, the habitat was
degraded, and important nectar sources
were lacking or depleted (Royer and
Royer 2012, pp. 9, 12, 27).
The lack of any examples of sites
where strong populations of Dakota
skippers occur in concert with grazing
indicates to us that it would not be
advisable at this time to allow take
caused by grazing in the counties listed
above—Kittson County, Minnesota, and
Eddy, McHenry, Richland, Rolette,
Sargent, and Stutsman Counties in
North Dakota. In these counties, Dakota
skipper primarily inhabits wet-mesic
prairie habitats that support plant
communities that are distinct from those
that occur on dry-mesic prairie
elsewhere in the species’ range.
The Service is committed to working
with private landowners, public land
managers, conservation agencies,
nongovernmental organizations, and the
scientific community to determine
whether any grazing of Dakota skipper
habitat in any of the counties may be
conducted in a manner that is
conducive to the species’ conservation.
We are seeking public comments on this
topic. In the meantime, the continuation
of hay production as the primary use of
these habitats—with mowing occurring
no earlier than July 16—is the most
compatible land use activity for the
Dakota skipper and would contribute
substantially to the conservation of the
species.
Peer Review
In accordance with our joint policy on
peer review published in the Federal
Register on July 1, 1994 (59 FR 34270),
we will seek the expert opinions of at
least three appropriate and independent
specialists regarding this proposed rule.
We have invited these peer reviewers to
comment during this public comment
period on our specific assumptions and
conclusions in this proposed rule.
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We will consider all comments and
information received during this
comment period on this proposed rule
during our preparation of a final
determination. Accordingly, the final
decision may differ from this proposal.
Public Hearings and Informational
Meetings
Section 4(b)(5) of the Act provides for
one or more public hearings on this
proposal, if requested. Requests must be
received within 45 days after the date of
publication of this proposed rule in the
Federal Register. Such requests must be
sent to the address shown in FOR
FURTHER INFORMATION CONTACT. We will
schedule public hearings on this
proposal, if any are requested, and
announce the dates, times, and places of
those hearings, as well as how to obtain
reasonable accommodations, in the
Federal Register and local newspapers
at least 15 days before the hearing.
We have scheduled informational
meetings regarding the proposed rule in
the locations specified in ADDRESSES.
Any interested individuals or
potentially affected parties seeking
additional information on the public
informational meetings should contact
the Twin Cities Ecological Services
Office (See FOR FURTHER INFORMATION
CONTACT). The U.S. Fish and Wildlife
Service is committed to providing
access to this event for all participants.
Please direct all requests for
interpreters, closed captioning, or other
accommodation to the Twin Cities
Ecological Services Office (See FOR
FURTHER INFORMATION CONTACT).
Required Determinations
Clarity of the Rule
We are required by Executive Orders
12866 and 12988 and by the
Presidential Memorandum of June 1,
1998, to write all rules in plain
language. This means that each rule we
publish must:
(1) Be logically organized;
(2) Use the active voice to address
readers directly;
(3) Use clear language rather than
jargon;
(4) Be divided into short sections and
sentences; and
(5) Use lists and tables wherever
possible.
If you feel that we have not met these
requirements, send us comments by one
of the methods listed above in
ADDRESSES. To better help us revise the
rule, your comments should be as
specific as possible. For example, you
should tell us the numbers of the
sections or paragraphs that are unclearly
written, which sections or sentences are
too long, the sections where you feel
lists or tables would be useful, etc.
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
Vertebrate population where endangered or threatened
Historic range
mstockstill on DSK4VPTVN1PROD with PROPOSALS2
Common name
*
INSECTS
*
*
Skipper, Dakota .......
VerDate Mar<15>2010
Scientific name
*
*
Hesperia dacotae ...
18:08 Oct 23, 2013
Jkt 232001
*
*
U.S.A. (IL, IA, MN,
ND, SD); Canada
(Manitoba, Saskatchewan).
PO 00000
Frm 00052
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 Field
Supervisor, Twin Cities Field Office (see
FOR FURTHER INFORMATION CONTACT).
Authors
The primary authors of this package
are the staff members of the Twin Cities
Field Office.
List of Subjects in 50 CFR Part 17
Endangered and threatened species,
Exports, Imports, Reporting and
recordkeeping requirements, and
Transportation.
Proposed Regulation Promulgation
Accordingly, we propose to amend
part 17, subchapter B of chapter I, title
50 of the Code of Federal Regulations,
as set forth below:
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. In § 17.11(h), add entries for
‘‘Skipper, Dakota’’ and ‘‘Skipperling,
Poweshiek’’ to the List of Endangered
and Threatened Wildlife in alphabetical
order under ‘‘Insects’’ to read as set
forth below:
■
§ 17.11 Endangered and threatened
wildlife.
*
Status
*
*
(h) * * *
Sfmt 4702
*
T
*
When listed
*
*
NA ...........................
Fmt 4701
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.
*
Critical
habitat
*
*
....................
E:\FR\FM\24OCP2.SGM
24OCP2
Special
rules
*
*
NA
17.47(b)
63625
Federal Register / Vol. 78, No. 206 / Thursday, October 24, 2013 / Proposed Rules
Species
Vertebrate population where endangered or threatened
Historic range
Common name
*
Skipperling,
Poweshiek.
*
Scientific name
*
Oarisma poweshiek
*
3. Amend § 17.47 by adding paragraph
(b) to read as follows:
Special rules—insects.
mstockstill on DSK4VPTVN1PROD with PROPOSALS2
*
*
*
*
*
(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:
(i) Recreational trail maintenance
activities;
(ii) Mowing of section line rights of
way; and
(iii) Routine livestock ranching
activities that are conducted in
accordance with applicable State,
Federal, tribal, and local laws and
regulations. For the purposes of this
rule, routine livestock ranching
activities include:
(A) Fence construction and
maintenance.
(B) Activities pertaining to livestock
gathering and management, such as the
installation and maintenance of corrals,
loading chutes, and other livestock
working facilities.
(C) Development and maintenance of
livestock watering facilities.
(D) Spot-spraying of herbicides for
noxious weed control (Broadcast
application of herbicides is not
allowed.).
(E) Haying, as set forth in this
paragraph (b)(3)(i)(E):
(1) In native haylands, which are
typically cut in August after the
needlegrass (Hesperostipa spp. or
Nassella viridula) awns drop, haying
after July 15 is allowed.
(2) In replanted grasslands (grasslands
replanted on formerly plowed or
cultivated lands) or in tame haylands
(grasslands comprising primarily
nonnative grass species, such as smooth
brome (Bromus inermis inermis)),
mowing may occur at any time.
VerDate Mar<15>2010
18:08 Oct 23, 2013
*
NA ...........................
*
■
§ 17.47
*
U.S.A. (IL, IA, IN,
MI, MN, WI, ND,
SD); Canada
(Manitoba).
Jkt 232001
Status
*
E
*
Dated: September 23, 2013.
Rowan W. Gould,
Acting Director, U.S. Fish and Wildlife
Service.
[FR Doc. 2013–24175 Filed 10–23–13; 8:45 am]
BILLING CODE 4310–55–P
DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[FWS–R3–ES–2013–0017; 4500030113]
RIN 1018–AZ58
Endangered and Threatened Wildlife
and Plants; Designation of Critical
Habitat for Dakota Skipper and
Poweshiek Skipperling
Fish and Wildlife Service,
Interior.
ACTION: Proposed rule.
AGENCY:
We, the U.S. Fish and
Wildlife Service, propose to designate
critical habitat for the Dakota skipper
and Poweshiek skipperling under the
Endangered Species Act of 1973, as
amended. The Endangered Species Act
requires that critical habitat be
designated to the maximum extent
prudent and determinable for species
determined to be endangered or
threatened species. The effect of this
regulation is to designate critical habitat
for the Dakota skipper and Poweshiek
skipperling under the Endangered
Species Act.
DATES: Written Comments: We will
accept comments received or
postmarked on or before December 23,
2013. Comments submitted
electronically using the Federal
eRulemaking Portal (see ADDRESSES
SUMMARY:
Frm 00053
Fmt 4701
*
....................
*
(F) Grazing of cattle, bison, or horses,
except in Kittson County, Minnesota,
and Eddy, McHenry, Richland, Rolette,
Sargent, and Stutsman Counties, North
Dakota, where the Dakota skipper
inhabits areas that may be especially
sensitive to the effects of grazing by
these types of livestock.
*
*
*
*
*
PO 00000
When listed
Sfmt 4702
*
Critical
habitat
Special
rules
*
NA
NA
*
section, below) must be received by
11:59 p.m. Eastern Time on the closing
date. We must receive requests for
public hearings, in writing, at the
address shown in ADDRESSES by
December 9, 2013.
Public Informational Meetings: To
better inform the public of the
implications of the proposed listing and
to answer any questions regarding this
proposed rule, we plan to hold five
public informational meetings. We have
scheduled informational meetings
regarding the proposed rule in the
following locations:
(1) Minot, North Dakota, on November
5, 2013, at the Souris Valley Suites, 800
37th Avenue SW;
(2) Milbank, South Dakota, on
November 6, 2013, at the Milbank
Chamber of Commerce, 1001 East 4th
Avenue;
(3) Milford, Iowa, on November 7,
2013, at the Iowa Lakeside Laboratory,
1838 Highway 86;
(4) Holly, Michigan, on November 13,
2013, at the Rose Pioneer Elementary
School, 7110 Milford Road; and
(5) Berlin, Wisconsin, on November
14, 2013, at the Berlin Public Library,
121 West Park Avenue.
Except for the meeting in Berlin,
Wisconsin, each informational meeting
will be from 5:30 p.m. to 8:00 p.m.; the
meeting in Berlin, Wisconsin will be
from 4:30 p.m. to 7:00 p.m.
ADDRESSES: You may submit comments
by one of the following methods:
(1) Electronically: Go to the Federal
eRulemaking Portal: https://
www.regulations.gov. In the Search box,
enter FWS–R3–ES–2013–0017, which is
the docket number for this rulemaking.
You may submit a comment by clicking
on ‘‘Comment Now!’’ If your comments
will fit in the provided comment box,
please use this feature of https://
www.regulations.gov, as it is most
compatible with our comment review
procedures. If you attach your
comments as a separate document, our
preferred file format is Microsoft Word.
If you attach multiple comments (such
as form letters), our preferred format is
a spreadsheet in Microsoft Excel.
(2) By hard copy: Submit by U.S. mail
or hand-delivery to: Public Comments
E:\FR\FM\24OCP2.SGM
24OCP2
]]>Agencies
[Federal Register Volume 78, Number 206 (Thursday, October 24, 2013)]
[Proposed Rules]
[Pages 63573-63625]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2013-24175]
[[Page 63573]]
Vol. 78
Thursday,
No. 206
October 24, 2013
Part II
Department of the Interior
-----------------------------------------------------------------------
Fish and Wildlife Service
-----------------------------------------------------------------------
50 CFR Part 17
Endangered and Threatened Wildlife and Plants; Threatened Status for
Dakota Skipper and Endangered Status for Poweshiek Skipperling;
Endangered and Threatened Wildlife and Plants; Designation of Critical
Habitat for Dakota Skipper and Poweshiek Skipperling; Proposed Rules
Federal Register / Vol. 78 , No. 206 / Thursday, October 24, 2013 /
Proposed Rules
[[Page 63574]]
-----------------------------------------------------------------------
DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[FWS-R3-ES-2013-0043; 4500030113]
RIN 1018-AY01
Endangered and Threatened Wildlife and Plants; Threatened Status
for Dakota Skipper and Endangered Status for Poweshiek Skipperling
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Proposed rule.
