Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List the Mardon Skipper as Threatened or Endangered, 54331-54352 [2012-21344]
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Vol. 77
Tuesday,
No. 171
September 4, 2012
Part IV
Department of the Interior
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Fish and Wildlife Service
50 CFR Part 17
Endangered and Threatened Wildlife and Plants; 12-Month Finding on a
Petition To List the Mardon Skipper as Threatened or Endangered;
Proposed Rule
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Federal Register / Vol. 77, No. 171 / Tuesday, September 4, 2012 / Proposed Rules
Information Relay Service (FIRS) at
800–877–8339.
SUPPLEMENTARY INFORMATION:
DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS–R1–ES–2012–0060;
4500030113]
Endangered and Threatened Wildlife
and Plants; 12-Month Finding on a
Petition To List the Mardon Skipper as
Threatened or Endangered
Fish and Wildlife Service,
Interior.
ACTION: Notice of 12-month petition
finding.
AGENCY:
We, the U.S. Fish and
Wildlife Service (Service), announce a
12-month finding on a petition to list
the mardon skipper (Polites mardon) as
a threatened or endangered species
under the Endangered Species Act of
1973, as amended (Act). After review of
the best available scientific and
commercial information, we find that
listing the mardon skipper is not
warranted at this time. However, we ask
the public to submit to us any new
information that becomes available
concerning the threats to the mardon
skipper or its habitat at any time. At our
discretion, after additional review of the
subspecies Polites mardon mardon and
Polites mardon klamathensis, we find
that listing for these subspecies is also
not warranted at this time.
DATES: The finding announced in this
document was made on September 4,
2012.
SUMMARY:
This finding is available on
the Internet at https://
www.regulations.gov at Docket Number
FWS–R1–ES–2012–0060. Supporting
documentation we used in preparing
this finding is available for public
inspection, by appointment, during
normal business hours at the U.S. Fish
and Wildlife Service, Washington Fish
and Wildlife Office, 510 Desmond Drive
SE., Suite 102, Lacey, WA 98503. Please
submit any new information, materials,
comments, or questions concerning this
finding to the above address.
FOR FURTHER INFORMATION CONTACT: Ken
Berg, Field Supervisor, Washington Fish
and Wildlife Office (see ADDRESSES); by
telephone at 360–753–9440; facsimile at
360–753–9008; or Paul Henson, Field
Supervisor, Oregon Fish and Wildlife
Office, 2600 SE 98th Avenue, Suite 100,
Portland, OR 97266; by telephone at
503–231–6179; facsimile at 503–231–
6195 mailto:. If you use a
telecommunications device for the deaf
(TDD), please call the Federal
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ADDRESSES:
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Background
Section 4(b)(3)(B) of the Act (16
U.S.C. 1531 et seq.), requires that, for
any petition to revise the Federal Lists
of Endangered and Threatened Wildlife
and Plants that contains substantial
scientific or commercial information
that listing the species may be
warranted, we make a finding within 12
months of the date of receipt of the
petition. In this finding, we will
determine that the petitioned action is:
(1) Not warranted, (2) warranted, or (3)
warranted, but the immediate proposal
of a regulation implementing the
petitioned action is precluded by other
pending proposals to determine whether
species are threatened or endangered
species, and expeditious progress is
being made to add or remove qualified
species from the Federal Lists of
Endangered and Threatened Wildlife
and Plants. Section 4(b)(3)(C) of the Act
requires that we treat a petition for
which the requested action is found to
be warranted but precluded as though
resubmitted on the date of such finding,
that is, requiring a subsequent finding to
be made within 12 months. We must
publish these 12-month findings in the
Federal Register.
Previous Federal Actions
On October 25, 1999, the Service
identified the mardon skipper (Polites
mardon) as a candidate species for
listing under the Act (64 FR 57539). The
identification of the mardon skipper as
a candidate species was based on
information compiled in the
Washington State Status Report for the
Mardon Skipper (Potter et al. 1999,
entire).
On December 11, 2002, we received a
petition dated December 10, 2002, from
The Xerces Society, Gifford Pinchot
Task Force, The Northwest
Environmental Defense Center, Center
for Biological Diversity, Oregon Natural
Resources Council, Friends of the San
Juans, and Northwest Ecosystem
Alliance (petitioners), requesting that
the mardon skipper be listed as an
endangered species, and that critical
habitat be designated under the Act
(Black et al. 2002, entire). Included in
the petition was supporting information
regarding the species’ taxonomy and
ecology, historical and current
distribution, present status, and actual
and potential causes of decline. We
acknowledged the receipt of the petition
in a letter to the petitioners, dated
January 22, 2003. In that letter we also
stated that the Service considered the
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mardon skipper as having been subject
to both a positive 90-day finding and a
‘‘warranted but precluded’’ 12-month
finding, with the Candidate Notice of
Review constituting publication of these
required findings. The Service’s
‘‘warranted but precluded’’ finding was
based on limited funding that was
dedicated to court-ordered or other
higher-priority listings.
From 2003 to 2011, the Service
continued to work with Federal, State,
and private parties to compile
information on the status and
distribution of the mardon skipper,
which is documented in the Service’s
candidate species assessment forms for
those years. Substantial new
information was collected regarding
mardon skipper populations,
distribution, and habitat requirements.
In 2009, we changed the listing priority
number for the mardon skipper from 5
to 8 (lower priority) due to the
documentation of many new
populations and increased protections
for the species and its habitat provided
by State and Federal special status
species programs.
In a settlement agreement with
plaintiff WildEarth Guardians, on May
10, 2011, the Service submitted a
workplan to the U.S. District Court for
the District of Columbia in re
Endangered Species Act Section 4
Deadline Litigation, No. 10–377 (EGS),
MDL Docket No. 2165 (D. DC May 10,
2011), and obtained the court’s approval
to systematically, over a period of 6
years, review and address the needs of
more than 250 candidate species to
determine if they should be added to the
Federal Lists of Endangered and
Threatened Wildlife and Plants. The
mardon skipper is one of 251 candidate
species identified in the May 2011
workplan. On October 26, 2011, the
Service published the intent to develop
a proposed listing for several candidate
species in the Puget Sound prairie
region (including the mardon skipper)
with funding allocated in Fiscal Year
2011 (76 FR 66830). We have since
determined that, as the distribution of
the mardon skipper includes additional
habitat other than prairie, the public
would be better served evaluating this
information and the species, separately.
This notice constitutes our 12-month
finding on the mardon skipper.
Substantial new information regarding
the mardon skipper has been compiled
since we originally advanced the
species to candidacy. Therefore, this
finding considers information presented
in the 2002 petition, as well as new
information compiled over the past
decade.
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Species Information
The mardon skipper is a small (20 to
24 millimeters; less than 1 inch), tawnyorange butterfly with a stout, hairy
body. The upper surface of the
forewings and hindwings is orange with
broad dark-brown borders, and the
ventral hindwings have a distinctive
pattern of light yellow to white
rectangular spots (Pyle 2002, p. 88).
Males are smaller than females, and
have a small, dark-brown, slender and
branched streak (stigma) on the upper
surface of the forewing. Females have a
more distinct ventral hindwing pattern.
The mardon skipper is differentiated
from other closely related Polites
species by its short, rounded wings,
reduced stigmal elements, and other
distinctive morphological features
(MacNeill 1993, p. 179). Like most
Hesperiinae butterflies, mardon
skippers have bent antennae clubs and
a characteristic basking posture in
which the forewings are held at a 45degree angle and the hind wings are
fully spread (Potter et al. 1999, p. 1).
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Taxonomy and Species Description
The mardon skipper is a butterfly in
the Order Lepidoptera (butterflies and
moths), superfamily Hesperioidae, and
family Hesperiidae (skippers), subfamily
Hesperiinae (grass skippers). It was
originally described by W. H. Edwards
(1881, pp. 47–48) as Pamphila mardon
from three males and three females
collected by H.K. Morrison in 1880. The
original type locality, stated by W.H.
Edwards as Mount Hood, Oregon, was
later correctly designated as small
prairies near Puget Sound, Washington
(Morrison 1883, p. 43). This type
location was further defined as ‘‘Tenino
Prairie, Thurston County, Washington’’
by Brown and Miller (1980, p. 53). The
mardon skipper is a rare species that
occurs in four disjunct areas that
include locations near the coast in
northwestern California and
southwestern Oregon, the southern
Oregon Cascades, the southern
Washington Cascades, and prairies in
the south Puget Sound region (James
and Nunallee 2011, p. 388).
In 1998, Mattoon et al. (p. 768)
proposed that the Oregon Cascade
populations be given subspecies status
as Polites mardon klamathensis, and the
Washington and northern California
populations be given subspecies status
as Polites mardon mardon. Adults of
P.m. klamathensis are described as
having a consistently tawnier dorsal and
ventral coloration when compared to
adults from other populations (Mattoon
et al. 1998, pp.771–772).
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The distinction between Polites
mardon klamathensis and P.m. mardon
was based largely on comparisons
between specimens collected in
northwestern California and the
southern Oregon Cascades. According to
Warren (2005, p. 49), the use of the
name P.m. mardon for California
populations should be considered
tentative because the series of P.m.
mardon from the northwestern
California (and coastal southwestern
Oregon) populations have not yet been
carefully compared to the series of P.m.
mardon from Washington due to the
small number of specimens available for
evaluation (Mattoon et al. 1998, p. 771).
The Catalogue of the Butterflies of the
United States and Canada (Pelham 2008,
p. 78) lists the full species followed by
both subspecies. However, in the
introduction of his Catalogue, Pelham
(2008, p. VII) notes that the subspecies
category is used without regard to its
validity. No additional taxonomic work
or genetic analyses have been done to
clarify the subspecific designations
described above (Kerwin 2011, p. 10).
Polites mardon is recognized as a valid
species by the Integrated Taxonomic
Information System (ITIS) while P.m.
klamathensis and P.m. mardon are
recognized as valid subspecies (ITIS
2011, P. mardon, entire). For the
purposes of this finding, we first
analyzed the threats to the species
Polites mardon as a whole. We then, at
our initiative, further considered the
threats to each of the currently
recognized subspecies: P.m. mardon
and P.m. klamathensis.
Distribution
The mardon skipper is a rare
northwestern butterfly with a
remarkably disjunct range. The species’
current range is known from four widely
separated locations: the south Puget
Sound region of Washington, the
southern Washington Cascades, the
Cascade Mountains of southern Oregon,
and coastal hills in northwestern
California and southwestern Oregon
(Kerwin 2011, pp. 8–9). The historical
range and abundance of mardon
skippers are unknown. The species was
originally described from specimens
collected at a south Puget Sound prairie
site in 1880 (Morrison 1883, p. 43), but
there are few historical records or
museum collections of this species
(Potter et al. 1999, p. 3). No estimates of
abundance are available from any site
prior to 1980 (Potter et al. 1999, p. 5).
The mardon skipper’s disjunct
distribution and strong association with
early-seral, semi-mesic grassland
habitats in the Pacific Northwest suggest
a relict distribution that was likely
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much more widespread in the past. Both
Pyle (2002, p. 89) and Runquist (2004a,
p. 6) suggest that the mardon skipper is
an ancient species. The species’ short,
rounded wing morphology is not
adapted to long-distance dispersal. The
apparent lack of intervening
populations between the distinct
geographic areas suggests the species
probably evolved under more open,
contiguous environmental conditions
(Runquist 2004a, p. 6). Populations in
each disjunct geographic region have
likely become isolated over long
geologic time scales, as evidenced by
the subspecies distinction between
Polites mardon mardon and P. m.
klamathensis. It is likely that mardon
skippers were historically more
widespread within each disjunct
geographic region prior to the
widespread loss of grassland and
montane meadow habitats due to fire
suppression, invasive species, and
development over the past century
(Potter et al. 1999, p. 5, Beyer and
Schultz 2010, p. 863; Schultz et al.
2011, p. 370).
In this assessment we use the term
‘‘site’’ to indicate a specific location
with species presence. Sites are usually
mapped as distinct habitat patches, such
as individual meadows in summary
reports (e.g., Black et al. 2010, p. 25).
Sites may include locations with a
single mardon skipper observation, or
locations that support many mardon
skippers observed over multiple years.
Sites are variable, and not all reports
define sites the same way. For purposes
of estimating the number of
populations, occupied meadows can be
considered to belong to the same
population if the sites are within the
annual dispersal distance for the
species, generally assumed to be 0.5 mi
(0.8 km) or less (Potter and Fleckenstein
2001, p.6). In this assessment we use the
term ‘‘populations’’ to represent local
clusters of sites that we assume are
likely to be associated and function as
a local population.
Summary of Mardon Skipper Current
Range and Distribution
In 1999, the mardon skipper was
known from approximately 14 extant
sites located in four distinct geographic
areas (Potter et al. 1999, p.5). Targeted
surveys from 2000 through 2011 have
documented a total of 165 sites with
mardon skipper presence representing
approximately 66 populations (Table 1).
New sites or populations have been
documented in each year that surveys
have been completed. For example, five
new sites were documented in 2011,
including four sites in the Washington
Cascades, and one site in the southern
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Oregon Cascades. It is very likely that
additional undocumented sites exist,
particularly in the Washington Cascades
and possibly in southwestern Oregon or
northwestern California, because not all
of the potential habitat areas have been
surveyed. The increase in known
populations since 1999 is due to
increased survey effort in areas not
previously surveyed, rather than to
increased habitat or expanding
populations (Kerwin 2011, p. 18). The
majority (76 percent) of the sites
throughout the species’ range occur on
Federal lands managed by the Forest
Service, Bureau of Land Management
(BLM), National Park Service, Fish and
Wildlife Service, and the Department of
Defense, as well as Tribal lands owned
by the Yakama Indian Reservation (17
percent). Due to the species’ disjunct
distribution, the populations in different
geographic regions are relatively
isolated, with two recognized
subspecies Polites mardon mardon and
P.m. klamathensis, occurring within the
species’ range.
Approximate
number of
documented
sites with species presence
(2000–2011)
Approximate
number of
populations
(local clusters
of sites)
Joint Base Lewis McChord—Dept. of Defense ............
4
1
Washington Dept. of Fish & Wildlife ............................
Wenatchee National Forest ..........................................
Gifford Pinchot National Forest ....................................
Conboy Lake National Wildlife Refuge ........................
Yakama Indian Reservation .........................................
Private ownership .........................................................
BLM—Coos Bay District ...............................................
Rogue River Siskiyou National Forest .........................
Oregon State Parks ......................................................
Six Rivers National Forest ............................................
Redwood National Park ................................................
Private ownership .........................................................
2
36
43
3
23
6
2
3
1
8
9
3
2
15
13
3
11
4
1
1
Geographic region
Site ownership
Polites mardon mardon
Washington—South Puget Sound Prairies (Pierce and
Thurston Counties).
Washington—South Cascades (Yakima, Klickitat, and
Skamania Counties).
Southwest Oregon—Curry County ...............................
Northwest California—Del Norte County ......................
2
1
1
Polites mardon klamathensis
Oregon—South Cascades Jackson County .................
BLM Medford District ....................................................
Rogue River Siskiyou National Forest .........................
Private ownership .........................................................
15
4
3
9
2
........................
Totals .....................................................................
..................................................................................
165
66
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Note: In this assessment we use the term ‘‘sites’’ for specific locations with documented species presence (some of which are single observations) and ‘‘populations’’ to represent local clusters of sites that we assume are likely to be closely associated and function as a local population.
Summary of Mardon Skipper
Population Estimates and Trends
Estimates of population sizes or
population trends over time for mardon
skippers are generally not available.
Surveys to estimate relative abundance
of mardon skippers are conducted by
systematically walking transects
through a site and counting the number
of adult mardon skippers encountered
(Seitz et al. 2007, p. 11). The majority
of survey efforts have been 1-day
counts, so it is not known if they were
conducted early or late in the adult
flight period. Multiple surveys during
the flight season and across a number of
years are required to assess population
sizes because the timing and length of
adult flight periods can vary widely
from year to year (Kerwin 2011, p. 19).
A few surveyors have used linetransect distance-sampling methods to
estimate mardon skipper populations,
but these techniques have generally
failed to provide statistically reliable
estimates at sites with small populations
(Runquist 2004b, p. 4, Arnold 2006, p.
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6). Runquist (2004a, pp. 4–5) used both
line-transect sampling and markrecapture sampling techniques to
estimate a mardon skipper population
in a small complex of three meadows in
the Oregon Cascades. Researchers
counted a total of 172 mardon skippers
on all line-transects over all days,
compared with a total of 238 mardon
skippers that were captured and marked
in the same meadows during the same
period (Runquist 2004a, p. 5). No
statistically reliable estimates of the
actual population size were derived
from this effort, but the author opines
that a total population estimate of 350–
400 individuals would be reasonable at
this site based on his observations
(Runquist 2004a, p. 5).
Line-transect distance sampling was
used to census mardon skippers across
approximately 800 acres (ac) (324
hectares (ha)) of Puget prairie habitat in
2009, and provided the first statistically
reliable estimates of the mardon skipper
populations at these sites (Potter 2010,
p. 4). At the Scatter Creek Wildlife Area
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in 2009, the population estimate during
the peak of the adult flight period was
801 mardon skippers at the South Unit
(95 percent confidence interval = 399–
1,286 skippers) and 204 at the North
Unit (95 percent confidence interval =
84–360) (Potter 2010, p. 4). These
estimates were derived from actual
counts of 312 skippers on the South
Unit and 93 skippers on the North Unit
(Potter 2009, p. 1). This was the most
comprehensive survey effort at this site
to date, so the results of the survey are
not directly comparable to previous
monitoring efforts at this site (Potter
2009, p. 2), but this population appears
to be relatively stable based on counts
conducted between 1997 and 2009
(Potter et al. 1999, p. 6; Harke 2001, p.
12; Potter 2009, p. 1).
Only one site (in Washington) has had
a full spectrum of censuses that have
covered the entire adult flight period
(Beyer and Black 2007, p. 8). In 2006,
the counts at this site (Grapefern
Meadow) went from 0 mardon skippers
counted on July 6, to 135 on July 9; 345
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on July 16; 128 on July 23; and 2 on
August 4 (Beyer and Black 2007, p. 8).
These counts demonstrate that the
number of mardon skippers present at a
site can fluctuate significantly over a
few days. The observed mardon skipper
population at this site has fluctuated
greatly over the past decade, with peak
counts ranging from 420 butterflies in
2004 to 34 in 2011. Although there have
been high counts of butterflies from
time to time, overall the populations on
the Wenatchee National Forest and
Gifford Pinchot National Forest appear
to be relatively stable. Data from the
Wenatchee National Forest show some
evidence of trends related to elevation,
with lower elevation population sites
(less than 3,300 feet (ft) [1,000 meters
(m)]) appearing to be stable, and midelevation sites (3,500–4000 ft [1,067–
1,220 m]) showing some local declines,
likely associated with cool, wet summer
conditions (St. Hilaire et al. 2010, p. 2).
In the Oregon Cascades, limited
population information for Polites
mardon klamathensis is available, as
few multiple-day surveys have been
conducted here. Black et al. (2010,
Appendix 1) report single-day counts
for multiple P.m. klamathensis sites
over a 5-year period, spanning 2005–
2010 (there were no counts for most
sites in 2008). In 2011, one new P.m.
klamathensis site was located on Bureau
of Reclamation Lands managed by BLM
(Black 2012, pers. comm.). Although
several of the P.m. klamathensis sites
appear to be small in size (fewer than 20
individuals), only a handful of these
sites had counts on more than a single
day in a year, and even in these few
cases there were never more than 2 days
of counts in any single year (Black et al.
2010, Appendix 1). Furthermore, the
dates for these counts range quite
widely from one year to the next, from
early or mid-June through the first week
of July, so whether these counts
occurred within the peak flight period is
unclear. For example, as described
above for Grapefern Meadow in
Washington, the only site where we
have data from mardon skipper counts
over the entire adult flight period, the
numbers of skippers counted on any
single day ranged anywhere from 0 to
345 over a 10-day period (Beyer and
Black 2007, p. 8). This high variability
in potential counts shows why singleday counts are not a credible means of
determining population abundance or
trend. Of the known sites for the
subspecies, most have had relatively
few individuals counted on any single
day over the period 2005 through 2010,
but it is not known whether the
observed numbers may represent an
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increase or decrease over historical
levels. One site, Pumpchance 125
Meadow, has generally had relatively
high numbers of P.m. klamathensis over
5 years of single-day counts (up to 304
individuals counted in 2009); historical
abundance of mardon skippers is not
known at this site. On the other hand,
the three sites that make up the Hobart
Peak complex, the one site where
historical abundance information is
available, appear to have lower numbers
of P. m. klamathensis than observed in
the past (Black et al. 2010, Appendix 1).
In general, however, based on the lack
of historical abundance information and
the uncertainty accompanying
individual day counts, we are unable to
determine population trends for P.m.
klamathensis.
Recent monitoring at Coon Mountain
in California found lower numbers of
mardon skippers in areas treated with
prescribed burning compared to
unburned areas in 2008. Three years
after the burn event, mardon skipper
numbers were still lower in burned
areas than in unburned areas, but the
overall population at this site appears to
be stable (Black et al. 2011, p. 13).
Monitoring efforts at other sites in
California have been inconsistent, but
the limited data for the historical sites
at High Divide Ridge indicate this
population is potentially stable within
the limited suitable habitat areas present
at these sites.
Mardon skippers can be locally
abundant where the species is present
(Pyle 1989, p. 28) with day counts of
greater than 100 individuals
documented at several sites across the
species’ geographic range (Black et al.
2010, pp. 70–71; St. Hilaire et al. 2010,
pp. 10–12; Black et al. 2011, p. 13).
Conversely, populations at many
locations within the species’ range are
apparently persisting at very low levels
with consistent peak counts of fewer
than 20 individuals.
Documented extirpations occurred at
five Puget Prairies sites from 1985
through 1999, resulting in a local
contraction of the species’ range in that
region (Potter et al. 1999, p. 6).
Extirpation at one historical site in the
Washington Cascades has been
documented (Potter et al. 1999, p. 4),
but there are at least three other extant
populations in the vicinity of this
historical site at the Conboy Lake
National Wildlife Refuge, including a
newly documented population in 2011
(USFWS unpublished data). Black et al.
(2010, p. 7) state that some Polites
mardon klamathensis sites in the
Oregon Cascades may possibly be
extirpated; however, they also stress
that more monitoring is needed to
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confirm this supposition. No historical
data is available at these sites prior to
2005, and many of these sites appear to
have always had very low numbers of
individuals according to single-day
counts (Black et al. 2010, pp. 70–72).
Black et al. (2010, p. 7) additionally
note that there are cases where one
individual mardon skipper may have
been found in past years but not in
subsequent surveys, but such instances
may represent errant findings and are
not indicative of sites or popultions that
have become extirpated.
With the apparent exception of a few
Polites mardon klamathensis
populations where more monitoring is
needed, and a few higher-elevation P.
m. mardon sites in the Washington
Cascades, most mardon skipper
populations now appear to be stable
across the species’ range.
Habitat
Mardon skippers are grass skippers in
the subfamily Hesperiinae, meaning the
larvae feed strictly on graminoids
(grasses and sedges) (Scott 1986, p. 424).
The mardon skipper’s habitat
requirements include food resources for
adults (flower nectar), larval host plants
(grasses and sedges), and site-specific
environmental and structural conditions
that support successful reproduction
and survival. This includes patches of
early-seral open grassland habitat that
are dominated by short-statured grasses
or sedges and forbs that are generally
free of overstory trees and shrubs.
Mardon skippers generally avoid areas
with tall grasses, shrubs, or trees (Henry
2010, p. 44). Grassland patches that are
as small as 0.5 ac [0.2 ha] are capable
of supporting small populations of
mardon skippers. However, most areas
that support populations of mardon
skippers consist of mixed forestgrassland complexes that support
multiple occupied ‘‘sites’’ with some
connectivity between habitat patches for
successful dispersal and movement of
individuals among sites.
The species’ larval development is
prolonged, lasting for 3 months or more
prior to diapause (Newcomer 1966a, p.
246; Henry 2010, p. 5). During this time
the larvae require succulent grasses for
successful development. Occupied sites
retain sufficient moisture to maintain
host plant palatability (green leaves) for
larval development (Beyer and Black
2007, p. 18; Kerwin 2011, p. 21).
Meadows that are too wet or too dry do
not support mardon skippers. Site
conditions and host plants selected by
mardon skippers vary across sites,
indicating the species is capable of
using multiple graminoids as larval food
(Beyer and Schultz 2010, p. 867).
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Although mardon skippers are not
selective for a specific grass species,
they do exhibit host plant specificity
within some localities (Beyer and
Schultz 2010, p. 869; Henry 2010, p.
15).
South Puget Sound Prairies
In the south Puget Sound region of
Washington, mardon skippers are found
in low-elevation (200–300 ft [60–90 m]),
glacial outwash grasslands (prairies)
with abundant Festuca roemeri
(Roemer’s fescue) interspersed with
Viola adunca (early blue violet) (Potter
et al. 1999, p. 5). Occupied prairies
range in size from 300 to greater than
1,000 ac [120 to more than 400 ha].
Mardon skippers oviposit (lay eggs) on
Roemer’s fescue almost exclusively at
Puget prairie sites, indicating a very
strong association with this grass
species (Henry 2010, p. 13). Roemer’s
fescue is a perennial bunchgrass native
to the Pacific Northwest. Although
Roemer’s fescue accounted for 50
percent of the total grass cover at the
sampled locations, mardon skippers
selected this species in 86 out of 88
observed ovipositions (Henry 2010, p.
13.). In addition to the presence of the
host plants, the structure of the
surrounding plant community is also
important for oviposition selection
(Henry 2010, p. 16). Mardon skippers
selected small, green (live) fescue tufts
in areas with at least 50 percent open
moss cover on the surrounding ground
(Henry 2010, p. 16). Mardon skippers
avoid areas that are heavily invaded
with Arrhenatherum elatius (tall
oatgrass) and Cytisus scoparius (Scot’s
broom) (Henry 2010, p. 44). The
oviposition habitat requirements of
mardon skippers in Puget prairies are
distinct from those of populations in the
southern Washington Cascades (Henry
2010, p. 19).
At Puget prairie sites, early blue violet
and Vicia sativa (common vetch) are
strongly preferred as nectar sources, and
Scot’s broom is strongly avoided (Hays
et al. 2000, p. 14). Nectaring was also
observed on Camassia quamash
(common camas), Lomatium
utriculatum (fine-leaved desert parsley),
Teesdalia nudicaulis (barestem
teesdalia), and Ranunculus occidentalis
(western buttercup) (Hays et al. 2000, p.
24).
Southern Washington Cascades
In the southern Washington Cascades,
the mardon skipper is found in open
grasslands and small montane meadows
within Abies grandis (Grand fir),
Psuedotsuga menziesii (Douglas-fir), or
Pinus contorta (lodgepole pine)/mixedconifer woodlands at mid to high
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elevations (1,800 to 5,600 ft [549 to
1,707 m]) (Potter et al. 2002, p. 12).
Occupied sites in the Washington
Cascades vary in size from small (0.5 ac
[0.2 ha]) meadows to large forest/
meadow complexes encompassing
hundreds of acres. Site conditions range
from relatively dry, ridgetop meadows
to small montane meadows associated
with wetlands, springs, or riparian
habitat (Potter et al. 2002, p. 13).
Wetland areas that are perennially
submerged do not support mardon
skippers, but the species is often found
in dry transitional zones along the
margins of wetlands. Water features
such as small streams or wetlands are
common at many Washington Cascades
sites (Kerwin 2011, p. 20). Alpine
meadows (more than approximately
6,000 ft [1,829 m] elevation) apparently
do not support this species, perhaps due
to the relatively short season these areas
are free from snow cover. Sites with
grassland vegetation, including grassy
forest openings, roadside meadows, and
young, grass-dominated tree plantations
support mardon skipper populations
(Potter et al. 2002, pp. 12–13).
In the Washington Cascades,
oviposition has been documented on 23
different graminoid species (Beyer and
Schultz 2010, p. 866). However, this
analysis indicated that mardon skippers
are selective for certain grass species
within different meadows. The most
frequently used oviposition plants
include Festuca idahoensis (Idaho
fescue), Poa pratensis (Kentucky
bluegrass), Danthonia intermedia
(timber oatgrass), Carex inops (longstolen sedge), and Festuca rubra (red
fescue) (Beyer and Schultz 2010, p.
866). Danthonia unispecta (one-spiked
oatgrass) appears to be an important
grass species at sites on the Wenatchee
National Forest. Females have been
observed ovipositing on this species
(Jepsen et al. 2008, p. 3), and higher
densities of adult butterflies are
commonly associated with patches of D.
unispecta (St. Hilaire et al. 2009, p. 7).
The variety of identified oviposition
plants suggests that females may not
always oviposit on specific host plants,
but within a community of possible
species that can be used by the larvae
(Beyer and Black 2007, p. 5). These
findings are significantly different from
the observations at Puget prairies sites,
which indicated mardon skippers were
strongly associated with a single grass
species (Henry 2010, p. 19).
Due to the range of plant communities
present at Washington Cascades sites,
there were no common habitat features
across all study sites other than the
presence of short-statured grasses and
sedges (Beyer and Schultz 2010, pp.
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869–870). Mardon skippers selected for
larger graminoids with greater total
cover and less bare ground selection
was also negatively influenced by the
presence of trees, indicating a
preference for selecting oviposition sites
away from trees and forest edges (Beyer
and Schultz, p. 869). Studies of mardon
skipper densities within individual
meadows also demonstrated that
mardon skippers are patchily
distributed within occupied sites, with
the highest densities tending to occur
near the center of a meadow away from
forested edges (Beyer and Black 2007, p.
18).
In the Washington Cascades, adults
have most frequently been observed
nectaring on vetch, Fragaria spp.
(strawberry), and Trifolium spp. (clover)
(Beyer and Black 2007, p. 15). Erysimum
asperum (wallflower), Erigeron
peregrinus (fleabane), Calochortus spp.
(sego lily), and Achillea millefolium
(yarrow) are also reported as nectar
sources from this region (Beyer and
Black 2007, p. 15; Potter and
Fleckenstein 2001, p. 6).
Southern Oregon Cascades
Populations of Polites mardon
klamathensis in southern Oregon
occupy small (0.5 to10 ac [0.25 to 4 ha]),
high-elevation (4,500 to 5,100 ft [1,372
to 1,555 m]) grassy meadows within
mixed-conifer forests that are associated
with an ephemeral or permanent water
source such as a stream or wetland
(Black et al. 2010, pp. 6–7). As seen at
many sites in Washington, mardon
skippers in the Oregon Cascades are
typically found along the margins of
forest wetlands in the narrow
transitional zone along the edge of a
water feature and the adjacent dry
uplands (Kerwin 2011, p. 21).
Occupied sites are dominated by
short-statured grass/sedge communities.
In the Oregon Cascades, the most
common oviposition plant was
Danthonia californica (California
oatgrass) (Beyer and Black 2007, p. 6).
Other species selected for oviposition
were red fescue, Roemer’s fescue,
Kentucky bluegrass, Deschampsia
cespitosa (tufted hairgrass), and Carex
spp. (sedges) (Beyer and Black 2007, p.
