Federal Register: February 9, 2010 (Volume 75, Number 26)
DOCID: fr09fe10-21 FR Doc 2010-2405
DEPARTMENT OF THE INTERIOR
Western Area Power Administration
CFR Citation: 50 CFR Part 17
FWS ID: [FWS-R6-ES-2009-0021 MO 92210-0-0010]
NOTICE: Part II
DOCUMENT ACTION: Notice of 12-month petition finding.
Endangered and Threatened Wildlife and Plants; 12-month Finding on a Petition to List the American Pika as Threatened or Endangered
DATES: The finding announced in this document was made on February 9, 2010.
We, the U.S. Fish and Wildlife Service (Service), announce a 12month finding on a petition to list the American pika (Ochotona princeps) as threatened or endangered under the Endangered Species Act of 1973, as amended. After review of all available scientific and commercial information, we find that listing the American pika, at the species level or any of the five recognized subspecies (O. p. princeps, O. p. saxatilis, O. p. fenisex, O. p. schisticeps, and O. p. uinta), 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 American pika, the five subspecies, or its habitat at any time.
Interior Department, Fish and Wildlife Service
Section 4(b)(3)(B) of the Endangered Species Act of 1973, as amended (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 indicating that listing the species may be warranted, we make a finding within 12 months of the date of receipt of the petition. In this 12 month finding, we may determine that the petitioned action is either: (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, 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 12month findings in the Federal Register.
Previous Federal Actions
On October 2, 2007, we received a petition dated October 1, 2007, from the Center for Biological Diversity (Center) requesting that the American pika (Ochotona princeps) be listed as threatened or endangered under the Act. Included in the petition was a request that we conduct a status review of each of the 36 recognized subspecies of American pikas to determine if separately listing any subspecies as threatened or endangered may be warranted. Specifically, the Center requested that seven American pika subspecies be listed as endangered: the Ruby Mountains pika (O. p. nevadensis), O. p. tutelata (no common name), the White Mountains pika (O. p. sheltoni), the grayheaded pika (O. p. schisticeps), the Taylor pika (O. p. taylori), the lavabed pika (O. p. goldmani), and the Bighorn Mountain pika (O. p. obscura). The Center requested that the remaining subspecies be listed as threatened. We acknowledged receipt of the petition in a letter to the Center dated October 18, 2007. In that letter, we also stated that we could not address its petition at that time, because existing court orders and settlement agreements for other listing actions required nearly all of our listing funding. We also concluded that emergency listing of the American pika was not warranted at that time.
We received a 60day notice of intent to sue from the Center dated January 3, 2008. We received a complaint from the Center on August 19, 2008. We submitted a settlement agreement to the Court on February 12, 2009, agreeing to submit a 90day finding to the Federal Register by May 1, 2009, and, if appropriate, to submit a 12month finding to the Federal Register by February 1, 2010.
We received a letter from the Center, dated November 3, 2008, that discussed and transmitted supplemental information found in recent scientific studies that had not been included in the original petition. We considered this additional information when making this finding.
In our 90day finding published on May 7, 2009 (74 FR 21301), we reviewed the petition, petition supplement, supporting information provided by the petitioner, and information in our files, and evaluated that information to determine whether the sources cited support the claims made in the petition. We found that the petitioner presented substantial information indicating that listing the American pika as threatened or endangered under the Act may be warranted, because of the present or threatened destruction, modification, or curtailment of its habitat or range as a result of effects related to global climate change. We also solicited additional data and information from the public, other governmental agencies, the scientific community, industry, and other interested parties concerning the status of the American pika throughout its range. The information collection period for submission of additional information ended on July 6, 2009. This notice constitutes our 12month finding on the October 1, 2007, petition to list the American pika as threatened or endangered. Species Information
Like other pika species, the American pika (hereafter pika, unless
stated otherwise) has an eggshaped body with short legs, moderately
large ears, and no visible tail (Smith and Weston 1990, p. 2). Fur
color varies among subspecies and across seasons, typically with
shorter, brownish fur in summer and longer, grayish fur in winter
(Smith and Weston 1990, p. 3). The species is intermediately sized,
with adult body lengths ranging from 162 to 216 millimeters (6.3 to 8.5 inches) and mean body mass ranging from 121 to 176
grams (4.3 to 6.2 ounces) (Hall 1981, p. 287; Smith and Weston 1990, p. 2).