-----------------------------------------------------------------------
SUMMARY: We, the U.S. Fish and Wildlife Service, propose to list the
Dakota skipper as a threatened species and the Poweshiek skipperling as
an endangered species under the Endangered Species Act of 1973, as
amended. If we finalize this rule as proposed, it would extend the
Act's protections to the Dakota skipper and the Poweshiek skipperling.
The effect of this regulation is to add the Dakota skipper and the
Poweshiek skipperling to the List of Endangered and Threatened
Wildlife. We also propose a special rule under section 4(d) of the Act
that outlines the prohibitions necessary and advisable for the
conservation of the Dakota skipper, if it is listed as a threatened
species.
DATES: Written Comments: We will accept comments received or postmarked
on or before December 23, 2013. Comments submitted electronically using
the Federal eRulemaking Portal (see ADDRESSES section, below) must be
received by 11:59 p.m. Eastern Time on the closing date. We must
receive requests for public hearings, in writing, at the address shown
in the ADDRESSES section by December 9, 2013.
Public Informational Meetings: To better inform the public of the
implications of the proposed listing and to answer any questions
regarding this proposed rule, we plan to hold five public informational
meetings. We have scheduled informational meetings regarding the
proposed rule in the following locations:
(1) Minot, North Dakota, on November 5, 2013, at the Souris Valley
Suites, 800 37th Avenue SW;
(2) Milbank, South Dakota, on November 6, 2013, at the Milbank
Chamber of Commerce, 1001 East 4th Avenue;
(3) Milford, Iowa, on November 7, 2013, at the Iowa Lakeside
Laboratory, 1838 Highway 86;
(4) Holly, Michigan, on November 13, 2013, at the Rose Pioneer
Elementary School, 7110 Milford Road; and
(5) Berlin, Wisconsin, on November 14, 2013, at the Berlin Public
Library, 121 West Park Avenue.
Except for the meeting in Berlin, Wisconsin, each informational
meeting will be from 5:30 p.m. to 8:00 p.m.; the meeting in Berlin,
Wisconsin will be from 4:30 p.m. to 7:00 p.m.
ADDRESSES: You may submit comments by one of the following methods:
(1) Electronically: Go to the Federal eRulemaking Portal: https://www.regulations.gov. In the Search box, enter FWS-R3-ES-2013-0043,
which is the docket number for this rulemaking. Then, in the Search
panel on the left side of the screen, under the Document Type heading,
click on the Proposed Rules link to locate this document. You may
submit a comment by clicking on ``Comment Now!''
(2) By hard copy: Submit by U.S. mail or hand-delivery to: Public
Comments Processing, Attn: FWS-R3-ES-2013-0043; Division of Policy and
Directives Management; U.S. Fish and Wildlife Service; 4401 N. Fairfax
Drive, MS 2042-PDM; Arlington, VA 22203.
We request that you send comments only by the methods described
above. We will post all comments on https://www.regulations.gov. This
generally means that we will post any personal information you provide
us (see the Public Comments section below for more information).
FOR FURTHER INFORMATION CONTACT: Pete Fasbender, Field Supervisor, U.S.
Fish and Wildlife Service, Twin Cities Ecological Services Office, 4101
American Boulevard East, Bloomington, Minnesota, 55425, by telephone
(612) 725-3548 or by facsimile (612) 725-3609. 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
(Act), if a species is determined to be an endangered or threatened
species throughout all or a significant portion of its range, we are
required to promptly publish a proposal in the Federal Register and
make a determination on our proposal within one year. Listing a species
as an endangered or threatened species can only be completed by issuing
a rule. A species may warrant protection through listing under the Act
if it meets the definition of an endangered or threatened species
throughout all or a significant portion of its range.
This rule consists of:
A proposed rule to list the Poweshiek skipperling as an
endangered species;
A proposed rule to list the Dakota skipper as threatened
species; and
A proposed special rule under section 4(d) of the Act that
outlines the prohibitions necessary and advisable for the conservation
of the Dakota skipper.
Elsewhere in today's Federal Register, we propose to designate
critical habitat for the Dakota skipper and Poweshiek skipperling under
the Act.
The basis for our action. Under the 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. Furthermore, whenever a species is listed as a
threatened species, we may issue regulations that are necessary and
advisable for the conservation of that species under section 4(d) of
the Act.
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, and other unknown stressors.
Existing regulatory mechanisms are inadequate to mitigate
these threats to both species.
We will seek peer review. We are seeking comments from
knowledgeable individuals with scientific expertise to review our
analysis of the best available science and application of that science
and to provide any additional scientific information to improve this
proposed rule. Because we will consider all comments and information
received during the comment period, our final
[[Page 63575]]
determinations may differ from this proposal.
Information Requested
We intend that any final action resulting from this proposed rule
will be based on the best scientific and commercial data available and
be as accurate and as effective as possible. Therefore, we request
comments or information from other concerned government agencies, the
scientific community, industry, or any other interested party
concerning this proposed rule. We particularly seek comments
concerning:
(1) The species' biology, range, and population trends, including:
(a) Habitat requirements for feeding, breeding, and sheltering;
(b) Genetics and taxonomy;
(c) Historical and current range including distribution patterns;
(d) Historical and current population levels, and current and
projected trends; and
(e) Past and ongoing conservation measures for the species, its
habitat, or both.
(2) The factors that are the basis for making a listing
determination for a species under section 4(a) of the Act (16 U.S.C.
1531 et seq.), which are:
(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.
(3) Biological, commercial trade, or other relevant data concerning
any threats (or lack thereof) to these species and existing regulations
that may be addressing those threats;
(4) Additional information concerning the historical and current
status, range, distribution, and population size of these species,
including the locations of any additional populations;
(5) Any information on the biological or ecological requirements of
these species and ongoing conservation measures for these species and
their habitat;
(6) Specific information on the amount and distribution of the
Dakota skipper and Poweshiek skipperling and their habitat; and
(7) Our approach to determining the status of each species at each
site, and our definitions of ``present,'' ``unknown,'' ``possibly
extirpated,'' and ``extirpated'' as described under Species Status,
below.
(8) Suitability of the proposed 4(d) rule for the conservation,
recovery, and management of the Dakota skipper.
(9) Whether it would be appropriate to allow routine livestock
grazing activities on lands inhabited by Dakota skipper in any
additional counties. The proposed 4(d) rule would allow routine
livestock grazing activities on lands inhabited by the Dakota skipper
in counties where the species does not primarily occur in relatively
flat and moist (wet-mesic or mesic) prairie habitats. Wet-mesic or
mesic habitats in which the Dakota skipper occurs are typically hayed
after July 15 and not grazed. We are seeking comments on whether or not
grazing may be implemented in these habitats in a manner that would
allow for the persistence of the Dakota skipper.
(10) Any information on Tribal regulations or Tribal conservation
efforts that may affect either the Dakota skipper or Poweshiek
skipperling and their habitat.
Please include sufficient information with your submission (such as
scientific journal articles or other publications) to allow us to
verify any scientific or commercial information you include.
Please note that submissions merely stating support for or
opposition to the action under consideration without providing
supporting information, although noted, will not be considered in
making a determination, as section 4(b)(1)(A) of the Act directs that
determinations as to whether any species is a threatened or endangered
species must be made ``solely on the basis of the best scientific and
commercial data available.''
You may submit your comments and materials concerning this proposed
rule by one of the methods listed in the ADDRESSES section. We request
that you send comments only by the methods described in the ADDRESSES
section.
If you submit information via https://www.regulations.gov, your
entire submission--including any personal identifying information--will
be posted on the Web site. If your submission is made via a hardcopy
that includes personal identifying information, you may request at the
top of your document that we withhold this information from public
review. However, we cannot guarantee that we will be able to do so. We
will post all hardcopy submissions on https://www.regulations.gov.
Please include sufficient information with your comments (such as
scientific journal articles or other publications) to allow us to
verify any scientific or commercial information you include.
Comments and materials we receive, as well as supporting
documentation we used in preparing this proposed rule, will be
available for public inspection on https://www.regulations.gov, or by
appointment, during normal business hours, at the U.S. Fish and
Wildlife Service, Twin Cities Ecological Services Office (see FOR
FURTHER INFORMATION CONTACT).
Previous Federal Actions
The U.S. Fish and Wildlife Service (Service) initiated proceedings
to list the Dakota skipper as a threatened species in 1978 (43 FR
28938), but withdrew the proposed rulemaking after Congress amended the
Endangered Species Act in 1979 (45 FR 58171). The Dakota skipper was
designated a category 2 candidate species in the May 22, 1984, Notice
of Review (49 FR 21664) and remained a category 2 species (January 6,
1989, 54 FR 572; November 21, 1991, 56 FR 58830; and November 15, 1994,
59 FR 59020). A category 2 candidate was defined as a species for which
information in the Service's possession indicates that listing was
possibly appropriate, but for which sufficient information on
biological vulnerability and threats was not currently available to
support a proposal for listing under the Act.
On January 21, 1994, the Service received a petition from the
Biodiversity Legal Foundation to list the Dakota skipper as an
endangered or threatened species and to designate critical habitat. We
made a 90-day finding that the petition presented substantial
information to indicate that the requested action may be warranted; the
finding was published in the Federal Register on July 28, 1994 (59 FR
38424). On February 27, 1995, we announced a 12-month finding in which
we determined that the species should remain as a category 2 candidate,
that timely appropriate prairie management and protection may eliminate
the need to list the species, and that researchers indicated that more
surveys, particularly in Minnesota, Iowa, and North Dakota, were needed
(60 FR 10535).
In a December 5, 1996 (61 FR 64481) decision, the Service
discontinued the practice of maintaining a list of species regarded as
``category-2 candidates.'' Instead, the Service would keep a single
list of candidate species--species for which the Service has on file
sufficient information to support issuance of a proposed listing rule.
In 2002, the Service reviewed the status of the Dakota skipper and
determined that it met the definition of a candidate species. The
Dakota skipper was assigned a listing priority number of 11 on June 13,
2002 (67 FR 40657).
[[Page 63576]]
The Dakota skipper remained a candidate species with a listing priority
number of 11 in subsequent notices, including May 4, 2004 (69 FR
24876), May 11, 2005 (70 FR 24870), and September 12, 2006 (71 FR
53756). The Service changed the listing priority 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, including December 10, 2008 (73 FR 75176), November 9, 2009
(74 FR 57804), November 10, 2010 (75 FR 69222), and October 26, 2011
(76 FR 66370).
On May 12, 2003, the Service received a petition from the
Biodiversity Conservation Alliance and five others to list the Dakota
skipper as endangered or threatened and to designate critical habitat.
The Service agreed with the petitioners, by virtue of having made it a
candidate in 2002, that the Dakota skipper warranted listing as
threatened or endangered under the Act. The petition did not contain
evidence supporting emergency listing or changing the listing priority
number; therefore, the Service took no further action on the petition.
On July 12, 2011, the Service filed a proposed settlement agreement
with the Center for Biological Diversity in a consolidated case in the
U.S. District Court for the District of Columbia. The settlement
agreement was approved by the court on September 9, 2011. As part of
this settlement agreement, the Service agreed to complete a proposed
listing rule or not warranted finding for the Dakota skipper by
September 30, 2013.
The Service identified the Poweshiek skipperling (Oarisma
poweshiek) as a candidate species, with a listing priority number of 2,
in a notice of review published in the Federal Register on October 26,
2011 (76 FR 66370).
Status Assessments for Dakota Skipper and Poweshiek Skipperling
Background
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 includes 3 other
subfamilies, and the genus Hesperia contains 18 species (Miller and
Brown 1981, p. 31; Ferris 1989 in Royer and Marrone 1992a, p. 1).