6). The primary nectar plants being
utilized are Potentilla diversifolia
(diverse-leaved cinquefoil), Wyethia
angustifolia (narrow-leaved mule’s
ears), Penstemon procerus (smallflowered penstemon), and Plectritis
congesta (sea blush) (Beyer and Black
2007, p. 16).
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Coastal Northwest California/Southwest
Oregon
The coastal populations of Polites
mardon mardon are found in small
meadows (0.5–5 ac [0.2–2 ha])
dominated by Idaho fescue in sparse
Pinus jeffreyi (Jeffrey pine) forests in
extreme northwestern California and
southwestern Oregon. Sites are located
in coastal hills approximately 7 to 15
miles (11 to 24 km) inland from the
Pacific coast, at elevations ranging from
approximately 1,500 to 3,000 ft (427 to
854 m). These sites are within the
coastal fog belt (Mattoon et al. 1998, p.
771). Meadow habitats at these sites are
associated with the western extent of
serpentine-based soils in the region
(Imper 2003, p. 4), and are more mesic
(moist) than typical serpentine
grasslands found in northwestern
California (Imper 2003, p. 4). Ross
(2010, p. 1) notes that the coastal
Oregon mardon skipper sites are
associated with serpentine-based soils
supporting moist-to-dry transitional
meadow habitats with abundant
bunchgrasses.
The most detailed description of
vegetation for sites in this area is for the
High Divide Ridge sites (Imper 2003, pp.
4–5). Both Idaho fescue and California
oatgrass are common at these sites
(Imper 2003, p. 5) and are likely used
as host plants for oviposition and larval
food. No oviposition or habitat selection
studies have been completed for these
populations, but Runquist (2004b, p. 2)
observed females ovipositing on Festuca
spp. at High Divide sites. The most
commonly selected nectar plants at
California sites are Phlox diffusa
(spreading phlox) and Viola adunca
(early blue violet; Arnold 2006, pp. 6–
7). Detailed observations of mardon
skipper behavior including oviposition,
plant selection, and adult nectar species
have not been reported for the coastal
Oregon sites. Ross (2008, p. 9) noted
observing mardon skippers nectaring on
Viola spp. and Calochortus spp. at a
coastal Oregon site.
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Biology
Mardon skippers are univoltine,
completing one life cycle annually (i.e.,
egg–larva–pupa–adult). Adults typically
emerge between May and July,
depending upon location and elevation
of the site, with adults in higher
elevation sites emerging later. Adults do
not all emerge on the same date, so
flight period duration at any given site
depends in part on the number of
skippers present. In 2007, at one
Washington site, Beyer and Black (2007,
p. 8) note that adult emergence went
from 0 adults on July 6 to 135 adults on
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July 9. In large populations the flight
period may extend for over a month,
while small populations may have
adults present for only 10 or fewer days
(Potter et al. 2002, p. 11). Within the
same geographic area, emergence dates
vary with elevation, with emergence
occurring earlier at lower elevations.
Weather influences emergence and
flight period duration. Wet or cold
conditions delay emergence; conversely,
warm, dry conditions promote earlier
emergence, and both may affect the
duration of the adult flight period
(Potter et al. 2002, p. 11).
Mark-recapture experiments indicate
adults can live up to 3 weeks (Runquist
2004a, p. 5), but most adults live only
7 to 9 days (Scott 1986, p. 25). During
their brief life as adult butterflies,
mardon skippers feed on flower nectar,
mate, and lay eggs on grasses or sedges
(see Habitat Requirements for details).
As with many butterfly species, males
are often observed ‘‘puddling’’ or
congregating on wet soils (Scott 1986, p.
68). During periods of adverse weather,
mardon skippers seek shelter low in the
vegetation, under grass or forbs. Mardon
skippers generally fly low to the ground,
often hovering over low grasses and
forbs, or darting from place to place
with a fast skipping flight. Mardon
skippers are non–migratory. Adults
generally disperse distances of up to
0.25 mile (mi) (0.4 kilometers [km]) over
relatively short periods, but there
appears to be very little dispersal
beyond their natal meadow complexes
(Runquist 2004a, p. 5). On occasion,
individual males have been detected up
to 1 mi (1.6 km) away from their original
location (Runquist 2004a, p. 5). Mardon
skippers have not been observed flying
through closed-canopy forest, but they
have been observed along open
corridors such as powerlines or roads
with nectar sources (Potter and
Fleckenstein 2001, p. 6).
After mating, females deposit their
eggs (oviposit) singly into tufts of lowgrowing grasses or sedges (host plants)
(James and Nunnalle 2011, p. 388). The
total number of eggs laid in the wild is
unknown, but Newcomer (1966a, p.
243) observed about 25 eggs per female
for captive Polites, and James and
Nunnallee (2011, p. 388) note that two
captive females produced 21 eggs total.
Eggs hatch in 7 to 10 days (Newcomer
1966a, p. 244; Henry 2010, p. 5). After
hatching, the larvae feed on host grasses
or sedges throughout the summer and
into the fall months (Beyer and Black
2007, p. 19, Henry 2010, p. 14). Larvae
use silk to construct a grass ‘‘nest’’ and
emerge from this shelter to feed on the
tender edges or leaf tips of host grasses
(James and Nunallee 2011, p. 388).
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These nests are tube-like structures up
to 0.78 inches (in) (2 centimeters [cm])
long that are oriented either vertically or
horizontally at the base of the host plant
(Beyer and Black 2007, p. 17). It does
not appear that the larvae disperse away
from the oviposit location (Beyer and
Black 2007, p. 17). Henry (2010, p. 14)
found six larvae at a Puget prairie site
in September 2009, confirming that
larvae feed on the same plants that the
females had selected during oviposition
(Henry 2010, p. 14). There are five
instars (stages) of larval development,
followed by the formation of a pupa and
emergence as an adult butterfly (James
and Nunallee 2011, p. 388).
Captive-rearing efforts suggest that
mardon skipper larvae overwinter as
pupae (Newcomer 1966a, p. 246; James
and Nunalle 2011, p. 388), but field
observations indicate that the larvae
overwinter in diapause, and feed again
in the spring before pupating (Henry
2009, p. 2; Henry 2010, p. 5). Beyer and
Black (2007, p. 19) found larvae present
at a Washington Cascades site as late as
October 21, and Henry (2009, p. 2)
found larvae at a Puget prairie site in
November and February. This aspect of
mardon skipper life history is not well
understood. Some captive-reared larvae
developed quickly, forming a pupa and
eclosing (emerging) as adults in the fall
(which is not known to occur in the
wild), while other captive-reared larvae
overwintered as pupa (James and
Nunallee 2011, p. 388). Other Polites
species have been recorded as
overwintering as larvae (P. mystic),
pupae (P. sabuleti), or both (P. peckius)
(Scott, 1986, pp. 443–445).
Conservation Measures
When the mardon skipper was first
identified as a Federal candidate for
listing in 1999 (64 FR 57539; October
25, 1999), the species was known from
approximately 14 extant sites located in
4 distinct geographic areas—south Puget
Sound prairies, the southern
Washington Cascades, the southern
Oregon Cascades, and northwestern
California (Potter et al. 1999, p. 5). At
that time, the species was not afforded
any special status or protections from
existing regulatory mechanisms (Potter
et al. 1999, p. 15). However, the
subsequent designation of the mardon
skipper as a State-listed endangered
species in Washington and as a Federal
candidate species has raised awareness
of the need for the species’
conservation. The species is now
designated as a Sensitive Species or
Special Status Species on Federal lands
within its range (discussed below), and
State natural resource agencies have
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identified mardon skippers as a priority
species for conservation.
State Laws and Conservation Plans
The mardon skipper is listed as an
endangered species in the State of
Washington by the Washington Fish and
Wildlife Commission (Washington
Administrative Codes 232–12–014,
Endangered Species; 232–12–011,
Threatened Species, Appendix D). The
Washington Department of Fish and
Wildlife (WDFW) has prepared a
Comprehensive Wildlife Conservation
Strategy (CWCS) (WDFW 2005). The
CWCS identifies the mardon skipper as
a ‘‘species of greatest conservation
need’’ and identifies specific
conservation actions for the species,
including the protection of known sites
and potential habitats and the
investigation of limiting factors, and
identifies development of a recovery
plan for the species as a priority (WDFW
2005, p. 326). The conservation plan
provides recommended management
actions that have contributed to the
amelioration of threats to the mardon
skipper where they are found on State
lands. Ongoing management for mardon
skipper habitat on State lands in the
Puget Prairie region is occurring through
partnerships between the Department of
Defense, The Nature Conservancy (now
Center for Natural Lands Management),
Washington State Department of Natural
Resources, Washington Department of
Fish and Wildlife, and U.S. Fish and
Wildlife Service among others. These
treatments have been effective for
restoring or maintaining mardon skipper
habitat at managed sites. Mardon
skippers have been documented using
many areas that were previously
unsuitable due to the presence of
invasive weeds after the habitat was
restored with herbicides to eliminate
tall oat grass, followed by management
(mowing, pulling) to control Scot’s
broom (Hays 2008, pp 1–2).
There are also a number of small
Prairie sites in the region that are
currently in protected status and are
actively being managed to maintain
butterfly habitats that may serve as
potential future reintroduction sites for
mardon skippers (Anderson 2008, p. 2,
Henry 2010, pp.3–4). Beginning in 2007,
the Fort Lewis Army Compatible Use
Buffer (ACUB) initiative has supported
the convening of a cooperative,
interdisciplinary and interagency
Butterfly Habitat Enhancement Team to
develop and implement habitat
improvements for mardon skipper and
other rare butterflies on formerly
occupied sites off of the Fort Lewis
reservation (Anderson 2008, p. 1). This
interagency team is a source of funding
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for mardon skipper habitat management,
population assessments, and mardon
skipper life history research at Puget
prairie sites. These projects continue to
maintain habitat and mardon skipper
populations at the Scatter Creek
Wildlife Area through prescribed fire,
direct seeding of native species,
mowing, and herbicide control of
Scotch broom (Cytisus scoparius) and
exotic grasses and forbs (WDFW 2011,
p.79). The ongoing management to
maintain mardon skipper populations
and habitat at Puget prairie sites afford
the species a high level of protection
against further losses of habitat or
populations.
Oregon has a State Endangered
Species Act, but the law does not cover
invertebrate species. The Oregon
Department of Fish and Wildlife
(ODFW) has prepared a Comprehensive
Conservation Strategy (ODFW 2006).
The strategy identifies the mardon
skipper as a ‘‘strategy species.’’ Strategy
species are found in low numbers at few
locations and are considered to be atrisk species. The plan targets
conservation actions for the most at-risk
species. The strategy generally identifies
special habitat needs, limiting factors,
and data gaps for the mardon skipper
(ODFW 2006, p. 351).
California has a State Endangered
Species Act, but the law does not apply
to insects. The State Comprehensive
Wildlife Action Plan (CDFG 2006) does
not specifically address the
conservation needs of the mardon
skipper, but the plan emphasizes
conservation of invertebrate species
listed on the State ‘‘special animal’’ list.
Special Status Species Policies on
National Forest and BLM Lands
The mardon skipper is listed as a
Sensitive Species by the U.S. Forest
Service in Washington and Oregon
(Forest Service Region 6), and in
California (Forest Service Region 5), and
as a Special Status Species by the
Bureau of Land Management (BLM) in
Oregon and Washington. For Oregon
and Washington BLM-administered
lands, Special Status Species policy
(BLM 6840) details the need to conserve
those species and the ecosystems on
which they depend. Conservation is
defined as the use of all methods and
procedures which are necessary to
improve the condition of Special Status
Species and their habitats to a point
where their Special Status recognition is
no longer warranted. Policy objectives
also state that actions authorized or
approved by the BLM do not contribute
to the need to list Special Status Species
under the Endangered Species Act
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(Interagency Special Status/Sensitive
Species Program [ISSSSP] 2011, entire).
On National Forest lands, Sensitive
Species are defined as those plant and
animal species identified by a Regional
Forester for which population viability
is a concern, as evidenced by significant
current or predicted downward trends
in population numbers or density and
habitat capability that would reduce a
species’ existing distribution (Forest
Service Manual [FSM] 2670.5).
Management of Sensitive Species ‘‘must
not result in a loss of species viability
or create significant trends toward
federal listing’’ (FSM 2670.32). The
Regional Forester is responsible for
identifying Sensitive Species and is
directed by policy to coordinate with
Federal and State agencies and other
sources, as appropriate, in order to focus
conservation management strategies and
to avert the need for Federal or State
listing as a result of National Forest
management activities (ISSSSP 2011,
entire).
The Pacific Northwest Regional Office
of the Forest Service and Oregon/
Washington State Office of the BLM
established the Interagency Special
Status/Sensitive Species Program
(ISSSSP) to facilitate the conservation
and management of rare species on
Federal lands. This interagency
collaboration focuses on regional-level
conservation approaches for Sensitive
and Special Status Species lists (ISSSSP
2011, entire).
With dedicated funding from the
ISSSSP, the Forest Service/BLM have:
(1) Formed the inter agency Mardon
Skipper Work Group, which meets semi
annually to share information and ideas
and to plan future conservation work for
mardon skippers;
(2) Developed a mardon skipper
survey protocol (Seitz et al. 2007,
entire);
(3) Funded multiple seasons of
mardon skipper surveys across Forest
Service, BLM, and other lands in
Oregon and Washington;
(4) Funded an oviposition habitat
study in cooperation with the Xerces
Society and Washington State
University to determine plants that
mardon skippers choose for egg laying
and larval hosts (Beyer 2009, entire);
(5) Contracted with the Xerces Society
to develop site-specific management
plans for all mardon skipper sites on
BLM lands in the southern Oregon
Cascades (Black et al. 2010, entire);
(6) Completed a Conservation
Assessment for the mardon skipper in
2007 (Kerwin and Huff 2007, entire);
and
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(7) Revised and updated the
Conservation Assessment in 2011
(Kerwin 2011, entire).
Additional site-management plans are
currently under development in 2012
with dedicated funding from the ISSSSP
for Forest Service mardon skipper sites
on the Wenatchee, Gifford Pinchot, and
Rogue River—Siskiyou National Forests,
as well as additional sites on the Coos
Bay BLM District.
The Forest Service/BLM Conservation
Assessment is a comprehensive review
of the mardon skipper’s status, threats,
and conservation needs, and provides
specific management guidance and
recommendations for protecting and
maintaining the species’ habitat on
Federal lands (Kerwin 2011, pp. 30–35).
The management considerations in the
Conservation Assessment provide
general guidance to Forest Service/BLM
administrative units for managing
mardon skipper sites and addressing
potential threats such as conifer
encroachment, invasive weeds,
livestock grazing, and off-road vehicles
(Kerwin 2011, pp. 31–33). The listing of
the mardon skipper as a Forest Service
Sensitive/BLM Special Status species
ensures that the species is considered
and addressed during the planning and
implementation of Forest Service and
BLM land management activities. The
Sensitive/Special Species status has
resulted in direct protection or
restoration of mardon skipper habitat at
many sites on Federal lands across the
species range. Examples include conifer
removal projects and placement of
boulders to block off-road vehicle access
(Kogut 2008, pp. 4–9), building grazing
exclosures to exclude cattle from
mardon skipper habitat (e.g., USFS
2003, p. 185); or eliminating grazing
impacts by closing grazing allotments or
reducing use (e.g., BLM 2008, p. 6). In
California, both the Forest Service and
the National Park Service have included
mardon skipper habitat protections in
the planning and implementation of
prescribed burn projects (e.g., Black et
al. 2011, p. 3; NPS 2010, pp. 26–27).
In summary, the majority of the
known occurrences of the mardon
skipper throughout its range are located
on Federal or State lands where the
species is assured a high level of
protection through existing regulations
or conservation management associated
with special status species programs.
Federal and State agencies have been
proactive in implementing effective
conservation measures for the mardon
skipper throughout its range. These
protective measures are currently in
place and are not dependent upon the
species being listed under the Act.
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Summary of Factors Affecting the
Species
Section 4 of the Act (16 U.S.C. 1533)
and implementing regulations (50 CFR
424) set forth procedures for adding
species to, removing species from, or
reclassifying species on the Federal
Lists of Endangered and Threatened
Wildlife and Plants. Under section
4(a)(1) of the Act, a species may be
determined to be an endangered or
threatened 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; or
(E) Other natural or manmade factors
affecting its continued existence.
In making this finding, information
pertaining to the mardon skipper in
relation to the five factors provided in
section 4(a)(1) of the Act is discussed
below. In considering what factors
might constitute threats, we must look
beyond the mere exposure of the species
to the factor to determine whether the
species responds to the factor in a way
that causes actual impacts to the
species. If there is exposure to a factor,
but no response, or only a positive
response, that factor is not a threat. If
there is exposure and the species
responds negatively, the factor may be
a threat and we then attempt to
determine how significant a threat it is.
If the threat is significant, it may drive
or contribute to the risk of extinction of
the species such that the species
warrants listing as a threatened or
endangered species as those terms are
defined by the Act. This does not
necessarily require empirical proof of a
threat. The combination of exposure and
some corroborating evidence of how the
species is likely impacted could suffice.
The mere identification of factors that
could impact a species negatively is not
sufficient to compel a finding that
listing is appropriate; we require
evidence that these factors are operative
threats that act on the species to the
point that the species meets the
definition of a threatened or endangered
species under the Act.
In making our 12-month finding on
the petition, we considered and
evaluated the best available scientific
and commercial information. Here we
evaluate the factors affecting the
petitioned species Polites mardon. In
addition, the Service has elected, at our
own discretion, to additionally evaluate
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the two subspecies Polites mardon
mardon and Polites mardon
klamathensis. For the sake of brevity,
we analyze the subspecies separately
from the species rangewide only in
those cases where the factors affecting
the subspecies are unique, or where
potential threats to the subspecies differ
in severity or scope of impact from
those affecting the species in the
remainder of its range. The evaluation of
the five factors, below, should thus be
interpreted as applying equally to the
species as a whole as well as to its
constituent subspecies, unless indicated
otherwise.
Factor A. The Present or Threatened
Destruction, Modification, or
Curtailment of Its Habitat or Range
Pyle (1989, p. 28) characterized
threats to the mardon skipper as any
factor that degrades its obligate
grassland habitats, including
development or land conversion,
overgrazing, the use of herbicides and
pesticides, encroachment by native and
invasive nonnative vegetation, and
succession from grassland to forest. In
addition to the threats listed above,
Black and others (2010, p. 12) identify
climate change, stochastic weather
events, and small, isolated populations
as threats for Polites mardon
klamathensis. Here we discuss the
potential threats associated with habitat
loss or degradation; the additional
threats identified by Black et al. (2010,
p. 12) are discussed under Factor E,
below.
Habitat Loss Associated With Land
Conversion
Prairies, which historically covered
over 145,000 ac (60,000 ha) of the south
Puget Sound region, have largely been
lost over the past 150 years (Crawford
and Hall 1997, p. 11). The primary
causes of historical prairie habitat loss
in the region are attributed to the
conversion of prairie habitat to urban
development and agricultural uses (over
60 percent of losses), and succession to
Douglas-fir forest (32 percent) (Crawford
and Hall 1997, p. 11). Today
approximately 8 percent of the original
prairies in the south Puget Sound area
remain, but only about 3 percent
contain native prairie vegetation
(Crawford and Hall 1997, p. 11). Today
approximately 8 percent of the original
prairies in the south Puget Sound area
remain, but only about 3 percent
contain native prairie vegetation.
Puget prairie sites with extant
populations of mardon skippers are
protected from further development
through either State or Federal
ownership. Habitats at these sites have
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been degraded by invasive species and
competing uses such as recreation or
military training (Schultz et al. 2011,
pp. 370–371), but these threats are now
being addressed through active
management, as referenced above under
‘‘Conservation Measures’’ and as
discussed further below.
Remaining prairie habitats in the
south Puget Sound region are relatively
small, isolated patches with little
potential connectivity between patches
(Schultz et al. 2011, p. 371). Because of
this, historical prairie sites where
mardon skippers have been extirpated
are unlikely to be re colonized naturally
due to isolation from extant populations
(Schultz et al. 2011, p. 371). However,
there are a number of small prairie sites
in the region that are currently in
protected status and are actively
managed to maintain butterfly habitats
that may serve as potential future
reintroduction sites for mardon skippers
(Anderson 2008, p. 2; Henry 2010, pp.
3–4).
In other portions of the mardon
skipper’s range, outside of the south
Puget prairie region, habitat loss due to
urban development or land conversion
has not been a significant threat due to
their locations primarily on Federal or
Tribal lands, in remote areas that have
historically been managed for grazing,
timber production, or recreation. There
have been minor historical losses of
mardon skipper habitat from the
placement of roads, trails, or buildings
in occupied meadow sites (Potter et al.
1999, p. 12), but these losses have not
been quantified and are relatively small.
There are no reported examples of
recent habitat loss from new road
construction or developments in
mardon skipper habitats on Federal
lands. Because of the protections the
mardon skipper receives as a Federal
special status/sensitive species
(described above under ‘‘Conservation
Measures’’) the threat of additional
habitat loss due to land conversion on
Forest Service or BLM lands is very low.
Twelve out of the 165 sites known for
mardon skipper are found on private
lands; the potential for future
development at these privately owned
sites is unknown. However, most of
these sites on private lands are located
near other extant populations on
neighboring Federal lands, indicating
that private lands sites are likely
subpopulations of these larger
populations on Federal lands. It is
therefore unlikely that any of the few
mardon skipper sites on private lands
support source populations of the
species.
Summary: The historical loss of
native prairie habitats to urban
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development and agriculture in the
south Puget Sound region has likely
resulted in a contraction of the species’
distribution within that portion of the
species’ range. However, Puget prairie
sites currently occupied by mardon
skippers are protected from further loss
due to development by State or Federal
ownership. Land conversion for roads
and other uses has historically resulted
in only minor losses of mardon skipper
habitat on Federal lands in all other
portions of the species’ range.
Additional habitat losses due to land
conversion or development on Federal
lands that support populations of Polites
mardon mardon and Polite mardon
klamathensis are not anticipated. Very
few of the known mardon skipper sites
are found on private lands, and most of
these sites are believed to be
subpopulations of larger populations
found on Federal lands that are
protected from conversion or
development. Therefore, continued
habitat loss due to land conversion is
not a significant threat to the mardon
skipper at the species or subspecies
levels.
Habitat Loss and Fragmentation
Associated With Forest Succession
Throughout the Pacific Northwest the
invasion of meadow or grassland
habitats by conifers represents a recent
and widespread phenomenon
potentially triggered by changes in
climate, the cessation of intensive
grazing, and wildfire suppression
(Haugo and Halpern 2007, pp. 285–286).
In Redwood National Park in California,
meadow habitats have declined due to
forest encroachment over the past
century (NPS 2010, pp. 44–45). At Joint
Base Lewis-McChord in Washington,
approximately 39 percent (over 16,200
ac [6,560 ha]) of the original prairie
habitat has transitioned to Douglas-fir
forest, and only a fraction of the original
prairie habitat remains as small, isolated
prairies (Tveten 1997, p. 124)
The loss of meadow habitats in the
Cascades is also well documented. At
one study site in the Oregon Cascades,
the area associated with mesic meadows
declined from 328 ac (133 ha) to 163 ac
(66 ha) during the period from 1946 to
2000 (Takaoka and Swanson 2008, p.
521). This represents a loss of
approximately 50 percent of the mesic
meadow habitat over a period of 54
years. Most xeric (dry) meadows were
fairly stable over the study period,
indicating that patterns of forest
succession in montane meadows are
complex and that diverse factors
influence these processes (Takaoka and
Swanson 2008, p. 521). The contraction
of mesic meadow habitats was strongly
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associated with a lack of fire
disturbance over the past half century
(Takaoka and Swanson 2008, p. 538).
Aerial photographs taken on the
Gifford Pinchot National Forest in the
southern Washington Cascades indicate
that the mardon skipper sites located
within a historical (1918–1919) burn
area were larger with much greater
potential for connectivity between sites
than exists today (Foster 2010, p. 3).
Forest succession over the past 60 years
has reduced the meadow habitats in this
landscape to a few isolated patches
ranging in size from 2 to 8 ac (0.8 to 3.2
ha) (Foster 2010, p. 2).
The loss of meadow habitats from
forest succession not only reduces the
amount of suitable grassland habitat
available for mardon skippers, it also
closes off potential dispersal corridors
between meadows, potentially resulting
in remnant, isolated populations (Beyer
and Schultz 2010, p. 870). In addition
to natural meadow habitats, many
mardon skipper sites in the Washington
Cascades are located in areas that were
clearcut for timber harvest in 1960s
through 1980s (Price and MendezTreneman 2000, p. 6; St. Hilaire et al.
2008, p. 5), and subsequently were
colonized by mardon skippers. Open
grass habitats in many of these old
clearcuts are now rapidly declining.
Because the mardon skipper requires
early seral habitats, conifer
encroachment is a potential threat at all
mardon skipper sites located on
National Forest or BLM lands in
Washington, Oregon, and California.
However, actual habitat degradation as
a result of this threat is ranked as high
at only a few mardon skipper sites,
primarily on the Wenatchee National
Forest, and a few in the range of P.m.
klamathensis (Kerwin 2011, pp. 49–60).
Land managers across the range of the
mardon skipper recognize conifer
encroachment as impacting meadow
habitats, and many local districts have
undertaken projects to reduce conifer
encroachment at mardon skipper
meadows. For example, Kerwin (2011,
p. 31) notes the implementation of
‘‘considerable meadow restoration
efforts for mardon skippers’’ on the
Gifford-Pinchot National Forest.
Examples of restoration activities range
from hand-cutting and removal of small
conifers on the Gifford Pinchot National
Forest in Washington (Kogut 2008, pp.
4–7) to prescribed burning projects on
the Six Rivers National Forest in
California (Black et al. 2011, p. 3). Some
level of grazing is also recognized as a
potential management tool for reducing
conifer encroachment (Kerwin 2011, p.
27). Habitat management activities can
be beneficial to the species, although
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site disturbance from these actions can
result in negative impacts to mardon
skipper populations if they are not
carefully planned and implemented
(Black 2011, p. 385).
Although conifer encroachment has
the potential to negatively impact
meadow habitats required by the
mardon skipper, Federal land managers
are actively managing sites to reduce
conifer encroachment and maintain
meadows to improve habitat for the
mardon skipper throughout its range, as
outlined in the management provisions
in the revised Forest Service/BLM
Conservation Assessment for the
Mardon Skipper (Kerwin 2011, pp. 30–
33), and in Management Plans for all
Southern Oregon Cascades Mardon
Skipper (Polites mardon klamathensis)
Sites on BLM Lands (Black et al. 2010,
pp. 15–17). Therefore, the impacts of
conifer encroachment do not presently
represent a threat to the mardon skipper
across its range, and continued active
management is expected to control this
threat in the future.
Discussion Specific to Polites mardon
klamathensis
Little information exists about
vegetation change over time in the
grasslands, shrublands, and woodlands
of southwestern Oregon (Hosten et al.
2007b, p. 1). A comparison of historical
and current photos shows a general loss
of high-elevation grassland to woody
shrub and tree domination, and
transition from shrubland and
woodland to conifer domination
(Hosten et al. 2007b, p. 31). The
encroachment of shade-tolerant conifers
into non-conifer vegetation, reduced
reproduction by pine, and the loss of
meadows support the generally
accepted belief that fire suppression has
negatively impacted historically open
vegetation types in the southern Oregon
Cascades (Hosten et al. 2007b, p. 1).
Historical anecdotes also identify
livestock grazing as playing a role in the
depletion of native perennial
bunchgrasses and subsequent invasion
of woody species (Hosten et al. 2007b,
p. 31).
The loss of open grassland habitats
from conifer succession has the
potential to impact populations of
Polites mardon klamathensis through
the gradual reduction and loss of
suitable habitat patches and by closing
off corridors between meadows,
reducing the potential for successful
dispersal to suitable habitat patches.
Studies with other butterfly species
have demonstrated that conifer
encroachment reduces dispersal
between populations and reduces gene
flow, resulting in small, isolated
populations with a greater risk of local
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extirpation (Roland and Matter 2007, p.
13702). Although identified as a
potential threat at some sites, conifer
encroachment within meadows is
currently being addressed through
management plans developed for P.m.
klamathensis sites on BLM lands (Black
et al. 2010, pp. 21–61). In 2011, the BLM
staff at the Medford District
implemented small conifer removal
projects at most of the sites identified
for this work, which has reduced the
imminency of continued habitat loss
within meadows (Mardon Skipper Work
Group [MSWG] 2011, in litt.). Present
management of these areas to reduce
conifer encroachment and enhance
meadow habitats appears to have
ameliorated this threat for P.m.
klamathensis.
Summary: The potential loss of
meadow habitats due to forest
succession is a concern at most mardon
skipper sites across the species’ range.
However, habitat loss due to succession
is a gradual process that occurs on a
scale of decades and can be checked
with appropriate low-impact
management methods, which is
presently occurring at many key sites
across the species’ and subspecies’
range. Because Federal managers have
implemented actions to substantially
ameliorate this threat, forest succession,
while still affecting habitat, is no longer
considered to be a threat to the mardon
skipper at the species or subspecies
levels.
Habitat Modifications Associated With
Fire
Fire is an important source of
disturbance that reduces conifer
encroachment and maintains meadow
and grassland habitats. Prescribed fire is
a tool that is often used by land
managers to maintain meadows or other
fire-adapted habitats (e.g., NPS 2010, p.
4). Although mardon skippers occur in
landscapes that have historically
burned, mardon skipper populations
may be vulnerable to local extirpation if
a fire burns all of the occupied habitats
at a population site (Black 2011, p. 384).
The use of prescribed fire is implicated
in the extirpation of mardon skippers
from one historical Puget Prairie site in
1992 (Stinson 2005, p. 10).
In California, the Coon Mountain
mardon skipper site on the Six Rivers
National Forest is being managed with
prescribed fire to maintain the meadow
habitat at the site and, consequently,
mardon skipper habitat. Working in
cooperation with the Xerces Society, the
Forest Service modified their original
plans to burn the entire site, and
established four experimental burn plots
with corresponding unburned areas.
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The experimental plots were burned in
the fall of 2008 (Black et al. 2011, pp.
3–4). Monitoring at the site in 2009
indicated mardon skippers were 3–27
times more abundant in unburned areas
compared to burned areas (Black 2011,
p. 384). Continued monitoring at the site
in 2010 and 2011 indicate that mardon
skipper densities in unburned patches
were consistently higher than in burned
patches (Black et al. 2011, p. 14);
however, mardon skippers are gradually
recolonizing the burned patches from
the adjacent unburned areas at the site
as their preferred habitat increases
(Black 2011, p. 384). Although peak
counts of mardon skippers in
subsequent years after the burn have not
been as high as they were prior to
burning in 2008, the authors note that
the overall population appears to be
stable, and is still considered the largest
known population in California (Black
et al. 2011, p. 13). As their preferred
habitat increases at these sites, the
mardon skipper population may expand
into the burned areas and increase over
time. Continued monitoring is needed to
fully assess the population response at
Coon Mountain.