American pikas are generalist herbivores that select different classes of vegetation (Huntley et al. 1986, p. 143) and use different parts of the same plants when grazing versus haying (Dearing 1997a, p. 1160). Feeding (the immediate consumption of vegetation) occurs year round; haying (the storage of vegetation for later consumption) and the creation of haypiles occurs only in summer months after the breeding season (Smith and Weston 1990, p. 4). The primary purpose of haypiles is overwintering sustenance, and individuals harvest more vegetation than necessary for these haypiles (Dearing 1997a, p. 1156). Pikas feed an average distance of 2 meters (m) (6.5 feet (ft)) from talus and will travel an average distance of 7 m (23 ft) when haying (Huntly et al. 1986, pp. 141142). Huntly et al. (1986, p. 142) found that no feeding occurred beyond 10 m (33 ft) from talus, but haying was observed up to 30 m (98 ft).
Vegetative communities immediately adjacent to pika locations are typically dominated by grasses (Huntly 1987, p. 275). When pikas are excluded from grazing near talus slopes, the biomass of forbs and sedges (Roach et al. 2001, p. 319) and cushion plants (Huntly 1987, p. 275) increases rapidly. Therefore, foraging pikas influence the presence of specific plant classes or functional groups, vegetative cover, and species richness (Huntly 1987, p. 274; Roach et al. 2001, p. 315), and modify habitat in their quest for food and survival (Aho et al. 1998, p. 405). Forbs and woody plants are typically found in pika haypiles (Huntly et al. 1986, p. 143), which provide the major source of sustenance for the winter (Dearing 1997a, p. 1156). High phenolic (chemical compounds characterized by high acidity) concentrations of forbs and shrubs prevent pikas from grazing immediately on these plant types; however, pikas cache these plants and delay consumption until the toxins decay to tolerable levels (Dearing 1997b, p. 774). Additionally, plants with high levels of the phenolics deter bacterial growth and exhibit superior preservation qualities (Dearing 1997b, p. 774).
Thermoregulation is an important aspect of American pika physiology, because individuals have a high normal body temperature of approximately 40 [deg]C (104 [deg]F) (MacArthur and Wang 1973, p. 11; Smith and Weston 1990, p. 3), and a relatively low lethal maximum body temperature threshold of approximately 43 [deg]C (109.4 [deg]F) (Smith and Weston 1990, p. 3). Most thermoregulation of individuals is behavioral, not physiological (Smith 1974b, p. 1372; Smith and Weston 1990, p. 3). In warmer environments, such as during midday sun and at lower elevation limits, pikas typically become inactive and withdraw into cooler talus openings (Smith 1974b, p. 1372; Smith and Weston 1990, p. 3). Belowsurface temperatures within talus openings can be as much as 24 [deg]C (43.2 [deg]F) cooler than surface temperatures during the hottest time of day (Finn 2009a, pers. comm.). Pikas avoid hyperthermia (heat stroke) during summer months by engaging in short bursts of surface activity followed by retreat to a cooler microclimate beneath the surface (MacArthur and Wang 1974, p. 357). Pikas can be nocturnal where daytime temperatures are stressful and restrict diurnal activity (Smith 1974b, p. 1371).