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).
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, depending on weather patterns. Females emerge slightly
later than males (Dana 1991, p. 1), 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 two to four
weeks, and mating occurs throughout this period (Braker 1985, p. 46;
McCabe and Post 1977a, p. 38; McCabe and Post 1977b, p. 36; McCabe
1979, p. 6; McCabe 1981, p. 180; Dana 1991, p. 15; Swengel and Swengel
1999, p. 282). 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. 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), bluebell
bellflower (Campanula rotundifolia), white prairie clover (Dalea
candida), upright prairie coneflower (Ratibida columnifera), fleabanes
(Erigeron spp.), blanketflowers (Gaillardia spp.), black-eyed Susan
(Rudbeckia hirta), groundplum milkvetch (Astragalus crassicarpus), and
yellow sundrops (Calylophus serrulatus) (McCabe and Post 1977b, p. 36;
Royer and Marrone 1992a, p. 21). 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). Swengel and
[[Page 63577]]
Swengel (1999, pp. 280-281) observed nectaring at 25 plant species, but
85 percent of the nectaring was at the following three plants, in
declining order of frequency: Purple coneflower, blanketflower, and
groundplum milkvetch. 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. 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.).
Dakota skipper larvae feed only 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 Panicum spp., Poa spp., and other native
grasses (Royer and Marrone 1992a, p. 25). Seasonal senescence patterns
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 (Dana 1991, p. 46).
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 with roads and crop fields
compared with movements in adjacent widespread prairie habitat. 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, 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 1999a, 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 1999a, 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 (Gaillardia aristata) (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
1999b, 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 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 (H. comata), and prairie dropseed, and a high
diversity and abundance of forbs, including purple coneflower, purple
prairie clover (Dalea purpurea), white prairie clover, yellow sundrops,
prairie groundsel (Packera plattensis), groundplum 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
[[Page 63578]]
(Zizia aptera), blanket flower (Gaillardia sp.), 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 inhabit Type B habitats. 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 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 twelve 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 skippers inhabit Type A habitats, occupy
the slightly higher, drier areas of wet-mesic prairie where nectar
sources are more abundant (Webster 2003, p. 7). 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 (Poa pratensis), 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 (Bromus inermis) 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 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; Minnesota sites generally had higher soil temperatures at all
depths than sites in North Dakota or South Dakota (Royer et al. 2008,
p. 11).
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 (Royer et al. 2008, pp. 2, 16). 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 ``larval nesting
zones'' (between the soil surface and 2 cm deep) 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.
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 of
the following five 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 species to be present at one Dakota
skipper site (Frenchman's Bluff Preserve in Minnesota) where the most
recent survey was from 1993. 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. 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) and one site with a 1998 record
(an unnamed site in North Dakota). 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. Little
information is known about the one unnamed site in North
[[Page 63579]]
Dakota; however, the best information we have indicates that the
habitat is still suitable for the species, and the North Dakota species
expert supports that the species is likely present.
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 is 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 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.
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 75 percent
of known Poweshiek skipperling sites and over 89 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 or
under unsuitable conditions (e.g., high wind speeds).
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.
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 every survey since that date--the
most recent detection was in 2012. 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. In several
cases, species experts provided input on occupancy based on their
familiarity 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 sites
with a present status have had a positive detection in 2002, 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 2012, except one
site where the species was detected in 2011 and no further surveys have
occurred. Likewise, 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 1993, two
sites with 1996 records, and one site with a 1998 record. 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: 20 sites in Canada that were surveyed only once 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; 2 sites with a 2006 detection; 25 sites in
Canada that were surveyed only once in 2007; 1 additional site with a
2007 detection; 7 sites with a positive detection in 2008; 2 sites with
a positive detection in 2009; and 27 sites with positive detections in
2012.
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 occurs east of western
Minnesota--an approximately 690-kilometer (km) (430-mile) reduction of
its range. Populations persist in
[[Page 63580]]
western Minnesota, northeastern South Dakota, North Dakota, southern
Manitoba, and southeastern Saskatchewan. Royer and Marrone (1992a, p.
5) stated 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 Royer (2002, pers. comm.) no longer
thinks that the species occurs 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 1999, 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 259 historically documented sites, there
are 91 sites where we consider the Dakota skipper to be present, 81
sites with unknown status, 40 possibly extirpated sites, and 47 that
are considered extirpated (Table 1). Approximately half (45 of 91) of
the sites where the species is considered to be present are located in
Canada, mostly within three isolated complexes, and were observed in
either 2002 or 2007 with no subsequent surveys. The remaining 46 sites
where the species is considered to be present are about equally
distributed among Minnesota (14 sites), North Dakota (18 sites), and
South Dakota (14 sites). Researchers made positive detections of the
species in 27 of these sites in 2012. Other sites with a present status
with relatively older positive detections and no subsequent surveys for
the species include 2 sites with positive detections in 1996, one site
with a positive detection in 1998, one site with a positive detection
in 2002, one site with a positive detection in 2003, one site with a
positive detection in 2005, 2 sites with a positive detection in 2006,
one site with a positive detection in 2007, 7 sites with a positive
detection in 2008, and 2 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.
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
----------------------------------------------------------------------------------------------------------------
Percent of
total
Possibly number of
State Present Unknown extirpated Extirpated Total historical
sites by
state
----------------------------------------------------------------------------------------------------------------
Illinois.................... ........... ........... .............. 1 1 0.4
Iowa........................ ........... ........... .............. 3 3 1
Minnesota................... 14 22 18 12 66 26
North Dakota................ 18 13 10 13 54 21
South Dakota................ 14 46 10 15 85 33
Manitoba.................... 31 0 2 3 36 14
Saskatchewan................ 14 0 0 0 14 5
-----------------------------------------------------------------------------------
Total Number of 91 81 40 47 259 ...........
Historically Documented
Sites..................
-----------------------------------------------------------------------------------
Percent of the Total 35 31 16 18 ........... 100
Number of 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).
[[Page 63581]]
The species was not observed at eight sites surveyed between 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 2013,
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 2013, unpubl. geodatabase). Of the 66 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 22
others (Service 2013, unpubl. geodatabase). Dakota skipper is
considered to be present at 14 sites in Minnesota in 6 counties: Clay,
Lincoln, Murray, Norman, Pipestone, and Pope, although 2 of those sites
have not been surveyed since 1996 and 1 site has not been surveyed
since 1993.
McCabe (1981, p. 187) observed very stable population numbers in
Minnesota prairies that he visited repeatedly from 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, to 56 percent
(10 of 18 sites) in 2008, to 6 percent (1 of 18 sites) in 2012 (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.). The cause for this sharp
decline is unknown.
[[Page 63582]]
[GRAPHIC] [TIFF OMITTED] TP24OC13.088
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 2013,
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 2013,
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 2013, unpubl.
geodatabase). Of the 18 sites where the species is possibly extirpated,
10 have not been surveyed since the species was last seen in 1988 or
earlier. Dakota skippers at two of the sites where the species is
possibly extirpated have not been observed since 1991 (Service 2013,
unpubl. geodatabase). The remaining 6 sites had positive observations
prior to 1993, were surveyed once more recently, and had a negative
observation (Service 2013, unpubl. geodatabase).
The status of Dakota skipper is unknown at 22 sites; Dakota skipper
have not been observed at 11 of these sites since the mid- to late
1990s, despite one or two years of survey effort at several sites. The
remaining 11 sites with unknown status have had positive observations
in 2007 or more recently, but are given this designation due to a
subsequent negative survey. 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
(Selby 2009a, p. Appendix 5 li, xxxiii and Appendix 4 xlix).
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 flight period
(Runquist
[[Page 63583]]
2012, pp. 13-14, 18-20; Runquist 2012a, pers. comm.); therefore, we
consider the status of the species at the Hole-in-the-Mountain preserve
to be unknown.
Relatively important populations of Dakota skipper in Minnesota may
still occur at the Prairie Coteau, Felton Prairie, and Glacial Lakes
complexes, but the 2012 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 flight period
(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 one-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 has not been resurveyed since 2008 (Service 2013, 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 25 mi (40 km) 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. l and liv) 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 seven hours of surveys in and
around the park (Selby 2009a, p. 1 and liv). Glacial Lakes State Park
surveys conducted in 2012 were outside of the Dakota skipper flight
period (Runquist 2012a, pers. comm.).
In summary, the Dakota skipper is now considered to be extirpated
or possibly extirpated from at least 30 of the 66 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 14 and 22 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. 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 2013, unpubl. geodatabase). The Dakota skipper is currently
present at 18 sites in 5 North Dakota counties, of these, 13 occur
within the Towner-Karlsruhe complex in McHenry County, 1 is within the
Sheyenne National Grasslands complex in Ransom County, 2 in northern
McKenzie County, 1 site is in Wells County, and 1 site in McLean
County. Of the 18 sites where we consider the Dakota skipper to be
present, 15 sites had positive observations of the species in 2012 and
the remaining 3 sites had positive observations between 1998 and 2003.
The status of the species is unknown at 13 sites; 10 of these sites
have not had positive records since the mid- to late 1990s and the
other 3 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 10 additional sites and 3
additional counties. Researcher 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).
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, p. 21-22; Royer et al. 2008, pp. 14-16). Five sites
within the Towner-Karlsruhe complex are owned by the North Dakota State
Land Department, and the remaining seven 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 1999b, 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 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
[[Page 63584]]
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.
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 4 sites
outside of the Towner-Karsruhe Complex and Sheyenne National Grasslands
complexes are thought to have extant (present) Dakota skipper
populations, including Garrison Training Center in McLean County. 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).
In summary, North Dakota contains approximately 21 percent (N= 53)
of all known historical locations of the species rangewide; however,
the current occupancy status of the Dakota skipper is unknown at 12
sites, and it is considered to be extirpated or possibly extirpated
from at least 23 of the 53 known sites in the state (Table 1). The
species is considered to be present at only 18 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 statewide surveys (ND state average = 17.4 encounters per
hour).