A large wildfire burned over 8,000 ac
(3,238 ha) at Mt. Adams in Washington
in 2008, including burning the forest
around at least one known mardon
skipper site (Eureka Meadow). Although
the fire burned the surrounding forest,
the meadow itself did not burn (likely
because it was still snow-covered at the
time of the fire), and 135 mardon
skippers were counted at the site in
2010 (Wainwright 2010, p. 1). The
Windy Valley site on the Rogue RiverSiskiyou National Forest in
southwestern Oregon is another
example of a mardon skipper
population surviving a recent wildfire
event. Much of the forest around this
meadow/wetland complex burned as
part of the Biscuit Fire in 2002, but the
site continues to support a large
population of mardon skippers that was
discovered in 2010 (Kerwin 2011, p. 51).
Wildfires are likely to have beneficial
effects for mardon skippers due to
resultant increases in early seral habitat,
although large wildfires also pose a risk
to mardon skippers if all occupied
habitat in a local area is burned.
Because wildfires typically result in a
mosaic of burned and unburned areas,
it is unlikely that wildfires would result
in the loss of multiple populations
across large areas within the species’ or
subspecies’ range.
Assessing whether wildfires or
prescribed fire used to manage mardon
skipper habitats poses a threat to the
species is a complex undertaking. Fire
disturbance is an integral process in
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natural ecosystems (Agee 1993, p. 3),
and has certainly played a pivotal role
in maintaining mardon skipper habitats.
Conservation scientists as well as
Federal land managers recognize that
the habitat benefits gained from using
prescribed fire to maintain mardon
skipper habitat must balance the lethal
effects fire can pose to mardon skippers
(Black 2011, p. 384; Kerwin 2011, p. 33).
The Coon Mountain experiment
demonstrates that prescribed fire can be
used to restore mardon skipper meadow
habitat and maintain a population at the
site, but the fire must be carefully
managed so that only a portion of the
occupied areas at a site is burned (Black
2011, p. 384).
Summary: Wildfires or prescribed
fires that maintain and restore meadow
habitats can be either beneficial or lethal
to mardon skippers, depending on the
timing and severity of the fire and the
condition of the habitat. Fire is an
important disturbance agent for
maintaining the early-seral habitats
mardon skippers require. Managers
using fire to restore habitat can and have
modified burn plans to meet both fire
objectives and protect mardon skippers,
which greatly reduces the potential
threat associated with prescribed fires.
Therefore, the use of prescribed fires for
habitat management is not considered to
be a threat to mardon skippers at either
the species or subspecies level.
Wildfires are also a potential threat on
a local scale, but it is unlikely that
wildfires would result in the loss of
multiple populations across large areas
within the species’ or subspecies’ range;
therefore, we do not consider it to be a
threat to mardon skippers at the species
or subspecies level.
Habitat Loss Associated With Invasive,
Nonnative Plants
The invasion and subsequent
dominance of nonnative plant species in
native grassland habitats is common and
has occurred rapidly at several current
and historical mardon skipper locations
associated with Puget prairies (Potter et
al. 1999, p. 10). Invasive grasses such as
tall oatgrass and the invasive shrub
Scot’s broom drastically alter the shortgrass/forb habitat structure that mardon
skippers select for oviposition or
nectaring sites (Hays et al. 2000, p. 28;
Schultz et al. 2011, p. 371). Habitat
utilization studies have demonstrated
that mardon skippers actively avoid
areas invaded by these species (Hays et
al. 2000, p. 28; Henry 2010, p. 44), but
will recolonize sites where these
invasive species have been removed
(Hays et al. 2000, p. 16). Scot’s broom
and tall oatgrass are present at south
Puget Sound prairie sites occupied by
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mardon skippers, but significant
portions of these sites are managed
annually to control these species (Hays
2010, p. 1). The Washington State
Department of Natural Resources, for
example, recommends restoration
techniques including mowing, hand
pulling, herbicide application, and
prescribed burning to restore or
maintain prairie habitats for the mardon
skipper (Potter et al. 1999, p. 8) .
Mardon skippers have been documented
using many areas that were previously
unsuitable due to the presence of
invasive weeds after the habitat was
restored with herbicides to eliminate
tall oatgrass, followed by management
(mowing, pulling) to control Scot’s
broom (Hays 2008, pp. 1–2).
Continued site management is
required to maintain mardon skipper
habitat and populations at south Puget
prairie sites (Schultz et al. 2011, p. 375).
Ongoing management for mardon
skipper habitat is occurring through
partnerships between the Department of
Defense, The Nature Conservancy (now
Center for Natural Lands Management),
Washington State Department of Natural
Resources, Washington Department of
Fish and Wildlife, and U.S. Fish and
Wildlife Service among others. The
prairie sites with extant populations of
mardon skippers also support a number
of other high-priority prairie species,
including Taylor’s checkerspot butterfly
(Euphydryas editha taylorii), a
candidate for listing under the Act
(Stinson 2005, p. 6). Based on the
importance of these sites for multiple
prairie-associated species, we expect
that State, Federal, and
nongovernmental organizations will
continue to place a high priority on
maintaining prairie habitats at these
sites for the benefit of mardon skippers
and other prairie species.
Not all mardon skipper sites have
been evaluated for the presence of
invasive, nonnative plants; however, the
problem is increasingly common (Potter
et al. 1999, p. 10). At least two sites
(Cave Creek and Lost Meadows) on the
Gifford Pinchot National Forest are
being actively managed to reduce
invasive Cirsium arvense (Canada
thistle) which has formed dense patches
and has been spreading throughout the
mardon skipper habitat (Kogut 2008, p.
9). Managing for invasive species is
required at a number of sites to maintain
mardon skipper habitat, but, as with
managing for conifer removal, the
management must be carefully planned
to avoid negative impacts to local
butterfly populations (Schultz et al.
2011, p. 373). We expect that Federal
land managers will continue to manage
sites to control invasive weeds and will
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do so in a way that improves habitat for
the mardon skipper, while minimizing
impacts to local populations as outlined
in the revised Forest Service/BLM
Conservation Assessment for the
Mardon Skipper (Kerwin 2011, pp. 30–
33), and in site-specific plans such as
those developed on the Gifford Pinchot
National Forest (USFS 2008, p. 57).
Summary: Invasive nonnative plants
have historically resulted in habitat loss
and degradation at a number of mardon
skipper sites, primarily in the Puget
prairies. Federal, State, and private land
managers have been actively managing
invasive weeds at the most degraded
sites to restore and maintain mardon
skipper habitat, and are likely to
continue to do so under their current
management plans, which substantially
reduces this potential threat. Based on
the ongoing partnership and
commitment of private, State, and
Federal entities to manage invasive
nonnative plants and restore prairie
habitats, the impact of invasive
nonnative plants appears to have been
sufficiently ameliorated throughout the
range of the mardon skipper such that
it does not pose a threat to the species
or either subspecies.
Habitat Modifications Associated With
Livestock Grazing
Current or historical livestock grazing
has occurred at essentially all mardon
skipper sites in the Washington and
Oregon Cascades. Historically (1900–
1930s), many areas in the Cascades were
intensively grazed by sheep (Miller and
Halpern 1998, p. 267), including several
known mardon skipper sites on the
Gifford Pinchot National Forest (USFS
2007a, p. 30; Foster 2010, p. 2). Sheep
grazing was largely replaced by cattle
grazing after the 1930s. Grazing
allotments at Mt. Adams in Washington
have been grazed for over 100 years
(USFS 2007a, pp. 30–31).
Long-term grazing can alter both the
structure and composition of plant
communities, rendering them
unsuitable to some butterfly species
(Dana 1991, p. 54; Ellis 2003, p. 292),
while benefiting other species,
depending on the specific habitat
requirements of each species (Kruess
and Tshcharntke 2002, p. 1575; Poyry et
al. 2005, p. 469; Vogel et al. 2007, pp.
81–82). Grazing can impact mardon
skipper populations by (1) direct
trampling of eggs, larvae, pupae, and
adults (Potter et al. 1999, p. 13; Black et
al. 2010, pp. 13–14); (2) removal of both
larval and adult food sources, and (3)
disturbing the soil, which allows weeds
to invade (Ellis 2003, pp. 292–293;
Schtickzelle et al. 2007, p. 657). One
grazing study found that both the
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abundance and recruitment of the bog
fritillary butterfly (Proclossiana
eunomia) were reduced by as much as
74 percent in grazed areas compared to
ungrazed sites (Schtickzelle et al. 2007,
p. 657). Dana (1991, p. 54) notes that
both the Dakota skipper (Hesperia
dacotae) and the ottoe skipper (Hesperia
ottoe) apparently decline or can be
extirpated in response to intensive
grazing, likely due to changes in the
composition and structure of the plant
communities at intensively grazed sites.
Although intensive livestock grazing
can be detrimental to many butterfly
species, moderate to light grazing can be
a useful method for halting succession
and maintaining butterfly habitats
where other habitat management
methods are impractical (Schtickzelle et
al. 2007, p. 658; Ellis 2003, p. 293). The
silver-spotted skipper (Hesperia
comma) is one species that has shown
a positive response to moderate grazing,
and depends on continued grazing to
maintain the short-statured grassland
habitats the species requires (Thomas
and Jones 1993, p. 473).
The impact of cattle grazing to
mardon skipper populations is likely
relative to the timing, duration, and
magnitude of the grazing at the site
(Black et al. 2010, p. 13). Large mardon
skipper populations are able to persist
in some heavily grazed habitats. Conrad
Meadows on the Wenatchee National
Forest is subjected to native ungulate
(deer and elk) grazing in the spring, and
then intensive cattle grazing during the
summer months. Conrad Meadows is a
large system of interconnected
meadows, wetlands, and forested areas
with complex vegetative structure and
site conditions. The meadow complex
supports the largest known population
of mardon skippers, with minimum
population counts of over 1,000 mardon
skippers in some years (St. Hilaire et al.
2010, p. 11). Conrad Meadows has been
in an active cattle grazing allotment for
80 years, and there continues to be a
robust population of mardon skippers at
this site (St. Hilaire et al. 2008, p. 15).
Because the timing of the onset of
livestock grazing tends to occur towards
the end or after the adult flight period
at Conrad Meadows, the grazing at this
site may not affect mardon skipper
populations to the same degree as sites
that are grazed throughout the flight
period (St. Hilaire et al. 2008, p. 14).
Ongoing monitoring at grazing
exclosures (2007–2010) on the
Wenatchee National Forest has shown
no clear pattern between mardon
skipper populations in grazed versus
ungrazed areas (St. Hilaire et al. 2010,
p. 7). The authors note that there are a
number of confounding variables
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associated with this monitoring project
and more research at these sites is
recommended. Anecdotal observations
within grazing exclosures indicate a
much higher abundance and diversity of
flowering forbs (adult nectar sources)
compared to outside the exclosures
(Jepsen et al. 2007, p. 17), but there
appears to be no clear pattern in the
number of mardon skippers within
exclosures versus outside exclosures (St.
Hilaire et al. 2010, p. 7). Mardon skipper
densities at sites grazed by cattle on the
Wenatchee National Forest are
comparable or higher than densities
observed at sites on the adjacent Gifford
Pinchot National Forest that are
subjected only to light native ungulate
grazing.
Because mardon skippers have
specific habitat requirements related to
graminoid cover, composition, and
structure (Beyer and Schultz 2010, pp.
867–868), it appears likely that
intensive livestock grazing that occurs
before or during the adult flight period
would have a negative effect on mardon
skipper reproductive success and larval
survival due to the loss of adult nectar
sources and larval host plants, and the
introduction of nonnative grasses, forbs,
or shrubs that do not meet the structural
requirements of mardon skippers. The
grasses most commonly used by mardon
skippers for oviposition and larval food
(e.g., Roemer’s fescue, California
oatgrass, Kentucky bluegrass
(nonnative), and sedges) (Beyer and
Black 2007, p. 6) are also some of the
most preferred forage species used by
cattle (Hosten et al. 2007, p. 20). These
effects are likely to be most profound at
sites where grazing impacts are
intensified due to the presence of
surface water or wet soils that attract
livestock (Hosten and Whitridge 2007,
p. 1), and the grazing use entirely
overlaps the adult flight period (Black et
al. 2010, p. 13). However, the removal
of livestock from sites that have
historically been grazed for decades
does not automatically restore degraded
habitats or improve mardon skipper
populations.
There are a number of sites that are
no longer in active grazing allotments
that continue to have chronically low or
declining populations of mardon
skippers, most likely due to degraded
habitat conditions associated with the
plant community composition (Black et
al. 2010, pp. 60–63; USFWS
unpublished data). The short-grass/forb
habitats preferred by mardon skippers
can become quickly degraded in the
absence of livestock grazing due to
presence of tall-structured nonnative
grasses and shrubs (Black et al. 2010, p.
61). The use of short-duration, low-
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intensity grazing may prove to be
beneficial or necessary for maintaining
mardon skipper habitat in some
situations (e.g., Black et al. 2010, p. 38).
Over the past 5 years, a number of
grazing allotments on both Forest
Service and BLM lands in both Oregon
and Washington have been retired.
Grazing allotments at most of the
southern Oregon Cascades BLM mardon
skipper sites for Polites mardon
klamathensis were retired in 2009
(Black et al. 2011, pp. 14–15). A major
grazing allotment (Ice Caves) on the
Gifford Pinchot National Forest was
discontinued in 2009, and was officially
closed in 2011. On the Wenatchee
National Forest, the Forest Service has
installed a number of grazing exclosures
to reduce grazing impacts and protect
key mardon skipper habitat areas (St.
Hilaire et al. 2010, p. 5). In general,
grazing impacts on Federal lands are
decreasing, with fewer animals being
allowed onto grazing allotments, with
shorter grazing periods, and placement
of exclosures in key locations to protect
sensitive habitats (e.g., USFS 2007b, p.
2). Active grazing allotments are still
present at several mardon skipper sites
within the range of the species, and
continued monitoring is needed to
assess the impact that grazing has on
these populations. Under current
management conditions, light to
moderate grazing can be potentially
beneficial in maintaining the habitat
structure preferred by mardon skippers,
and based on the most recent
conservation assessment for the mardon
skipper, intensive grazing does not
appear to be a significant factor in
habitat degradation for the species
across its range (Kerwin 2011, Appendix
A).
Summary: Cattle grazing can have
either negative or beneficial effects to
mardon skippers depending upon the
timing, duration, and intensity of the
grazing. Robust mardon skipper
populations are able to persist in some
heavily grazed habitats, while other
areas that have been heavily grazed have
generally poor habitat conditions and
support only low numbers of mardon
skippers. Grazing is likely to be
beneficial for maintaining mardon
skipper habitat at sites that are vegetated
with tall-statured nonnative grasses and
shrubs. Potential negative impacts from
grazing on Federal lands have been
substantially reduced due to the closure
of a number of grazing allotments in key
areas, as well as changes in management
practices to reduce grazing intensity and
protect key habitat areas. Therefore,
livestock grazing does not represent a
threat to the mardon skipper at the
species level at this time, nor is it likely
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to be so in the future due to current
management efforts. We have no
information to indicate that it is a threat
to the subspecies Polites mardon
mardon.
Discussion specific to Polites mardon
klamathensis:
Current or historical livestock grazing
has occurred at all Polites mardon
klamathensis sites in the Oregon
Cascades for over 100 years (Hosten et
al. 2007, p. 13), and habitat conditions
at some sites have been excessively
degraded by grazing (Black et al. 2010,
pp. 22–23). Until recently all of the
occupied sites were located in active
grazing allotments. With the recent
designation of the Cascades-Siskiyou
National Monument (Monument) in
2000, the BLM initiated a review of
grazing impacts on Federal lands within
the Monument. This review determined
that four grazing allotments within the
Monument failed to meet BLM
standards for maintaining populations
of threatened and endangered and other
locally important species (BLM 2008, p.
6). The major reasons for not meeting
this standard included the threat to
special status species including the
mardon skipper, the favoring of noxious
weeds (e.g., Canada thistle at high
elevations) over native plants; and the
invasion of the nonnative Poa bulbosa
(bulbous bluegrass) (BLM 2008, p. 6).
Although overgrazing is considered to
have had negative impacts on several
P.m. klamathensis sites in the past
(Black. 2010, p. 14), some of these sites
have now been retired from grazing, and
others are now being managed in
accordance with a management plan
developed by The Xerces Society for
Invertebrate Conservation for all P.m.
klamathensis sites on BLM lands in
southern Oregon, including provisions
specific to grazing, such as avoiding
grazing during the flight period of adults
and keeping grazing periods short and
interspersed with long recovery period
for the habitat (Black et al. 2010, entire).
In 2009, grazing allotments at 10
mardon skipper sites located on BLM
lands within the Monument were
retired (Black et al. 2010, pp. 14). The
remaining sites on BLM lands that are
still within active grazing allotments
have existing or planned grazing
exclosures to protect core mardon
skipper habitat areas (Black et al. 2010,
pp. 23–61). Four Polites mardon
klamathensis sites located on the Rogue
River–Siskiyou National Forest are in
active grazing allotments, and Jepsen et
al. (2007b, pp. 24–25) reported that
grazing had degraded habitat at three of
these sites. However, more recently
Kerwin (2011, pp. 49–60) reviewed the
P.m. klamathensis sites in his
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conservation assessment and found that
none faced a serious threat from grazing
(with exception of Hobart Peak, where
effects from grazing were considered
‘‘unknown’’), and additionally noting
that several of the grazed sites are in
excellent condition. Remaining sites in
active grazing allotments on Federal
lands are expected to continue to
exhibit reduced grazing impacts due to
the placement of existing or planned
grazing exclosures around core habitat
areas (Black et al. 2010, pp. 23–61;
Kerwin 2011, p. 32).
Summary: The threats from active
livestock grazing have been
substantially reduced from all Federal
lands sites within the range of Polites
mardon klamathensis. Planned or
existing grazing exclosures are likely to
protect core habitat areas at some key
sites, but the effectiveness of grazing
exclosures for maintaining mardon
skipper habitat structure and
populations remains unknown. We
expect that mardon skipper habitat
conditions within exclosures will
generally improve with the removal of
livestock grazing, but these areas will
require monitoring and possible
management actions to insure that
invasive weeds or tall-statured
nonnative grasses do not become a
secondary threat in the absence of
grazing, as recommended in the revised
Forest Service/BLM Conservation
Assessment for the Mardon Skipper
(Kerwin 2011, pp. 30–33), and in
Management Plans for all Southern
Oregon Cascades Mardon Skipper
(Polites mardon klamathensis) Sites on
BLM Lands (Black et al. 2010, pp. 15–
17). The potential negative impacts of
grazing on Federal lands within the
range of P.m.klamathensis have been
substantially reduced due to the closure
of a number of grazing allotments in key
areas, as well as changes in management
practices to reduce grazing intensity and
protect key habitat areas. Therefore, we
do not consider the effects of livestock
grazing to be a threat to P.m.
klamathensis.
Habitat Loss Associated With Off-Road
Vehicles and Recreation
Recreational activities, including offtrail walking, off-trail horseback riding,
and off-road vehicle use, may directly
kill some mardon skippers by trampling
and crushing larvae (Potter et al. 1999,
p. 12). Off-road vehicle use has the
greatest impact on mardon skipper
habitat because vehicle tires can destroy
native plants and disturb soils, leading
to invasion by weeds. Small, roadside
meadows are vulnerable to damage or
destruction associated with off-road
vehicle use. Currently, this threat
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applies to a few locations across the
range of the species (Kerwin 2011, pp.
37–41). In 2008, a mardon skipper site
located on private lands in Del Norte
County, California, was partially
destroyed when the site was used as a
dump for logging slash and debris (Ross
2008a, p. 5; Devlin 2009, pers. comm.).
At least one historical locale in the
southern Washington Cascades was
destroyed by this practice in 1997 or
1998 (Potter et al. 1999, p. 11). Military
training activities at Joint Base LewisMcChord have also resulted in damage
to mardon skipper habitat (Potter et al.
1999, p. 12), but the majority of the
prairie habitat at this site is protected
from vehicle damage due to the
presence of unexploded ordnance
(Stinson 2005, p. 12). Over the past 10
years, Federal land managers have
installed access barriers (e.g., placement
of road-side boulders, gates, or
exclosures) and posted educational
signs in attempts to reduce illegal offroad vehicles and other recreational
uses at almost all mardon skipper sites
where these problems have been noted
(Kogut 2008, p. 8). These measures have
substantially reduced these threats on
Federal lands, which constitutes the
majority of the range occupied by the
species. Therefore, habitat loss
associated with off-road vehicles and
recreation is not a significant concern
for the mardon skipper at the species
level at this time, nor is it likely to
become so. In addition, we have no
information to indicate that it has a
significant impact on the subspecies
Polites mardon mardon.
Discussion specific to Polites mardon
klamathensis:
Management plans developed for
Polites mardon klamathensis sites on
BLM lands identified off-road vehicle
use and recreation (camping) within
meadows as a potential threat at several
sites (Black et al. 2010, pp. 21–61). In
2011, both BLM staff at Medford District
and Forest Service staff on the Rogue
River–Siskiyou National Forest
implemented a number of projects to
reduce these impacts at P.m.
klamathensis sites through the strategic
placement of boulders to block vehicle
access, and by posting signs at most of
the sites identified for this work (MSWG
2011, in litt.). These measures are
expected to substantially reduce any
potential impacts from off-road vehicles
and other recreational uses.
Summary: Off-road vehicles and other
recreational activities have historically
resulted in minor habitat losses and
degradation at a number of sites across
the range of the mardon skipper.
However, this threat has been
substantially reduced on Federal lands
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where the majority of these activities
occur through the placement of access
barriers and signs. Because private lands
comprise an insubstantial portion of the
species’ range, we do not consider any
such activities on private lands, if they
should occur, to pose a threat to the
mardon skipper. Therefore, habitat loss
or degradation as a consequence of offroad vehicles and other recreational
uses is not considered to be a threat at
either the species or subspecies levels.
srobinson on DSK4SPTVN1PROD with PROPOSALS3
Summary of Factor A
In summary, the potential negative
impacts to mardon skipper habitat
associated with forest succession, fire,
invasive nonnative plants, livestock
grazing, and off-road vehicle use have
been substantially reduced or
eliminated on Federal and State lands
through the development and
implementation of conservation plans
and habitat restoration projects. Habitat
degradation associated with intensive
livestock grazing continues to occur at
a few sites, but grazing impacts have
been substantially reduced or
eliminated at many key sites across the
species’ range with recent closures of
Federal grazing allotments and the
implementation of site-specific
conservation plans for the benefit of the
mardon skipper. Habitat degradation
from off-road vehicle use has been
reduced or eliminated at many sites by
installing vehicle barriers or closing
roads. Meadow habitat restoration
activities (prescribed burning, herbicide
treatments) can be lethal to mardon
skippers, but careful planning and
implementation of habitat restoration
projects designed with these concerns in
mind have minimized the risks
associated with these positive efforts for
skipper conservation. Because the vast
majority of mardon skipper sites are
found on Federal or State lands, and
most of the sites that are found on
private lands are subpopulations of
larger populations on Federal lands, we
do not consider habitat degradation that
may occur on private lands to pose a
threat to the mardon skipper. Based on
these ongoing conservation actions on
Federal and State lands, we do not
consider Factor A, the present or
threatened destruction, modification, or
curtailment of its habitat or range, to
pose a threat to the mardon skipper as
a species now or in the future, nor do
we have any information to indicate that
it is a threat to either subspecies Polites
mardon mardon or Polites mardon
klamathensis, now or in the future.
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Factor B. Overutilization for
Commercial, Recreational, Scientific, or
Educational Purposes
Insect collecting is a valuable
component of research, including
systematics work, and is often necessary
for documenting the existence of
populations (Potter et al. 1999, p. 14).
Rare butterflies, such as the mardon
skipper, could be potentially desirable.
Most mardon skipper populations are
easily accessible and could be
vulnerable to collectors (Potter et al.
1999, p.14). However, we currently have
no information indicating that mardon
skipper populations at either the species
or subspecies level have been negatively
affected by collection or scientific
research activities (Kerwin 2011, p. 26),
and therefore have determined that
overutilization for commercial,
recreational, scientific, or educational
purposes is not a threat to the mardon
skipper at the species or subspecies
level now or in the future.
Factor C. Disease or Predation
Disease and predation are usually
naturally occurring factors that may
pose a heightened threat to populations
that are vulnerable due to other factors,
but no specific examples are known for
the mardon skipper. Predatory insects
(ants, wasps, spiders, etc.) commonly
prey on butterfly eggs, larvae, and pupae
(Scott, 1986, p. 70), but no studies have
specifically researched this aspect of
mardon skipper ecology. At Puget
Prairie sites, mardon skipper larvae
were found only in the smallest tufts of
bunchgrass, while potential larval
predators (spiders, ants) were
commonly observed in larger clumps of
bunchgrass (Henry 2010, p. 18). The
author suggests that larval survival rates
from predation are likely influenced by
the fine-scale structure of individual
host plants and the density of vegetation
surrounding host plants, but
acknowledged that more research is
needed to understand how these factors
influence mardon skipper survival rates
(Henry 2010, p. 18). We currently have
no information indicating mardon
skipper populations have been
negatively affected by disease or
predation outside the normal range of
variability; therefore, we do not
consider disease or predation to pose a
threat to the mardon skipper at the
species or subspecies levels.
Factor D. The Inadequacy of Existing
Regulatory Mechanisms
State Laws
The mardon skipper is listed as an
endangered species in the State of
Washington by the Washington Fish and
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54345
Wildlife Commission (Washington
Administrative Codes 232–12–014,
Endangered Species; 232–12–011,
Threatened Species, Appendix D). This
designation provides protection from
directly harming the species (e.g.,
collecting) (Black et al. 2002, p. 19).
State regulatory mechanisms in the
States of Oregon and California do not
apply to the mardon skipper, as
Oregon‘s State Endangered Species Act
does not cover invertebrate species, and
California’s State Endangered Species
Act does not apply to insects.
We have no information to indicate
that the inadequacy of existing State
regulatory mechanisms may pose a
threat to the mardon skipper, rangewide
or at the subspecies level.
Special Status Species Policies on
National Forest and BLM Lands
As discussed above under
‘‘Conservation Measures,’’ the mardon
skipper is listed as a Sensitive Species
by the U.S. Forest Service in
Washington, Oregon (Forest Service
Region 6), and California (Forest Service
Region 5) and as a Special Status
Species by the Bureau of Land
Management (BLM) in Oregon and
Washington. We have no information to
indicate that the inadequacy of existing
Federal regulatory mechanisms may
pose a threat to the mardon skipper,
rangewide or at the subspecies level.
Summary of the Inadequacy of Existing
Regulatory Mechanisms
When the mardon skipper was
originally identified as a Federal
candidate in 1999, the species had no
protection mechanisms under the
auspices of either State or Federal
agencies. Since that time, both Federal
and State land managers have
developed conservation plans and
policies that provide a high level of
protection for the species. Existing laws
and regulations do not protect mardon
skipper habitats where they occur on
private land. However, there are few
mardon skipper populations known to
occur on private lands. The majority of
the species’ occurrences are on Federal
or State lands where the species is
assured a high level of protection
through its recognition as a Sensitive
Species or Special Status Species
(Federal lands) or through State
Conservation Plans (California, Oregon,
and Washington). We did not identify
any threats to the mardon skipper at
either the species or subspecies levels
that existing regulatory mechanisms
have failed to address. Therefore, we
have no information to indicate that the
inadequacy of existing regulatory
mechanisms is a threat to the mardon
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skipper at either the species or
subspecies levels.
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Factor E. Other Natural or Manmade
Factors Affecting Its Continued
Existence
Application of Pesticides and
Herbicides
Aerial applications of pesticide pose a
potential threat to mardon skippers. The
lepidopteran-specific insecticide,
Bacillus thuringiensis var. kurstaki
(Btk), has been aerially applied to
control the Asian gypsy moth
(Lymantria dispar) in the Puget Sound
region, and in the Washington Cascades
to control spruce budworm
(Choristoneura occidentalis) (Potter et
al. 1999, p. 13). Although grasslands are
not targeted for application, small
meadows may receive aerial
applications due to the location of these
habitats within the wooded target area
or from aerial drift. Drift from aerial
applications can be lethal to non target
butterflies up to 1.8 miles (3 km) away
from the target area in steep,
mountainous terrain (Whaley et al.
1998, p. 539). Lepidoptera, such as the
mardon skipper, that are single-brooded,
spring-active species with caterpillars
actively feeding during the application
period of Btk are especially vulnerable
(Wagner and Miller 1995, p. 21).
Several of the southern Washington
Cascade mardon skipper sites are
located in areas where widespread
applications of Btk were used on State,
tribal, and private lands to control
spruce budworm outbreaks in the late
1990s (Potter et al. 1999, p. 13). Btk
application is implicated in the local
decline of at least one mardon skipper
population on non-Federal lands from
1998 to 2000 (Potter and Fleckenstein
2001, pp. 7–8). The use of Btk has
diminished in the southern Cascades
over the past decade as spruce budworm
populations have declined. There have
been no reported applications of Btk on
Federal lands in close proximity to
mardon skipper sites. The risks
associated with Btk application can be
greatly reduced with adequate buffers to
avoid pesticide drift into sensitive
habitats (Black et al. 2010, p. 19).
Although Btk application poses a
potential threat to mardon skipper
populations, we are not aware of any
Btk applications over the past 10 years
that would have had the potential to
affect mardon skipper populations. The
aerial application of pesticides remains
a potential threat, but any local
application of lepidopteran-specific
pesticides on Federal lands will be
subject to environmental review
consistent with National Environmental
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Policy Act procedures, and existing
special status/sensitive species policies
of the Forest Service and BLM are likely
to provide for a high level of protection.
Herbicides are commonly used to
manage mardon skipper habitat and
control invasive nonnative plants in
south Puget Sound prairies (Schultz et
al. 2011, p. 373); and have been used at
mardon skipper sites on the Gifford
Pinchot National Forest. Herbicide use
may affect mardon skippers by
damaging larval or adult food sources,
or through the direct ingestion of a toxic
substance. Loss of non target plants can
be avoided by using grass-specific
herbicides, such as sethoxydim, which
has been used effectively to control
invasive grasses such as tall oatgrass,
while having minimal impacts on native
bunchgrasses and forbs (Schultz et al.
2011, p. 373).
There are currently dozens of
herbicide formulations that are available
for general use. The toxicity of an
herbicide to butterflies varies from non
toxic to potentially lethal depending
upon the compounds used. All
herbicides are required to be tested on
honeybees (Apis spp.) as part of
registration requirements (USFS 2005,
p. 252), but there are relatively few
studies that evaluate the effects of
herbicides on butterflies (Russell and
Schultz 2010, p. 53). One study with the
Karner blue butterfly (Lycaeides melissa
samuelis) found that direct applications
of some herbicide compounds with
glyphosate had no apparent effect on
egg survival and larval development
(Sucoff et al. 2001, p. 18). However,
treatments with a glyphosate-triclopyr
mix did significantly lower egg hatching
rates (Sucoff, et al. 2001, p. 18). Use of
the grass-specific herbicide compounds
sethoxydim or fluazifop-p-butyl with
the non-ionic surfactant Preference can
stress butterflies, resulting in reduced
survival and increased rates of
development from larvae to adult, as
well as decreased wing area in some
species of butterflies (Russell and
Schultz 2010, p. 53). Stark and others
(2012, pp. 26–27) found that Behr’s
metalmark butterfly (Apodemia virgulti)
exposed to field rates of triclopyr,
sethoxydim, and imazapyr reduced the
number of adults that emerged from
pupation, perhaps due to effects from
inert ingredients or indirect effects on
food plant quality. These studies
indicate that direct applications of
herbicides can result in reduced
survival in some butterfly species,
emphasizing the need for careful
management using selective
applications in habitats occupied by
mardon skippers.