Habitat occupied by American pikas is often patchily distributed, leading to a local population structure that is composed of islandlike sites commonly termed a metapopulation (Smith and Weston 1990, p. 4; Moilanen et al. 1998, pp. 531532). A metapopulation is composed of many largely discrete local populations, and metapopulation dynamics are characterized by extinction and recolonization occurring within independent local populations (Hanski 1999, cited in Meredith 2002, p. 47). Local populations that make up each metapopulation frequently become extirpated and can be subsequently reestablished by immigration (Smith 1974a, p. 1112; Moilanen et al. 1998, p. 532). American pikas within metapopulations often exhibit a low emigration rate, especially in adults. Juveniles usually have short migration distances; however, exceptions occur (Peacock 1997, pp. 346348).
Dynamics of American pika populations are sufficiently asynchronous (not occurring at the same time), so that simultaneous extinction of entire metapopulations is unlikely (Smith 1980, p. 11; Moilanen et al. 1998, p. 532). When a single population becomes extirpated, distance to a source of colonizing pikas is an influential factor determining the probability of recolonization (Smith 1980, p. 11). American pika populations on small and mediumsized islands are more likely to be extirpated, with the probability of extirpation being higher on more distant islands (Smith 1980, p. 12).
Historically, researchers hypothesized that American pika juveniles are philopatric (remain in or return to their birthplace), dispersing only if no territory is available within their birth place (various studies cited in Smith and Weston 1990, p. 6). However, Peacock (1997, pp. 346348) demonstrated that juvenile emigration to other population sites occurred over both long (2 kilometers (km); 1.24 miles (mi)) and short distances, and acted to support population stability by replacing deceased adults. Territory availability is a key factor for dispersal patterns, and local pika populations lack clusters of highly related individuals (Peacock 1997, pp. 347348).
Dispersal by American pikas is governed by physical limitations. Smith (1974a, p. 1116) suggested that it was difficult for juveniles to disperse over distances greater than 300 m (984 ft) in lowelevation (2,500 m (8,200 ft)) populations. Lower elevations are warmer in summer and represent the lower edge of the elevational range of the species (Smith 1974a, p. 1112). While dispersal distances of 3 km (1.9 mi) have been documented at other locations and elevational ranges (Hafner and Sullivan 1995, p. 312), it is believed that the maximum individual dispersal distance is probably between 10 and 20 km (6.2 and 12.4 mi) (Hafner and Sullivan 1995, p. 312). This conclusion is based on genetic (Hafner and Sullivan 1995, pp. 302321) and biogeographical (Hafner 1994, pp. 375382) analysis. Genetic analysis revealed that pika metapopulations are separated by between 10 and 100 km (6.2 to 62 mi) (Hafner and Sullivan 1995, p. 312). Biogeographical analysis demonstrated that, during the warmer period of the midHolocene (about 6,500 years ago), the species retreated to cooler sites, and the species subsequently expanded its range somewhat as climatic conditions cooled (Hafner 1994, p. 381). However, the species has not recolonized vacant habitat patches greater than 20 km (12.4 mi) from refugia sites and has recolonized less than 7.8 percent of available patches within 20 km (12.4 mi) of those same refugia sites (Hafner 1994, p. 381). The lack of recolonization is due to habitat becoming unsuitable from vegetation filling in talus areas (removing pika habitat) or from habitat becoming too dry due to environmental changes resulting from historical changes in climate (Hafner 1994, p. 381).
Individual pikas are territorial, maintaining a defended territory
of 410 to 709 square meters (m\2\) (4,413 to 7,631 square feet
(ft\2\)), but fully using overlapping home ranges of 861 to 2,182 m\2\
(9,268 to 23,486 ft\2\) (various studies cited in Smith and Weston
1990, p. 5). Individuals mark their territories with scent and defend the territories through
aggressive fights and chases (Smith and Weston 1990, p. 5).
Adults with adjacent territories form monogamous mating pairs. Males are sexually monogamous, but make little investment in rearing offspring (Smith and Weston 1990, pp. 56). Females give birth to average litter sizes of 2.4 to 3.7 twice a year (Smith and Weston 1990, p. 4). However, fewer than 10 percent of weaned juveniles originate from the second litter, because mothers only wean the second litter if the first litter is lost (various studies cited in Smith and Weston 1990, p. 4).