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 135 additional locations in North
Dakota that were surveyed for the species from 1991-2012 (USFWS 2013,
unpubl. geodatabase). Many of these sites have been surveyed multiple
times over multiple years (USFWS 2013, 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
appear suitable for the species and have a good potential of finding
the species, in other words, sites are not randomly selected across the
landscape. Therefore, these sites have a higher likelihood of detecting
the species 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) of the species in South
Dakota, 85 sites have been documented across 11 counties in the State,
but recent surveys indicate that the species is declining in the State
(Service 2013, unpubl. geodatabase). Of the 85 historical sites, Dakota
skipper is presumed extirpated from 15 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 46 sites. Twenty-six sites in South Dakota with previous
Dakota skipper records were surveyed in 2012; the species was detected
at 9 of those sites (Service 2013, 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 2013, unpubl. geodatabase;
Skadsen 2012a, pers. comm.). The proportion of positive surveys at
known sites has fluctuated over time; however, the 2012 surveys had the
lowest positive detection rate (35 percent) 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 2012, pp. 4-5; Skadsen, 2012,
pers. comm.; Skadsen 2003, p. 10; Skadsen 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 2012,
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 2013, 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; 2 or 3 new sites have been
discovered each survey year since 2005 (3 sites in 2005, 2 sites in
2006, 2 sites in 2007, zero sites in 2010, and 2 sites in 2012). 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,
[[Page 63585]]
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 2013,
unpubl. geodatabase)), a significant proportion of the un-surveyed area
is likely not suitable for the Dakota skipper. For example, there is an
estimated 1,620,549 acres (ac) (655,813 hectares (ha)) of unbroken
(untilled) grasslands (excluding Conservation Reserve Program (CRP)
grasslands, which generally do not provide habitat for the Dakota
skipper (Larson 2013, pers. comm.)) in the 9 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, these unbroken grasslands
may not 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 73 additional
locations in South Dakota that were surveyed from 1991 through 2012
(USFWS 2013, unpubl. geodatabase). Several of these sites have been
surveyed multiple times in one year or during multiple years (USFWS
2013, 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. New potential sites surveyed are generally focused on prairie
habitat that appear suitable for the species and have a good potential
of finding the species, in other words, sites are not randomly selected
across the landscape. Therefore, these sites have a higher likelihood
of detecting the species 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, and 35 percent (9 of 26 sites) in 2012 (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 63586]]
[GRAPHIC] [TIFF OMITTED] TP24OC13.089
The Outer Coteau des Prairies sub-section of the North Central
Glaciated Plains section of Bailey's Eco-regions is thought to be a
stronghold for Dakota skipper, since nearly 40 percent of the total
documented Dakota skipper sites are within that subsection (83 of the
259 documented sites--Service 2013, unpubl. geodatabase). Most of these
Outer Coteau des Prairie sites are in South Dakota; 73 of the 85 Dakota
skipper sites in South Dakota are within the Outer Coteau des Prairies
subsection (Service 2013, unpubl. geodatabase). Dakota skipper is
considered to be present at only 10 of those 73 sites--the species
status is unknown at 41 of those sites, possibly extirpated at 8 sites,
and extirpated at the remaining 13 sites within that ecoregion
subsection in South Dakota (Service 2013, 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 46 sites and it is
considered to be extirpated or possibly extirpated from at least 25 of
the 85 known sites in the State, although large areas of grasslands
remain in South Dakota and substantial additional populations of Dakota
skipper would be expected 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 85 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. The proportion of positive surveys at
known sites has fluctuated over time; however, the 2012 surveys had the
lowest positive detection rate (35 percent) for the last 16 years
(since 1996)--much less than comparable survey years in South Dakota.
Manitoba
Manitoba historically contained approximately 14 percent (N = 36)
of the known locations of the Dakota skipper rangewide. The Dakota
skipper is considered present at 1 isolated site and 30 sites split
between 2 distinct complexes, 14 sites near Griswold and 16 sites along
Lake Manitoba. The 14 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 presumed extirpated or possibly extirpated from five sites in
Manitoba, including from the Tallgrass Prairie Preserve, where it has
not been 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). Population
[[Page 63587]]
estimates and trends at these sites have not been examined
quantitatively; however, the population appears to be stable at 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).
Dakota skipper was first recorded near Miniota in 1944 and then at
two additional sites in the early 1990s. In 2002, the species was
observed at 19 sites near Lundar, within about 25 km (16 mi) east of
Lake Manitoba (Webster 2003, p. 4); however, most of these sites have
not been surveyed since. 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). 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). The areas near Brandon and the high ground within
the wetland complexes near Oak Lake may still contain 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 200 km (125 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 one
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
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
[[Page 63588]]
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 2000a, p. 7).
McAlpine (1972, pp. 85-92) described the various life-history stages of
Poweshiek skipperling. McAlpine (1972, pp. 85-93) observed hatching of
larvae Poweshiek skipperling after about nine 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). After hatching, Poweshiek
skipperling larvae crawl to the base of grasses, but unlike Dakota
skippers, Poweshiek skipperling do not form shelters underground
(McAlpine 1972, pp. 88-92; Borkin 1995a, p. 9; Borkin 2008, pers.
comm.). Poweshiek skipperling are not known to form shelters, 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.
Food and Water
For the Poweshiek skipperling, preferred nectar plants vary across
its geographic range. Smooth ox-eye (Heliopsis helianthoides) and
purple coneflower were noted as the favored nectar plants in Iowa,
Minnesota, and North Dakota (Swengel and Swengel 1999, p. 280). Other
nectar species used, in descending order of number of observations,
were stiff tickseed (Coreopsis palmata), black-eyed Susan, and
palespike lobelia (Lobelia spicata) (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). 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 (Sporobolus heterolepis) (Borkin 1995b, p. 6); larvae
have also been observed feeding on little bluestem (Schizachyrium
scoparium) (Borkin 1995b, pp. 5-6) and sideoats grama (Bouteloua
curtipendula) (Dana 2005a, pers. comm.). Poweshiek skipperling 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).
In southwestern Minnesota dry hill prairies, Poweshiek skipperling
oviposition was observed on prairie dropseed, little bluestem, big
bluestem (Andropogon gerardii), porcupine grass (Hesperostipa spartea),
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 1995a, p. 6).
Dana (2005b, pers. comm.) noted that larvae and ovipositing females
prefer grasses with ``very fine, threadlike structures'' and
hypothesized that Poweshiek skipperling lack a specific host and may
adapt to acceptable plant species at a site.
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 maximum dispersal distance of 1.6 km
(1.0 mi) is 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). 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 or
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 Poweshiek skipperling (mean mobility of 2) (Burke
et al. 2011, p. 2279; Fitzsimmons 2012, pers. comm.), a more
conservative estimated dispersal distance would be that of the Dakota
skipper, approximately 1 km (0.6 mi) (Cochrane and Delphey 2002, p. 6).
In summary, 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, and wet-mesic to dry tallgrass
prairie. McCabe and Post (McCabe and Post 1977a, p. 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 1977a, p. 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
[[Page 63589]]
(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, 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-mesic, and dry-mesic prairie habitats (Borkin
1995b, p. 6). The dry-mesic habitats contain ``extensive patches of
prairie dropseed and little bluestem grasses'' (Borkin 1995b, 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
1995b, p. 7). Like Dakota skipper, 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
microclimalogical (climate in a small space, such as at or near the
soil surface) levels within ``larval nesting zones'' (between the soil
surface and 2 cm deep) 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
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).
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 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 87 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 nearly 50
percent of all known Poweshiek skipperling locations rangewide. Numbers
and distribution dropped dramatically in subsequent years, however, and
the species has not been seen in Minnesota since 2007. 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
[[Page 63590]]
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 24 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. 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
flight season 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. There is one population of Poweshiek skipperling in Wisconsin
with fairly consistent numbers observed over the last 5 years (17 to 63
individuals counted, no consistent measure of effort) and one
population in Manitoba with fairly consistent numbers (typically
hundreds of individuals observed each year). To summarize, of the 296
documented sites, there are 14 sites where we consider the Poweshiek
skipperling to be present, 131 sites with unknown status, 98 possibly
extirpated sites, and 53 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
----------------------------------------------------------------------------------------------------------------
Percent of
the total
Possibly number of
State Present Unknown extirpated Extirpated Total historical
sites by
state
----------------------------------------------------------------------------------------------------------------
Illinois.................... ........... ........... .............. 3 3 1
Indiana..................... ........... ........... .............. 1 1 0.3
Iowa........................ ........... 4 24 13 41 14
Michigan.................... 10 1 .............. 6 17 6
Minnesota................... ........... 67 68 7 142 48
North Dakota................ ........... 10 6 1 17 6
South Dakota................ ........... 48 .............. 22 70 24
Wisconsin................... 3 1 .............. .............. 4 1
Manitoba.................... 1 ........... .............. .............. 1 0.3
-----------------------------------------------------------------------------------
Total Number of 14 131 98 53 296 ...........
Historically Documented
Sites..................
-----------------------------------------------------------------------------------
Percent of the Total 5% 44% 33% 18% ........... ...........
Number of 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 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.). 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,
[[Page 63591]]
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.
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). 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 Hoffman Prairie site because
the species had not been seen in the last two survey years; however,
Selby believes that the species may be extirpated from this site (Selby
2012a, pers. comm.), so we have assigned a status of extirpated to this
site.
To summarize, 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
ten sites (Table 2) in four counties in Michigan: Jackson, Lenawee,
Oakland, and Washtenaw. The species has been observed very recently
(2007-2012) 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 one site;
Bullard Lake in Livingston County, where Poweshiek skipperling were
last seen in 2007, but not in subsequent surveys in 2008 and 2009
(Cuthrell 2012a, 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 ten extant (present) Poweshiek skipperling
occurrences are considered to have at least good viability (Michigan
Natural Features Inventory 2011, unpubl. data). Three of these sites
(Buckthorn 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.). The largest
extant (present) Poweshiek skipperling population in Michigan is at
Long Lake Fen, where 225 individuals (1.3/hr.) were counted during 2012
surveys, down from 389 individuals (2.2/hr.) observed in the previous
survey year with similar sampling effort. Long Lake Fen is likely the
largest population of Poweshiek skipperling in the United States, and
is subjected to intense development pressure. The fourth site, Grand
River Fen (also known as Liberty Fen) in Jackson County, is
approximately 100 km (62 mi) from the other three sites. 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 (Cuthrell, 2012a, pers. comm.; 2012b, 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
[[Page 63592]]
in Michigan. In 2010, eight (0.1/hr.) Poweshiek skipperling were
recorded at Park Lydon in Washtenaw County; 12 individuals were counted
in 2011 (0.1/hr.), and 22 were counted in 2012 (0.2/hr.) (Cuthrell
2012a, 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, nine (0.07/hr.) were seen in 2011 (Cuthrell 2012a,
pers. comm.; Cuthrell 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
2013b, pers. comm.). The Eaton Road site is approximately 1 mi (0.6 km)
from the Long Lake Fen site and is considered a sub-site within Long
Lake Fen (Cuthrell 2013b, 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 10 of the sites. The occupancy is unknown at 1 site, and the species
is considered to be extirpated at 6 sites.
Minnesota
Minnesota historically contained approximately 48 percent (N=142)
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 142 distinct
historical site records in the State (Dana 2012d, pers. comm; Service
2013, unpubl. geodatabase). Poweshiek skipperling are presumed
extirpated or possibly extirpated from at least 75 of these known
sites. The status of the species is unknown at 67 sites, although 31 of
those locations have not been surveyed since 2003, and the species has
undergone a sharp decline in the State since then.
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). The 2008 surveys
documented no Poweshiek skipperling records on any of the 58 sites
surveyed (Selby 2009a, p. 1).
An extensive survey effort was also 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 it 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 2007 survey
despite good survey conditions (Selby 2009a, p. xxxv).
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 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.).
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, or 2012) 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
[[Page 63593]]
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).
To summarize, Poweshiek skipperling was historically documented in
approximately 142 sites in Minnesota (Table 2). The species is not
considered to be present at any of these sites (Table 2). The occupancy
is unknown at 67 sites, and the species is considered to be extirpated
or possibly extirpated at 7 and 68 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 2013,
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 seven sites and four counties (Cass,
Dickey, LaMoure, and Grand Forks) in North Dakota. The status of the
species is unknown at 10 sites, where the species was last observed
between 1996 and 2001, but not during the most recent 1-2 year(s)
surveyed. The status of the species is also unknown at one site where
the species was observed in 1996 with no recent surveys for the
species, but the habitat was recently rated as poor (Service 2013,
unpubl. geodatabase). 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 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
three years of survey work (1995-1997) in southeast 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
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[hellip]'' In six 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 10
sites, and the species is considered to be extirpated or possibly
extirpated at 1 and 6 sites, respectively (Table 2).
South Dakota
South Dakota historically contained approximately 24 percent (N=70)
of all known records of Poweshiek skipperlings rangewide (Table 2). The
Poweshiek skipperling has been historically documented at approximately
70 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
48 sites and presumed extirpated at the remaining 22 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 2012: 6 sites in 2009, 10 sites in 2010, 1
sites in 2011, and 10 sites in 2012 (Skadsen 2009, p. 12; Skadsen 2011,
p. 5; Skadsen 2010, pers. comm.; Skadsen 2012a, pers. comm.; Skadsen
2012, p. 3). The 2009 to 2012 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).