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Herbicides are recognized as an
important tool for managing invasive
plants and maintaining habitat for
butterflies. Potential adverse effects of
herbicides to mardon skippers can be
minimized through selective
applications. Federal and State land
managers currently using herbicides to
manage invasive plants at mardon
skipper sites are using best management
practices to minimize effects to non
target plant species and to butterflies
(Hays 2010, p. 1; USFS 2008, p. 57).
These methods include using selective
herbicide treatments and only treating a
small portion of the habitat area within
the site in any given year (USFS 2008,
p. 57; Schultz et al. 2011, p. 373). We
expect Federal and State land managers
will continue to manage sites to control
invasive weeds and to do so in a way
that improves habitat for the mardon
skipper, while minimizing impacts to
local populations as outlined in the
revised Forest Service/BLM
Conservation Assessment for the
Mardon Skipper (Kerwin 2011, pp. 30–
33), and in site-specific plans such as
those developed on the Gifford Pinchot
National Forest (USFS 2008, p. 57).
Based on this information, we do not
consider the use of herbicides to be a
threat to mardon skipper at either the
species level or subspecies levels.
Summary: The widespread
application of pesticides and herbicides
may affect the mardon skipper and its
habitat. However, there are no
documented instances of Btk
applications occurring on Federal lands
in close proximity to mardon skipper
sites. Further, Federal and State land
managers have successfully used
herbicides to restore and maintain
mardon skipper habitat at a number of
sites in Washington. Based on this
information, we do not consider the use
of pesticides or herbicides to be a threat
to the species or either subspecies.
Climate Change
Over the next century, climate change
at global and regional scales is predicted
to result in changes in butterfly species
distributions and altered life histories
(McLaughlin et al. 2002, p. 6074; Hill et
al. 2002, p. 2163; Singer and Parmesan
2010, p. 3161). Rare butterflies,
including the mardon skipper, may be
vulnerable to climate change, as their
populations are often fragmented due to
habitat losses that restrict the species’
ability to adapt to changing
environmental conditions (Schultz et al.
2011, p. 375). Likewise, butterflies with
limited dispersal capability, such as the
mardon skipper, may be vulnerable to
climate change if suitable alternative
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habitats are not located within the
dispersal distance for the species.
Changes in regional climate can
benefit some butterfly species. The
habitat-generalist Sachem skipper
(Atalopedes campestris) has expanded
its range more than 435 mi (700 km)
northward from California into central
Washington in the last 50 years (Crozier
2004, p. 231). Crozier’s (2004, p. 231)
study suggested that the range
expansion has been due to a warming
trend, and each step in the range
expansion coincided with warmer
winters (which affects larval survival
rates). Similarly, populations of the
silver-spotted skipper (Hesperia
comma) in southern England have
increased over the past 20 years, due in
part to warmer summer temperatures,
which have increased the availability of
thermally suitable habitats for the
species (Davies et al. 2006, p. 247).
Recent butterfly range expansions
linked to climate change are generally
limited to highly mobile, habitatgeneralist species, while many habitatspecialist butterfly species have
declined due to complex interactions of
climate, habitat loss, and fragmentation
(Warren et al. 2001, p. 65; Hill et al.
2002, p. 2170).
In the Pacific Northwest, mean annual
temperatures rose 0.8 °Celsius (° C) (1.5
°Fahrenheit (° F)) in the 20th century
and are expected to continue to warm
from 0.1 to 0.6 °C (0.2 to 1 °F) per
decade (Mote and Salathe 2010, p. 29).
Global climate models project an
increase of 1 to 2 percent in annual
average precipitation, with some models
predicting wetter autumns and winters
with drier summers (Mote and Salathe
2010, p. 29). Regional models of
potential climate changes are much
more variable, but the models generally
indicate a warming trend in mean
annual temperature, reduced snowpack,
and increased frequency of extreme
weather events (Salathe et al. 2010, pp.
72–73). Downscaled regional climate
models, such as those presented by
https://www.climatewizard.org have
tremendous variation in projections for
annual changes in temperature or
precipitation depending upon the
climate model or scenario. Averaged
values across large areas generally
indicate a general warming trend in
mean annual temperature consistent
with the climate projections reported by
Salathe and others (2010, pp. 72–73).
Predicted climate changes in the
Pacific Northwest have implications for
forest disturbances that are important
for maintaining montane meadow
habitats. Both the frequency and
intensity of wildfires and mountain pine
beetle (Dendroctonus ponderosae)
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outbreaks are expected to increase over
the next century in the Pacific
Northwest (Littell et al. 2010, p. 130).
The gradual loss of montane meadow
habitats over the past century is linked
to fire suppression and lack of
disturbance. One study in the Cascades
found that the majority of mesic
meadow habitats that were historically
burned (1880–1946) have contracted
over the past half century (Takaoka and
Swanson 2008, p. 539). Increased fires
over the next century are likely to result
in increased meadow habitat and
improved connectivity between
meadows occupied by mardon skippers.
Similarly, mountain pine beetle
outbreaks can result in the widespread
mortality of lodgepole pine trees, a
common tree species that is invading
meadow habitats at many mardon
skipper sites. Where invading trees are
killed, marginal areas along the edges of
existing meadows are likely to revert
rapidly back to dominance by meadow
species (Haugo et al. 2011, p. 17).
Climate change is also likely to affect
the rate of conifer succession in
montane meadow habitats. A decrease
in summer precipitation and soil
moisture may reduce the rate of conifer
encroachment in montane meadows at
mesic sites (Haugo et al. 2011, p. 17),
which may prove beneficial to mardon
skippers by increasing available
meadow habitats. Increased wildfire or
insect disturbances associated with
climate change are likely to have
beneficial effects for mardon skippers
due to increases in early seral habitat,
although large wildfires also pose a risk
to mardon skippers if all occupied
habitat in a local area is burned.
Because wildfires typically result in a
mosaic of burned and unburned areas,
it is unlikely that increased incidence of
wildfires associated with climate change
would result in the loss of multiple
populations across large areas within
the species’ or subspecies’ range.
How mardon skipper populations will
respond to future climate change is
unknown. There are no retrospective
studies for the species that have
examined how annual weather patterns
such as annual or seasonal
precipitation, snowpack, and
temperature have influenced mardon
skipper populations from year to year.
We do know that prolonged periods of
cool, wet weather during the spring or
summer months can delay adult
emergence and reduce the abundance of
mardon skippers. Because the mardon
skipper at the species level is
distributed across a broad range of
elevations and habitat types, and has
documented use of several host-plant
species, it may not be as vulnerable to
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climate change as some other narrowly
distributed butterfly species. In the
Washington Cascades the majority of
mardon skipper sites occur in the midelevation montane zone, where there is
a potential for upslope movement and
colonization of higher elevation habitats
in response to climate change over time.
Based on the above information, we do
not have data to suggest that climate
change poses a threat to the species
Polites mardon, or the subspecies
Polites mardon mardon.
Discussion specific to Polites mardon
klamathensis
Populations of Polites mardon
klamathensis may be vulnerable to the
effects of climate change due to the
subspecies’ limited distribution,
apparently smaller populations, and
limited dispersal capability. All P.m.
klamathensis sites are located in the
high-elevation montane zone of the
southern Oregon Cascades, where there
is little potential for upslope movement
or colonization of higher elevation
habitats in response to climate change
over time. Regional models of potential
climate changes in the Pacific
Northwest are variable, but the models
generally indicate a warming trend in
mean temperature, reduced snowpack,
and increased frequency of extreme
weather events (Salathe et al. 2010, pp.
72–73). All P.m. klamathensis sites are
associated with mesic soils and
permanent or ephemeral water sources
(Black et al. 2010, p. 12).
Black et al. (2010, p. 60) notes that
habitat within portions of the meadow
complex are marginal for P.m.
klamathensis because the sites are
currently too dry, but the habitat may
have been wetter in the past. Runquist
(2004a, p. 5) observed over 200 skippers
at this complex in 2002. Although multi
day surveys have not been completed
here, the population at this meadow
complex appears to have declined
(Black et al. 2010, pp. 60–61).
Given the restricted distribution of
P.m. klamathensis, and the strong
association of the subspecies with mesic
sites, a projected warming trend in
regional climate is a potential concern
for P.m. klamathensis, depending on the
changes in the environment that may
manifest as a result. We acknowledge
this concern and the need for
monitoring of these populations in the
face of climate change. However, at the
present time, due to the multiple
uncertainties associated with regional
climate models, the actual changes that
may be realized and how they would
impact the species, the timeframes
involved, and the questions surrounding
P.m. klamathensis abundance
information, we can not conclude that
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climate change is a threat to P.m.
klamathensis or likely to become so.
Summary: Because the mardon
skipper is distributed across a range of
elevations and habitat types, and has
documented use of several host-plant
species, it may not be as vulnerable to
climate change as some other narrowly
distributed species. Despite the
potential for future climate change in
the Pacific Northwest as discussed
above, we have not identified, nor are
we aware of, any data on an appropriate
scale to evaluate habitat or population
trends for the mardon skipper or to
make reliable predictions about future
trends and whether the species will be
significantly impacted. Due to the
uncertainty associated with regional
climate models and how any potential
environmental changes may possibly
impact the species, we conclude that
climate change is not a threat to mardon
skippers at the species or subspecies
levels or likely to become so.
Stochastic Weather Events and Small,
Isolated Populations
Adverse weather (freezing
temperatures, heavy rain events, or
prolonged drought) can extirpate local
butterfly populations by killing adults,
larvae, or larval food plants (Guppy and
Shephard 2001, p. 59). Even large
populations of butterflies (greater than
5,000 individuals) can rapidly decline
in response to successive seasons of
unfavorable weather conditions during
reproduction and larval development
(Ehrlich et al. 1980, pp. 102–103). The
decline in mardon skipper numbers at
some Washington Cascades sites in 2009
is an example of how variations in
seasonal weather can have a profound
effect on local mardon skipper
populations. The exact weather event
that caused the decline is unknown, but
unseasonably warm weather in May and
June caused a rapid snowmelt to occur
in these high-elevation meadows,
followed by at least 4 days of freezing
temperatures in late June during the
period when mardon skipper adults
typically emerge (Kogut 2009, p. 1). The
adult flight period in 2009 occurred
later, in mid-July, and was very brief,
and the total numbers of adults were
approximately 80 to 95 percent less than
what had typically been counted at
these sites during the previous 6 years
(Kogut 2009, p. 1).
The weather effect was not limited to
mardon skippers; other butterfly species
were also affected, including the closely
related Sonora skipper (Polites sonora),
which was apparently absent from all
sites where the species commonly cooccurs with mardon skippers at Cowlitz
Valley (Kogut 2009, p. 1). The apparent
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weather-related effect was also noted at
sites on the adjacent WenatcheeOkanogan National Forest, where the
emergence of adults occurred later, and
the adult flight period was shorter than
in previous years (St. Hilaire et al. 2009,
p. 2), although the effect to the
populations was not as severe as that
seen on the Gifford Pinchot National
Forest. Populations at lower elevation
sites did not appear to be affected by
these same weather events (St. Hilaire et
al. 2009, p. 3). Subsequent years (2010
and 2011) have generally been cool and
wet during the mardon skipper flight
season, so the populations at the
Cowlitz Valley sites have not recovered
and have continued to gradually decline
since 2009, but populations at other
locations in the Washington Cascades
have not shown a similar pattern of
decline and are apparently stable. It is
evident that adverse weather conditions
can profoundly impact local mardon
skipper populations. Because the
species occurs across a broad range of
elevations and habitat types, it is
unlikely that a stochastic weather event
is likely to affect all populations
simultaneously.
Butterfly populations with very low
numbers of individuals (e.g., fewer than
20 butterflies) are vulnerable to
extirpation from random events such as
inclement weather, wildfire, or other
potential threats identified above (e.g.,
Schtickzelle et al. 2005, p. 578). There
are a number of studies that
demonstrate that habitat patch size,
local population size, and proximity to
adjacent populations have important
implications for the long-term
persistence of butterfly populations
with limited dispersal capabilities (e.g.,
Thomas and Jones, 1993, p. 472; Hanski
et al. 1995, p. 618; Saccheri et al. 1998,
p. 492; Maes et al. 2004, pp. 234–235).
Studies that examined butterfly
population dynamics generally define
‘‘small’’ populations as having fewer
than 500 adults and ‘‘very small’’ as
having fewer than 100 adults at peak
emergence (e.g., Maes et al. 2004, p.
232; Davies et al. 2005, p. 192). (As
described below, for mardon skippers,
counts of at least 100 individuals are
generally considered to be large).
Extremely small butterfly populations
(fewer than 20 individuals) are not only
highly vulnerable to environmental
factors such as adverse weather
conditions (Schtickzelle et al. 2005, p.
578), but such small populations are
also at increased risk of extinction due
to genetic effects associated with
inbreeding (Saccheri et al. 1998, p. 491;
Nieminen et al. 2001, p. 243).
Inbreeding in small populations of the
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Glanville fritillary butterfly (Melitaea
cinxia) resulted in reduced egg hatching
rates, larval survival, and adult
longevity (Nieminen et al. 2001, p. 243).
Long-term studies of the silverspotted skipper (Hesperia comma) in
England have documented a series of
local population extinctions and
colonizations over a 20-year period
(Thomas and Jones 1993, p. 472; Davies
et al. 2005, p. 189). These studies found
that large habitat patches tended to
support large populations of skippers,
and that no extinctions occurred in
habitat patches that supported
populations of greater than 225
individuals; sites with 10 populations of
fewer than 225 skippers, however, went
extinct and the probability of extinction
increased with isolation from the
nearest population (Thomas and Jones
1993, pp. 476–478). Populations of
silver-spotted skipper have expanded in
recent years, and most of the sites that
had documented extinctions in 1991
have subsequently been recolonized by
dispersing individuals from adjacent
sites (Davies et al. 2005, p. 195).
Most populations of mardon skippers
consist of a series of one or more
occupied meadows located within close
proximity to each other. These
populations or local ‘‘clusters’’ of sites
likely function as small
metapopulations with some dispersal of
individuals between local sites (Kerwin
2011, pp. 21–23). Mardon skipper
‘‘metapopulations’’ likely experience
local site-scale extinctions and
recolonizations as local populations
expand and contract in response to
changing climate or habitat conditions,
such as with the silver-spotted skipper
in England (Davies et al. 2005, p. 195),
although on a smaller scale, as silverspotted skippers likely have greater
dispersal capability than mardon
skippers (Kerwin 2011, p. 23). However,
there is strong evidence that mardon
skippers exhibit similar metapopulation
dynamics. The large number of mardon
skipper sites in the Washington
Cascades that are located in young
clearcuts or roadside areas that were
previously forested demonstrate that the
species is capable of dispersing away
from their core habitats and colonizing
adjacent early-seral habitats that support
host grasses and forbs (e.g., Kerwin
2011, p. 14).
Mardon skippers can be locally
abundant where the species is present
(Pyle 1989, p. 28) with single-day
counts of greater than 100 individuals
documented at many sites across the
species’ entire geographic range (for the
mardon skipper, populations in the
hundreds are relatively large) (Black et
al. 2010, pp. 70–71; St. Hilaire et al.
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2010, pp.10–12; Black et al. 2011, p. 13).
Conversely, there are a number of
apparently very small populations
within the species’ range with peak
counts of fewer than 20 individuals.
Because the number of mardon skippers
present at a site can vary tremendously
over the course of a few days (Beyer and
Black 2007, p. 8), and the timing of the
flight period can vary due to a variety
of conditions, including elevation and
weather conditions, there is little
certainty of actual population sizes
associated with these individual day
counts. A single day, peak count of 100
skippers potentially represents a total
population of more than 200 skippers
based on observations during an
experimental mark-recapture study
(Runquist 2004a, p. 5), because not all
butterflies emerge on the same date, and
not all butterflies present at a site are
likely to be counted during a survey.
Since 1999, mardon skippers have
been documented at approximately 165
sites across the species’ range.
Considering that local clusters of sites
likely function as small
metapopulations, there are
approximately 66 populations of
mardon skippers currently known, and,
with the exception of the Puget prairies,
it is likely that there are additional
undocumented populations present in
all portions of the species’ range
because not all suitable habitats have
been searched for mardon skippers
(Kerwin 2011, p. 18). Each region within
the species’ range supports one or more
‘‘large’’ populations of mardon skippers
(in the case of the mardon skipper,
‘‘large’’ is defined as single-day counts
of more than 100 individuals, which
likely represents a much larger total
population).
All extant Puget prairie sites likely
support total populations from more
than 100 up to 1,000 individuals
(Schultz et al. 2011, p. 370). The largest
mardon skipper populations occur in
the Washington Cascades, with at least
2 populations of greater than 1,000
individuals, and at least 11 other
populations that have supported
populations from 100 to 400 skippers
over the past decade (unpublished data).
In the Oregon Cascades, there are 2
populations that number from 100 to
300 individuals, and in the coastal areas
of northwest California/southwestern
Oregon, there are at least 3 populations
with more than 100 individuals. In total,
at least 22 of the approximately 66
populations rangewide support large
populations of mardon skippers, and
these sites represent the majority of the
species’ total populations.
Conversely, there are many individual
‘‘sites’’ with single-day counts of fewer
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than 20 individuals. Most of these sites
are closely associated with larger local
populations. A few sites may represent
small, isolated populations that are
vulnerable to local extirpation
associated with stochastic weather
events, but these generally represent
only a small portion of the total species’
populations. Because the mardon
skipper has presumably limited
dispersal capabilities, if an isolated
population were to become extirpated,
some isolated sites are unlikely to be
reestablished due to long distances or
physical barriers (e.g., extensive forested
areas) between extant populations
(Kerwin 2011, p. 23).
The mardon skipper is a naturally rare
species across its disjunct range. Given
the limited information concerning
mardon skipper population trends
rangewide, and the presence of multiple
‘‘large’’ populations in each distinct
region within the species range, the
majority of the species’ total
populations appear to be relatively
secure from threats associated with
small populations.
Discussion specific to Polites mardon
klamathensis:
The distribution of Polites mardon
klamathensis appears to be restricted to
22 sites likely representing
approximately 11 populations in the
southern Oregon Cascades. Surveys in
recent years have searched over 200
sites in the vicinity of these known
populations and have failed to detect
the species, indicating the subspecies is
highly restricted in its distribution to a
few small meadow complexes within a
small geographic area (Black et al. 2010,
p. 7). However, one small site was
documented on Bureau of Reclamation
lands managed by BLM in 2011 (Black
2012, pers. comm.), indicating it is
possible that additional undocumented
P.m. klamathensis sites may exist in the
area. Although populations of P.m.
klamathensis appear to be relatively
small, it is difficult to draw any reliable
conclusions on population sizes based
on the limited data available, since the
majority of sites have only been visited
once during the flight season in recent
years (Black et al. 2010, pp. 70–72).
Additional multiple-day surveys are
needed to confirm if populations are as
small as they appear based on the
limited survey data collected thus far, or
whether past single-day counts may
have just missed the peak flight period.
As discussed earlier, due to the
variability of mardon flight periods
between sites and years, as well as
extreme fluctuations in numbers of
individuals that may be present from
day to day, a single-day survey in a year
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54349
is insufficient to indicate trends or
abundance.
In summary, total population sizes at
all Polites mardon klamathensis sites
are unknown due to limited surveys,
although counts at most sites indicate
that populations of this subspecies may
be relatively small. Unfortunately the
high variability in potential counts from
day to day for this subspecies
undermines the credibility of any
single-day counts for the purpose of
determining population status or trend,
and raises questions as to whether
counts of zero or few individuals on any
one day accurately reflect population
numbers or abundance. Based on the
lack of historical abundance information
and the uncertainty accompanying the
numbers of individuals associated with
individual day counts, we do not have
reliable information to suggest that P.m.
klamathensis is such a small isolated
population that stochastic weather
events would pose a significant threat to
the subspecies as a whole.
Summary: Prolonged periods of cool
wet weather during the spring and
summer months are known to
negatively affect mardon skipper
populations. Small butterfly
populations are particularly vulnerable
to these effects. Given the limited
information concerning mardon skipper
population trends rangewide, and the
presence of multiple ‘‘large’’
populations in each distinct region
within the species’ range, the majority
of the species’ total populations and
those of the subspecies Polites mardon
mardon appear to be relatively secure
from threats associated with small
populations. Additionally, due to the
limited population and abundance
information we have for the the
subspecies Polites mardon
klamathensis, we conclude that we do
not have reliable information to indicate
that populations of this subspecies are
so small or isolated as to represent a
threat to P.m. klamathensis as a whole.
Finding
As required by the Act, we considered
the five factors in assessing whether the
mardon skipper is a threatened or
endangered species throughout all of its
range. We additionally considered
whether either of the two recognized
subspecies comprising the species
mardon skipper may be a threatened or
endangered species throughout all or a
significant portion of their ranges. We
examined the best scientific and
commercial information available
regarding the past, present, and future
threats faced by the mardon skipper and
its subspecies. We reviewed the
petition, information available in our
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files, other available published and
unpublished information, and consulted
with recognized mardon skipper experts
and other Federal, State, and tribal
agencies.
The Species Mardon Skipper (Polites
mardon)
The mardon skipper is a little-studied
species; however, the species has
received considerable attention and
funding for surveys since becoming a
Federal candidate species in 1999. The
number of documented locations of
mardon skippers has expanded from
fewer than 10 in 1998 to 165 in 2011;
this increase in known occurrences of
the species is largely due to increased
survey effort. Since 1999, new site
locations have been documented each
year that targeted surveys have been
conducted. In the past 5 years,
significant new populations have been
located in the Washington Cascades and
in coastal areas of Oregon and
California, with local sites supporting
populations of hundreds of mardon
skippers. It is likely that there are
additional, undocumented populations,
particularly in the Washington
Cascades, and possibly in southwestern
Oregon and northern California because
not all available habitat for the species
has yet been surveyed. The majority of
the sites throughout the species’ range
occur on Federal lands managed by the
Forest Service, Bureau of Land
Management, National Park Service,
Fish and Wildlife Service, and the
Department of Defense (76 percent).
Current management actions, policies,
and protections associated with State
and Federal special-status-species
programs now afford the species a high
level of security from habitat loss or
destruction across the species’ range.
Potential threats to mardon skipper
habitat associated with forest
succession, fire, invasive nonnative
plants, livestock grazing, and off-road
vehicle use have been substantially
reduced or eliminated on State and
Federal lands through the development
of conservations plans and
implementation of habitat restoration
projects. Habitat degradation associated
with intensive livestock grazing
continues to occur at some sites, but
grazing impacts have been substantially
reduced or eliminated at many key sites
across the species’ range with recent
closures of Federal grazing allotments.
Habitat degradation from off-road
vehicle use has been reduced or
eliminated at many sites by installing
vehicle barriers or closing roads.
Meadow habitat restoration activities
(prescribed burning, herbicide
treatments) can be lethal to mardon
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skippers if not conducted properly, but
these risks have been minimized
through careful planning and
implementation of habitat restoration
projects. Ongoing threats that are not
currently addressed by existing
conservation plans include potential
habitat loss on private lands, but there
are relatively few known mardon
skipper sites on private lands. Climate
change may affect the mardon skipper
and its habitat. Because the mardon
skipper is distributed across a range of
elevations and habitat types, and has
documented use of multiple host-plant
species, it may not be as vulnerable to
climate change as some other more
narrowly distributed specialist species.
Based on our review of the best
available scientific and commercial
information pertaining to the five
factors, we find that the threats are not
so severe or broad in scope as to
indicate that the mardon skipper is in
danger of extinction (endangered), or
likely to become endangered within the
foreseeable future (threatened),
throughout all of its range. Therefore,
we find that the mardon skipper does
not meet the definition of an
endangered or threatened species
throughout its range.
The mardon skipper is listed as
endangered by the State of Washington.
Washington’s listing of the mardon
skipper was based on a status
assessment of the species conducted in
1999 (Potter 1999), and relied on much
of the same information that the Service
considered in placing the mardon
skipper on the candidate list that same
year. A substantial amount of new
information has become available since
that time, however, which we have
evaluated in making the present finding.
Although the State of Washington has
updated information on new population
data and conservation efforts for the
mardon skipper in their annual reports,
they have not reconsidered the listed
status of the species based on this
information. Our analysis of the best
available information considers the
many positive conservation measures
that have been implemented by both
Federal and State agencies throughout
the range of the mardon skipper,
including actions by the State of
Washington, to recover the species and
ameliorate the threats that initially led
to its State listing and Federal
candidacy 13 years ago. In addition, we
considered the numerous additional
populations of the species (and
subspecies) that have been documented
since the mardon skipper first became a
Federal candidate and was listed by the
State. Our current evaluation of the best
available information according to the
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Federal Endangered Species Act, as
detailed in this finding, does not lead us
to conclude that the mardon skipper
meets the definition of an endangered
species or threatened species
throughout all or a significant portion of
its range.
The Subspecies Polites mardon
mardon and Polites mardon
klamathensis
Polites mardon mardon
Polites mardon mardon faces the
same threats as discussed in the
rangewide evaluation previously, and
we consider all conclusions reached
regarding the degree of threat for the
species as a whole to apply equally to
the subspecies P. m. mardon. As a
result, we find that this subspecies does
not meet the definition of an
endangered or threatened species
throughout its range.
Polites mardon klamathensis
Polites mardon klamathensis faces the
same threats as discussed in the
rangewide evaluation previously;
however, where relevant we have
assessed threats specific or unique to
the subspecies Polites mardon
klamathensis separately throughout the
rangewide evaluation. In general, we
consider all conclusions reached
regarding the degree of threat for the
species as a whole to apply equally to
the subspecies P. m klamathensis. As a
result, we find that this subspecies does
not meet the definition of an
endangered or threatened species
throughout its range.
Significant Portion of the Range
Having determined that the species
Polites mardon and the subspecies
Polites mardon. mardon and Polites
mardon klamathensis do not meet the
definition of a threatened or endangered
species, we next consider whether there
are any significant portions of the range
where the mardon skipper is in danger
of extinction or is likely to become in
danger of extinction in the foreseeable
future.
In determining whether a species is a
threatened or endangered species in a
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) meeting the
definition of a threatened or endangered
species. To identify only those portions
that warrant further consideration, we
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determine whether there is substantial
information indicating 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.
Applying the process described above
for determining whether a species is
threatened or endangered in a
significant portion of its range, we
considered the status question first to
determine if any threats or potential
threats acting individually or
collectively threaten or endanger the
species in some portion of its range. In
analyzing the status of the mardon
skipper across its range, the only area
we identified where threats may be
concentrated is the Puget prairies. We
therefore considered whether the threats
to the Puget prairie populations of
Polites mardon or Polites mardon
mardon are such that the species may be
in danger of extinction there, now or
within the foreseeable future, such that
the Puget prairie populations may
warrant further consideration as a
potential significant portion of the
range.
Although the rangewide mardon
skipper population is relatively secure
under current conditions, the Puget
prairies represent the only portion of the
species’ historical and current
distribution where there are confirmed
extirpations of historical populations,
and we can reasonably infer that the
species’ range has contracted due to the
historical loss of Puget prairie habitat
over the past century. We therefore
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considered the likely future condition of
the Puget prairie populations under the
presently observed rates of population
change. Historically, mardon skippers
were known to be present at eight Puget
prairie sites, and are currently restricted
to three known populations. The trends
of the remaining populations are
unknown due to limited and
inconsistent monitoring data, but appear
to have been relatively stable over the
past decade, with 2 populations
estimated to consist of hundreds of
mardon skippers, and 1 population with
likely over 1,000 skippers (Schultz et al.
2011, p. 370). Puget prairie sites with
extant populations of mardon skippers
are protected from further development
through either State or Federal
ownership. Mardon skipper habitat at
these sites is: (1) Actively being
managed to restore and maintain
mardon skippers and other prairie
species; or (2) at Joint Base LewisMcChord being maintained by regular
wildfires, and large areas of habitat are
protected from development, off-road
vehicle use, and military training due to
the presence of unexploded ordnance.
In addition, Joint Base Lewis-McChord
is cooperating in an interagency effort to
restore and maintain prairie habitats for
the mardon skipper and other prairie
species, discussed below.
Remaining prairie habitats in the
south Puget Sound region are relatively
small, isolated patches with little
potential connectivity between patches
(Schultz et al. 2011, p. 371). Because of
this, historical prairie sites where
mardon skippers have been extirpated
are unlikely to be recolonized due to
isolation from extant populations
(Schultz et al. 2011, p. 371). There are
a number of small prairie sites in the
region that are currently in protected
status and are actively being managed to
maintain butterfly habitats that may
serve as potential future reintroduction
sites for mardon skippers (Anderson
2008, p. 2; Henry 2010, pp. 3–4).
Beginning in 2007, the Joint Base LewisMcChord Army Compatible Use Buffer
(ACUB) initiative has supported the
convening of a cooperative,
interdisciplinary and interagency
Butterfly Habitat Enhancement Team to
develop and implement habitat
improvements for mardon skipper and
other rare butterflies on formerly
occupied sites off the military
reservation (Anderson 2008, p. 1). This
interagency team is a source of funding
for mardon skipper habitat management,
population assessments, and mardon
skipper life-history research at Puget
prairie sites. These projects continue to
maintain habitat and mardon skipper
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54351
populations at the Scatter Creek
Wildlife Area. The ongoing management
to maintain mardon skipper populations
and habitat at Puget prairie sites afford
the species a high level of protection
against further losses of habitat or
populations. Because these conservation
efforts have been implemented, are
effective, and are expected to continue,
we consider the Puget prairie
population of the mardon skipper as not
likely to become in danger of extinction
within the foreseeable future.
As the best available information
indicates that the Puget prairie
population of mardon skipper at either
the species or subspecies level is not
likely to become in danger of extinction
within the foreseeable future, we
conclude that Puget prairie does not
warrant further consideration as a
potential significant portion of the range
at this point in time. We did not identify
any other potential significant portions
of the range of the mardon skipper
(Polites mardon, Polites mardon
mardon, or Polites mardon
klamathensis) that may meet the
definition of a threatened or endangered
species.
In Defenders of Wildlife v. Norton,
258 F.3d 1136, 1145 (9th Cir. 2001), the
court ruled that a species may be an
endangered species in a significant
portion of its range ‘‘if there are major
geographical areas in which it is no
longer viable but once was.’’ Where the
area in which the species is expected to
survive is ‘‘much smaller than its
historical range,’’ the determination of
whether the species warrants listing
turns on whether the lost portion of the
range would be significant. As
discussed above, the Puget Prairie
population of the mardon skipper is the
only portion of the species’ range that is
known to have contracted from the
historical distribution. We conclude that
current and future conservation efforts
are expected to maintain mardon
skippers and restore the species to
additional Puget prairie habitats.
