Daily Rules, Proposed Rules, and Notices of the Federal Government
Section 4(b)(3)(B) of the Act (16 U.S.C. 1531
On October 25, 1999, the Service identified the mardon skipper (
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
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
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.
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
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
In 1998, Mattoon
The distinction between
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
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
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
In 1999, the mardon skipper was known from approximately 14 extant sites located in four distinct geographic areas (Potter
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
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
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
In the Oregon Cascades, limited population information for
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
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
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
With the apparent exception of a few
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).
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
At Puget prairie sites, early blue violet and
In the southern Washington Cascades, the mardon skipper is found in open grasslands and small montane meadows within
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
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,
Occupied sites are dominated by short-statured grass/sedge communities. In the Oregon Cascades, the most common oviposition plant was
The coastal populations of
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
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
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
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
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
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 (
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.
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
(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
(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., Black
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.
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
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
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
Remaining prairie habitats in the south Puget Sound region are relatively small, isolated patches with little potential connectivity between patches (Schultz
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
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