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 three sites in
Wisconsin (Table 2); two sites are within the Southern Unit of the
Kettle Moraine State Forest in Waukesha County. The third site, 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 another site within the
[[Page 63594]]
Kettle Moraine State Forest. 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.). The larger of the two populations at Kettle Moraine
State Forest inhabits a 6-ha (15-ac) prairie remnant on Scuppernong
Prairie SNA, which had record counts exceeding 100 individuals in 1994,
1995, 1998, and 1999 (Borkin 1995a, p. 10; Borkin 1996, p. 7; Borkin
2000b, 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.). There was some concern that a controlled
burn in late March of 2012 may correlate with lower numbers observed
during the 2012 flight (Borkin 2012a, pers. comm.); however, this
difference is within the range of variation observed over the previous
four years (Wisconsin DNR 2012, in litt.).
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, pers. comm.; Borkin 2012a,
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 wild fire (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, there were no photographs or voucher specimens to
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 three days.
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 2000b, 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 three sites and the occupancy is unknown one site (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's 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). The preserve has detailed management
recommendations to facilitate recovery of the Poweshiek skipperling
(Westwood 2010, p. 5).
[[Page 63595]]
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
Tall Grass Prairie Preserve (Environment Canada 2012, p. ii).
Summary of Factors Affecting the Species
Section 4 of the Act (16 U.S.C. 1533), and its implementing
regulations at 50 CFR Part 424, set forth the procedures for adding
species to the Federal Lists of Endangered and Threatened Wildlife and
Plants. Under section 4(a)(1) of the Act, we may list a species based
on any of the following 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; and (E) other natural or manmade
factors affecting its continued existence. Listing actions may be
warranted based on any of the above threat factors, singly or in
combination. Each of these factors is discussed below.
We evaluated the level of impact to the population at each site of
stressors at 170 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 rule. These 170 sites are found across the
current range of the species in Minnesota, North Dakota, and South
Dakota. Two Dakota skipper 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 2013, 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; therefore, the number of sites
evaluated varies with each stressor.
We evaluated the level of impact to the species from stressors at
68 Poweshiek skipperling sites where the occupancy status of the site
is considered to be present or unknown, as defined in the Background
section of this proposed rule. Although we did not evaluate every
stressor at all 145 Poweshiek skipperling sites with present or unknown
occupancy, the 68 sites that were evaluated are representative of all
those sites in terms of geography (sites in Iowa, Michigan, Minnesota,
North Dakota, South Dakota, and Wisconsin were evaluated), ownership,
and management. To determine the levels of impact to the population at
each site, we used the best available and most recent information,
including reports, discussions with site managers, and information from
natural heritage databases (Service 2012, unpubl. data; Service 2013,
unpubl. geodatabase). We only evaluated a particular stressor at any
one site if we had sufficient information to determine if the level of
impact was high, medium, or low (as defined below); therefore, the
number of sites evaluated varies with each stressor.
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
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 170 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 proposed rule (Table 3).
These 170 sites are found across the current range of the species in
Minnesota, North Dakota, and South Dakota. Two 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 2013, 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 68 Poweshiek skipperling
sites with present or unknown status (Table 4). Although we did not
evaluate Factor A stressors at all 145 Poweshiek skipperling sites with
present or unknown occupancy, the 68 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 (59
sites for Dakota skipper and 32 sites for Poweshiek skipperling)
experience at least two habitat-related
[[Page 63596]]
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 170 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 2013, Unpubl. Data)
----------------------------------------------------------------------------------------------------------------
Medium Total
Stressor High level level of Low level number of
of impact impact of impact rated sites
----------------------------------------------------------------------------------------------------------------
Destruction & Conversion (Agricultural & Nonagricultural 3 87 60 150
Development)...............................................
Wind Development............................................ 1 0 8 9
Flooding.................................................... 0 6 6 12
Invasive Species............................................ 13 31 18 62
Fire........................................................ 9 4 6 19
Grazing..................................................... 10 29 14 53
Haying & Mowing............................................. 2 11 27 40
Lack of Management.......................................... 10 5 3 18
Size/Isolation.............................................. 50 35 58 143
Herbicide and/or Pesticide Use.............................. 5 2 9 16
----------------------------------------------------------------------------------------------------------------
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 68 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. Data; Service 2013, Unpubl. Data)
----------------------------------------------------------------------------------------------------------------
Medium Total
Stressor High level level of Low level number of
of impact impact of impact rated sites
----------------------------------------------------------------------------------------------------------------
Destruction & Conversion (Agricultural & Nonagricultural 1 13 40 54
Development)...............................................
Wind Development............................................ 0 0 6 6
Flooding/Hydrology.......................................... 2 4 14 20
Invasive Species............................................ 9 30 12 51
Fire........................................................ 7 3 14 24
Grazing..................................................... 7 14 2 23
Haying & Mowing............................................. 0 3 7 10
Lack of Management.......................................... 5 6 2 13
Size/Isolation.............................................. 25 24 19 68
Herbicide and/or Pesticide Use.............................. 3 1 6 10
----------------------------------------------------------------------------------------------------------------
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 threat of such
conversion to extant populations is not well known and may now be
secondary to other threats. 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 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 threat
to Dakota skippers in the important Towner-Karlsruhe complex (Royer and
Royer 1998, p. 22; Lenz 1999b, 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
[[Page 63597]]
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 150 Dakota skipper and
54 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 2013, 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 threat 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
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.
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.). Much of the Dakota skipper's range
and some of the Poweshiek skipperling's range overlaps with major areas
of oil and gas development, which have been increasing rapidly in parts
of both species' ranges. 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,
is a future stressor to Dakota skipper populations in McKenzie County
(Royer and Royer 2012b, p. 16). Oil company officials anticipate that
production will 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). Oil and gas development can double the density of
roads on range lands (Naugle et al. 2009, pp. 11, 46), increase
pipelines, and increase the number of gravel pits to accommodate the
increased road construction (Mueller 2013, pers. comm.). 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. 2009, p. 11). 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. 2009, p. 11). The
habitat fragmentation associated with oil and gas development may
amplify other threats 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. No such
spills are known to have occurred in the region, however, and the
likelihood 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;
[[Page 63598]]
Shaffer et al. 2012, p.). 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
threat 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 distribution 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 as a result of
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 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 150 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 87
sites, and 60 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 organization (e.g., The Nature Conservancy), or
educational institution (e.g., South Dakota State University).
Similarly, 54 Poweshiek skipperling sites with present or unknown
status were assessed that had sufficient information: The level of
threat was high at one site and moderate at 13 sites, and 40 sites are
protected from destruction or conversion through a conservation
easement or fee title ownership by a conservation agency (Table 4). At
least 5 of the 14 sites where the Poweshiek skipperling is considered
to still be present have a medium 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 threat 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).
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 12 Dakota
skipper sites with present or unknown status and 20 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
[[Page 63599]]
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 10 of the Michigan prairie fen Poweshiek skipperling sites where
the species is present and one with unknown occupancy (Service 2013,
unpubl. data). 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
Inventory 2011, 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 2013, 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 2013, unpubl. data).
Similarly, we assessed 20 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). Flooding is a stressor
with moderate impact to the populations at 3 Poweshiek skipperling
sites (including a site in Wisconsin--one of the 14 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 10 of 14 Poweshiek skipperling sites that
have a present status) and 1 site in North Dakota (Service 2012 unpubl.
data; Service 2013, unpubl. data).
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 threat 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 (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). Leafy
spurge and Kentucky bluegrass have been cited as one of the major
threats 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.). 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
not growing when Dakota skipper and Poweshiek skipperling larvae are
feeding, 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
62 Dakota skipper sites and 51 Poweshiek skipperling sites that had
sufficient information to evaluate the stressor (Table 3 and Table 4;
Service 2012
[[Page 63600]]
unpubl. data; Service 2013, 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 13 of the 62
assessed Dakota skipper sites, a moderate level of impact to
populations at 31 sites, and low impact to populations at 18 sites.
Sites with high and moderate level of impact occur throughout the
species range in Minnesota, North and South Dakota (Service 2012
unpubl. data; Service 2013, unpubl. data). Similarly, invasive species
are a stressor of high level of impact to populations at 9 of the 51
evaluated Poweshiek skipperling sites, moderate of level impact to
populations at 30 sites, and low level of impact to populations at 12
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 11 of the 14 sites
where the species is still present (Service 2013, 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
Manitoba's Tall Grass Prairie Preserve (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 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. At Prairie Coteau Preserve in Minnesota,
Schlicht (2001a, pp. 9-10) found greater flower abundance on regularly
burned than rarely burned sites, but Dakota skipper abundance showed
the greatest decline on the burned sites.
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
threat 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 threat 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). 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
[[Page 63601]]
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 2000a, p. 2),
where they are exposed to fires during their larval stages. 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 1995b, 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 increase 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 four years after burns (Swengel
1996, p. 83). Poweshiek skipperling had the most negative initial
response to fire among six species of prairie-obligate butterfly
species (Swengel 1996, p. 83). Numbers were still lower than expected
one year post-fire, exceeded expectations after two years, and declined
slightly after three years (Swengel 1996, p. 83). In habitats that had
not been burned for four or more years, Poweshiek skipperling abundance
was about as low as in habitats sampled less than one year after being
burned (Swengel 1996, p. 83).
Swengel's (1996, p. 83) observations are consistent with other
findings. That is, Poweshiek skipperling numbers decline in burned
areas for 1-2 years after the burn then rebound, but may decline again
if management does not maintain the habitat (Skadsen 2001, p. 37;
Webster 2003, p. 12). In general, recovery times of 1-5 years post burn
have been predicted (Swengel 1996, pp. 73, 79, 81; Panzer 2002, pp.
1302-1303); however, Vogel et. al (2010, p. 671) found that habitat-
specialist butterfly abundance recovery time was approximately 50
months after prescribed fires. 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 the typical post-fire rebound.
We assessed the stressor posed by fire at 19 Dakota skipper sites
with present or unknown status and 24 Poweshiek skipperling sites with
present or unknown site status where we had sufficient information to
evaluate the stressor (Tables 3 and 4; Service 2012 unpubl. data;
Service 2013, unpubl. data). We considered fire a stressor of high
level of impact to populations at 9 of the 19 evaluated Dakota skipper
sites and 7 of the 24 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 three years; or, habitat is divided into two
or more burn units, each unit is burned no more frequently than once
every three 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 threat of
moderate severity at 4 of the 19 evaluated Dakota skipper sites and 3
of the 24 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 four 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 four 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 19
evaluated Dakota skipper sites and 14 of the 24 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
[[Page 63602]]
conducted with conservation of prairie invertebrates as a primary
objective, it 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. Furthermore, in contrast to the permanent habitat
destruction and larval mortality caused by plowing or mining, for
example, some habitats can remain suitable for Dakota skipper 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 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 (Service 2006, p. 2; Smart et al. in
prep.).
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). Schlicht
(1997b, p. 5) found that the Dakota skipper was relatively abundant on
prairies subjected to light grazing regimes, but absent on nearby idle
prairies that were no longer used for grazing; moreover, he observed
more Dakota skippers 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.
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.
The intensity at which grazing occurs may dictate the level of
impact to the Dakota skipper and Poweshiek skipperling. 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 two 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 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 2013, unpubl. geodatabase). Spomer (2004, p. 4)
found that larval host plants and
[[Page 63603]]
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 1977b, p. 36; 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 threat to Dakota skipper in the wet-
mesic habitats of Manitoba (Webster 2007, pp. i-ii, 6). 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 threat to Dakota
skippers and Poweshiek skipperlings, but that occasional light grazing
is not a long-term threat 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 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 proposed 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). 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 threat 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 53
Dakota skipper sites and 23 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 2013, 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
[[Page 63604]]
(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 four 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 threat, 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 lead to further management actions
(see Invasive Species and Secondary Succession).