Therefore, we have determined that
neither the full species mardon skipper,
nor the subspecies Polites mardon
mardon or Polites mardon
klamathensis, is an endangered or
threatened species in a significant
portion of its range.
We do not find that the mardon
skipper, or the subspecies Polites
mardon mardon or Polites mardon
klamathensis, are in danger of
extinction now, nor are they likely to
become in danger of extinction within
the foreseeable future throughout all or
a significant portion of their range.
Therefore, listing the mardon skipper
Polites mardon, the subspecies P. m.
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mardon, or the subspecies Polites
mardon klamathensis, as a threatened or
endangered species under the Act is not
warranted at this time.
We request that you submit any new
information concerning the status of, or
threats to, the mardon skipper to our
Washington Fish and Wildlife Office
(see ADDRESSES section) whenever it
becomes available. New information
will help us monitor the mardon
skipper and encourage its conservation.
If an emergency situation develops for
the mardon skipper or any other
species, we will act to provide
immediate protection.
We will continue to monitor the
condition of the mardon skipper
throughout its range. In the event that
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conditions or threats change and the
species becomes imperiled, we could
again consider whether it is appropriate
to list the species as endangered or
threatened under the Act. We will
continue to provide technical assistance
to Federal, State, and other entities and
encourage them to address the
conservation needs of the mardon
skipper. We will continue to work with
these agencies and entities to collect
additional biological information,
monitor the status of the mardon
skipper, and monitor the progress of its
conservation efforts.
References Cited
A complete list of references cited is
available on the Internet at https://
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www.regulations.gov and upon request
from the Washington Fish and Wildlife
Office (see ADDRESSES section).
Author(s)
The primary authors of this notice are
staff members of the Washington Fish
and Wildlife Office.
Authority
The authority for this section is
section 4 of the Endangered Species Act
of 1973, as amended (16 U.S.C. 1531 et
seq.).
Dated: August 20, 2012.
Benjamin N. Tuggle,
Acting Director, Fish and Wildlife Service.
[FR Doc. 2012–21344 Filed 8–31–12; 8:45 am]
BILLING CODE 4310–55–P
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[Federal Register Volume 77, Number 171 (Tuesday, September 4, 2012)]
[Proposed Rules]
[Pages 54331-54352]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-21344]
[[Page 54331]]
Vol. 77
Tuesday,
No. 171
September 4, 2012
Part IV
Department of the Interior
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Fish and Wildlife Service
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50 CFR Part 17
Endangered and Threatened Wildlife and Plants; 12-Month Finding on a
Petition To List the Mardon Skipper as Threatened or Endangered;
Proposed Rule
Federal Register / Vol. 77 , No. 171 / Tuesday, September 4, 2012 /
Proposed Rules
[[Page 54332]]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R1-ES-2012-0060; 4500030113]
Endangered and Threatened Wildlife and Plants; 12-Month Finding
on a Petition To List the Mardon Skipper as Threatened or Endangered
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Notice of 12-month petition finding.
-----------------------------------------------------------------------
SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a
12-month finding on a petition to list the mardon skipper (Polites
mardon) as a threatened or endangered species under the Endangered
Species Act of 1973, as amended (Act). After review of the best
available scientific and commercial information, we find that listing
the mardon skipper is not warranted at this time. However, we ask the
public to submit to us any new information that becomes available
concerning the threats to the mardon skipper or its habitat at any
time. At our discretion, after additional review of the subspecies
Polites mardon mardon and Polites mardon klamathensis, we find that
listing for these subspecies is also not warranted at this time.
DATES: The finding announced in this document was made on September 4,
2012.
ADDRESSES: This finding is available on the Internet at https://www.regulations.gov at Docket Number FWS-R1-ES-2012-0060. Supporting
documentation we used in preparing this finding is available for public
inspection, by appointment, during normal business hours at the U.S.
Fish and Wildlife Service, Washington Fish and Wildlife Office, 510
Desmond Drive SE., Suite 102, Lacey, WA 98503. Please submit any new
information, materials, comments, or questions concerning this finding
to the above address.
FOR FURTHER INFORMATION CONTACT: Ken Berg, Field Supervisor, Washington
Fish and Wildlife Office (see ADDRESSES); by telephone at 360-753-9440;
facsimile at 360-753-9008; or Paul Henson, Field Supervisor, Oregon
Fish and Wildlife Office, 2600 SE 98th Avenue, Suite 100, Portland, OR
97266; by telephone at 503-231-6179; facsimile at 503-231-6195 mailto:.
If you use a telecommunications device for the deaf (TDD), please call
the Federal Information Relay Service (FIRS) at 800-877-8339.
SUPPLEMENTARY INFORMATION:
Background
Section 4(b)(3)(B) of the Act (16 U.S.C. 1531 et seq.), requires
that, for any petition to revise the Federal Lists of Endangered and
Threatened Wildlife and Plants that contains substantial scientific or
commercial information that listing the species may be warranted, we
make a finding within 12 months of the date of receipt of the petition.
In this finding, we will determine that the petitioned action is: (1)
Not warranted, (2) warranted, or (3) warranted, but the immediate
proposal of a regulation implementing the petitioned action is
precluded by other pending proposals to determine whether species are
threatened or endangered species, and expeditious progress is being
made to add or remove qualified species from the Federal Lists of
Endangered and Threatened Wildlife and Plants. Section 4(b)(3)(C) of
the Act requires that we treat a petition for which the requested
action is found to be warranted but precluded as though resubmitted on
the date of such finding, that is, requiring a subsequent finding to be
made within 12 months. We must publish these 12-month findings in the
Federal Register.
Previous Federal Actions
On October 25, 1999, the Service identified the mardon skipper
(Polites mardon) as a candidate species for listing under the Act (64
FR 57539). The identification of the mardon skipper as a candidate
species was based on information compiled in the Washington State
Status Report for the Mardon Skipper (Potter et al. 1999, entire).
On December 11, 2002, we received a petition dated December 10,
2002, from The Xerces Society, Gifford Pinchot Task Force, The
Northwest Environmental Defense Center, Center for Biological
Diversity, Oregon Natural Resources Council, Friends of the San Juans,
and Northwest Ecosystem Alliance (petitioners), requesting that the
mardon skipper be listed as an endangered species, and that critical
habitat be designated under the Act (Black et al. 2002, entire).
Included in the petition was supporting information regarding the
species' taxonomy and ecology, historical and current distribution,
present status, and actual and potential causes of decline. We
acknowledged the receipt of the petition in a letter to the
petitioners, dated January 22, 2003. In that letter we also stated that
the Service considered the mardon skipper as having been subject to
both a positive 90-day finding and a ``warranted but precluded'' 12-
month finding, with the Candidate Notice of Review constituting
publication of these required findings. The Service's ``warranted but
precluded'' finding was based on limited funding that was dedicated to
court-ordered or other higher-priority listings.
From 2003 to 2011, the Service continued to work with Federal,
State, and private parties to compile information on the status and
distribution of the mardon skipper, which is documented in the
Service's candidate species assessment forms for those years.
Substantial new information was collected regarding mardon skipper
populations, distribution, and habitat requirements. In 2009, we
changed the listing priority number for the mardon skipper from 5 to 8
(lower priority) due to the documentation of many new populations and
increased protections for the species and its habitat provided by State
and Federal special status species programs.
In a settlement agreement with plaintiff WildEarth Guardians, on
May 10, 2011, the Service submitted a workplan to the U.S. District
Court for the District of Columbia in re Endangered Species Act Section
4 Deadline Litigation, No. 10-377 (EGS), MDL Docket No. 2165 (D. DC May
10, 2011), and obtained the court's approval to systematically, over a
period of 6 years, review and address the needs of more than 250
candidate species to determine if they should be added to the Federal
Lists of Endangered and Threatened Wildlife and Plants. The mardon
skipper is one of 251 candidate species identified in the May 2011
workplan. On October 26, 2011, the Service published the intent to
develop a proposed listing for several candidate species in the Puget
Sound prairie region (including the mardon skipper) with funding
allocated in Fiscal Year 2011 (76 FR 66830). We have since determined
that, as the distribution of the mardon skipper includes additional
habitat other than prairie, the public would be better served
evaluating this information and the species, separately.
This notice constitutes our 12-month finding on the mardon skipper.
Substantial new information regarding the mardon skipper has been
compiled since we originally advanced the species to candidacy.
Therefore, this finding considers information presented in the 2002
petition, as well as new information compiled over the past decade.
[[Page 54333]]
Species Information
The mardon skipper is a small (20 to 24 millimeters; less than 1
inch), tawny-orange butterfly with a stout, hairy body. The upper
surface of the forewings and hindwings is orange with broad dark-brown
borders, and the ventral hindwings have a distinctive pattern of light
yellow to white rectangular spots (Pyle 2002, p. 88). Males are smaller
than females, and have a small, dark-brown, slender and branched streak
(stigma) on the upper surface of the forewing. Females have a more
distinct ventral hindwing pattern. The mardon skipper is differentiated
from other closely related Polites species by its short, rounded wings,
reduced stigmal elements, and other distinctive morphological features
(MacNeill 1993, p. 179). Like most Hesperiinae butterflies, mardon
skippers have bent antennae clubs and a characteristic basking posture
in which the forewings are held at a 45-degree angle and the hind wings
are fully spread (Potter et al. 1999, p. 1).
Taxonomy and Species Description
The mardon skipper is a butterfly in the Order Lepidoptera
(butterflies and moths), superfamily Hesperioidae, and family
Hesperiidae (skippers), subfamily Hesperiinae (grass skippers). It was
originally described by W. H. Edwards (1881, pp. 47-48) as Pamphila
mardon from three males and three females collected by H.K. Morrison in
1880. The original type locality, stated by W.H. Edwards as Mount Hood,
Oregon, was later correctly designated as small prairies near Puget
Sound, Washington (Morrison 1883, p. 43). This type location was
further defined as ``Tenino Prairie, Thurston County, Washington'' by
Brown and Miller (1980, p. 53). The mardon skipper is a rare species
that occurs in four disjunct areas that include locations near the
coast in northwestern California and southwestern Oregon, the southern
Oregon Cascades, the southern Washington Cascades, and prairies in the
south Puget Sound region (James and Nunallee 2011, p. 388).
In 1998, Mattoon et al. (p. 768) proposed that the Oregon Cascade
populations be given subspecies status as Polites mardon klamathensis,
and the Washington and northern California populations be given
subspecies status as Polites mardon mardon. Adults of P.m. klamathensis
are described as having a consistently tawnier dorsal and ventral
coloration when compared to adults from other populations (Mattoon et
al. 1998, pp.771-772).
The distinction between Polites mardon klamathensis and P.m. mardon
was based largely on comparisons between specimens collected in
northwestern California and the southern Oregon Cascades. According to
Warren (2005, p. 49), the use of the name P.m. mardon for California
populations should be considered tentative because the series of P.m.
mardon from the northwestern California (and coastal southwestern
Oregon) populations have not yet been carefully compared to the series
of P.m. mardon from Washington due to the small number of specimens
available for evaluation (Mattoon et al. 1998, p. 771). The Catalogue
of the Butterflies of the United States and Canada (Pelham 2008, p. 78)
lists the full species followed by both subspecies. However, in the
introduction of his Catalogue, Pelham (2008, p. VII) notes that the
subspecies category is used without regard to its validity. No
additional taxonomic work or genetic analyses have been done to clarify
the subspecific designations described above (Kerwin 2011, p. 10).
Polites mardon is recognized as a valid species by the Integrated
Taxonomic Information System (ITIS) while P.m. klamathensis and P.m.
mardon are recognized as valid subspecies (ITIS 2011, P. mardon,
entire). For the purposes of this finding, we first analyzed the
threats to the species Polites mardon as a whole. We then, at our
initiative, further considered the threats to each of the currently
recognized subspecies: P.m. mardon and P.m. klamathensis.
Distribution
The mardon skipper is a rare northwestern butterfly with a
remarkably disjunct range. The species' current range is known from
four widely separated locations: the south Puget Sound region of
Washington, the southern Washington Cascades, the Cascade Mountains of
southern Oregon, and coastal hills in northwestern California and
southwestern Oregon (Kerwin 2011, pp. 8-9). The historical range and
abundance of mardon skippers are unknown. The species was originally
described from specimens collected at a south Puget Sound prairie site
in 1880 (Morrison 1883, p. 43), but there are few historical records or
museum collections of this species (Potter et al. 1999, p. 3). No
estimates of abundance are available from any site prior to 1980
(Potter et al. 1999, p. 5).
The mardon skipper's disjunct distribution and strong association
with early-seral, semi-mesic grassland habitats in the Pacific
Northwest suggest a relict distribution that was likely much more
widespread in the past. Both Pyle (2002, p. 89) and Runquist (2004a, p.
6) suggest that the mardon skipper is an ancient species. The species'
short, rounded wing morphology is not adapted to long-distance
dispersal. The apparent lack of intervening populations between the
distinct geographic areas suggests the species probably evolved under
more open, contiguous environmental conditions (Runquist 2004a, p. 6).
Populations in each disjunct geographic region have likely become
isolated over long geologic time scales, as evidenced by the subspecies
distinction between Polites mardon mardon and P. m. klamathensis. It is
likely that mardon skippers were historically more widespread within
each disjunct geographic region prior to the widespread loss of
grassland and montane meadow habitats due to fire suppression, invasive
species, and development over the past century (Potter et al. 1999, p.
5, Beyer and Schultz 2010, p. 863; Schultz et al. 2011, p. 370).
In this assessment we use the term ``site'' to indicate a specific
location with species presence. Sites are usually mapped as distinct
habitat patches, such as individual meadows in summary reports (e.g.,
Black et al. 2010, p. 25). Sites may include locations with a single
mardon skipper observation, or locations that support many mardon
skippers observed over multiple years. Sites are variable, and not all
reports define sites the same way. For purposes of estimating the
number of populations, occupied meadows can be considered to belong to
the same population if the sites are within the annual dispersal
distance for the species, generally assumed to be 0.5 mi (0.8 km) or
less (Potter and Fleckenstein 2001, p.6). In this assessment we use the
term ``populations'' to represent local clusters of sites that we
assume are likely to be associated and function as a local population.
Summary of Mardon Skipper Current Range and Distribution
In 1999, the mardon skipper was known from approximately 14 extant
sites located in four distinct geographic areas (Potter et al. 1999,
p.5). Targeted surveys from 2000 through 2011 have documented a total
of 165 sites with mardon skipper presence representing approximately 66
populations (Table 1). New sites or populations have been documented in
each year that surveys have been completed. For example, five new sites
were documented in 2011, including four sites in the Washington
Cascades, and one site in the southern
[[Page 54334]]
Oregon Cascades. It is very likely that additional undocumented sites
exist, particularly in the Washington Cascades and possibly in
southwestern Oregon or northwestern California, because not all of the
potential habitat areas have been surveyed. The increase in known
populations since 1999 is due to increased survey effort in areas not
previously surveyed, rather than to increased habitat or expanding
populations (Kerwin 2011, p. 18). The majority (76 percent) of the
sites throughout the species' range occur on Federal lands managed by
the Forest Service, Bureau of Land Management (BLM), National Park
Service, Fish and Wildlife Service, and the Department of Defense, as
well as Tribal lands owned by the Yakama Indian Reservation (17
percent). Due to the species' disjunct distribution, the populations in
different geographic regions are relatively isolated, with two
recognized subspecies Polites mardon mardon and P.m. klamathensis,
occurring within the species' range.
----------------------------------------------------------------------------------------------------------------
Approximate
number of Approximate
documented number of
Geographic region Site ownership sites with populations
species (local
presence clusters of
(2000-2011) sites)
----------------------------------------------------------------------------------------------------------------
Polites mardon mardon
----------------------------------------------------------------------------------------------------------------
Washington--South Puget Sound Prairies Joint Base Lewis McChord--Dept. of 4 1
(Pierce and Thurston Counties). Defense.
Washington Dept. of Fish & Wildlife 2 2
Washington--South Cascades (Yakima, Wenatchee National Forest.......... 36 15
Klickitat, and Skamania Counties). Gifford Pinchot National Forest.... 43 13
Conboy Lake National Wildlife 3 3
Refuge. 23 11
Yakama Indian Reservation.......... 6 4
Private ownership..................
Southwest Oregon--Curry County............. BLM--Coos Bay District............. 2 1
Rogue River Siskiyou National 3 1
Forest.
Oregon State Parks................. 1
Northwest California--Del Norte County..... Six Rivers National Forest......... 8 2
Redwood National Park.............. 9 1
Private ownership.................. 3 1
----------------------------------------------------------------------------------------------------------------
Polites mardon klamathensis
----------------------------------------------------------------------------------------------------------------
Oregon--South Cascades Jackson County...... BLM Medford District............... 15 9
Rogue River Siskiyou National 4 2
Forest.
Private ownership.................. 3 ..............
--------------------------------------------------------------------
Totals................................. ................................... 165 66
----------------------------------------------------------------------------------------------------------------
Note: In this assessment we use the term ``sites'' for specific locations with documented species presence (some
of which are single observations) and ``populations'' to represent local clusters of sites that we assume are
likely to be closely associated and function as a local population.
Summary of Mardon Skipper Population Estimates and Trends
Estimates of population sizes or population trends over time for
mardon skippers are generally not available. Surveys to estimate
relative abundance of mardon skippers are conducted by systematically
walking transects through a site and counting the number of adult
mardon skippers encountered (Seitz et al. 2007, p. 11). The majority of
survey efforts have been 1-day counts, so it is not known if they were
conducted early or late in the adult flight period. Multiple surveys
during the flight season and across a number of years are required to
assess population sizes because the timing and length of adult flight
periods can vary widely from year to year (Kerwin 2011, p. 19).
A few surveyors have used line-transect distance-sampling methods
to estimate mardon skipper populations, but these techniques have
generally failed to provide statistically reliable estimates at sites
with small populations (Runquist 2004b, p. 4, Arnold 2006, p. 6).
Runquist (2004a, pp. 4-5) used both line-transect sampling and mark-
recapture sampling techniques to estimate a mardon skipper population
in a small complex of three meadows in the Oregon Cascades. Researchers
counted a total of 172 mardon skippers on all line-transects over all
days, compared with a total of 238 mardon skippers that were captured
and marked in the same meadows during the same period (Runquist 2004a,
p. 5). No statistically reliable estimates of the actual population
size were derived from this effort, but the author opines that a total
population estimate of 350-400 individuals would be reasonable at this
site based on his observations (Runquist 2004a, p. 5).
Line-transect distance sampling was used to census mardon skippers
across approximately 800 acres (ac) (324 hectares (ha)) of Puget
prairie habitat in 2009, and provided the first statistically reliable
estimates of the mardon skipper populations at these sites (Potter
2010, p. 4). At the Scatter Creek Wildlife Area in 2009, the population
estimate during the peak of the adult flight period was 801 mardon
skippers at the South Unit (95 percent confidence interval = 399-1,286
skippers) and 204 at the North Unit (95 percent confidence interval =
84-360) (Potter 2010, p. 4). These estimates were derived from actual
counts of 312 skippers on the South Unit and 93 skippers on the North
Unit (Potter 2009, p. 1). This was the most comprehensive survey effort
at this site to date, so the results of the survey are not directly
comparable to previous monitoring efforts at this site (Potter 2009, p.
2), but this population appears to be relatively stable based on counts
conducted between 1997 and 2009 (Potter et al. 1999, p. 6; Harke 2001,
p. 12; Potter 2009, p. 1).
Only one site (in Washington) has had a full spectrum of censuses
that have covered the entire adult flight period (Beyer and Black 2007,
p. 8). In 2006, the counts at this site (Grapefern Meadow) went from 0
mardon skippers counted on July 6, to 135 on July 9; 345
[[Page 54335]]
on July 16; 128 on July 23; and 2 on August 4 (Beyer and Black 2007, p.
8). These counts demonstrate that the number of mardon skippers present
at a site can fluctuate significantly over a few days. The observed
mardon skipper population at this site has fluctuated greatly over the
past decade, with peak counts ranging from 420 butterflies in 2004 to
34 in 2011. Although there have been high counts of butterflies from
time to time, overall the populations on the Wenatchee National Forest
and Gifford Pinchot National Forest appear to be relatively stable.
Data from the Wenatchee National Forest show some evidence of trends
related to elevation, with lower elevation population sites (less than
3,300 feet (ft) [1,000 meters (m)]) appearing to be stable, and mid-
elevation sites (3,500-4000 ft [1,067-1,220 m]) showing some local
declines, likely associated with cool, wet summer conditions (St.
Hilaire et al. 2010, p. 2).
In the Oregon Cascades, limited population information for Polites
mardon klamathensis is available, as few multiple-day surveys have been
conducted here. Black et al. (2010, Appendix 1) report single-day
counts for multiple P.m. klamathensis sites over a 5-year period,
spanning 2005-2010 (there were no counts for most sites in 2008). In
2011, one new P.m. klamathensis site was located on Bureau of
Reclamation Lands managed by BLM (Black 2012, pers. comm.). Although
several of the P.m. klamathensis sites appear to be small in size
(fewer than 20 individuals), only a handful of these sites had counts
on more than a single day in a year, and even in these few cases there
were never more than 2 days of counts in any single year (Black et al.
2010, Appendix 1). Furthermore, the dates for these counts range quite
widely from one year to the next, from early or mid-June through the
first week of July, so whether these counts occurred within the peak
flight period is unclear. For example, as described above for Grapefern
Meadow in Washington, the only site where we have data from mardon
skipper counts over the entire adult flight period, the numbers of
skippers counted on any single day ranged anywhere from 0 to 345 over a
10-day period (Beyer and Black 2007, p. 8). This high variability in
potential counts shows why single-day counts are not a credible means
of determining population abundance or trend. Of the known sites for
the subspecies, most have had relatively few individuals counted on any
single day over the period 2005 through 2010, but it is not known
whether the observed numbers may represent an increase or decrease over
historical levels. One site, Pumpchance 125 Meadow, has generally had
relatively high numbers of P.m. klamathensis over 5 years of single-day
counts (up to 304 individuals counted in 2009); historical abundance of
mardon skippers is not known at this site. On the other hand, the three
sites that make up the Hobart Peak complex, the one site where
historical abundance information is available, appear to have lower
numbers of P. m. klamathensis than observed in the past (Black et al.
2010, Appendix 1). In general, however, based on the lack of historical
abundance information and the uncertainty accompanying individual day
counts, we are unable to determine population trends for P.m.
klamathensis.
Recent monitoring at Coon Mountain in California found lower
numbers of mardon skippers in areas treated with prescribed burning
compared to unburned areas in 2008. Three years after the burn event,
mardon skipper numbers were still lower in burned areas than in
unburned areas, but the overall population at this site appears to be
stable (Black et al. 2011, p. 13). Monitoring efforts at other sites in
California have been inconsistent, but the limited data for the
historical sites at High Divide Ridge indicate this population is
potentially stable within the limited suitable habitat areas present at
these sites.
Mardon skippers can be locally abundant where the species is
present (Pyle 1989, p. 28) with day counts of greater than 100
individuals documented at several sites across the species' geographic
range (Black et al. 2010, pp. 70-71; St. Hilaire et al. 2010, pp. 10-
12; Black et al. 2011, p. 13). Conversely, populations at many
locations within the species' range are apparently persisting at very
low levels with consistent peak counts of fewer than 20 individuals.
Documented extirpations occurred at five Puget Prairies sites from
1985 through 1999, resulting in a local contraction of the species'
range in that region (Potter et al. 1999, p. 6). Extirpation at one
historical site in the Washington Cascades has been documented (Potter
et al. 1999, p. 4), but there are at least three other extant
populations in the vicinity of this historical site at the Conboy Lake
National Wildlife Refuge, including a newly documented population in
2011 (USFWS unpublished data). Black et al. (2010, p. 7) state that
some Polites mardon klamathensis sites in the Oregon Cascades may
possibly be extirpated; however, they also stress that more monitoring
is needed to confirm this supposition. No historical data is available
at these sites prior to 2005, and many of these sites appear to have
always had very low numbers of individuals according to single-day
counts (Black et al. 2010, pp. 70-72). Black et al. (2010, p. 7)
additionally note that there are cases where one individual mardon
skipper may have been found in past years but not in subsequent
surveys, but such instances may represent errant findings and are not
indicative of sites or popultions that have become extirpated.
With the apparent exception of a few Polites mardon klamathensis
populations where more monitoring is needed, and a few higher-elevation
P. m. mardon sites in the Washington Cascades, most mardon skipper
populations now appear to be stable across the species' range.
Habitat
Mardon skippers are grass skippers in the subfamily Hesperiinae,
meaning the larvae feed strictly on graminoids (grasses and sedges)
(Scott 1986, p. 424). The mardon skipper's habitat requirements include
food resources for adults (flower nectar), larval host plants (grasses
and sedges), and site-specific environmental and structural conditions
that support successful reproduction and survival. This includes
patches of early-seral open grassland habitat that are dominated by
short-statured grasses or sedges and forbs that are generally free of
overstory trees and shrubs. Mardon skippers generally avoid areas with
tall grasses, shrubs, or trees (Henry 2010, p. 44). Grassland patches
that are as small as 0.5 ac [0.2 ha] are capable of supporting small
populations of mardon skippers. However, most areas that support
populations of mardon skippers consist of mixed forest-grassland
complexes that support multiple occupied ``sites'' with some
connectivity between habitat patches for successful dispersal and
movement of individuals among sites.
The species' larval development is prolonged, lasting for 3 months
or more prior to diapause (Newcomer 1966a, p. 246; Henry 2010, p. 5).
During this time the larvae require succulent grasses for successful
development. Occupied sites retain sufficient moisture to maintain host
plant palatability (green leaves) for larval development (Beyer and
Black 2007, p. 18; Kerwin 2011, p. 21). Meadows that are too wet or too
dry do not support mardon skippers. Site conditions and host plants
selected by mardon skippers vary across sites, indicating the species
is capable of using multiple graminoids as larval food (Beyer and
Schultz 2010, p. 867).
[[Page 54336]]
Although mardon skippers are not selective for a specific grass
species, they do exhibit host plant specificity within some localities
(Beyer and Schultz 2010, p. 869; Henry 2010, p. 15).
South Puget Sound Prairies
In the south Puget Sound region of Washington, mardon skippers are
found in low-elevation (200-300 ft [60-90 m]), glacial outwash
grasslands (prairies) with abundant Festuca roemeri (Roemer's fescue)
interspersed with Viola adunca (early blue violet) (Potter et al. 1999,
p. 5). Occupied prairies range in size from 300 to greater than 1,000
ac [120 to more than 400 ha]. Mardon skippers oviposit (lay eggs) on
Roemer's fescue almost exclusively at Puget prairie sites, indicating a
very strong association with this grass species (Henry 2010, p. 13).
Roemer's fescue is a perennial bunchgrass native to the Pacific
Northwest. Although Roemer's fescue accounted for 50 percent of the
total grass cover at the sampled locations, mardon skippers selected
this species in 86 out of 88 observed ovipositions (Henry 2010, p.
13.). In addition to the presence of the host plants, the structure of
the surrounding plant community is also important for oviposition
selection (Henry 2010, p. 16). Mardon skippers selected small, green
(live) fescue tufts in areas with at least 50 percent open moss cover
on the surrounding ground (Henry 2010, p. 16). Mardon skippers avoid
areas that are heavily invaded with Arrhenatherum elatius (tall
oatgrass) and Cytisus scoparius (Scot's broom) (Henry 2010, p. 44). The
oviposition habitat requirements of mardon skippers in Puget prairies
are distinct from those of populations in the southern Washington
Cascades (Henry 2010, p. 19).
At Puget prairie sites, early blue violet and Vicia sativa (common
vetch) are strongly preferred as nectar sources, and Scot's broom is
strongly avoided (Hays et al. 2000, p. 14). Nectaring was also observed
on Camassia quamash (common camas), Lomatium utriculatum (fine-leaved
desert parsley), Teesdalia nudicaulis (barestem teesdalia), and
Ranunculus occidentalis (western buttercup) (Hays et al. 2000, p. 24).
Southern Washington Cascades
In the southern Washington Cascades, the mardon skipper is found in
open grasslands and small montane meadows within Abies grandis (Grand
fir), Psuedotsuga menziesii (Douglas-fir), or Pinus contorta (lodgepole
pine)/mixed-conifer woodlands at mid to high elevations (1,800 to 5,600
ft [549 to 1,707 m]) (Potter et al. 2002, p. 12). Occupied sites in the
Washington Cascades vary in size from small (0.5 ac [0.2 ha]) meadows
to large forest/meadow complexes encompassing hundreds of acres. Site
conditions range from relatively dry, ridgetop meadows to small montane
meadows associated with wetlands, springs, or riparian habitat (Potter
et al. 2002, p. 13). Wetland areas that are perennially submerged do
not support mardon skippers, but the species is often found in dry
transitional zones along the margins of wetlands. Water features such
as small streams or wetlands are common at many Washington Cascades
sites (Kerwin 2011, p. 20). Alpine meadows (more than approximately
6,000 ft [1,829 m] elevation) apparently do not support this species,
perhaps due to the relatively short season these areas are free from
snow cover. Sites with grassland vegetation, including grassy forest
openings, roadside meadows, and young, grass-dominated tree plantations
support mardon skipper populations (Potter et al. 2002, pp. 12-13).
In the Washington Cascades, oviposition has been documented on 23
different graminoid species (Beyer and Schultz 2010, p. 866). However,
this analysis indicated that mardon skippers are selective for certain
grass species within different meadows. The most frequently used
oviposition plants include Festuca idahoensis (Idaho fescue), Poa
pratensis (Kentucky bluegrass), Danthonia intermedia (timber oatgrass),
Carex inops (long-stolen sedge), and Festuca rubra (red fescue) (Beyer
and Schultz 2010, p. 866). Danthonia unispecta (one-spiked oatgrass)
appears to be an important grass species at sites on the Wenatchee
National Forest. Females have been observed ovipositing on this species
(Jepsen et al. 2008, p. 3), and higher densities of adult butterflies
are commonly associated with patches of D. unispecta (St. Hilaire et
al. 2009, p. 7). The variety of identified oviposition plants suggests
that females may not always oviposit on specific host plants, but
within a community of possible species that can be used by the larvae
(Beyer and Black 2007, p. 5). These findings are significantly
different from the observations at Puget prairies sites, which
indicated mardon skippers were strongly associated with a single grass
species (Henry 2010, p. 19).
Due to the range of plant communities present at Washington
Cascades sites, there were no common habitat features across all study
sites other than the presence of short-statured grasses and sedges
(Beyer and Schultz 2010, pp. 869-870). Mardon skippers selected for
larger graminoids with greater total cover and less bare ground
selection was also negatively influenced by the presence of trees,
indicating a preference for selecting oviposition sites away from trees
and forest edges (Beyer and Schultz, p. 869). Studies of mardon skipper
densities within individual meadows also demonstrated that mardon
skippers are patchily distributed within occupied sites, with the
highest densities tending to occur near the center of a meadow away
from forested edges (Beyer and Black 2007, p. 18).