Adult pikas can be territorially aggressive to juveniles, and parents can become aggressive to their own offspring within 3 to 4 weeks after birth (Smith and Weston 1990, p. 4). To survive the winter, juveniles need to establish their own territories and create haypiles before the winter snowpack (Smith and Weston 1990, p. 6; Peacock 1997, p. 348). However, establishing a territory and building a haypile does not ensure survival.
Yearly average mortality in pika populations is between 37 and 53 percent. Few pikas live to be 4 years of age (Peacock 1997, p. 346), however, some individuals survive up to 7 years (Smith 2009, p. 2). Taxonomy
Historically, many taxonomic forms have been identified within Nearctic pikas, including as many as 13 species and 37 subspecies (Hafner and Smith 2009, p. 1). Initially, 13 species and 25 subspecies of Nearctic (a biogeographic region that includes the Arctic and temperate areas of North America and Greenland) pikas were described (Richardson 1828, cited in Hafner and Smith 2009). Howell (1924, pp. 1011) performed a full taxonomic revision of the American pika and recognized 3 species: Ochotona collaris, Ochotona princeps (16 subspecies), and Ochotona schisticeps (9 subspecies). Later, Hall (1981, pp. 286292) described 36 subspecies of American pika spread throughout western Canada and the western United States. The petition (Wolf et al. 2007) from the Center of Biological Diversity that requested that all American pika subspecies be listed as threatened or endangered was based on the Hall (1981, pp. 286292) taxonomy.
These references, in addition to others (Hafner and Smith 2009, p. 5) were used as the set of authoritative resources on pika taxonomy until genetic work identified four major genetic units of the American pika in the northern Rocky Mountains, Sierra Nevada, southern Rocky Mountains, and Cascade Range (Hafner and Sullivan 1995, p. 308). Further molecular phylogenetic and morphometric studies indicate the existence of five cohesive genetic units that have been referred to as ``distinct evolutionarily significant units'' (Galbreath et al. 2009a, p. 17; Galbreath et al. 2009b, pp. 7, 52). These studies support a revision of the subspecific taxonomy of the American pika to include five recognized subspecies: Ochotona princeps princeps (Northern Rockies), O. p. saxatilis (Southern Rockies), O. p. fenisex (Coast Mountains and Cascade Range), O. p. schisticeps (Sierra Nevada and Great Basin), and O. p. uinta (Uinta Mountains and Wasatch Range of Central Utah) (Hafner and Smith 2009, pp. 1625). The previously described 36 subspecies (Hall 1981, pp. 286292) are now referred to as subspecies synonyms, with each subspecies synonym corresponding to a subspecies described by Hafner and Smith (2009, pp. 1625). We are making our finding based on the most recent information that has identified five subspecies of American pika. The petition (Wolf et al. 2007) from the Center of Biological Diversity no longer contains the best available information on taxonomy.
Historic Distribution and Habitat
The restriction of American pikas to their current distribution (discussed below) is relatively recent. The shift in habitat range was shaped by longterm climate change and attendant impacts on vegetation.
The geographic distribution of American pika may have encompassed
not only the western United States and Canada during the last glacial
maximum (30,000 years ago or later), but also parts of the eastern United States (Grayson 2005, p. 2104). Archaeological and
paleontological records for pika demonstrate that approximately 12,000 years ago, pikas were living at relatively low elevations (less than 2,000 m (6,560 ft)) in areas devoid of talus (Mead 1987, p. 169; Grayson 2005, p. 2104). By the Wisconsinan glacial period
(approximately 40,000 to 10,000 years ago), American pikas were restricted to the intermontane region of the western United States and Canada.