Of the 53 Dakota skipper sites assessed, we found the level of
impact to Dakota skipper populations from grazing to be high at 10
sites, moderate at 29 sites, and low at 14 sites (Service 2012 unpubl.
data; Service 2013, unpubl. data). Moderate- to high-level impacts to
populations were primarily at South Dakota sites (N=28)--other 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 10 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 19 Poweshiek skipperling sites for which we had sufficient
information to assess grazing, the level of impact to populations from
grazing is high at 7 sites, moderate at 14 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 14 sites where grazing is a moderate
level of impact to Poweshiek skipperling populations, 10 have habitat
rated as fair to excellent. The habitat quality was rated as poor at 3
of the 6 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.).
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 are 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
[[Page 63605]]
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).
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 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 1999b, 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 40
Dakota skipper sites and 10 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 2013,
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
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 threats, 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 three 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 27 of the 40 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 13 of the 40 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 2 of the 40 Dakota skipper sites assessed and a stressor
of moderate-level impacts to the populations at 11 of the 40 Dakota
skipper sites assessed. Of the 10 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 10 sites.
In summary, haying is a current and ongoing threat 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 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.
We assessed the stressor posed by lack of management for
populations at 18 Dakota skipper sites and 13
[[Page 63606]]
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 2013, 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 secondary succession
and invasive species (e.g., smooth brome). Ten of the 18 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. Five of the 13 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 threats 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 170 Dakota skipper sites for which we evaluated for one or
more habitat stressors, at least 136 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 2013, unpubl. data). Fifty-eight sites have 2 or
more documented stressors of moderate to high levels of impact to
populations, and 23 sites have three 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 2013, unpubl. data).
Twenty-three of these sites had 3 or more documented stressors at
moderate or high levels of impact. Sites with three or more stressors
are found across the current range of the species in the United States;
these sites occur in Minnesota, North Dakota, and South Dakota.
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 68 Poweshiek skipperling sites with present or
unknown status that we analyzed for one or more habitat stressors, 55
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 2013, unpubl. data). Fifty-
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
2013, unpubl. data). Thirty-seven 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, North Dakota, South
Dakota, Wisconsin, and Manitoba (Service 2013, unpubl. data). Thirty-
seven of these sites had 3 or more documented stressors at moderate or
high levels of impact to the population for both species. These sites
are found across most of the current range of the species and occur in
Iowa, Michigan, Minnesota, North Dakota, South Dakota, and Manitoba
(Service 2013, 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
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 mitchellii), 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
[[Page 63607]]
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. 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 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.
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 1979 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 2003a, entire; Selby 2003b, entire; Selby 2004b, entire, Selby
2006, entire); however, skipper numbers were too low to collect
sufficient data to test hypotheses (Selby 2006, 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 2013, 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 2013, 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 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 threat of conversion and may provide dispersal
corridors or buffer sites from external threats (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 U.S. Department of Agriculture Natural Resources
Conservation Service 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 (Larson 2013, pers.
comm.). 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
(Table 5; 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 (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 172) 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
[[Page 63608]]
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 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 2012, 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 2012, 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 2012, 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 seven 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 14
Dakota skipper sites in Day County: 2 sites where the species is
considered to be present, and 12 sites that have an unknown occupancy.
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 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.
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.
[[Page 63609]]
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 this and other species in the future. If
this program is successful, the conservation benefit could be possible
if it could facilitate reintroduction and augmentation efforts into
areas where the species has declined or disappeared. Furthermore, this
propagation effort may lead to 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; 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). No collection threats are known or likely
for the Poweshiek skipperling (Royer and Marrone 1992b, p. 16).
Collection is not currently a threat 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.
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. 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 1995b, 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 and ant
species and predation by various insects. 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.
The University of Michigan (at Dearborn) has plans to study Wolbachia
bacteria on one or both of the species.
Predation by birds or insects is not considered a major component
of Dakota skipper or Poweshiek skipperling population dynamics and does
not likely impact the species. McCabe (1981, p. 187), however, noted
three kinds of predators to Dakota skippers, including Ambush bugs
(Hemiptera: Phymata sp.), flower spiders (Aranaea: Misumena spp.), and
orb weavers (various Araneldae). Although flower spiders and ambush
bugs are effective predators of nectar-feeding insects (McCabe 1981,
pp. 187-188) and may cause mortality to some individuals, no evidence
indicates that these predators have population level impacts to either
the Dakota skipper or Poweshiek skipperling. Similarly, Orb weaver
spiders appear to be successful predators of ``old, warn individuals''
(McCabe 1981, p. 188), but no evidence indicates that these predators
have population-level impacts to the Dakota skipper and Poweshiek
skipperling.
Therefore, we do not consider either disease or predation to be a
significant stressor to the Dakota skipper or Poweshiek skipperling
populations at this time, nor do we expect these stressors to become
threats in the future.
Factor D. The Inadequacy of Existing Regulatory Mechanisms
Existing regulatory mechanisms vary by location, but generally do
not mitigate for the numerous threats that the Dakota skipper and
Poweshiek skipperling face.
State Regulations
The Dakota skipper is listed as threatened 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 is listed as a
species of special concern in Minnesota, which conveys no prohibitions
against take of the species. The Minnesota DNR has proposed to list
Poweshiek skipperling as endangered and to change the status of Dakota
skipper from threatened to endangered (Minnesota DNR 2012), but it is
unclear when this may go into effect. The Poweshiek skipperling is
listed as threatened under state endangered species statutes in Iowa
and Michigan and as endangered in Wisconsin. 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
[[Page 63610]]
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), 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 threats may result in direct mortality of both
species, such as ill-timed fires, most threats to the species are
indirect and state laws that regulate direct harm to the species do not
address these threats. In Iowa, for example, Poweshiek skipperling
populations are likely now extirpated due to habitat destruction and
conversion and other undetermined threats, despite its presence on the
State's list of threatened species since 1994. In Wisconsin, where
threats 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 threats to the State's small and
isolated populations.
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 February 8,
2012). 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 this has not been done for either of these species. 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/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.
Although there are no genetic studies on the Poweshiek skipperling,
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 172 separate
sites where the species is known to be or may still be present (sites
with present (91) or unknown (81) 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).
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
[[Page 63611]]
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, 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 2013, unpubl. data).
Using a more conservative maximum dispersal of 1.0 km (0.6 mi),
approximately 56 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 2013, unpubl. data). For Dakota skipper, if
we use a maximum dispersal distance of 1 km (0.6 miles), approximately
84 percent of Dakota skipper sites with present or unknown status are
effectively isolated.
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) from the Wilton Road population; fewer than 100 individuals
have been counted at this site each year (See Population Distribution
and Status). Numbers at Wilton Road are currently too small (less 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
100 km (62 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. Only 2 of the 11 Poweshiek skipperling sites with
present status in Michigan are located within 1 mi (1.6 km) 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)
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, 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
143 Dakota skipper sites and 68 Poweshiek skipperling sites with
present or unknown status--many of the sites with where the species is
present in Canada were not evaluated because we had little or no
information on the size of sites (Service 2012 unpubl. data; Service
2013, 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
[[Page 63612]]
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 threat 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 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.
Dakota skipper populations on about 35 percent of the evaluated
sites (50 of 143 sites) face a high level of impact to populations due
to a combination of size and isolation (Service 2012, 2013, unpubl.
data). Approximately 24 percent of evaluated sites (35 sites) face a
moderate level of impact to populations due to small size and
isolation. About 40 percent of Dakota skipper sites (50 of the 143
evaluated sites) in the United States inhabit sites that 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 37
percent of rated sites (25 of 68 sites), on 24 sites (35 percent) the
threat is considered to have a moderate level of impact to populations,
and on 28 percent (19 of the 68 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 2 sites are
within 1 km (0.6 mi) of another site where the species is present
(Service 2013, 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 two percent of Poweshiek sites with
present or unknown status are within the estimated maximum dispersal
distance from one another as are about 16 percent of Dakota skipper
sites with present or unknown occupancy. The small populations are
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 and all but one site surveyed in
2012.
Climate Change
Our analyses under the Act include consideration of ongoing and
projected changes in climate. The terms ``climate'' and ``climate
change'' are defined by the Intergovernmental Panel on Climate Change
(IPCC). The term ``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 2007a, p. 78). 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
2007a, p. 78).
Scientific measurements spanning several decades demonstrate that
changes in climate are occurring, and that the rate of change has been
faster since the 1950s. Examples include warming of the global climate
system, and substantial increases in precipitation in some regions of
the world and decreases in other regions. (For these and other
examples, see IPCC 2007a, p. 30; and Solomon et al. 2007, pp. 35-54,
82-85). Results of scientific analyses presented by the IPCC show that
most of the observed increase in global average temperature since the
mid-20th century cannot be explained by natural variability in climate,
and is ``very likely'' (defined by the IPCC as 90 percent or higher
probability) due to the observed increase in greenhouse gas (GHG)
concentrations in the atmosphere as a result of human activities,
particularly carbon dioxide emissions from use of fossil fuels (IPCC
2007a, pp. 5-6 and figures SPM.3 and SPM.4; Solomon et al. 2007, pp.
21-35). Further confirmation of the role of GHGs comes from analyses by
Huber and Knutti (2011, p. 4), who concluded it is extremely likely
that approximately 75 percent of global warming since 1950 has been
caused by human activities.
Scientists use a variety of climate models, which include
consideration of natural processes and variability, as well as various
scenarios of potential levels and timing of GHG emissions, to evaluate
the causes of changes already observed and to project future changes in
temperature and other climate conditions (Meehl et al. 2007, entire;
Ganguly et al. 2009, pp. 11555, 15558; Prinn et al. 2011, pp. 527,
529). All combinations of models and emissions scenarios yield very
similar projections of increases in the most common measure of climate
change, average global surface temperature (commonly known as global
warming), until about 2030. Although projections of the magnitude and
rate of warming differ after about 2030, the overall trajectory of all
the projections is one of increased global warming through the end of
this century, even for the projections based on scenarios that assume
that GHG emissions will stabilize or decline. Thus, there is strong
scientific support for projections that warming will continue through
the 21st century, and that the magnitude and rate of change will be
influenced substantially by the extent of GHG emissions (IPCC 2007a,
pp. 44-45; Meehl et al. 2007, pp. 760-764 and 797-811; Ganguly et al.
2009, pp. 15555-15558; Prinn et al. 2011, pp. 527, 529). (See IPCC
2007b, p. 8, for a summary of other global projections of climate-
related changes, such as frequency of heat waves and changes in
precipitation. Also see IPCC 2011(entire) for a summary of observations
and projections of extreme climate events.)
Various changes in climate may 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 interactions of climate with other variables
(e.g., habitat fragmentation) (IPCC 2007, pp. 8-14, 18-19). Identifying
likely effects often involves aspects of climate change vulnerability
analysis. Vulnerability refers to the degree to which a species (or
system) is susceptible to, and unable to cope with,
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adverse effects of climate change, including climate variability and
extremes. Vulnerability is a function of the type, magnitude, and rate
of climate change and variation to which a species is exposed, its
sensitivity, and its adaptive capacity (IPCC 2007a, p. 89; see also
Glick et al. 2011, pp. 19-22). There is no single method for conducting
such analyses that applies to all situations (Glick et al. 2011, p. 3).
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 threat 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), 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
threat 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 could experience the effects of climate change.