In the Washington Cascades, adults have most frequently been
observed nectaring on vetch, Fragaria spp. (strawberry), and Trifolium
spp. (clover) (Beyer and Black 2007, p. 15). Erysimum asperum
(wallflower), Erigeron peregrinus (fleabane), Calochortus spp. (sego
lily), and Achillea millefolium (yarrow) are also reported as nectar
sources from this region (Beyer and Black 2007, p. 15; Potter and
Fleckenstein 2001, p. 6).
Southern Oregon Cascades
Populations of Polites mardon klamathensis in southern Oregon
occupy small (0.5 to10 ac [0.25 to 4 ha]), high-elevation (4,500 to
5,100 ft [1,372 to 1,555 m]) grassy meadows within mixed-conifer
forests that are associated with an ephemeral or permanent water source
such as a stream or wetland (Black et al. 2010, pp. 6-7). As seen at
many sites in Washington, mardon skippers in the Oregon Cascades are
typically found along the margins of forest wetlands in the narrow
transitional zone along the edge of a water feature and the adjacent
dry uplands (Kerwin 2011, p. 21).
Occupied sites are dominated by short-statured grass/sedge
communities. In the Oregon Cascades, the most common oviposition plant
was Danthonia californica (California oatgrass) (Beyer and Black 2007,
p. 6). Other species selected for oviposition were red fescue, Roemer's
fescue, Kentucky bluegrass, Deschampsia cespitosa (tufted hairgrass),
and Carex spp. (sedges) (Beyer and Black 2007, p. 6). The primary
nectar plants being utilized are Potentilla diversifolia (diverse-
leaved cinquefoil), Wyethia angustifolia (narrow-leaved mule's ears),
Penstemon procerus (small-flowered penstemon), and Plectritis congesta
(sea blush) (Beyer and Black 2007, p. 16).
[[Page 54337]]
Coastal Northwest California/Southwest Oregon
The coastal populations of Polites mardon mardon are found in small
meadows (0.5-5 ac [0.2-2 ha]) dominated by Idaho fescue in sparse Pinus
jeffreyi (Jeffrey pine) forests in extreme northwestern California and
southwestern Oregon. Sites are located in coastal hills approximately 7
to 15 miles (11 to 24 km) inland from the Pacific coast, at elevations
ranging from approximately 1,500 to 3,000 ft (427 to 854 m). These
sites are within the coastal fog belt (Mattoon et al. 1998, p. 771).
Meadow habitats at these sites are associated with the western extent
of serpentine-based soils in the region (Imper 2003, p. 4), and are
more mesic (moist) than typical serpentine grasslands found in
northwestern California (Imper 2003, p. 4). Ross (2010, p. 1) notes
that the coastal Oregon mardon skipper sites are associated with
serpentine-based soils supporting moist-to-dry transitional meadow
habitats with abundant bunchgrasses.
The most detailed description of vegetation for sites in this area
is for the High Divide Ridge sites (Imper 2003, pp. 4-5). Both Idaho
fescue and California oatgrass are common at these sites (Imper 2003,
p. 5) and are likely used as host plants for oviposition and larval
food. No oviposition or habitat selection studies have been completed
for these populations, but Runquist (2004b, p. 2) observed females
ovipositing on Festuca spp. at High Divide sites. The most commonly
selected nectar plants at California sites are Phlox diffusa (spreading
phlox) and Viola adunca (early blue violet; Arnold 2006, pp. 6-7).
Detailed observations of mardon skipper behavior including oviposition,
plant selection, and adult nectar species have not been reported for
the coastal Oregon sites. Ross (2008, p. 9) noted observing mardon
skippers nectaring on Viola spp. and Calochortus spp. at a coastal
Oregon site.
Biology
Mardon skippers are univoltine, completing one life cycle annually
(i.e., egg-larva-pupa-adult). Adults typically emerge between May and
July, depending upon location and elevation of the site, with adults in
higher elevation sites emerging later. Adults do not all emerge on the
same date, so flight period duration at any given site depends in part
on the number of skippers present. In 2007, at one Washington site,
Beyer and Black (2007, p. 8) note that adult emergence went from 0
adults on July 6 to 135 adults on July 9. In large populations the
flight period may extend for over a month, while small populations may
have adults present for only 10 or fewer days (Potter et al. 2002, p.
11). Within the same geographic area, emergence dates vary with
elevation, with emergence occurring earlier at lower elevations.
Weather influences emergence and flight period duration. Wet or cold
conditions delay emergence; conversely, warm, dry conditions promote
earlier emergence, and both may affect the duration of the adult flight
period (Potter et al. 2002, p. 11).
Mark-recapture experiments indicate adults can live up to 3 weeks
(Runquist 2004a, p. 5), but most adults live only 7 to 9 days (Scott
1986, p. 25). During their brief life as adult butterflies, mardon
skippers feed on flower nectar, mate, and lay eggs on grasses or sedges
(see Habitat Requirements for details). As with many butterfly species,
males are often observed ``puddling'' or congregating on wet soils
(Scott 1986, p. 68). During periods of adverse weather, mardon skippers
seek shelter low in the vegetation, under grass or forbs. Mardon
skippers generally fly low to the ground, often hovering over low
grasses and forbs, or darting from place to place with a fast skipping
flight. Mardon skippers are non-migratory. Adults generally disperse
distances of up to 0.25 mile (mi) (0.4 kilometers [km]) over relatively
short periods, but there appears to be very little dispersal beyond
their natal meadow complexes (Runquist 2004a, p. 5). On occasion,
individual males have been detected up to 1 mi (1.6 km) away from their
original location (Runquist 2004a, p. 5). Mardon skippers have not been
observed flying through closed-canopy forest, but they have been
observed along open corridors such as powerlines or roads with nectar
sources (Potter and Fleckenstein 2001, p. 6).
After mating, females deposit their eggs (oviposit) singly into
tufts of low-growing grasses or sedges (host plants) (James and
Nunnalle 2011, p. 388). The total number of eggs laid in the wild is
unknown, but Newcomer (1966a, p. 243) observed about 25 eggs per female
for captive Polites, and James and Nunnallee (2011, p. 388) note that
two captive females produced 21 eggs total. Eggs hatch in 7 to 10 days
(Newcomer 1966a, p. 244; Henry 2010, p. 5). After hatching, the larvae
feed on host grasses or sedges throughout the summer and into the fall
months (Beyer and Black 2007, p. 19, Henry 2010, p. 14). Larvae use
silk to construct a grass ``nest'' and emerge from this shelter to feed
on the tender edges or leaf tips of host grasses (James and Nunallee
2011, p. 388). These nests are tube-like structures up to 0.78 inches
(in) (2 centimeters [cm]) long that are oriented either vertically or
horizontally at the base of the host plant (Beyer and Black 2007, p.
17). It does not appear that the larvae disperse away from the oviposit
location (Beyer and Black 2007, p. 17). Henry (2010, p. 14) found six
larvae at a Puget prairie site in September 2009, confirming that
larvae feed on the same plants that the females had selected during
oviposition (Henry 2010, p. 14). There are five instars (stages) of
larval development, followed by the formation of a pupa and emergence
as an adult butterfly (James and Nunallee 2011, p. 388).
Captive-rearing efforts suggest that mardon skipper larvae
overwinter as pupae (Newcomer 1966a, p. 246; James and Nunalle 2011, p.
388), but field observations indicate that the larvae overwinter in
diapause, and feed again in the spring before pupating (Henry 2009, p.
2; Henry 2010, p. 5). Beyer and Black (2007, p. 19) found larvae
present at a Washington Cascades site as late as October 21, and Henry
(2009, p. 2) found larvae at a Puget prairie site in November and
February. This aspect of mardon skipper life history is not well
understood. Some captive-reared larvae developed quickly, forming a
pupa and eclosing (emerging) as adults in the fall (which is not known
to occur in the wild), while other captive-reared larvae overwintered
as pupa (James and Nunallee 2011, p. 388). Other Polites species have
been recorded as overwintering as larvae (P. mystic), pupae (P.
sabuleti), or both (P. peckius) (Scott, 1986, pp. 443-445).
Conservation Measures
When the mardon skipper was first identified as a Federal candidate
for listing in 1999 (64 FR 57539; October 25, 1999), the species was
known from approximately 14 extant sites located in 4 distinct
geographic areas--south Puget Sound prairies, the southern Washington
Cascades, the southern Oregon Cascades, and northwestern California
(Potter et al. 1999, p. 5). At that time, the species was not afforded
any special status or protections from existing regulatory mechanisms
(Potter et al. 1999, p. 15). However, the subsequent designation of the
mardon skipper as a State-listed endangered species in Washington and
as a Federal candidate species has raised awareness of the need for the
species' conservation. The species is now designated as a Sensitive
Species or Special Status Species on Federal lands within its range
(discussed below), and State natural resource agencies have
[[Page 54338]]
identified mardon skippers as a priority species for conservation.
State Laws and Conservation Plans
The mardon skipper is listed as an endangered species in the State
of Washington by the Washington Fish and Wildlife Commission
(Washington Administrative Codes 232-12-014, Endangered Species; 232-
12-011, Threatened Species, Appendix D). The Washington Department of
Fish and Wildlife (WDFW) has prepared a Comprehensive Wildlife
Conservation Strategy (CWCS) (WDFW 2005). The CWCS identifies the
mardon skipper as a ``species of greatest conservation need'' and
identifies specific conservation actions for the species, including the
protection of known sites and potential habitats and the investigation
of limiting factors, and identifies development of a recovery plan for
the species as a priority (WDFW 2005, p. 326). The conservation plan
provides recommended management actions that have contributed to the
amelioration of threats to the mardon skipper where they are found on
State lands. Ongoing management for mardon skipper habitat on State
lands in the Puget Prairie region is occurring through partnerships
between the Department of Defense, The Nature Conservancy (now Center
for Natural Lands Management), Washington State Department of Natural
Resources, Washington Department of Fish and Wildlife, and U.S. Fish
and Wildlife Service among others. These treatments have been effective
for restoring or maintaining mardon skipper habitat at managed sites.
Mardon skippers have been documented using many areas that were
previously unsuitable due to the presence of invasive weeds after the
habitat was restored with herbicides to eliminate tall oat grass,
followed by management (mowing, pulling) to control Scot's broom (Hays
2008, pp 1-2).
There are also a number of small Prairie sites in the region that
are currently in protected status and are actively being managed to
maintain butterfly habitats that may serve as potential future
reintroduction sites for mardon skippers (Anderson 2008, p. 2, Henry
2010, pp.3-4). Beginning in 2007, the Fort Lewis Army Compatible Use
Buffer (ACUB) initiative has supported the convening of a cooperative,
interdisciplinary and interagency Butterfly Habitat Enhancement Team to
develop and implement habitat improvements for mardon skipper and other
rare butterflies on formerly occupied sites off of the Fort Lewis
reservation (Anderson 2008, p. 1). This interagency team is a source of
funding for mardon skipper habitat management, population assessments,
and mardon skipper life history research at Puget prairie sites. These
projects continue to maintain habitat and mardon skipper populations at
the Scatter Creek Wildlife Area through prescribed fire, direct seeding
of native species, mowing, and herbicide control of Scotch broom
(Cytisus scoparius) and exotic grasses and forbs (WDFW 2011, p.79). The
ongoing management to maintain mardon skipper populations and habitat
at Puget prairie sites afford the species a high level of protection
against further losses of habitat or populations.
Oregon has a State Endangered Species Act, but the law does not
cover invertebrate species. The Oregon Department of Fish and Wildlife
(ODFW) has prepared a Comprehensive Conservation Strategy (ODFW 2006).
The strategy identifies the mardon skipper as a ``strategy species.''
Strategy species are found in low numbers at few locations and are
considered to be at-risk species. The plan targets conservation actions
for the most at-risk species. The strategy generally identifies special
habitat needs, limiting factors, and data gaps for the mardon skipper
(ODFW 2006, p. 351).
California has a State Endangered Species Act, but the law does not
apply to insects. The State Comprehensive Wildlife Action Plan (CDFG
2006) does not specifically address the conservation needs of the
mardon skipper, but the plan emphasizes conservation of invertebrate
species listed on the State ``special animal'' list.
Special Status Species Policies on National Forest and BLM Lands
The mardon skipper is listed as a Sensitive Species by the U.S.
Forest Service in Washington and Oregon (Forest Service Region 6), and
in California (Forest Service Region 5), and as a Special Status
Species by the Bureau of Land Management (BLM) in Oregon and
Washington. For Oregon and Washington BLM-administered lands, Special
Status Species policy (BLM 6840) details the need to conserve those
species and the ecosystems on which they depend. Conservation is
defined as the use of all methods and procedures which are necessary to
improve the condition of Special Status Species and their habitats to a
point where their Special Status recognition is no longer warranted.
Policy objectives also state that actions authorized or approved by the
BLM do not contribute to the need to list Special Status Species under
the Endangered Species Act (Interagency Special Status/Sensitive
Species Program [ISSSSP] 2011, entire).
On National Forest lands, Sensitive Species are defined as those
plant and animal species identified by a Regional Forester for which
population viability is a concern, as evidenced by significant current
or predicted downward trends in population numbers or density and
habitat capability that would reduce a species' existing distribution
(Forest Service Manual [FSM] 2670.5). Management of Sensitive Species
``must not result in a loss of species viability or create significant
trends toward federal listing'' (FSM 2670.32). The Regional Forester is
responsible for identifying Sensitive Species and is directed by policy
to coordinate with Federal and State agencies and other sources, as
appropriate, in order to focus conservation management strategies and
to avert the need for Federal or State listing as a result of National
Forest management activities (ISSSSP 2011, entire).
The Pacific Northwest Regional Office of the Forest Service and
Oregon/Washington State Office of the BLM established the Interagency
Special Status/Sensitive Species Program (ISSSSP) to facilitate the
conservation and management of rare species on Federal lands. This
interagency collaboration focuses on regional-level conservation
approaches for Sensitive and Special Status Species lists (ISSSSP 2011,
entire).
With dedicated funding from the ISSSSP, the Forest Service/BLM
have:
(1) Formed the inter agency Mardon Skipper Work Group, which meets
semi annually to share information and ideas and to plan future
conservation work for mardon skippers;
(2) Developed a mardon skipper survey protocol (Seitz et al. 2007,
entire);
(3) Funded multiple seasons of mardon skipper surveys across Forest
Service, BLM, and other lands in Oregon and Washington;
(4) Funded an oviposition habitat study in cooperation with the
Xerces Society and Washington State University to determine plants that
mardon skippers choose for egg laying and larval hosts (Beyer 2009,
entire);
(5) Contracted with the Xerces Society to develop site-specific
management plans for all mardon skipper sites on BLM lands in the
southern Oregon Cascades (Black et al. 2010, entire);
(6) Completed a Conservation Assessment for the mardon skipper in
2007 (Kerwin and Huff 2007, entire); and
[[Page 54339]]
(7) Revised and updated the Conservation Assessment in 2011 (Kerwin
2011, entire).
Additional site-management plans are currently under development in
2012 with dedicated funding from the ISSSSP for Forest Service mardon
skipper sites on the Wenatchee, Gifford Pinchot, and Rogue River--
Siskiyou National Forests, as well as additional sites on the Coos Bay
BLM District.
The Forest Service/BLM Conservation Assessment is a comprehensive
review of the mardon skipper's status, threats, and conservation needs,
and provides specific management guidance and recommendations for
protecting and maintaining the species' habitat on Federal lands
(Kerwin 2011, pp. 30-35). The management considerations in the
Conservation Assessment provide general guidance to Forest Service/BLM
administrative units for managing mardon skipper sites and addressing
potential threats such as conifer encroachment, invasive weeds,
livestock grazing, and off-road vehicles (Kerwin 2011, pp. 31-33). The
listing of the mardon skipper as a Forest Service Sensitive/BLM Special
Status species ensures that the species is considered and addressed
during the planning and implementation of Forest Service and BLM land
management activities. The Sensitive/Special Species status has
resulted in direct protection or restoration of mardon skipper habitat
at many sites on Federal lands across the species range. Examples
include conifer removal projects and placement of boulders to block
off-road vehicle access (Kogut 2008, pp. 4-9), building grazing
exclosures to exclude cattle from mardon skipper habitat (e.g., USFS
2003, p. 185); or eliminating grazing impacts by closing grazing
allotments or reducing use (e.g., BLM 2008, p. 6). In California, both
the Forest Service and the National Park Service have included mardon
skipper habitat protections in the planning and implementation of
prescribed burn projects (e.g., Black et al. 2011, p. 3; NPS 2010, pp.
26-27).
In summary, the majority of the known occurrences of the mardon
skipper throughout its range are located on Federal or State lands
where the species is assured a high level of protection through
existing regulations or conservation management associated with special
status species programs. Federal and State agencies have been proactive
in implementing effective conservation measures for the mardon skipper
throughout its range. These protective measures are currently in place
and are not dependent upon the species being listed under the Act.
Summary of Factors Affecting the Species
Section 4 of the Act (16 U.S.C. 1533) and implementing regulations
(50 CFR 424) set forth procedures for adding species to, removing
species from, or reclassifying species on the Federal Lists of
Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of
the Act, a species may be determined to be an endangered or threatened
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; or
(E) Other natural or manmade factors affecting its continued
existence.
In making this finding, information pertaining to the mardon
skipper in relation to the five factors provided in section 4(a)(1) of
the Act is discussed below. In considering what factors might
constitute threats, we must look beyond the mere exposure of the
species to the factor to determine whether the species responds to the
factor in a way that causes actual impacts to the species. If there is
exposure to a factor, but no response, or only a positive response,
that factor is not a threat. If there is exposure and the species
responds negatively, the factor may be a threat and we then attempt to
determine how significant a threat it is. If the threat is significant,
it may drive or contribute to the risk of extinction of the species
such that the species warrants listing as a threatened or endangered
species as those terms are defined by the Act. This does not
necessarily require empirical proof of a threat. The combination of
exposure and some corroborating evidence of how the species is likely
impacted could suffice. The mere identification of factors that could
impact a species negatively is not sufficient to compel a finding that
listing is appropriate; we require evidence that these factors are
operative threats that act on the species to the point that the species
meets the definition of a threatened or endangered species under the
Act.
In making our 12-month finding on the petition, we considered and
evaluated the best available scientific and commercial information.
Here we evaluate the factors affecting the petitioned species Polites
mardon. In addition, the Service has elected, at our own discretion, to
additionally evaluate the two subspecies Polites mardon mardon and
Polites mardon klamathensis. For the sake of brevity, we analyze the
subspecies separately from the species rangewide only in those cases
where the factors affecting the subspecies are unique, or where
potential threats to the subspecies differ in severity or scope of
impact from those affecting the species in the remainder of its range.
The evaluation of the five factors, below, should thus be interpreted
as applying equally to the species as a whole as well as to its
constituent subspecies, unless indicated otherwise.
Factor A. The Present or Threatened Destruction, Modification, or
Curtailment of Its Habitat or Range
Pyle (1989, p. 28) characterized threats to the mardon skipper as
any factor that degrades its obligate grassland habitats, including
development or land conversion, overgrazing, the use of herbicides and
pesticides, encroachment by native and invasive nonnative vegetation,
and succession from grassland to forest. In addition to the threats
listed above, Black and others (2010, p. 12) identify climate change,
stochastic weather events, and small, isolated populations as threats
for Polites mardon klamathensis. Here we discuss the potential threats
associated with habitat loss or degradation; the additional threats
identified by Black et al. (2010, p. 12) are discussed under Factor E,
below.
Habitat Loss Associated With Land Conversion
Prairies, which historically covered over 145,000 ac (60,000 ha) of
the south Puget Sound region, have largely been lost over the past 150
years (Crawford and Hall 1997, p. 11). The primary causes of historical
prairie habitat loss in the region are attributed to the conversion of
prairie habitat to urban development and agricultural uses (over 60
percent of losses), and succession to Douglas-fir forest (32 percent)
(Crawford and Hall 1997, p. 11). Today approximately 8 percent of the
original prairies in the south Puget Sound area remain, but only about
3 percent contain native prairie vegetation (Crawford and Hall 1997, p.
11). Today approximately 8 percent of the original prairies in the
south Puget Sound area remain, but only about 3 percent contain native
prairie vegetation.
Puget prairie sites with extant populations of mardon skippers are
protected from further development through either State or Federal
ownership. Habitats at these sites have
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been degraded by invasive species and competing uses such as recreation
or military training (Schultz et al. 2011, pp. 370-371), but these
threats are now being addressed through active management, as
referenced above under ``Conservation Measures'' and as discussed
further below.
Remaining prairie habitats in the south Puget Sound region are
relatively small, isolated patches with little potential connectivity
between patches (Schultz et al. 2011, p. 371). Because of this,
historical prairie sites where mardon skippers have been extirpated are
unlikely to be re colonized naturally due to isolation from extant
populations (Schultz et al. 2011, p. 371). However, there are a number
of small prairie sites in the region that are currently in protected
status and are actively managed to maintain butterfly habitats that may
serve as potential future reintroduction sites for mardon skippers
(Anderson 2008, p. 2; Henry 2010, pp. 3-4).
In other portions of the mardon skipper's range, outside of the
south Puget prairie region, habitat loss due to urban development or
land conversion has not been a significant threat due to their
locations primarily on Federal or Tribal lands, in remote areas that
have historically been managed for grazing, timber production, or
recreation. There have been minor historical losses of mardon skipper
habitat from the placement of roads, trails, or buildings in occupied
meadow sites (Potter et al. 1999, p. 12), but these losses have not
been quantified and are relatively small. There are no reported
examples of recent habitat loss from new road construction or
developments in mardon skipper habitats on Federal lands. Because of
the protections the mardon skipper receives as a Federal special
status/sensitive species (described above under ``Conservation
Measures'') the threat of additional habitat loss due to land
conversion on Forest Service or BLM lands is very low. Twelve out of
the 165 sites known for mardon skipper are found on private lands; the
potential for future development at these privately owned sites is
unknown. However, most of these sites on private lands are located near
other extant populations on neighboring Federal lands, indicating that
private lands sites are likely subpopulations of these larger
populations on Federal lands. It is therefore unlikely that any of the
few mardon skipper sites on private lands support source populations of
the species.
Summary: The historical loss of native prairie habitats to urban
development and agriculture in the south Puget Sound region has likely
resulted in a contraction of the species' distribution within that
portion of the species' range. However, Puget prairie sites currently
occupied by mardon skippers are protected from further loss due to
development by State or Federal ownership. Land conversion for roads
and other uses has historically resulted in only minor losses of mardon
skipper habitat on Federal lands in all other portions of the species'
range. Additional habitat losses due to land conversion or development
on Federal lands that support populations of Polites mardon mardon and
Polite mardon klamathensis are not anticipated. Very few of the known
mardon skipper sites are found on private lands, and most of these
sites are believed to be subpopulations of larger populations found on
Federal lands that are protected from conversion or development.
Therefore, continued habitat loss due to land conversion is not a
significant threat to the mardon skipper at the species or subspecies
levels.
Habitat Loss and Fragmentation Associated With Forest Succession
Throughout the Pacific Northwest the invasion of meadow or
grassland habitats by conifers represents a recent and widespread
phenomenon potentially triggered by changes in climate, the cessation
of intensive grazing, and wildfire suppression (Haugo and Halpern 2007,
pp. 285-286). In Redwood National Park in California, meadow habitats
have declined due to forest encroachment over the past century (NPS
2010, pp. 44-45). At Joint Base Lewis-McChord in Washington,
approximately 39 percent (over 16,200 ac [6,560 ha]) of the original
prairie habitat has transitioned to Douglas-fir forest, and only a
fraction of the original prairie habitat remains as small, isolated
prairies (Tveten 1997, p. 124)
The loss of meadow habitats in the Cascades is also well
documented. At one study site in the Oregon Cascades, the area
associated with mesic meadows declined from 328 ac (133 ha) to 163 ac
(66 ha) during the period from 1946 to 2000 (Takaoka and Swanson 2008,
p. 521). This represents a loss of approximately 50 percent of the
mesic meadow habitat over a period of 54 years. Most xeric (dry)
meadows were fairly stable over the study period, indicating that
patterns of forest succession in montane meadows are complex and that
diverse factors influence these processes (Takaoka and Swanson 2008, p.
521). The contraction of mesic meadow habitats was strongly associated
with a lack of fire disturbance over the past half century (Takaoka and
Swanson 2008, p. 538).
Aerial photographs taken on the Gifford Pinchot National Forest in
the southern Washington Cascades indicate that the mardon skipper sites
located within a historical (1918-1919) burn area were larger with much
greater potential for connectivity between sites than exists today
(Foster 2010, p. 3). Forest succession over the past 60 years has
reduced the meadow habitats in this landscape to a few isolated patches
ranging in size from 2 to 8 ac (0.8 to 3.2 ha) (Foster 2010, p. 2).
The loss of meadow habitats from forest succession not only reduces
the amount of suitable grassland habitat available for mardon skippers,
it also closes off potential dispersal corridors between meadows,
potentially resulting in remnant, isolated populations (Beyer and
Schultz 2010, p. 870). In addition to natural meadow habitats, many
mardon skipper sites in the Washington Cascades are located in areas
that were clearcut for timber harvest in 1960s through 1980s (Price and
Mendez-Treneman 2000, p. 6; St. Hilaire et al. 2008, p. 5), and
subsequently were colonized by mardon skippers. Open grass habitats in
many of these old clearcuts are now rapidly declining. Because the
mardon skipper requires early seral habitats, conifer encroachment is a
potential threat at all mardon skipper sites located on National Forest
or BLM lands in Washington, Oregon, and California. However, actual
habitat degradation as a result of this threat is ranked as high at
only a few mardon skipper sites, primarily on the Wenatchee National
Forest, and a few in the range of P.m. klamathensis (Kerwin 2011, pp.
49-60).
Land managers across the range of the mardon skipper recognize
conifer encroachment as impacting meadow habitats, and many local
districts have undertaken projects to reduce conifer encroachment at
mardon skipper meadows. For example, Kerwin (2011, p. 31) notes the
implementation of ``considerable meadow restoration efforts for mardon
skippers'' on the Gifford-Pinchot National Forest. Examples of
restoration activities range from hand-cutting and removal of small
conifers on the Gifford Pinchot National Forest in Washington (Kogut
2008, pp. 4-7) to prescribed burning projects on the Six Rivers
National Forest in California (Black et al. 2011, p. 3). Some level of
grazing is also recognized as a potential management tool for reducing
conifer encroachment (Kerwin 2011, p. 27). Habitat management
activities can be beneficial to the species, although
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site disturbance from these actions can result in negative impacts to
mardon skipper populations if they are not carefully planned and
implemented (Black 2011, p. 385).
Although conifer encroachment has the potential to negatively
impact meadow habitats required by the mardon skipper, Federal land
managers are actively managing sites to reduce conifer encroachment and
maintain meadows to improve habitat for the mardon skipper throughout
its range, as outlined in the management provisions in the revised
Forest Service/BLM Conservation Assessment for the Mardon Skipper
(Kerwin 2011, pp. 30-33), and in Management Plans for all Southern
Oregon Cascades Mardon Skipper (Polites mardon klamathensis) Sites on
BLM Lands (Black et al. 2010, pp. 15-17). Therefore, the impacts of
conifer encroachment do not presently represent a threat to the mardon
skipper across its range, and continued active management is expected
to control this threat in the future.
Discussion Specific to Polites mardon klamathensis
Little information exists about vegetation change over time in the
grasslands, shrublands, and woodlands of southwestern Oregon (Hosten et
al. 2007b, p. 1). A comparison of historical and current photos shows a
general loss of high-elevation grassland to woody shrub and tree
domination, and transition from shrubland and woodland to conifer
domination (Hosten et al. 2007b, p. 31). The encroachment of shade-
tolerant conifers into non-conifer vegetation, reduced reproduction by
pine, and the loss of meadows support the generally accepted belief
that fire suppression has negatively impacted historically open
vegetation types in the southern Oregon Cascades (Hosten et al. 2007b,
p. 1). Historical anecdotes also identify livestock grazing as playing
a role in the depletion of native perennial bunchgrasses and subsequent
invasion of woody species (Hosten et al. 2007b, p. 31).
The loss of open grassland habitats from conifer succession has the
potential to impact populations of Polites mardon klamathensis through
the gradual reduction and loss of suitable habitat patches and by
closing off corridors between meadows, reducing the potential for
successful dispersal to suitable habitat patches. Studies with other
butterfly species have demonstrated that conifer encroachment reduces
dispersal between populations and reduces gene flow, resulting in
small, isolated populations with a greater risk of local extirpation
(Roland and Matter 2007, p. 13702). Although identified as a potential
threat at some sites, conifer encroachment within meadows is currently
being addressed through management plans developed for P.m.
klamathensis sites on BLM lands (Black et al. 2010, pp. 21-61). In
2011, the BLM staff at the Medford District implemented small conifer
removal projects at most of the sites identified for this work, which
has reduced the imminency of continued habitat loss within meadows
(Mardon Skipper Work Group [MSWG] 2011, in litt.). Present management
of these areas to reduce conifer encroachment and enhance meadow
habitats appears to have ameliorated this threat for P.m. klamathensis.
Summary: The potential loss of meadow habitats due to forest
succession is a concern at most mardon skipper sites across the
species' range. However, habitat loss due to succession is a gradual
process that occurs on a scale of decades and can be checked with
appropriate low-impact management methods, which is presently occurring
at many key sites across the species' and subspecies' range. Because
Federal managers have implemented actions to substantially ameliorate
this threat, forest succession, while still affecting habitat, is no
longer considered to be a threat to the mardon skipper at the species
or subspecies levels.
Habitat Modifications Associated With Fire
Fire is an important source of disturbance that reduces conifer
encroachment and maintains meadow and grassland habitats. Prescribed
fire is a tool that is often used by land managers to maintain meadows
or other fire-adapted habitats (e.g., NPS 2010, p. 4). Although mardon
skippers occur in landscapes that have historically burned, mardon
skipper populations may be vulnerable to local extirpation if a fire
burns all of the occupied habitats at a population site (Black 2011, p.
384). The use of prescribed fire is implicated in the extirpation of
mardon skippers from one historical Puget Prairie site in 1992 (Stinson
2005, p. 10).
In California, the Coon Mountain mardon skipper site on the Six
Rivers National Forest is being managed with prescribed fire to
maintain the meadow habitat at the site and, consequently, mardon
skipper habitat. Working in cooperation with the Xerces Society, the
Forest Service modified their original plans to burn the entire site,
and established four experimental burn plots with corresponding
unburned areas. The experimental plots were burned in the fall of 2008
(Black et al. 2011, pp. 3-4). Monitoring at the site in 2009 indicated
mardon skippers were 3-27 times more abundant in unburned areas
compared to burned areas (Black 2011, p. 384). Continued monitoring at
the site in 2010 and 2011 indicate that mardon skipper densities in
unburned patches were consistently higher than in burned patches (Black
et al. 2011, p. 14); however, mardon skippers are gradually
recolonizing the burned patches from the adjacent unburned areas at the
site as their preferred habitat increases (Black 2011, p. 384).
Although peak counts of mardon skippers in subsequent years after the
burn have not been as high as they were prior to burning in 2008, the
authors note that the overall population appears to be stable, and is
still considered the largest known population in California (Black et
al. 2011, p. 13). As their preferred habitat increases at these sites,
the mardon skipper population may expand into the burned areas and
increase over time. Continued monitoring is needed to fully assess the
population response at Coon Mountain.