Lowelevation populations of American pikas became extinct in the northern half of the Great Basin between 7,000 and 5,000 years ago (Grayson 1987, p. 370). Fossil records indicate that the species inhabited sites farther south and at lower elevations than the current distribution during the late Wisconsinan and early Holocene periods (approximately 40,000 to 7,500 years ago), but warming and drying climatic trends in the middle Holocene period (approximately 7,500 to 4,500 years ago) forced populations into the current distribution of montane refugia (Grayson 2005, p. 2103; Smith and Weston 1990, p. 2). During the late Wisconsinan and early Holocene, nowextirpated American pika populations in the Great Basin occurred at an average elevation of 1,750 m (5,740 ft), which is 783 m (2,569 ft) lower than 18 extant (in existence) Great Basin pika populations (Grayson 2005, p. 2106). Current Distribution and Habitat
Ochotona princeps princeps is patchily distributed in cool, rocky habitat, primarily in highelevation alpine habitats (see below for exceptions), from the Northern Rocky Mountains of central British Columbia and Alberta through Idaho and Montana, several mountain ranges of Wyoming, the Ruby Mountains of Nevada, the Wasatch Range of Idaho and Utah, and the Park Range and Front Range of Colorado north of the Colorado River (Hafner and Smith 2009, p.19). O. p. saxatilis occupies habitat in the southern Rocky Mountains south of the Colorado River (Front Range, San Juan Mountains, Sangre de Cristo Range), and isolated highlands including the La Sal Mountains of southeastern Utah, Grand Mesa of Colorado, and Jemez Mountains of New Mexico (Hafner and Smith 2009, pp. 2122). O. p. schisticeps occupies habitats in volcanic peaks of northern California, throughout the Sierra Nevada of California and Nevada, and isolated highlands throughout the Great Basin of Nevada, eastern Oregon (north to the Blue Mountains), and southwestern Utah (Hafner and Smith 2009, pp. 2324). O. p. fenisex occupies habitats from the Coast Mountains and Cascade Range from central British Columbia south to southern Oregon (Hafner and Smith 2009, p. 20). O. p. uinta is patchily distributed in habitats in the Uinta Mountains and Wasatch Range of central Utah (Hafner and Smith 2009, p. 24).
Temperature restrictions influence the species' distribution
because hyperthermia or death can occur after brief exposures (as
little as 6 hours) to ambient temperatures greater than 25.5 [deg]C
(77.9 [deg]F), if individuals cannot seek refuge from heat stress
(Smith 1974b, p. 1372). Therefore, American pika habitat progressively
increases in elevation in the southern extent of the distribution
(Smith and Weston 1990, p. 2). In the northern part of its distribution
(southwestern Canada), populations occur from sea level to 3,000 m
(9,842 ft), but in the southern extent (New Mexico, Nevada, and [[Page 6441]]
southern California) populations rarely exist below 2,500 m (8,202 ft) (Smith and Weston 1990, p. 2). Some exceptions exist in the southern portion of the species' range. For example, pikas in 10 percent of 420 study sites in the Sierra Nevada Mountains, Great Basin, and Oregon Cascade Mountains occur below 2,500 m and as low as 1,645 m (5,396 ft) at McKenzie Pass in the Cascade Mountains of Oregon (Millar and Westfall 2009, p. 16). Beever et al. (2008, p. 10) recently discovered a new population of American pika in the Hays Canyon Range of northwestern Nevada at elevations ranging from 1,914 to 2,136 m (6,280 to 7,008 ft).
American pikas primarily inhabit talus fields fringed by suitable vegetation in alpine or subalpine areas (Smith and Weston 1990, pp. 2 4). A generalist herbivore that does not hibernate, the species relies on haypiles of summer vegetation stored within talus openings to persist throughout the winter months (Smith and Weston 1990, p. 3). Alpine meadows that provide forage are important to pika survival in montane environments. The species also occupies other habitats that include volcanic land features (Beever 2002, p. 26; Millar and Westfall 2009, p. 10) and anthropogenic settings such as mine tailings, piles of lumber, stone walls, rockwork dams, and historic foundations (Smith 1974a, p. 1112; Smith 1974b, p. 1369; Lutton 1975, p. 231; Crisafulli 2009, pers. comm.; Millar and Westfall 2009, p. 10).