Prairie Plant Harvesting
A potential, future threat to the Dakota skipper and Poweshiek
skipperling is collection of purple coneflower (blacksamson 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,
including intensive 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. In southwest 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
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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.).
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 threats 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 threat 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 threats 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 threat 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 threat 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 spread of nonnative gypsy
moths (Lymantria dispar dispar) has increased efforts to control this
damaging species and may also pose a threat, 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/GypsyMothPesticides.html, accessed May 24, 2012).
Herbicide and pesticide use was assessed at 16 present and unknown
Dakota skipper sites and 10 Poweshiek skipperling sites occupied with
present or unknown occupancy where we had sufficient information to
evaluate the stressor (Service 2012, 2013, unpubl. data). We considered
the level of impact to populations posed by herbicide and pesticide use
to be low if herbicides or pesticides are used, if the site is only
spot sprayed when and where necessary (Smart et al. 2011, p. 182) and
their use is not expected to change in the future. The level of threat
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 four 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--one in North Dakota and one in South Dakota. The level of
impact to populations posed by herbicide and pesticide use was
considered to be high at 3 of the 10 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 threat 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.
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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 threats described throughout Factors A, C and E of this proposed
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 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 threat 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. 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. 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 surveys had the lowest
positive detection rate (35 percent) 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). 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 stressors and indicate that they are a current
threat 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 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 threats 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 threat with the most significant impacts to the Poweshiek
skipperling are one or more unknown stressors 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 insecticides, herbicide and
pesticide use, and prairie plant harvest are also threats to both
species. Collectively, these threats 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
[[Page 63616]]
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. 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 2012, p. 7).
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 threats described in this finding may cumulatively or
synergistically impact the Dakota skipper and Poweshiek skipperling
beyond the scope of each individual threat. 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
threats are likely acting cumulatively to further increase impacts on
the already vulnerable, small and isolated populations of Poweshiek
skipperling and Dakota skipper.
Proposed Determinations
Section 4 of the Act (16 U.S.C. 1533), and its implementing
regulations at 50 CFR part 424, set forth the procedures for adding
species to the Federal Lists of Endangered and Threatened Wildlife and
Plants. Under section 4(a)(1) of the Act, we may list a species based
on (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. Listing actions may be warranted based on any of
the above threat factors, singly or in combination.
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 2 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 50 percent of sites where it had been recorded
rangewide. It is presumed extirpated from Illinois and Iowa and no
longer occurs east of western Minnesota--an approximately 430-mi (690-
km) reduction of its range. Much of the rangewide decline in the
species has been observed in the last few years. Since 1985,
researchers have surveyed 10 or more sites in 27 years; the average
positive detection rate for those years is 69 percent rangewide. Since
2010, the percent of surveyed sites with positive detections of the
species has dropped from 80 percent in 2010, to 42 percent in 2011, and
to 35 percent in 2012. 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 2012 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 259 historical locations, the species is presumed extirpated
or possibly extirpated from at least 87 (34 percent) of those sites,
and the occupancy of the species is unknown at approximately 81 (31
percent) sites. Of the 81 sites where the occupancy is unknown, at
least 72 sites are subject to one or more threats that have a moderate
to high impact on those populations--these sites are distributed across
Minnesota, North Dakota, and South Dakota. The 9 sites with unknown
occupancy without moderate- to high-level threats are scattered in
various counties in Minnesota and South Dakota, and the skipper is
thought to still be present at approximately 91 (35 percent) of the 259
historical locations, although 23 of these sites have not been surveyed
since 2002. Of those 91 sites, at least 83 sites are subject to one or
more threats that have a moderate to high impact on those populations,
such as conversion to agriculture, lack of management, and small size
and isolation. The remaining 8 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 (45 of 91)
of the locations where the species is considered to be present are
located on privately owned fall hayed prairies in Canada, mostly within
3 isolated complexes, and have not been surveyed since 2007. All 45 of
those Canadian sites have one or more stressors of moderate to high
level of impact to
[[Page 63617]]
populations. A fair number of populations in Canada are being managed
in a manner conducive to the conservation of the Dakota skipper and the
threats at those sites are not immediate. However, few (4-5 sites) of
these Canadian populations are protected (on Federal land). The
remaining sites where the species is considered to be present are about
equally distributed among Minnesota (14 sites), North Dakota (18
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 major threats, acting individually or synergistically,
continue today (see Summary of Factors Affecting the 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 stressors 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 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 stressors, and may only be a few
years behind those declines experienced by 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 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. However, few
of these populations are protected, many are vulnerable to changes in
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 North Dakota and South
Dakota, is likely to continue. Therefore, on the basis of the best
available scientific and commercial information, we propose listing the
Dakota skipper as threatened in accordance with sections 3(6) 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--primarily in North Dakota, South Dakota,
Manitoba, and Saskatchewan. 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.
Furthermore, we believe the species to be present in at least 8 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. Threats to the survival of the Dakota
skipper occur throughout the species range and are not restricted to
any particular significant portion of that range. Accordingly, our
assessment and proposed determination applies to the Dakota skipper
throughout its range.
Significant Portion of the Range
In determining whether a species is threatened or endangered in a
[[Page 63618]]
significant portion of its range, we first identify any portions of the
range of the species that warrant further consideration. The range of a
species can theoretically be divided into portions an infinite number
of ways. However, there is no purpose to analyzing portions of the
range that are not reasonably likely to be both (1) Significant and (2)
threatened or endangered. To identify only those portions that warrant
further consideration, we determine whether substantial information
indicates that: (1) The portions may be significant, and (2) the
species may be in danger of extinction there or likely to become so
within the foreseeable future. In practice, a key part of this analysis
is whether the threats are geographically concentrated in some way. If
the threats to the species are essentially uniform throughout its
range, no portion is likely to warrant further consideration. Moreover,
if any concentration of threats applies only to portions of the
species' range that are not significant, such portions will not warrant
further consideration.
If we identify portions that warrant further consideration, we then
determine whether the species is threatened or endangered in these
portions of its range. Depending on the biology of the species, its
range, and the threats it faces, the Service may address either the
significance question or the status question first. Thus, if the
Service considers significance first and determines that a portion of
the range is not significant, the Service need not determine whether
the species is threatened or endangered there. Likewise, if the Service
considers status first and determines that the species is not
threatened or endangered in a portion of its range, the Service need
not determine if that portion is significant. However, if the Service
determines that both a portion of the range of a species is significant
and the species is threatened or endangered there, the Service will
specify that portion of the range as threatened or endangered under
section 4(c)(1) of the ESA.
We evaluated the current range of the Dakota skipper to determine
if potential threats for the species have any apparent geographic
concentration. We examined potential habitat threats from effects of
habitat loss, fragmentation, degradation, and modification from
agriculture, development, invasive species, secondary succession,
grazing, and haying (Factor A); overutilization for scientific or
recreational collection (Factor B); disease and predation (Factor C);
the inadequacy of existing regulatory mechanisms (Factor D); and the
effects of habitat fragmentation and small population size and
isolation, climate change, pharmaceuticals, insecticides, pesticides,
prairie plant harvest, and unknown stressors (Factor E). As discussed
above, although the specific threats affecting the species may be
different at individual sites or in different parts of the Dakota
skipper's range, on the whole threats are occurring throughout the
species' range. The Dakota skipper is thought to still be present at
approximately 91 sites, at least 83 of which are subject to one or more
threats that have a moderate to high impact on those populations. On no
portions of its range are threats significantly concentrated or
substantially greater than in other portions of its range; therefore,
we find that impacts to the Dakota skipper are essentially uniform
throughout its range, indicating that the entire range warrants a
threatened status under the Act. As discussed above, our review of the
best available scientific and commercial information indicates that the
Dakota skipper is not in danger of extinction (endangered) but is
likely to become endangered within the foreseeable future (threatened)
throughout all of its range. Therefore, we find that listing the Dakota
skipper as a threatened species under the Act throughout its entire
range is warranted at this time.
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 87 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 29 percent each
year (2004-2012), with a low of 13 percent at sites surveyed in 2012.
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 Minnesota 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. Iowa sites were not surveyed in 2012.
Poweshiek skipperling have historically been documented at
approximately 296 sites; now we consider the species to be present at
only 14 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 2 small and isolated native-
prairie remnants in Wisconsin, 10 small and isolated prairie fen
remnants in Michigan, and a prairie complex in Manitoba. These sites
represent only 5 percent of the total number of sites ever documented
for the species. The numbers observed at these sites are relatively
small (less than 100 at all but 2 sites), and all of these sites have
at least one documented threat that have 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 1.2
to 2.2 during the last 4 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
[[Page 63619]]
considered to have unknown occupancy at 131 sites--throughout the range
of the species (Iowa, Michigan, Minnesota, North Dakota, and South
Dakota), 54 of these sites were included in the threats assessment. Of
the 54 sites where the occupancy is unknown that had sufficient
information to assess, at least 43 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.
Summary
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 stressors 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 14
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
moderate- to high-level threats that have moderate- to high-level
effects on those populations that is ongoing and immediate. Therefore,
on the basis of the best available scientific and commercial
information, we propose 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 stressors 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 stressors that
has 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 stressors 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. The Poweshiek skipperling proposed
for listing in this rule is highly restricted in its range, and the
threats occur throughout its range. Therefore, we assessed the status
of the species throughout its entire range. The threats to the survival
of the Poweshiek skipperling occur throughout the species' range and
are not restricted to any particular significant portion of that range.
Accordingly, our assessment and proposed determination applies to the
Poweshiek skipperling throughout its entire range.
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
[[Page 63620]]
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, Tribal, 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.
If these 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.
Although the Dakota skipper and Poweshiek skipperling are only
proposed for listing under the Act at this time, please let us know if
you are interested in participating in recovery efforts for these
species. Additionally, we invite you to submit any new information on
this 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.
Section 7(a)(4) of the Act requires Federal agencies to confer with the
Service on any action that is likely to jeopardize the continued
existence of a species proposed for listing or result in destruction or
adverse modification of proposed critical habitat. 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 Natural Resources Conservation Service; 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.
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.
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.
Our policy, as published in the Federal Register on July 1, 1994
(59 FR 34272), is to identify to the maximum
[[Page 63621]]
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 proposed listing on proposed and ongoing activities within the
range of species proposed for listing. The following activities could
potentially result in a violation of section 9 of the Act; 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) 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;
(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) Unauthorized modification, removal, or destruction of the
prairie vegetation, soils, or hydrology in which the Dakota skipper and
Poweshiek skipperling are known to occur; 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).
Special Rule
Under section 4(d) of the Act, the Secretary may publish a special
rule that modifies the standard protections for threatened species in
the Service's regulations at 50 CFR 17.31, which implement section 9 of
the Act, with special measures that are determined to be necessary and
advisable to provide for the conservation of the species. As a means to
promote conservation efforts on behalf of the Dakota skipper, we are
proposing a special rule for this species under section 4(d) of the
Act. In the case of a special 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 special
rule contains the prohibitions necessary and appropriate to conserve
that species.
As discussed above, the primary factors supporting the proposed
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 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 stressors.
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 special rule under section 4(d) of the Act, but the
section 4(d) special 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, we are proposing a 4(d) special rule that
outlines the prohibitions, and exceptions to those prohibitions,
necessary and advisable for the conservation of the Dakota skipper.
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) and a wide variety of peer-
reviewed publications and government reports have documented recent
loss of native grassland (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 Dakota skipper (Wright and Wimberly 2013, p.
2).
As with agricultural policies (Doherty et al. 2013, p. 15), the
prohibitions against take of Dakota skipper that would become effective
if the species is listed 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 is frequently a priority of programs to conserve
native grassland ecosystems in the northern Great Plains (e.g., Service
2011, p. 5). We believe that allowing 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
would facilitate the coordination and partnerships needed to recover
the species.