A large wildfire burned over 8,000 ac (3,238 ha) at Mt. Adams in
Washington in 2008, including burning the forest around at least one
known mardon skipper site (Eureka Meadow). Although the fire burned the
surrounding forest, the meadow itself did not burn (likely because it
was still snow-covered at the time of the fire), and 135 mardon
skippers were counted at the site in 2010 (Wainwright 2010, p. 1). The
Windy Valley site on the Rogue River-Siskiyou National Forest in
southwestern Oregon is another example of a mardon skipper population
surviving a recent wildfire event. Much of the forest around this
meadow/wetland complex burned as part of the Biscuit Fire in 2002, but
the site continues to support a large population of mardon skippers
that was discovered in 2010 (Kerwin 2011, p. 51). Wildfires are likely
to have beneficial effects for mardon skippers due to resultant
increases in early seral habitat, although large wildfires also pose a
risk to mardon skippers if all occupied habitat in a local area is
burned. Because wildfires typically result in a mosaic of burned and
unburned areas, it is unlikely that wildfires would result in the loss
of multiple populations across large areas within the species' or
subspecies' range.
Assessing whether wildfires or prescribed fire used to manage
mardon skipper habitats poses a threat to the species is a complex
undertaking. Fire disturbance is an integral process in
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natural ecosystems (Agee 1993, p. 3), and has certainly played a
pivotal role in maintaining mardon skipper habitats. Conservation
scientists as well as Federal land managers recognize that the habitat
benefits gained from using prescribed fire to maintain mardon skipper
habitat must balance the lethal effects fire can pose to mardon
skippers (Black 2011, p. 384; Kerwin 2011, p. 33). The Coon Mountain
experiment demonstrates that prescribed fire can be used to restore
mardon skipper meadow habitat and maintain a population at the site,
but the fire must be carefully managed so that only a portion of the
occupied areas at a site is burned (Black 2011, p. 384).
Summary: Wildfires or prescribed fires that maintain and restore
meadow habitats can be either beneficial or lethal to mardon skippers,
depending on the timing and severity of the fire and the condition of
the habitat. Fire is an important disturbance agent for maintaining the
early-seral habitats mardon skippers require. Managers using fire to
restore habitat can and have modified burn plans to meet both fire
objectives and protect mardon skippers, which greatly reduces the
potential threat associated with prescribed fires. Therefore, the use
of prescribed fires for habitat management is not considered to be a
threat to mardon skippers at either the species or subspecies level.
Wildfires are also a potential threat on a local scale, but it is
unlikely that wildfires would result in the loss of multiple
populations across large areas within the species' or subspecies'
range; therefore, we do not consider it to be a threat to mardon
skippers at the species or subspecies level.
Habitat Loss Associated With Invasive, Nonnative Plants
The invasion and subsequent dominance of nonnative plant species in
native grassland habitats is common and has occurred rapidly at several
current and historical mardon skipper locations associated with Puget
prairies (Potter et al. 1999, p. 10). Invasive grasses such as tall
oatgrass and the invasive shrub Scot's broom drastically alter the
short-grass/forb habitat structure that mardon skippers select for
oviposition or nectaring sites (Hays et al. 2000, p. 28; Schultz et al.
2011, p. 371). Habitat utilization studies have demonstrated that
mardon skippers actively avoid areas invaded by these species (Hays et
al. 2000, p. 28; Henry 2010, p. 44), but will recolonize sites where
these invasive species have been removed (Hays et al. 2000, p. 16).
Scot's broom and tall oatgrass are present at south Puget Sound prairie
sites occupied by mardon skippers, but significant portions of these
sites are managed annually to control these species (Hays 2010, p. 1).
The Washington State Department of Natural Resources, for example,
recommends restoration techniques including mowing, hand pulling,
herbicide application, and prescribed burning to restore or maintain
prairie habitats for the mardon skipper (Potter et al. 1999, p. 8) .
Mardon skippers have been documented using many areas that were
previously unsuitable due to the presence of invasive weeds after the
habitat was restored with herbicides to eliminate tall oatgrass,
followed by management (mowing, pulling) to control Scot's broom (Hays
2008, pp. 1-2).
Continued site management is required to maintain mardon skipper
habitat and populations at south Puget prairie sites (Schultz et al.
2011, p. 375). Ongoing management for mardon skipper habitat is
occurring through partnerships between the Department of Defense, The
Nature Conservancy (now Center for Natural Lands Management),
Washington State Department of Natural Resources, Washington Department
of Fish and Wildlife, and U.S. Fish and Wildlife Service among others.
The prairie sites with extant populations of mardon skippers also
support a number of other high-priority prairie species, including
Taylor's checkerspot butterfly (Euphydryas editha taylorii), a
candidate for listing under the Act (Stinson 2005, p. 6). Based on the
importance of these sites for multiple prairie-associated species, we
expect that State, Federal, and nongovernmental organizations will
continue to place a high priority on maintaining prairie habitats at
these sites for the benefit of mardon skippers and other prairie
species.
Not all mardon skipper sites have been evaluated for the presence
of invasive, nonnative plants; however, the problem is increasingly
common (Potter et al. 1999, p. 10). At least two sites (Cave Creek and
Lost Meadows) on the Gifford Pinchot National Forest are being actively
managed to reduce invasive Cirsium arvense (Canada thistle) which has
formed dense patches and has been spreading throughout the mardon
skipper habitat (Kogut 2008, p. 9). Managing for invasive species is
required at a number of sites to maintain mardon skipper habitat, but,
as with managing for conifer removal, the management must be carefully
planned to avoid negative impacts to local butterfly populations
(Schultz et al. 2011, p. 373). We expect that Federal land managers
will continue to manage sites to control invasive weeds and will do so
in a way that improves habitat for the mardon skipper, while minimizing
impacts to local populations as outlined in the revised Forest Service/
BLM Conservation Assessment for the Mardon Skipper (Kerwin 2011, pp.
30-33), and in site-specific plans such as those developed on the
Gifford Pinchot National Forest (USFS 2008, p. 57).
Summary: Invasive nonnative plants have historically resulted in
habitat loss and degradation at a number of mardon skipper sites,
primarily in the Puget prairies. Federal, State, and private land
managers have been actively managing invasive weeds at the most
degraded sites to restore and maintain mardon skipper habitat, and are
likely to continue to do so under their current management plans, which
substantially reduces this potential threat. Based on the ongoing
partnership and commitment of private, State, and Federal entities to
manage invasive nonnative plants and restore prairie habitats, the
impact of invasive nonnative plants appears to have been sufficiently
ameliorated throughout the range of the mardon skipper such that it
does not pose a threat to the species or either subspecies.
Habitat Modifications Associated With Livestock Grazing
Current or historical livestock grazing has occurred at essentially
all mardon skipper sites in the Washington and Oregon Cascades.
Historically (1900-1930s), many areas in the Cascades were intensively
grazed by sheep (Miller and Halpern 1998, p. 267), including several
known mardon skipper sites on the Gifford Pinchot National Forest (USFS
2007a, p. 30; Foster 2010, p. 2). Sheep grazing was largely replaced by
cattle grazing after the 1930s. Grazing allotments at Mt. Adams in
Washington have been grazed for over 100 years (USFS 2007a, pp. 30-31).
Long-term grazing can alter both the structure and composition of
plant communities, rendering them unsuitable to some butterfly species
(Dana 1991, p. 54; Ellis 2003, p. 292), while benefiting other species,
depending on the specific habitat requirements of each species (Kruess
and Tshcharntke 2002, p. 1575; Poyry et al. 2005, p. 469; Vogel et al.
2007, pp. 81-82). Grazing can impact mardon skipper populations by (1)
direct trampling of eggs, larvae, pupae, and adults (Potter et al.
1999, p. 13; Black et al. 2010, pp. 13-14); (2) removal of both larval
and adult food sources, and (3) disturbing the soil, which allows weeds
to invade (Ellis 2003, pp. 292-293; Schtickzelle et al. 2007, p. 657).
One grazing study found that both the
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abundance and recruitment of the bog fritillary butterfly (Proclossiana
eunomia) were reduced by as much as 74 percent in grazed areas compared
to ungrazed sites (Schtickzelle et al. 2007, p. 657). Dana (1991, p.
54) notes that both the Dakota skipper (Hesperia dacotae) and the ottoe
skipper (Hesperia ottoe) apparently decline or can be extirpated in
response to intensive grazing, likely due to changes in the composition
and structure of the plant communities at intensively grazed sites.
Although intensive livestock grazing can be detrimental to many
butterfly species, moderate to light grazing can be a useful method for
halting succession and maintaining butterfly habitats where other
habitat management methods are impractical (Schtickzelle et al. 2007,
p. 658; Ellis 2003, p. 293). The silver-spotted skipper (Hesperia
comma) is one species that has shown a positive response to moderate
grazing, and depends on continued grazing to maintain the short-
statured grassland habitats the species requires (Thomas and Jones
1993, p. 473).
The impact of cattle grazing to mardon skipper populations is
likely relative to the timing, duration, and magnitude of the grazing
at the site (Black et al. 2010, p. 13). Large mardon skipper
populations are able to persist in some heavily grazed habitats. Conrad
Meadows on the Wenatchee National Forest is subjected to native
ungulate (deer and elk) grazing in the spring, and then intensive
cattle grazing during the summer months. Conrad Meadows is a large
system of interconnected meadows, wetlands, and forested areas with
complex vegetative structure and site conditions. The meadow complex
supports the largest known population of mardon skippers, with minimum
population counts of over 1,000 mardon skippers in some years (St.
Hilaire et al. 2010, p. 11). Conrad Meadows has been in an active
cattle grazing allotment for 80 years, and there continues to be a
robust population of mardon skippers at this site (St. Hilaire et al.
2008, p. 15). Because the timing of the onset of livestock grazing
tends to occur towards the end or after the adult flight period at
Conrad Meadows, the grazing at this site may not affect mardon skipper
populations to the same degree as sites that are grazed throughout the
flight period (St. Hilaire et al. 2008, p. 14).
Ongoing monitoring at grazing exclosures (2007-2010) on the
Wenatchee National Forest has shown no clear pattern between mardon
skipper populations in grazed versus ungrazed areas (St. Hilaire et al.
2010, p. 7). The authors note that there are a number of confounding
variables associated with this monitoring project and more research at
these sites is recommended. Anecdotal observations within grazing
exclosures indicate a much higher abundance and diversity of flowering
forbs (adult nectar sources) compared to outside the exclosures (Jepsen
et al. 2007, p. 17), but there appears to be no clear pattern in the
number of mardon skippers within exclosures versus outside exclosures
(St. Hilaire et al. 2010, p. 7). Mardon skipper densities at sites
grazed by cattle on the Wenatchee National Forest are comparable or
higher than densities observed at sites on the adjacent Gifford Pinchot
National Forest that are subjected only to light native ungulate
grazing.
Because mardon skippers have specific habitat requirements related
to graminoid cover, composition, and structure (Beyer and Schultz 2010,
pp. 867-868), it appears likely that intensive livestock grazing that
occurs before or during the adult flight period would have a negative
effect on mardon skipper reproductive success and larval survival due
to the loss of adult nectar sources and larval host plants, and the
introduction of nonnative grasses, forbs, or shrubs that do not meet
the structural requirements of mardon skippers. The grasses most
commonly used by mardon skippers for oviposition and larval food (e.g.,
Roemer's fescue, California oatgrass, Kentucky bluegrass (nonnative),
and sedges) (Beyer and Black 2007, p. 6) are also some of the most
preferred forage species used by cattle (Hosten et al. 2007, p. 20).
These effects are likely to be most profound at sites where grazing
impacts are intensified due to the presence of surface water or wet
soils that attract livestock (Hosten and Whitridge 2007, p. 1), and the
grazing use entirely overlaps the adult flight period (Black et al.
2010, p. 13). However, the removal of livestock from sites that have
historically been grazed for decades does not automatically restore
degraded habitats or improve mardon skipper populations.
There are a number of sites that are no longer in active grazing
allotments that continue to have chronically low or declining
populations of mardon skippers, most likely due to degraded habitat
conditions associated with the plant community composition (Black et
al. 2010, pp. 60-63; USFWS unpublished data). The short-grass/forb
habitats preferred by mardon skippers can become quickly degraded in
the absence of livestock grazing due to presence of tall-structured
nonnative grasses and shrubs (Black et al. 2010, p. 61). The use of
short-duration, low-intensity grazing may prove to be beneficial or
necessary for maintaining mardon skipper habitat in some situations
(e.g., Black et al. 2010, p. 38).
Over the past 5 years, a number of grazing allotments on both
Forest Service and BLM lands in both Oregon and Washington have been
retired. Grazing allotments at most of the southern Oregon Cascades BLM
mardon skipper sites for Polites mardon klamathensis were retired in
2009 (Black et al. 2011, pp. 14-15). A major grazing allotment (Ice
Caves) on the Gifford Pinchot National Forest was discontinued in 2009,
and was officially closed in 2011. On the Wenatchee National Forest,
the Forest Service has installed a number of grazing exclosures to
reduce grazing impacts and protect key mardon skipper habitat areas
(St. Hilaire et al. 2010, p. 5). In general, grazing impacts on Federal
lands are decreasing, with fewer animals being allowed onto grazing
allotments, with shorter grazing periods, and placement of exclosures
in key locations to protect sensitive habitats (e.g., USFS 2007b, p.
2). Active grazing allotments are still present at several mardon
skipper sites within the range of the species, and continued monitoring
is needed to assess the impact that grazing has on these populations.
Under current management conditions, light to moderate grazing can be
potentially beneficial in maintaining the habitat structure preferred
by mardon skippers, and based on the most recent conservation
assessment for the mardon skipper, intensive grazing does not appear to
be a significant factor in habitat degradation for the species across
its range (Kerwin 2011, Appendix A).
Summary: Cattle grazing can have either negative or beneficial
effects to mardon skippers depending upon the timing, duration, and
intensity of the grazing. Robust mardon skipper populations are able to
persist in some heavily grazed habitats, while other areas that have
been heavily grazed have generally poor habitat conditions and support
only low numbers of mardon skippers. Grazing is likely to be beneficial
for maintaining mardon skipper habitat at sites that are vegetated with
tall-statured nonnative grasses and shrubs. Potential negative impacts
from grazing on Federal lands have been substantially reduced due to
the closure of a number of grazing allotments in key areas, as well as
changes in management practices to reduce grazing intensity and protect
key habitat areas. Therefore, livestock grazing does not represent a
threat to the mardon skipper at the species level at this time, nor is
it likely
[[Page 54344]]
to be so in the future due to current management efforts. We have no
information to indicate that it is a threat to the subspecies Polites
mardon mardon.
Discussion specific to Polites mardon klamathensis:
Current or historical livestock grazing has occurred at all Polites
mardon klamathensis sites in the Oregon Cascades for over 100 years
(Hosten et al. 2007, p. 13), and habitat conditions at some sites have
been excessively degraded by grazing (Black et al. 2010, pp. 22-23).
Until recently all of the occupied sites were located in active grazing
allotments. With the recent designation of the Cascades-Siskiyou
National Monument (Monument) in 2000, the BLM initiated a review of
grazing impacts on Federal lands within the Monument. This review
determined that four grazing allotments within the Monument failed to
meet BLM standards for maintaining populations of threatened and
endangered and other locally important species (BLM 2008, p. 6). The
major reasons for not meeting this standard included the threat to
special status species including the mardon skipper, the favoring of
noxious weeds (e.g., Canada thistle at high elevations) over native
plants; and the invasion of the nonnative Poa bulbosa (bulbous
bluegrass) (BLM 2008, p. 6). Although overgrazing is considered to have
had negative impacts on several P.m. klamathensis sites in the past
(Black. 2010, p. 14), some of these sites have now been retired from
grazing, and others are now being managed in accordance with a
management plan developed by The Xerces Society for Invertebrate
Conservation for all P.m. klamathensis sites on BLM lands in southern
Oregon, including provisions specific to grazing, such as avoiding
grazing during the flight period of adults and keeping grazing periods
short and interspersed with long recovery period for the habitat (Black
et al. 2010, entire).
In 2009, grazing allotments at 10 mardon skipper sites located on
BLM lands within the Monument were retired (Black et al. 2010, pp. 14).
The remaining sites on BLM lands that are still within active grazing
allotments have existing or planned grazing exclosures to protect core
mardon skipper habitat areas (Black et al. 2010, pp. 23-61). Four
Polites mardon klamathensis sites located on the Rogue River-Siskiyou
National Forest are in active grazing allotments, and Jepsen et al.
(2007b, pp. 24-25) reported that grazing had degraded habitat at three
of these sites. However, more recently Kerwin (2011, pp. 49-60)
reviewed the P.m. klamathensis sites in his conservation assessment and
found that none faced a serious threat from grazing (with exception of
Hobart Peak, where effects from grazing were considered ``unknown''),
and additionally noting that several of the grazed sites are in
excellent condition. Remaining sites in active grazing allotments on
Federal lands are expected to continue to exhibit reduced grazing
impacts due to the placement of existing or planned grazing exclosures
around core habitat areas (Black et al. 2010, pp. 23-61; Kerwin 2011,
p. 32).
Summary: The threats from active livestock grazing have been
substantially reduced from all Federal lands sites within the range of
Polites mardon klamathensis. Planned or existing grazing exclosures are
likely to protect core habitat areas at some key sites, but the
effectiveness of grazing exclosures for maintaining mardon skipper
habitat structure and populations remains unknown. We expect that
mardon skipper habitat conditions within exclosures will generally
improve with the removal of livestock grazing, but these areas will
require monitoring and possible management actions to insure that
invasive weeds or tall-statured nonnative grasses do not become a
secondary threat in the absence of grazing, as recommended in the
revised Forest Service/BLM Conservation Assessment for the Mardon
Skipper (Kerwin 2011, pp. 30-33), and in Management Plans for all
Southern Oregon Cascades Mardon Skipper (Polites mardon klamathensis)
Sites on BLM Lands (Black et al. 2010, pp. 15-17). The potential
negative impacts of grazing on Federal lands within the range of
P.m.klamathensis have been substantially reduced due to the closure of
a number of grazing allotments in key areas, as well as changes in
management practices to reduce grazing intensity and protect key
habitat areas. Therefore, we do not consider the effects of livestock
grazing to be a threat to P.m. klamathensis.
Habitat Loss Associated With Off-Road Vehicles and Recreation
Recreational activities, including off-trail walking, off-trail
horseback riding, and off-road vehicle use, may directly kill some
mardon skippers by trampling and crushing larvae (Potter et al. 1999,
p. 12). Off-road vehicle use has the greatest impact on mardon skipper
habitat because vehicle tires can destroy native plants and disturb
soils, leading to invasion by weeds. Small, roadside meadows are
vulnerable to damage or destruction associated with off-road vehicle
use. Currently, this threat applies to a few locations across the range
of the species (Kerwin 2011, pp. 37-41). In 2008, a mardon skipper site
located on private lands in Del Norte County, California, was partially
destroyed when the site was used as a dump for logging slash and debris
(Ross 2008a, p. 5; Devlin 2009, pers. comm.). At least one historical
locale in the southern Washington Cascades was destroyed by this
practice in 1997 or 1998 (Potter et al. 1999, p. 11). Military training
activities at Joint Base Lewis-McChord have also resulted in damage to
mardon skipper habitat (Potter et al. 1999, p. 12), but the majority of
the prairie habitat at this site is protected from vehicle damage due
to the presence of unexploded ordnance (Stinson 2005, p. 12). Over the
past 10 years, Federal land managers have installed access barriers
(e.g., placement of road-side boulders, gates, or exclosures) and
posted educational signs in attempts to reduce illegal off-road
vehicles and other recreational uses at almost all mardon skipper sites
where these problems have been noted (Kogut 2008, p. 8). These measures
have substantially reduced these threats on Federal lands, which
constitutes the majority of the range occupied by the species.
Therefore, habitat loss associated with off-road vehicles and
recreation is not a significant concern for the mardon skipper at the
species level at this time, nor is it likely to become so. In addition,
we have no information to indicate that it has a significant impact on
the subspecies Polites mardon mardon.
Discussion specific to Polites mardon klamathensis:
Management plans developed for Polites mardon klamathensis sites on
BLM lands identified off-road vehicle use and recreation (camping)
within meadows as a potential threat at several sites (Black et al.
2010, pp. 21-61). In 2011, both BLM staff at Medford District and
Forest Service staff on the Rogue River-Siskiyou National Forest
implemented a number of projects to reduce these impacts at P.m.
klamathensis sites through the strategic placement of boulders to block
vehicle access, and by posting signs at most of the sites identified
for this work (MSWG 2011, in litt.). These measures are expected to
substantially reduce any potential impacts from off-road vehicles and
other recreational uses.
Summary: Off-road vehicles and other recreational activities have
historically resulted in minor habitat losses and degradation at a
number of sites across the range of the mardon skipper. However, this
threat has been substantially reduced on Federal lands
[[Page 54345]]
where the majority of these activities occur through the placement of
access barriers and signs. Because private lands comprise an
insubstantial portion of the species' range, we do not consider any
such activities on private lands, if they should occur, to pose a
threat to the mardon skipper. Therefore, habitat loss or degradation as
a consequence of off-road vehicles and other recreational uses is not
considered to be a threat at either the species or subspecies levels.
Summary of Factor A
In summary, the potential negative impacts to mardon skipper
habitat associated with forest succession, fire, invasive nonnative
plants, livestock grazing, and off-road vehicle use have been
substantially reduced or eliminated on Federal and State lands through
the development and implementation of conservation plans and habitat
restoration projects. Habitat degradation associated with intensive
livestock grazing continues to occur at a few sites, but grazing
impacts have been substantially reduced or eliminated at many key sites
across the species' range with recent closures of Federal grazing
allotments and the implementation of site-specific conservation plans
for the benefit of the mardon skipper. Habitat degradation from off-
road vehicle use has been reduced or eliminated at many sites by
installing vehicle barriers or closing roads. Meadow habitat
restoration activities (prescribed burning, herbicide treatments) can
be lethal to mardon skippers, but careful planning and implementation
of habitat restoration projects designed with these concerns in mind
have minimized the risks associated with these positive efforts for
skipper conservation. Because the vast majority of mardon skipper sites
are found on Federal or State lands, and most of the sites that are
found on private lands are subpopulations of larger populations on
Federal lands, we do not consider habitat degradation that may occur on
private lands to pose a threat to the mardon skipper. Based on these
ongoing conservation actions on Federal and State lands, we do not
consider Factor A, the present or threatened destruction, modification,
or curtailment of its habitat or range, to pose a threat to the mardon
skipper as a species now or in the future, nor do we have any
information to indicate that it is a threat to either subspecies
Polites mardon mardon or Polites mardon klamathensis, now or in the
future.
Factor B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
Insect collecting is a valuable component of research, including
systematics work, and is often necessary for documenting the existence
of populations (Potter et al. 1999, p. 14). Rare butterflies, such as
the mardon skipper, could be potentially desirable. Most mardon skipper
populations are easily accessible and could be vulnerable to collectors
(Potter et al. 1999, p.14). However, we currently have no information
indicating that mardon skipper populations at either the species or
subspecies level have been negatively affected by collection or
scientific research activities (Kerwin 2011, p. 26), and therefore have
determined that overutilization for commercial, recreational,
scientific, or educational purposes is not a threat to the mardon
skipper at the species or subspecies level now or in the future.
Factor C. Disease or Predation
Disease and predation are usually naturally occurring factors that
may pose a heightened threat to populations that are vulnerable due to
other factors, but no specific examples are known for the mardon
skipper. Predatory insects (ants, wasps, spiders, etc.) commonly prey
on butterfly eggs, larvae, and pupae (Scott, 1986, p. 70), but no
studies have specifically researched this aspect of mardon skipper
ecology. At Puget Prairie sites, mardon skipper larvae were found only
in the smallest tufts of bunchgrass, while potential larval predators
(spiders, ants) were commonly observed in larger clumps of bunchgrass
(Henry 2010, p. 18). The author suggests that larval survival rates
from predation are likely influenced by the fine-scale structure of
individual host plants and the density of vegetation surrounding host
plants, but acknowledged that more research is needed to understand how
these factors influence mardon skipper survival rates (Henry 2010, p.
18). We currently have no information indicating mardon skipper
populations have been negatively affected by disease or predation
outside the normal range of variability; therefore, we do not consider
disease or predation to pose a threat to the mardon skipper at the
species or subspecies levels.
Factor D. The Inadequacy of Existing Regulatory Mechanisms
State Laws
The mardon skipper is listed as an endangered species in the State
of Washington by the Washington Fish and Wildlife Commission
(Washington Administrative Codes 232-12-014, Endangered Species; 232-
12-011, Threatened Species, Appendix D). This designation provides
protection from directly harming the species (e.g., collecting) (Black
et al. 2002, p. 19).
State regulatory mechanisms in the States of Oregon and California
do not apply to the mardon skipper, as Oregon`s State Endangered
Species Act does not cover invertebrate species, and California's State
Endangered Species Act does not apply to insects.
We have no information to indicate that the inadequacy of existing
State regulatory mechanisms may pose a threat to the mardon skipper,
rangewide or at the subspecies level.
Special Status Species Policies on National Forest and BLM Lands
As discussed above under ``Conservation Measures,'' the mardon
skipper is listed as a Sensitive Species by the U.S. Forest Service in
Washington, Oregon (Forest Service Region 6), and California (Forest
Service Region 5) and as a Special Status Species by the Bureau of Land
Management (BLM) in Oregon and Washington. We have no information to
indicate that the inadequacy of existing Federal regulatory mechanisms
may pose a threat to the mardon skipper, rangewide or at the subspecies
level.
Summary of the Inadequacy of Existing Regulatory Mechanisms
When the mardon skipper was originally identified as a Federal
candidate in 1999, the species had no protection mechanisms under the
auspices of either State or Federal agencies. Since that time, both
Federal and State land managers have developed conservation plans and
policies that provide a high level of protection for the species.
Existing laws and regulations do not protect mardon skipper habitats
where they occur on private land. However, there are few mardon skipper
populations known to occur on private lands. The majority of the
species' occurrences are on Federal or State lands where the species is
assured a high level of protection through its recognition as a
Sensitive Species or Special Status Species (Federal lands) or through
State Conservation Plans (California, Oregon, and Washington). We did
not identify any threats to the mardon skipper at either the species or
subspecies levels that existing regulatory mechanisms have failed to
address. Therefore, we have no information to indicate that the
inadequacy of existing regulatory mechanisms is a threat to the mardon
[[Page 54346]]
skipper at either the species or subspecies levels.
Factor E. Other Natural or Manmade Factors Affecting Its Continued
Existence
Application of Pesticides and Herbicides
Aerial applications of pesticide pose a potential threat to mardon
skippers. The lepidopteran-specific insecticide, Bacillus thuringiensis
var. kurstaki (Btk), has been aerially applied to control the Asian
gypsy moth (Lymantria dispar) in the Puget Sound region, and in the
Washington Cascades to control spruce budworm (Choristoneura
occidentalis) (Potter et al. 1999, p. 13). Although grasslands are not
targeted for application, small meadows may receive aerial applications
due to the location of these habitats within the wooded target area or
from aerial drift. Drift from aerial applications can be lethal to non
target butterflies up to 1.8 miles (3 km) away from the target area in
steep, mountainous terrain (Whaley et al. 1998, p. 539). Lepidoptera,
such as the mardon skipper, that are single-brooded, spring-active
species with caterpillars actively feeding during the application
period of Btk are especially vulnerable (Wagner and Miller 1995, p.
21).
Several of the southern Washington Cascade mardon skipper sites are
located in areas where widespread applications of Btk were used on
State, tribal, and private lands to control spruce budworm outbreaks in
the late 1990s (Potter et al. 1999, p. 13). Btk application is
implicated in the local decline of at least one mardon skipper
population on non-Federal lands from 1998 to 2000 (Potter and
Fleckenstein 2001, pp. 7-8). The use of Btk has diminished in the
southern Cascades over the past decade as spruce budworm populations
have declined. There have been no reported applications of Btk on
Federal lands in close proximity to mardon skipper sites. The risks
associated with Btk application can be greatly reduced with adequate
buffers to avoid pesticide drift into sensitive habitats (Black et al.
2010, p. 19). Although Btk application poses a potential threat to
mardon skipper populations, we are not aware of any Btk applications
over the past 10 years that would have had the potential to affect
mardon skipper populations. The aerial application of pesticides
remains a potential threat, but any local application of lepidopteran-
specific pesticides on Federal lands will be subject to environmental
review consistent with National Environmental Policy Act procedures,
and existing special status/sensitive species policies of the Forest
Service and BLM are likely to provide for a high level of protection.
Herbicides are commonly used to manage mardon skipper habitat and
control invasive nonnative plants in south Puget Sound prairies
(Schultz et al. 2011, p. 373); and have been used at mardon skipper
sites on the Gifford Pinchot National Forest. Herbicide use may affect
mardon skippers by damaging larval or adult food sources, or through
the direct ingestion of a toxic substance. Loss of non target plants
can be avoided by using grass-specific herbicides, such as sethoxydim,
which has been used effectively to control invasive grasses such as
tall oatgrass, while having minimal impacts on native bunchgrasses and
forbs (Schultz et al. 2011, p. 373).
There are currently dozens of herbicide formulations that are
available for general use. The toxicity of an herbicide to butterflies
varies from non toxic to potentially lethal depending upon the
compounds used. All herbicides are required to be tested on honeybees
(Apis spp.) as part of registration requirements (USFS 2005, p. 252),
but there are relatively few studies that evaluate the effects of
herbicides on butterflies (Russell and Schultz 2010, p. 53). One study
with the Karner blue butterfly (Lycaeides melissa samuelis) found that
direct applications of some herbicide compounds with glyphosate had no
apparent effect on egg survival and larval development (Sucoff et al.
2001, p. 18). However, treatments with a glyphosate-triclopyr mix did
significantly lower egg hatching rates (Sucoff, et al. 2001, p. 18).
Use of the grass-specific herbicide compounds sethoxydim or fluazifop-
p-butyl with the non-ionic surfactant Preference can stress
butterflies, resulting in reduced survival and increased rates of
development from larvae to adult, as well as decreased wing area in
some species of butterflies (Russell and Schultz 2010, p. 53). Stark
and others (2012, pp. 26-27) found that Behr's metalmark butterfly
(Apodemia virgulti) exposed to field rates of triclopyr, sethoxydim,
and imazapyr reduced the number of adults that emerged from pupation,
perhaps due to effects from inert ingredients or indirect effects on
food plant quality. These studies indicate that direct applications of
herbicides can result in reduced survival in some butterfly species,
emphasizing the need for careful management using selective
applications in habitats occupied by mardon skippers.
Herbicides are recognized as an important tool for managing
invasive plants and maintaining habitat for butterflies. Potential
adverse effects of herbicides to mardon skippers can be minimized
through selective applications. Federal and State land managers
currently using herbicides to manage invasive plants at mardon skipper
sites are using best management practices to minimize effects to non
target plant species and to butterflies (Hays 2010, p. 1; USFS 2008, p.