Pikas use talus, which can include rockice features, and other habitat types for den sites, food storage, and nesting (Smith and Weston 1990, p. 4; Beever et al. 2003, p. 39). Rockice features are defined as glacial or periglacial (i.e., around or near glaciers) derived landforms in highelevation, semiarid temperature mountain ranges and arctic landscapes (Millar and Westfall 2008, pp. 9091). Talus, rockice feature till, and volcanic features (described below) also provide microclimate conditions suitable for pika survival by creating cooler, moist refugia in summer months (Beever 2002, p. 27; Millar and Westfall 2009, p. 1921) and insulating individuals in the colder winter months (Smith 1978, p. 137; Millar and Westfall 2009, p. 21).
Among 420 sites surveyed by Millar and Westfall (2009, p. 10), 83 percent of the pika sites occurred in rockice feature till, most notably rockglacier and boulderstream landforms, which contain topographicclimatic conditions that are favored by pikas (Millar and Westfall 2009, p. 20).
Pikas also inhabit more atypical habitats that include lava tubes, caves, valley trenches, fault scarps, fault cracks, and cliff faces, which provide suitable habitat and thermal refuge (Beever 2002, pp. 26, 28; Millar and Westfall 2009, p. 10). For example, in Lava Beds National Monument in northern California and Craters of the Moon National Monument in southern Idaho, pikas typically inhabit large, contiguous areas of volcanic habitat (Beever 2002, p. 28). Within this habitat type, forage vegetation is accessible within distances comparable to dimensions of home ranges (Beever 2002, p. 28). Pikas select habitat that includes topographical features characterized by rocks large enough to provide necessary interstitial spaces for underground movement and tunneling. Like talus and rockice features, these habitats provide pikas with cool refugia during conditions that may result in heat stress, which in addition to behavioral thermoregulation mechanisms, allow pika to persist in these low elevation and potentially thermally challenging environments (Beever 2002, pp. 2728).
We relied on information from the International Union for Conservation and Nature of Natural Resources (IUCN), NatureServe, published literature, and public submissions during the information collection period on our 90day finding to evaluate the status of American pika populations.
The IUCN Red List of Threatened Species provides taxonomic, conservation status, and distribution information on plants and animals (IUCN 2009, p. 2). The IUCN Red List system is designed to determine the relative risk of extinction for species, and to catalogue and highlight plant and animal species that are facing a higher risk of global extinction. The IUCN identified the status of the American pika species as Least Concern in 2008 under the Red List review process (Beever and Smith 2008, p. 3). According to IUCN (version 3.1): ``a taxon is Least Concern when it has been evaluated against the criteria and does not qualify for Critically Endangered, Endangered, Vulnerable or Near Threatened. Widespread and abundant taxa are included in this category.'' The IUCN uses five quantitative criteria to determine whether a taxon is threatened or not, and if threatened, which category of threat it belongs in (i.e., critically endangered, endangered, or vulnerable). ``To list a particular taxon in any of the categories of threat, only one of the criteria needs to be met. The five criteria are: (1) Declining population (past, present and/or projected); (2) Geographic range size, and fragmentation, decline or fluctuations; (3) Small population size and fragmentation, decline, or fluctuations; (4) Very small population or very restricted distribution; and (5) Quantitative analysis of extinction risk (e.g., Population Viability Analysis) (IUCN Standards and Petitions Working Group 2008, p. 11).''
However, the IUCN (using the Hall (1981) taxonomic classification, as Vulnerable or Near Threatened) considers eight American pika subspecies synonyms. These subspecies synonyms are Ochotona princeps goldmani, O. p. lasalensis, O. p nevadensis, O. p. nigrescens, O. p. obscura, O. p. sheltoni, O. p. tutelata, and O. p. schisticeps (Beever and Smith 2008, p. 3). A vulnerable species or subspecies is facing a high risk of extinction in the wild. A near threatened species or subspecies is close to qualifying as or is likely to qualify as vulnerable in the near future (IUCN, section 3.1). Status for the eight subspecies synonyms applies under the Hall (1981) taxonomic classification of the American pika but may not apply to any of the subspecies described by Hafner and Smith (2009, pp. 1625). For example, a status of ``vulnerable'' for O. p. goldmani does not imply that O. p. princeps (described by Hafner and Smith 2009, pp. 1720) is vulnerable as well because the range of O. p. goldmani does not constitute the entire range of O. p. princeps.