In light of the socioeconomic and policy factors that are leading
to the conversion of native prairie to
[[Page 63622]]
agricultural cropland and because there is evidence that some grazing
practices are conducive to conservation of Dakota skipper in parts of
its range, we determine that it is necessary and advisable to allow
take of the species caused by certain ranching activities. Whereas
conversion to cropland would kill any Dakota skipper larvae present and
destroy any habitat value for the species into the foreseeable future,
some habitats can remain suitable for Dakota skipper when grazed (Dana
1991, p. 54; Schlicht 1997, p. 5; Skadsen 1997, pp. 24-29). In
addition, 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 (Service 2006, p. 2; Smart
et al. in prep.). However, some grazing practices are adverse for
Dakota skipper; therefore, we will work with private landowners, public
land managers, state and Federal conservation agencies, and
nongovernmental organizations to identify, refine, and implement
grazing practices that are conducive to the species' conservation.
Provisions of the Proposed Special Rule for 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 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). This proposed 4(d) special rule proposes that all
prohibitions in 50 CFR 17.31(a) and (b) will apply to the Dakota
skipper except in the specific instances as outlined below. The
proposed 4(d) special 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
First, the Service proposes that incidental take that is caused by
the routine livestock ranching and recreational trail maintenance
activities described below and that are implemented on private, state,
and tribal lands 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 rule, routine livestock ranching and recreational trail
maintenance activities include:
(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 conserve Dakota skipper habitat.
(2) Livestock Gathering and Management: The installation and
maintenance of corrals, loading chutes, and other livestock working
facilities that 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 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 phenology (growth stage) of the weed
species. Control of noxious weeds may also be important to protect
Dakota skipper habitat because native plant diversity may decline when
nonnative plant species invade tallgrass prairie (Boettcher et al.
1993, p. 35). Broadcast application of herbicides, however, may result
in significant deterioration of habitat quality for Dakota skippers
(Smart et al. 2011, p. 184). Therefore, incidental take of Dakota
skipper that may result from spot-spraying of herbicides would be
allowed.
(5) Haying: Stock cows need to be maintained through the non-
growing season; thus, haying 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 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 allowed. Dakota skippers are unlikely
to occur in replanted grasslands (grasslands replanted on formerly
plowed or cultivated lands) or in tame hayland (grassland comprised
primarily of nonnative grass species, such as smooth brome (Bromus
inermis inermis)). Therefore, mowing before July 16 is allowed on
replanted and tame grasslands.
[[Page 63623]]
(6) Mowing 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 winter snow will not
catch and block vehicle access and that they are suitable for hiking
and other intended recreational activities, respectively. These areas
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
caused by mowing of section line rights of way and recreational trails
is allowed.
(7) Livestock (e.g., cattle or bison) grazing, except on lands
where Dakota skipper occurs in the following states and counties:
Minnesota--Kittson; North Dakota--Eddy, McHenry, Richland, Rolette,
Sargent, and Stutsman. In those counties Dakota skippers inhabit
relatively flat and moist habitats where they may be especially
sensitive to effects of grazing (Royer et al. 2008, pp. 11, 16),
including trampling, soil compaction, and loss of important nectar
sources; haying conducted after the Dakota skipper flight period is the
predominant management on sites inhabited by the species in these
counties. In all other states and counties, incidental take of Dakota
skippers that may result from grazing is allowed under this rule.
In the drier and hillier habitats that the species inhabits outside
of the counties listed above, grazing may benefit Dakota skipper
depending on its intensity. Moreover, in contrast to the permanent
habitat destruction caused by plowing, mining, and certain other
activities, native plant diversity in tallgrass prairie may recover
from overgrazing if it has not been too severe or prolonged. 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). Nevertheless, grazing can also have significant deleterious
effects on Dakota skipper; for example, a strong population of the
species at a grazed site in South Dakota was extirpated after a change
in ownership resulted in significant overgrazing (Skadsen 2006, p. 5).
Therefore, we intend to cooperate with ranchers and our state and
tribal conservation partners to identify, test, and implement grazing
practices that effectively conserve Dakota skipper populations. By
allowing grazing in the geographic areas where the Dakota skipper
primarily inhabits dry-mesic prairie, we may slow the loss of native
prairie conversion for crop production and also maintain partnerships
that are critical for conserving the species.
In the counties where this rule would not allow take caused by
livestock grazing, Dakota skipper almost exclusively inhabits
relatively flat and moist prairie habitats that are mowed for hay.
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 when 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 (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 skipper 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 Dakota skipper, for example,
habitat on steep slopes was ``in good condition'', whereas ``lesser
slopes'' were ``moderately grazed'' and some areas were ``overgrazed''
(Skadsen 1999, p. 29).
The best available information indicates that in the counties where
this rule would not allow take caused by livestock grazing the species
may be extant at 19 sites and only 1 of those is currently grazed. The
single grazed site is in McHenry County, North Dakota, and is owned by
the State of North Dakota. The habitat at the site is described as
``marginal'' for Dakota skipper and there ``has never been a strong''
presence of the species, based on surveys of the site conducted since
about 1991 (Royer 2013, pers. comm.). Since Dakota skipper was recorded
there in 1998, only one survey has been conducted--in 2012 (Royer and
Royer 1998, p. 9; Royer and Royer 2012, p. 3). No Dakota skippers were
found there during two surveys in 2012, although they were present at a
hayed site across the road (Royer and Royer 2012, p. 42). At three
other sites in the counties where this rule would not allow take caused
by grazing, grazing was likely the primary factor that led to the
species' extirpation. At each of these sites grazing was described as
``heavy'' or ``substantial'', the habitat was degraded, and important
nectar sources were lacking or depleted (Royer and Royer 2012, pp. 9,
12, 27).
The lack of any examples of sites where strong populations of
Dakota skippers occur in concert with grazing indicates to us that it
would not be advisable at this time to allow take caused by grazing in
the counties listed above--Kittson County, Minnesota, and Eddy,
McHenry, Richland, Rolette, Sargent, and Stutsman Counties in North
Dakota. In these counties, Dakota skipper primarily inhabits wet-mesic
prairie habitats that support plant communities that are distinct from
those that occur on dry-mesic prairie elsewhere in the species' range.
The Service is committed to working with private landowners, public
land managers, conservation agencies, nongovernmental organizations,
and the scientific community to determine whether any grazing of Dakota
skipper habitat in any of the counties may be conducted in a manner
that is conducive to the species' conservation. We are seeking public
comments on this topic. In the meantime, the continuation of hay
production as the primary use of these habitats--with mowing occurring
no earlier than July 16--is the most compatible land use activity for
the Dakota skipper and would contribute substantially to the
conservation of the species.
Peer Review
In accordance with our joint policy on peer review published in the
Federal Register on July 1, 1994 (59 FR 34270), we will seek the expert
opinions of at least three appropriate and independent specialists
regarding this proposed rule. We have invited these peer reviewers to
comment during this public comment period on our specific assumptions
and conclusions in this proposed rule.
[[Page 63624]]
We will consider all comments and information received during this
comment period on this proposed rule during our preparation of a final
determination. Accordingly, the final decision may differ from this
proposal.
Public Hearings and Informational Meetings
Section 4(b)(5) of the Act provides for one or more public hearings
on this proposal, if requested. Requests must be received within 45
days after the date of publication of this proposed rule in the Federal
Register. Such requests must be sent to the address shown in FOR
FURTHER INFORMATION CONTACT. We will schedule public hearings on this
proposal, if any are requested, and announce the dates, times, and
places of those hearings, as well as how to obtain reasonable
accommodations, in the Federal Register and local newspapers at least
15 days before the hearing.
We have scheduled informational meetings regarding the proposed
rule in the locations specified in ADDRESSES. Any interested
individuals or potentially affected parties seeking additional
information on the public informational meetings should contact the
Twin Cities Ecological Services Office (See FOR FURTHER INFORMATION
CONTACT). The U.S. Fish and Wildlife Service is committed to providing
access to this event for all participants. Please direct all requests
for interpreters, closed captioning, or other accommodation to the Twin
Cities Ecological Services Office (See FOR FURTHER INFORMATION
CONTACT).
Required Determinations
Clarity of the Rule
We are required by Executive Orders 12866 and 12988 and by the
Presidential Memorandum of June 1, 1998, to write all rules in plain
language. This means that each rule we publish must:
(1) Be logically organized;
(2) Use the active voice to address readers directly;
(3) Use clear language rather than jargon;
(4) Be divided into short sections and sentences; and
(5) Use lists and tables wherever possible.
If you feel that we have not met these requirements, send us
comments by one of the methods listed above in ADDRESSES. To better
help us revise the rule, your comments should be as specific as
possible. For example, you should tell us the numbers of the sections
or paragraphs that are unclearly written, which sections or sentences
are too long, the sections where you feel lists or tables would be
useful, etc.
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.
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
Field Supervisor, Twin Cities Field Office (see FOR FURTHER INFORMATION
CONTACT).
Authors
The primary authors of this package are the staff members of the
Twin Cities Field Office.
List of Subjects in 50 CFR Part 17
Endangered and threatened species, Exports, Imports, Reporting and
recordkeeping requirements, and Transportation.
Proposed Regulation Promulgation
Accordingly, we propose to amend part 17, subchapter B of chapter
I, title 50 of the Code of Federal Regulations, as set forth below:
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. In Sec. 17.11(h), add entries for ``Skipper, Dakota'' and
``Skipperling, Poweshiek'' to the List of Endangered and Threatened
Wildlife in alphabetical order under ``Insects'' to read as set forth
below:
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. (IL, IA, MN, NA................. T ........... NA 17.47(b)
ND, SD); Canada
(Manitoba,
Saskatchewan).
[[Page 63625]]
* * * * * * *
Skipperling, Poweshiek........... Oarisma poweshiek... U.S.A. (IL, IA, IN, NA................. E ........... NA NA
MI, MN, WI, ND,
SD); 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:
(i) Recreational trail maintenance activities;
(ii) Mowing of section line rights of way; and
(iii) Routine livestock ranching activities that are conducted in
accordance with applicable State, Federal, tribal, and local laws and
regulations. For the purposes of this rule, routine livestock ranching
activities include:
(A) Fence construction and maintenance.
(B) Activities pertaining to livestock gathering and management,
such as the installation and maintenance of corrals, loading chutes,
and other livestock working facilities.
(C) Development and maintenance of livestock watering facilities.
(D) Spot-spraying of herbicides for noxious weed control (Broadcast
application of herbicides is not allowed.).
(E) Haying, as set forth in this paragraph (b)(3)(i)(E):
(1) In native haylands, which are typically cut in August after the
needlegrass (Hesperostipa spp. or Nassella viridula) awns drop, haying
after July 15 is allowed.
(2) In replanted grasslands (grasslands replanted on formerly
plowed or cultivated lands) or in tame haylands (grasslands comprising
primarily nonnative grass species, such as smooth brome (Bromus inermis
inermis)), mowing may occur at any time.
(F) Grazing of cattle, bison, or horses, except in Kittson County,
Minnesota, and Eddy, McHenry, Richland, Rolette, Sargent, and Stutsman
Counties, North Dakota, where the Dakota skipper inhabits areas that
may be especially sensitive to the effects of grazing by these types of
livestock.
* * * * *
Dated: September 23, 2013.
Rowan W. Gould,
Acting Director, U.S. Fish and Wildlife Service.
[FR Doc. 2013-24175 Filed 10-23-13; 8:45 am]
BILLING CODE 4310-55-P
