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Daily Rules, Proposed Rules, and Notices of the Federal Government

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 subspeciesPolites mardon mardonandPolites 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 athttp://www.regulations.govat 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 (seeADDRESSES); 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. 1531et 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 theFederal 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 (Potteret 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 (Blacket 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 inre 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.

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 relatedPolitesspecies 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 (Potteret 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) asPamphila mardonfrom 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, Mattoonet al.(p. 768) proposed that the Oregon Cascade populations be given subspecies status asPolites mardon klamathensis,and the Washington and northern California populations be given subspecies status asPolites 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 (Mattoonet al.1998, pp.771-772).

The distinction betweenPolites mardon klamathensisandP.m. mardonwas 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 nameP.m. mardonfor California populations should be considered tentative because the series ofP.m. mardonfrom the northwestern California (and coastal southwestern Oregon) populations have not yet been carefully compared to the series ofP.m. mardonfrom Washington due to the small number of specimens available for evaluation (Mattoonet 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 mardonis recognized as a valid species by the Integrated Taxonomic Information System (ITIS) whileP.m. klamathensisandP.m. mardonare recognized as valid subspecies (ITIS 2011,P. mardon,entire). For the purposes of this finding, we first analyzed the threats to the speciesPolites mardonas a whole. We then, at our initiative, further considered the threats to each of the currently recognized subspecies:P.m. mardonandP.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 (Potteret al.1999, p. 3). No estimates of abundance are available from any site prior to 1980 (Potteret 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 betweenPolites mardon mardonandP. 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 (Potteret al.1999, p. 5, Beyer and Schultz 2010, p. 863; Schultzet 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., Blacket 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 (Potteret 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 southernOregon 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 subspeciesPolites mardon mardonandP.m. klamathensis,occurring within the species' range.

Table 1—Summary of known populations of the mardon skipper by subspecies. Multiple sites may be considered to comprise a single population, depending on proximity (see Note, below). Geographic region Site ownership Approximate number of documented sites with species presence
  • (2000-2011)
  • Approximate number of populations (local clusters of sites)
    Polites mardon mardon Washington—South Puget Sound Prairies (Pierce and Thurston Counties) Joint Base Lewis McChord—Dept. of Defense 4 1 Washington Dept. of Fish & Wildlife 2 2 Washington—South Cascades (Yakima, Klickitat, and Skamania Counties) Wenatchee National Forest
  • Gifford Pinchot National Forest
  • Conboy Lake National Wildlife Refuge
  • Yakama Indian Reservation
  • Private ownership
  • 36
  • 43
  • 3
  • 23
  • 6
  • 15
  • 13
  • 3
  • 11
  • 4
  • Southwest Oregon—Curry County BLM—Coos Bay District 2 1 Rogue River Siskiyou National Forest 3 1 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 Forest 4 2 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 (Seitzet 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 (Potteret 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; 345on 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. Hilaireet al.2010, p. 2).

    In the Oregon Cascades, limited population information forPolites mardon klamathensisis available, as few multiple-day surveys have been conducted here. Blacket al.(2010, Appendix 1) report single-day counts for multipleP.m. klamathensissites over a 5-year period, spanning 2005-2010 (there were no counts for most sites in 2008). In 2011, one newP.m. klamathensissite was located on Bureau of Reclamation Lands managed by BLM (Black 2012, pers. comm.). Although several of theP.m. klamathensissites 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 (Blacket 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 ofP.m. klamathensisover 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 ofP. m. klamathensisthan observed in the past (Blacket 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 forP.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 (Blacket 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 (Blacket al.2010, pp. 70-71; St. Hilaireet al.2010, pp. 10-12; Blacket 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 (Potteret al.1999, p. 6). Extirpation at one historical site in the Washington Cascades has been documented (Potteret 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). Blacket al.(2010, p. 7) state that somePolites mardon klamathensissites 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 (Blacket al.2010, pp. 70-72). Blacket 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 fewPolites mardon klamathensispopulations where more monitoring is needed, and a few higher-elevationP. m. mardonsites 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).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 abundantFestuca roemeri(Roemer's fescue) interspersed withViola 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 withArrhenatherum elatius(tall oatgrass) andCytisus 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 andVicia sativa(common vetch) are strongly preferred as nectar sources, and Scot's broom is strongly avoided (Hayset al.2000, p. 14). Nectaring was also observed onCamassia quamash(common camas),Lomatium utriculatum(fine-leaved desert parsley),Teesdalia nudicaulis(barestem teesdalia), andRanunculus occidentalis(western buttercup) (Hayset al.2000, p. 24).

    Southern Washington Cascades

    In the southern Washington Cascades, the mardon skipper is found in open grasslands and small montane meadows withinAbies grandis(Grand fir),Psuedotsuga menziesii(Douglas-fir), orPinus contorta(lodgepole pine)/mixed-conifer woodlands at mid to high elevations (1,800 to 5,600 ft [549 to 1,707 m]) (Potteret 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 (Potteret 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 (Potteret 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 includeFestuca idahoensis(Idaho fescue),Poa pratensis(Kentucky bluegrass),Danthonia intermedia(timber oatgrass),Carex inops(long-stolen sedge), andFestuca 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 (Jepsenet al.2008, p. 3), and higher densities of adult butterflies are commonly associated with patches ofD. unispecta(St. Hilaireet 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,Fragariaspp. (strawberry), andTrifoliumspp. (clover) (Beyer and Black 2007, p. 15).Erysimum asperum(wallflower),Erigeron peregrinus(fleabane),Calochortusspp. (sego lily), andAchillea 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 ofPolites mardon klamathensisin 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 (Blacket 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 wasDanthonia 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), andCarexspp. (sedges) (Beyer and Black 2007, p. 6). The primary nectar plants being utilized arePotentilla diversifolia(diverse-leaved cinquefoil),Wyethia angustifolia(narrow-leaved mule's ears),Penstemon procerus(small-flowered penstemon), andPlectritis congesta(sea blush) (Beyer and Black 2007, p. 16).

    Coastal Northwest California/Southwest Oregon

    The coastal populations ofPolites mardon mardonare found in small meadows (0.5-5 ac [0.2-2 ha]) dominated by Idaho fescue in sparsePinus 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 (Mattoonet 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 arePhlox diffusa(spreading phlox) andViola 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 onViolaspp. andCalochortusspp. 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 (Potteret 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 (Potteret 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 captivePolites,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). OtherPolitesspecies 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 (Potteret al.1999, p. 5). At that time, the species was not afforded any special status or protections from existing regulatory mechanisms (Potteret 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 haveidentified 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 (Seitzet 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 (Blacket al.2010, entire);

    (6) Completed a Conservation Assessment for the mardon skipper in 2007 (Kerwin and Huff 2007, entire); and

    (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., Blacket 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 speciesPolites mardon.In addition, the Service has elected, at our own discretion, to additionally evaluate the two subspeciesPolites mardon mardonandPolites 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 forPolites mardon klamathensis.Here we discuss the potential threats associated with habitat loss or degradation; the additional threats identified by Blacket 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 havebeen degraded by invasive species and competing uses such as recreation or military training (Schultzet 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 (Schultzet 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 (Schultzet 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 (Potteret 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 ofPolites mardon mardonandPolite mardon klamathensisare 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