57). These methods include using selective herbicide treatments and
only treating a small portion of the habitat area within the site in
any given year (USFS 2008, p. 57; Schultz et al. 2011, p. 373). We
expect Federal and State land managers will continue to manage sites to
control invasive weeds and to do so in a way that improves habitat for
the mardon skipper, while minimizing impacts to local populations as
outlined in the revised Forest Service/BLM Conservation Assessment for
the Mardon Skipper (Kerwin 2011, pp. 30-33), and in site-specific plans
such as those developed on the Gifford Pinchot National Forest (USFS
2008, p. 57). Based on this information, we do not consider the use of
herbicides to be a threat to mardon skipper at either the species level
or subspecies levels.
Summary: The widespread application of pesticides and herbicides
may affect the mardon skipper and its habitat. However, there are no
documented instances of Btk applications occurring on Federal lands in
close proximity to mardon skipper sites. Further, Federal and State
land managers have successfully used herbicides to restore and maintain
mardon skipper habitat at a number of sites in Washington. Based on
this information, we do not consider the use of pesticides or
herbicides to be a threat to the species or either subspecies.
Climate Change
Over the next century, climate change at global and regional scales
is predicted to result in changes in butterfly species distributions
and altered life histories (McLaughlin et al. 2002, p. 6074; Hill et
al. 2002, p. 2163; Singer and Parmesan 2010, p. 3161). Rare
butterflies, including the mardon skipper, may be vulnerable to climate
change, as their populations are often fragmented due to habitat losses
that restrict the species' ability to adapt to changing environmental
conditions (Schultz et al. 2011, p. 375). Likewise, butterflies with
limited dispersal capability, such as the mardon skipper, may be
vulnerable to climate change if suitable alternative
[[Page 54347]]
habitats are not located within the dispersal distance for the species.
Changes in regional climate can benefit some butterfly species. The
habitat-generalist Sachem skipper (Atalopedes campestris) has expanded
its range more than 435 mi (700 km) northward from California into
central Washington in the last 50 years (Crozier 2004, p. 231).
Crozier's (2004, p. 231) study suggested that the range expansion has
been due to a warming trend, and each step in the range expansion
coincided with warmer winters (which affects larval survival rates).
Similarly, populations of the silver-spotted skipper (Hesperia comma)
in southern England have increased over the past 20 years, due in part
to warmer summer temperatures, which have increased the availability of
thermally suitable habitats for the species (Davies et al. 2006, p.
247). Recent butterfly range expansions linked to climate change are
generally limited to highly mobile, habitat-generalist species, while
many habitat-specialist butterfly species have declined due to complex
interactions of climate, habitat loss, and fragmentation (Warren et al.
2001, p. 65; Hill et al. 2002, p. 2170).
In the Pacific Northwest, mean annual temperatures rose 0.8
[deg]Celsius ([deg] C) (1.5 [deg]Fahrenheit ([deg] F)) in the 20th
century and are expected to continue to warm from 0.1 to 0.6 [deg]C
(0.2 to 1 [deg]F) per decade (Mote and Salathe 2010, p. 29). Global
climate models project an increase of 1 to 2 percent in annual average
precipitation, with some models predicting wetter autumns and winters
with drier summers (Mote and Salathe 2010, p. 29). Regional models of
potential climate changes are much more variable, but the models
generally indicate a warming trend in mean annual temperature, reduced
snowpack, and increased frequency of extreme weather events (Salathe et
al. 2010, pp. 72-73). Downscaled regional climate models, such as those
presented by https://www.climatewizard.org have tremendous variation in
projections for annual changes in temperature or precipitation
depending upon the climate model or scenario. Averaged values across
large areas generally indicate a general warming trend in mean annual
temperature consistent with the climate projections reported by Salathe
and others (2010, pp. 72-73).
Predicted climate changes in the Pacific Northwest have
implications for forest disturbances that are important for maintaining
montane meadow habitats. Both the frequency and intensity of wildfires
and mountain pine beetle (Dendroctonus ponderosae) outbreaks are
expected to increase over the next century in the Pacific Northwest
(Littell et al. 2010, p. 130). The gradual loss of montane meadow
habitats over the past century is linked to fire suppression and lack
of disturbance. One study in the Cascades found that the majority of
mesic meadow habitats that were historically burned (1880-1946) have
contracted over the past half century (Takaoka and Swanson 2008, p.
539). Increased fires over the next century are likely to result in
increased meadow habitat and improved connectivity between meadows
occupied by mardon skippers. Similarly, mountain pine beetle outbreaks
can result in the widespread mortality of lodgepole pine trees, a
common tree species that is invading meadow habitats at many mardon
skipper sites. Where invading trees are killed, marginal areas along
the edges of existing meadows are likely to revert rapidly back to
dominance by meadow species (Haugo et al. 2011, p. 17).
Climate change is also likely to affect the rate of conifer
succession in montane meadow habitats. A decrease in summer
precipitation and soil moisture may reduce the rate of conifer
encroachment in montane meadows at mesic sites (Haugo et al. 2011, p.
17), which may prove beneficial to mardon skippers by increasing
available meadow habitats. Increased wildfire or insect disturbances
associated with climate change are likely to have beneficial effects
for mardon skippers due to increases in early seral habitat, although
large wildfires also pose a risk to mardon skippers if all occupied
habitat in a local area is burned. Because wildfires typically result
in a mosaic of burned and unburned areas, it is unlikely that increased
incidence of wildfires associated with climate change would result in
the loss of multiple populations across large areas within the species'
or subspecies' range.
How mardon skipper populations will respond to future climate
change is unknown. There are no retrospective studies for the species
that have examined how annual weather patterns such as annual or
seasonal precipitation, snowpack, and temperature have influenced
mardon skipper populations from year to year. We do know that prolonged
periods of cool, wet weather during the spring or summer months can
delay adult emergence and reduce the abundance of mardon skippers.
Because the mardon skipper at the species level is distributed across a
broad range of elevations and habitat types, and has documented use of
several host-plant species, it may not be as vulnerable to climate
change as some other narrowly distributed butterfly species. In the
Washington Cascades the majority of mardon skipper sites occur in the
mid-elevation montane zone, where there is a potential for upslope
movement and colonization of higher elevation habitats in response to
climate change over time. Based on the above information, we do not
have data to suggest that climate change poses a threat to the species
Polites mardon, or the subspecies Polites mardon mardon.
Discussion specific to Polites mardon klamathensis
Populations of Polites mardon klamathensis may be vulnerable to the
effects of climate change due to the subspecies' limited distribution,
apparently smaller populations, and limited dispersal capability. All
P.m. klamathensis sites are located in the high-elevation montane zone
of the southern Oregon Cascades, where there is little potential for
upslope movement or colonization of higher elevation habitats in
response to climate change over time. Regional models of potential
climate changes in the Pacific Northwest are variable, but the models
generally indicate a warming trend in mean temperature, reduced
snowpack, and increased frequency of extreme weather events (Salathe et
al. 2010, pp. 72-73). All P.m. klamathensis sites are associated with
mesic soils and permanent or ephemeral water sources (Black et al.
2010, p. 12).
Black et al. (2010, p. 60) notes that habitat within portions of
the meadow complex are marginal for P.m. klamathensis because the sites
are currently too dry, but the habitat may have been wetter in the
past. Runquist (2004a, p. 5) observed over 200 skippers at this complex
in 2002. Although multi day surveys have not been completed here, the
population at this meadow complex appears to have declined (Black et
al. 2010, pp. 60-61).
Given the restricted distribution of P.m. klamathensis, and the
strong association of the subspecies with mesic sites, a projected
warming trend in regional climate is a potential concern for P.m.
klamathensis, depending on the changes in the environment that may
manifest as a result. We acknowledge this concern and the need for
monitoring of these populations in the face of climate change. However,
at the present time, due to the multiple uncertainties associated with
regional climate models, the actual changes that may be realized and
how they would impact the species, the timeframes involved, and the
questions surrounding P.m. klamathensis abundance information, we can
not conclude that
[[Page 54348]]
climate change is a threat to P.m. klamathensis or likely to become so.
Summary: Because the mardon skipper is distributed across a range
of elevations and habitat types, and has documented use of several
host-plant species, it may not be as vulnerable to climate change as
some other narrowly distributed species. Despite the potential for
future climate change in the Pacific Northwest as discussed above, we
have not identified, nor are we aware of, any data on an appropriate
scale to evaluate habitat or population trends for the mardon skipper
or to make reliable predictions about future trends and whether the
species will be significantly impacted. Due to the uncertainty
associated with regional climate models and how any potential
environmental changes may possibly impact the species, we conclude that
climate change is not a threat to mardon skippers at the species or
subspecies levels or likely to become so.
Stochastic Weather Events and Small, Isolated Populations
Adverse weather (freezing temperatures, heavy rain events, or
prolonged drought) can extirpate local butterfly populations by killing
adults, larvae, or larval food plants (Guppy and Shephard 2001, p. 59).
Even large populations of butterflies (greater than 5,000 individuals)
can rapidly decline in response to successive seasons of unfavorable
weather conditions during reproduction and larval development (Ehrlich
et al. 1980, pp. 102-103). The decline in mardon skipper numbers at
some Washington Cascades sites in 2009 is an example of how variations
in seasonal weather can have a profound effect on local mardon skipper
populations. The exact weather event that caused the decline is
unknown, but unseasonably warm weather in May and June caused a rapid
snowmelt to occur in these high-elevation meadows, followed by at least
4 days of freezing temperatures in late June during the period when
mardon skipper adults typically emerge (Kogut 2009, p. 1). The adult
flight period in 2009 occurred later, in mid-July, and was very brief,
and the total numbers of adults were approximately 80 to 95 percent
less than what had typically been counted at these sites during the
previous 6 years (Kogut 2009, p. 1).
The weather effect was not limited to mardon skippers; other
butterfly species were also affected, including the closely related
Sonora skipper (Polites sonora), which was apparently absent from all
sites where the species commonly co-occurs with mardon skippers at
Cowlitz Valley (Kogut 2009, p. 1). The apparent weather-related effect
was also noted at sites on the adjacent Wenatchee-Okanogan National
Forest, where the emergence of adults occurred later, and the adult
flight period was shorter than in previous years (St. Hilaire et al.
2009, p. 2), although the effect to the populations was not as severe
as that seen on the Gifford Pinchot National Forest. Populations at
lower elevation sites did not appear to be affected by these same
weather events (St. Hilaire et al. 2009, p. 3). Subsequent years (2010
and 2011) have generally been cool and wet during the mardon skipper
flight season, so the populations at the Cowlitz Valley sites have not
recovered and have continued to gradually decline since 2009, but
populations at other locations in the Washington Cascades have not
shown a similar pattern of decline and are apparently stable. It is
evident that adverse weather conditions can profoundly impact local
mardon skipper populations. Because the species occurs across a broad
range of elevations and habitat types, it is unlikely that a stochastic
weather event is likely to affect all populations simultaneously.
Butterfly populations with very low numbers of individuals (e.g.,
fewer than 20 butterflies) are vulnerable to extirpation from random
events such as inclement weather, wildfire, or other potential threats
identified above (e.g., Schtickzelle et al. 2005, p. 578). There are a
number of studies that demonstrate that habitat patch size, local
population size, and proximity to adjacent populations have important
implications for the long-term persistence of butterfly populations
with limited dispersal capabilities (e.g., Thomas and Jones, 1993, p.
472; Hanski et al. 1995, p. 618; Saccheri et al. 1998, p. 492; Maes et
al. 2004, pp. 234-235). Studies that examined butterfly population
dynamics generally define ``small'' populations as having fewer than
500 adults and ``very small'' as having fewer than 100 adults at peak
emergence (e.g., Maes et al. 2004, p. 232; Davies et al. 2005, p. 192).
(As described below, for mardon skippers, counts of at least 100
individuals are generally considered to be large). Extremely small
butterfly populations (fewer than 20 individuals) are not only highly
vulnerable to environmental factors such as adverse weather conditions
(Schtickzelle et al. 2005, p. 578), but such small populations are also
at increased risk of extinction due to genetic effects associated with
inbreeding (Saccheri et al. 1998, p. 491; Nieminen et al. 2001, p.
243). Inbreeding in small populations of the Glanville fritillary
butterfly (Melitaea cinxia) resulted in reduced egg hatching rates,
larval survival, and adult longevity (Nieminen et al. 2001, p. 243).
Long-term studies of the silver-spotted skipper (Hesperia comma) in
England have documented a series of local population extinctions and
colonizations over a 20-year period (Thomas and Jones 1993, p. 472;
Davies et al. 2005, p. 189). These studies found that large habitat
patches tended to support large populations of skippers, and that no
extinctions occurred in habitat patches that supported populations of
greater than 225 individuals; sites with 10 populations of fewer than
225 skippers, however, went extinct and the probability of extinction
increased with isolation from the nearest population (Thomas and Jones
1993, pp. 476-478). Populations of silver-spotted skipper have expanded
in recent years, and most of the sites that had documented extinctions
in 1991 have subsequently been recolonized by dispersing individuals
from adjacent sites (Davies et al. 2005, p. 195).
Most populations of mardon skippers consist of a series of one or
more occupied meadows located within close proximity to each other.
These populations or local ``clusters'' of sites likely function as
small metapopulations with some dispersal of individuals between local
sites (Kerwin 2011, pp. 21-23). Mardon skipper ``metapopulations''
likely experience local site-scale extinctions and recolonizations as
local populations expand and contract in response to changing climate
or habitat conditions, such as with the silver-spotted skipper in
England (Davies et al. 2005, p. 195), although on a smaller scale, as
silver-spotted skippers likely have greater dispersal capability than
mardon skippers (Kerwin 2011, p. 23). However, there is strong evidence
that mardon skippers exhibit similar metapopulation dynamics. The large
number of mardon skipper sites in the Washington Cascades that are
located in young clearcuts or roadside areas that were previously
forested demonstrate that the species is capable of dispersing away
from their core habitats and colonizing adjacent early-seral habitats
that support host grasses and forbs (e.g., Kerwin 2011, p. 14).
Mardon skippers can be locally abundant where the species is
present (Pyle 1989, p. 28) with single-day counts of greater than 100
individuals documented at many sites across the species' entire
geographic range (for the mardon skipper, populations in the hundreds
are relatively large) (Black et al. 2010, pp. 70-71; St. Hilaire et al.
[[Page 54349]]
2010, pp.10-12; Black et al. 2011, p. 13). Conversely, there are a
number of apparently very small populations within the species' range
with peak counts of fewer than 20 individuals. Because the number of
mardon skippers present at a site can vary tremendously over the course
of a few days (Beyer and Black 2007, p. 8), and the timing of the
flight period can vary due to a variety of conditions, including
elevation and weather conditions, there is little certainty of actual
population sizes associated with these individual day counts. A single
day, peak count of 100 skippers potentially represents a total
population of more than 200 skippers based on observations during an
experimental mark-recapture study (Runquist 2004a, p. 5), because not
all butterflies emerge on the same date, and not all butterflies
present at a site are likely to be counted during a survey.
Since 1999, mardon skippers have been documented at approximately
165 sites across the species' range. Considering that local clusters of
sites likely function as small metapopulations, there are approximately
66 populations of mardon skippers currently known, and, with the
exception of the Puget prairies, it is likely that there are additional
undocumented populations present in all portions of the species' range
because not all suitable habitats have been searched for mardon
skippers (Kerwin 2011, p. 18). Each region within the species' range
supports one or more ``large'' populations of mardon skippers (in the
case of the mardon skipper, ``large'' is defined as single-day counts
of more than 100 individuals, which likely represents a much larger
total population).
All extant Puget prairie sites likely support total populations
from more than 100 up to 1,000 individuals (Schultz et al. 2011, p.
370). The largest mardon skipper populations occur in the Washington
Cascades, with at least 2 populations of greater than 1,000
individuals, and at least 11 other populations that have supported
populations from 100 to 400 skippers over the past decade (unpublished
data). In the Oregon Cascades, there are 2 populations that number from
100 to 300 individuals, and in the coastal areas of northwest
California/southwestern Oregon, there are at least 3 populations with
more than 100 individuals. In total, at least 22 of the approximately
66 populations rangewide support large populations of mardon skippers,
and these sites represent the majority of the species' total
populations.
Conversely, there are many individual ``sites'' with single-day
counts of fewer than 20 individuals. Most of these sites are closely
associated with larger local populations. A few sites may represent
small, isolated populations that are vulnerable to local extirpation
associated with stochastic weather events, but these generally
represent only a small portion of the total species' populations.
Because the mardon skipper has presumably limited dispersal
capabilities, if an isolated population were to become extirpated, some
isolated sites are unlikely to be reestablished due to long distances
or physical barriers (e.g., extensive forested areas) between extant
populations (Kerwin 2011, p. 23).
The mardon skipper is a naturally rare species across its disjunct
range. Given the limited information concerning mardon skipper
population trends rangewide, and the presence of multiple ``large''
populations in each distinct region within the species range, the
majority of the species' total populations appear to be relatively
secure from threats associated with small populations.
Discussion specific to Polites mardon klamathensis:
The distribution of Polites mardon klamathensis appears to be
restricted to 22 sites likely representing approximately 11 populations
in the southern Oregon Cascades. Surveys in recent years have searched
over 200 sites in the vicinity of these known populations and have
failed to detect the species, indicating the subspecies is highly
restricted in its distribution to a few small meadow complexes within a
small geographic area (Black et al. 2010, p. 7). However, one small
site was documented on Bureau of Reclamation lands managed by BLM in
2011 (Black 2012, pers. comm.), indicating it is possible that
additional undocumented P.m. klamathensis sites may exist in the area.
Although populations of P.m. klamathensis appear to be relatively
small, it is difficult to draw any reliable conclusions on population
sizes based on the limited data available, since the majority of sites
have only been visited once during the flight season in recent years
(Black et al. 2010, pp. 70-72). Additional multiple-day surveys are
needed to confirm if populations are as small as they appear based on
the limited survey data collected thus far, or whether past single-day
counts may have just missed the peak flight period. As discussed
earlier, due to the variability of mardon flight periods between sites
and years, as well as extreme fluctuations in numbers of individuals
that may be present from day to day, a single-day survey in a year is
insufficient to indicate trends or abundance.
In summary, total population sizes at all Polites mardon
klamathensis sites are unknown due to limited surveys, although counts
at most sites indicate that populations of this subspecies may be
relatively small. Unfortunately the high variability in potential
counts from day to day for this subspecies undermines the credibility
of any single-day counts for the purpose of determining population
status or trend, and raises questions as to whether counts of zero or
few individuals on any one day accurately reflect population numbers or
abundance. Based on the lack of historical abundance information and
the uncertainty accompanying the numbers of individuals associated with
individual day counts, we do not have reliable information to suggest
that P.m. klamathensis is such a small isolated population that
stochastic weather events would pose a significant threat to the
subspecies as a whole.
Summary: Prolonged periods of cool wet weather during the spring
and summer months are known to negatively affect mardon skipper
populations. Small butterfly populations are particularly vulnerable to
these effects. Given the limited information concerning mardon skipper
population trends rangewide, and the presence of multiple ``large''
populations in each distinct region within the species' range, the
majority of the species' total populations and those of the subspecies
Polites mardon mardon appear to be relatively secure from threats
associated with small populations. Additionally, due to the limited
population and abundance information we have for the the subspecies
Polites mardon klamathensis, we conclude that we do not have reliable
information to indicate that populations of this subspecies are so
small or isolated as to represent a threat to P.m. klamathensis as a
whole.
Finding
As required by the Act, we considered the five factors in assessing
whether the mardon skipper is a threatened or endangered species
throughout all of its range. We additionally considered whether either
of the two recognized subspecies comprising the species mardon skipper
may be a threatened or endangered species throughout all or a
significant portion of their ranges. We examined the best scientific
and commercial information available regarding the past, present, and
future threats faced by the mardon skipper and its subspecies. We
reviewed the petition, information available in our
[[Page 54350]]
files, other available published and unpublished information, and
consulted with recognized mardon skipper experts and other Federal,
State, and tribal agencies.
The Species Mardon Skipper (Polites mardon)
The mardon skipper is a little-studied species; however, the
species has received considerable attention and funding for surveys
since becoming a Federal candidate species in 1999. The number of
documented locations of mardon skippers has expanded from fewer than 10
in 1998 to 165 in 2011; this increase in known occurrences of the
species is largely due to increased survey effort. Since 1999, new site
locations have been documented each year that targeted surveys have
been conducted. In the past 5 years, significant new populations have
been located in the Washington Cascades and in coastal areas of Oregon
and California, with local sites supporting populations of hundreds of
mardon skippers. It is likely that there are additional, undocumented
populations, particularly in the Washington Cascades, and possibly in
southwestern Oregon and northern California because not all available
habitat for the species has yet been surveyed. The majority of the
sites throughout the species' range occur on Federal lands managed by
the Forest Service, Bureau of Land Management, National Park Service,
Fish and Wildlife Service, and the Department of Defense (76 percent).
Current management actions, policies, and protections associated
with State and Federal special-status-species programs now afford the
species a high level of security from habitat loss or destruction
across the species' range. Potential threats to mardon skipper habitat
associated with forest succession, fire, invasive nonnative plants,
livestock grazing, and off-road vehicle use have been substantially
reduced or eliminated on State and Federal lands through the
development of conservations plans and implementation of habitat
restoration projects. Habitat degradation associated with intensive
livestock grazing continues to occur at some sites, but grazing impacts
have been substantially reduced or eliminated at many key sites across
the species' range with recent closures of Federal grazing allotments.
Habitat degradation from off-road vehicle use has been reduced or
eliminated at many sites by installing vehicle barriers or closing
roads. Meadow habitat restoration activities (prescribed burning,
herbicide treatments) can be lethal to mardon skippers if not conducted
properly, but these risks have been minimized through careful planning
and implementation of habitat restoration projects. Ongoing threats
that are not currently addressed by existing conservation plans include
potential habitat loss on private lands, but there are relatively few
known mardon skipper sites on private lands. Climate change may affect
the mardon skipper and its habitat. Because the mardon skipper is
distributed across a range of elevations and habitat types, and has
documented use of multiple host-plant species, it may not be as
vulnerable to climate change as some other more narrowly distributed
specialist species.
Based on our review of the best available scientific and commercial
information pertaining to the five factors, we find that the threats
are not so severe or broad in scope as to indicate that the mardon
skipper is in danger of extinction (endangered), or likely to become
endangered within the foreseeable future (threatened), throughout all
of its range. Therefore, we find that the mardon skipper does not meet
the definition of an endangered or threatened species throughout its
range.
The mardon skipper is listed as endangered by the State of
Washington. Washington's listing of the mardon skipper was based on a
status assessment of the species conducted in 1999 (Potter 1999), and
relied on much of the same information that the Service considered in
placing the mardon skipper on the candidate list that same year. A
substantial amount of new information has become available since that
time, however, which we have evaluated in making the present finding.
Although the State of Washington has updated information on new
population data and conservation efforts for the mardon skipper in
their annual reports, they have not reconsidered the listed status of
the species based on this information. Our analysis of the best
available information considers the many positive conservation measures
that have been implemented by both Federal and State agencies
throughout the range of the mardon skipper, including actions by the
State of Washington, to recover the species and ameliorate the threats
that initially led to its State listing and Federal candidacy 13 years
ago. In addition, we considered the numerous additional populations of
the species (and subspecies) that have been documented since the mardon
skipper first became a Federal candidate and was listed by the State.
Our current evaluation of the best available information according to
the Federal Endangered Species Act, as detailed in this finding, does
not lead us to conclude that the mardon skipper meets the definition of
an endangered species or threatened species throughout all or a
significant portion of its range.
The Subspecies Polites mardon mardon and Polites mardon
klamathensis
Polites mardon mardon
Polites mardon mardon faces the same threats as discussed in the
rangewide evaluation previously, and we consider all conclusions
reached regarding the degree of threat for the species as a whole to
apply equally to the subspecies P. m. mardon. As a result, we find that
this subspecies does not meet the definition of an endangered or
threatened species throughout its range.
Polites mardon klamathensis
Polites mardon klamathensis faces the same threats as discussed in
the rangewide evaluation previously; however, where relevant we have
assessed threats specific or unique to the subspecies Polites mardon
klamathensis separately throughout the rangewide evaluation. In
general, we consider all conclusions reached regarding the degree of
threat for the species as a whole to apply equally to the subspecies P.
m klamathensis. As a result, we find that this subspecies does not meet
the definition of an endangered or threatened species throughout its
range.
Significant Portion of the Range
Having determined that the species Polites mardon and the
subspecies Polites mardon. mardon and Polites mardon klamathensis do
not meet the definition of a threatened or endangered species, we next
consider whether there are any significant portions of the range where
the mardon skipper is in danger of extinction or is likely to become in
danger of extinction in the foreseeable future.
In determining whether a species is a threatened or endangered
species in a 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) meeting the definition of a threatened or
endangered species. To identify only those portions that warrant
further consideration, we
[[Page 54351]]
determine whether there is substantial information indicating 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.
Applying the process described above for determining whether a
species is threatened or endangered in a significant portion of its
range, we considered the status question first to determine if any
threats or potential threats acting individually or collectively
threaten or endanger the species in some portion of its range. In
analyzing the status of the mardon skipper across its range, the only
area we identified where threats may be concentrated is the Puget
prairies. We therefore considered whether the threats to the Puget
prairie populations of Polites mardon or Polites mardon mardon are such
that the species may be in danger of extinction there, now or within
the foreseeable future, such that the Puget prairie populations may
warrant further consideration as a potential significant portion of the
range.
Although the rangewide mardon skipper population is relatively
secure under current conditions, the Puget prairies represent the only
portion of the species' historical and current distribution where there
are confirmed extirpations of historical populations, and we can
reasonably infer that the species' range has contracted due to the
historical loss of Puget prairie habitat over the past century. We
therefore considered the likely future condition of the Puget prairie
populations under the presently observed rates of population change.
Historically, mardon skippers were known to be present at eight Puget
prairie sites, and are currently restricted to three known populations.
The trends of the remaining populations are unknown due to limited and
inconsistent monitoring data, but appear to have been relatively stable
over the past decade, with 2 populations estimated to consist of
hundreds of mardon skippers, and 1 population with likely over 1,000
skippers (Schultz et al. 2011, p. 370). Puget prairie sites with extant
populations of mardon skippers are protected from further development
through either State or Federal ownership. Mardon skipper habitat at
these sites is: (1) Actively being managed to restore and maintain
mardon skippers and other prairie species; or (2) at Joint Base Lewis-
McChord being maintained by regular wildfires, and large areas of
habitat are protected from development, off-road vehicle use, and
military training due to the presence of unexploded ordnance. In
addition, Joint Base Lewis-McChord is cooperating in an interagency
effort to restore and maintain prairie habitats for the mardon skipper
and other prairie species, discussed below.
Remaining prairie habitats in the south Puget Sound region are
relatively small, isolated patches with little potential connectivity
between patches (Schultz et al. 2011, p. 371). Because of this,
historical prairie sites where mardon skippers have been extirpated are
unlikely to be recolonized due to isolation from extant populations
(Schultz et al. 2011, p. 371). There are a number of small prairie
sites in the region that are currently in protected status and are
actively being managed to maintain butterfly habitats that may serve as
potential future reintroduction sites for mardon skippers (Anderson
2008, p. 2; Henry 2010, pp. 3-4). Beginning in 2007, the Joint Base
Lewis-McChord Army Compatible Use Buffer (ACUB) initiative has
supported the convening of a cooperative, interdisciplinary and
interagency Butterfly Habitat Enhancement Team to develop and implement
habitat improvements for mardon skipper and other rare butterflies on
formerly occupied sites off the military reservation (Anderson 2008, p.
1). This interagency team is a source of funding for mardon skipper
habitat management, population assessments, and mardon skipper life-
history research at Puget prairie sites. These projects continue to
maintain habitat and mardon skipper populations at the Scatter Creek
Wildlife Area. The ongoing management to maintain mardon skipper
populations and habitat at Puget prairie sites afford the species a
high level of protection against further losses of habitat or
populations. Because these conservation efforts have been implemented,
are effective, and are expected to continue, we consider the Puget
prairie population of the mardon skipper as not likely to become in
danger of extinction within the foreseeable future.
As the best available information indicates that the Puget prairie
population of mardon skipper at either the species or subspecies level
is not likely to become in danger of extinction within the foreseeable
future, we conclude that Puget prairie does not warrant further
consideration as a potential significant portion of the range at this
point in time. We did not identify any other potential significant
portions of the range of the mardon skipper (Polites mardon, Polites
mardon mardon, or Polites mardon klamathensis) that may meet the
definition of a threatened or endangered species.
In Defenders of Wildlife v. Norton, 258 F.3d 1136, 1145 (9th Cir.
2001), the court ruled that a species may be an endangered species in a
significant portion of its range ``if there are major geographical
areas in which it is no longer viable but once was.'' Where the area in
which the species is expected to survive is ``much smaller than its
historical range,'' the determination of whether the species warrants
listing turns on whether the lost portion of the range would be
significant. As discussed above, the Puget Prairie population of the
mardon skipper is the only portion of the species' range that is known
to have contracted from the historical distribution. We conclude that
current and future conservation efforts are expected to maintain mardon
skippers and restore the species to additional Puget prairie habitats.
Therefore, we have determined that neither the full species mardon
skipper, nor the subspecies Polites mardon mardon or Polites mardon
klamathensis, is an endangered or threatened species in a significant
portion of its range.
We do not find that the mardon skipper, or the subspecies Polites
mardon mardon or Polites mardon klamathensis, are in danger of
extinction now, nor are they likely to become in danger of extinction
within the foreseeable future throughout all or a significant portion
of their range. Therefore, listing the mardon skipper Polites mardon,
the subspecies P. m.
[[Page 54352]]
mardon, or the subspecies Polites mardon klamathensis, as a threatened
or endangered species under the Act is not warranted at this time.
We request that you submit any new information concerning the
status of, or threats to, the mardon skipper to our Washington Fish and
Wildlife Office (see ADDRESSES section) whenever it becomes available.
New information will help us monitor the mardon skipper and encourage
its conservation. If an emergency situation develops for the mardon
skipper or any other species, we will act to provide immediate
protection.
We will continue to monitor the condition of the mardon skipper
throughout its range. In the event that conditions or threats change
and the species becomes imperiled, we could again consider whether it
is appropriate to list the species as endangered or threatened under
the Act. We will continue to provide technical assistance to Federal,
State, and other entities and encourage them to address the
conservation needs of the mardon skipper. We will continue to work with
these agencies and entities to collect additional biological
information, monitor the status of the mardon skipper, and monitor the
progress of its conservation efforts.
References Cited
A complete list of references cited is available on the Internet at
https://www.regulations.gov and upon request from the Washington Fish
and Wildlife Office (see ADDRESSES section).
Author(s)
The primary authors of this notice are staff members of the
Washington Fish and Wildlife Office.
Authority
The authority for this section is section 4 of the Endangered
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).
Dated: August 20, 2012.
Benjamin N. Tuggle,
Acting Director, Fish and Wildlife Service.
[FR Doc. 2012-21344 Filed 8-31-12; 8:45 am]
BILLING CODE 4310-55-P