NatureServe is a nonprofit organization that, in part, collects and manages species information and data in an effort to increase our understanding of species, ecosystems, and conservation issues (NatureServe 2009a, p. 1). NatureServe also assesses available scientific information to determine species status based on factors, including population number and size, trends, and threats. NatureServe provides comprehensive reports for species, including American pika. The report (Nature Service 2009b, pp. 17) for the American pika includes taxonomic information, conservation status information, lists of natural heritage records, species distribution by watershed, ecology and life history information, population delineation, population viability, and references. The report does not contain information on threats or a justification for designation of conservation status within states and provinces.
In a review conducted in 1996, NatureServe assigned the American
pika a global status of secure (i.e., common; widespread and abundant) in the United States and the Canadian provinces of
Alberta and British and Columbia (NatureServe 2009b, pp. 12; Quinlan 2009, pers. comm.). Within the United States, NatureServe considers the species secure or apparently secure (i.e., uncommon but not rare; some cause for longterm concern due to declines or other factors) in Colorado, Idaho, Montana, Oregon, Washington, and Wyoming. NatureServe assigned the American pika a status of vulnerable in California and Utah (i.e., vulnerable in the jurisdiction due to a restricted range, relatively few populations, recent and widespread declines, or other factors making it vulnerable to extirpation), and a status of imperiled in Nevada and New Mexico (i.e., imperiled in the jurisdiction, because of rarity due to very restricted range, very few populations, steep declines, or other factors making it very vulnerable to extirpation from the jurisdiction).
Northern Rocky Mountain Subspecies (Ochotona princeps princeps)
The Northern Rocky Mountains subspecies (Ochotona princeps princeps) occurs primarily in Canada, Montana, Idaho, and Wyoming, with a smaller amount of occupied habitat in Washington, Nevada, Utah, and Colorado. Data on status and trends of O. p. princeps are lacking for portions of the subspecies range. Available data consists mostly of a list of sites verified to be occupied in recent surveys. In locations where pika surveys have been conducted, we do not have historical information of the subspecies' at those sites for comparison.
The Canadian Endangered Species Conservation Council (2005) assigned a ranking of secure to Ochotona princeps princeps in Alberta and British Columbia, which are the only two provinces where this subspecies occurs in Canada. The ranking is based upon occurrence of large numbers of pikas in secure habitat (British Columbia Conservation Data Centre 2009, p. 1; Court 2009, pers. comm.). Pikas are common in suitable habitat in the mountains on both provincial lands and in national parks (Court 2009, pers. comm.). The population is thought to be stable in Alberta, Canada (Court 2009, pers. comm.). Greater than 100 occurrences of O. p. princeps occur within Alberta (Court 2009, pers. comm.). We do not have population trend information for British Columbia. We do not have any information to suggest the distribution of the pika is changing in Canada.
In Montana, there is little historical information to assess whether habitat loss has occurred or if populations are stable. Limited available data does not indicate a decline. Approximately 90 percent of available habitat in Glacier National Park is occupied (National Park Service (NPS) 2009, p. 9). Based upon occupancy rates elsewhere (Utah Division of Wildlife Resources (UDWR) 2009, pp. 6, 11), we conclude the occupancy rate of pikas within Glacier National Park is high.
Limited data are available for pika distribution, abundance, and population status in Wyoming. American pikas occur in every Wyoming mountain range except Laramie, Wasatch, and Black Hills (Wyoming Game and Fish Department (WGFD) 2009, p. 1). American pikas are believed to occur in all locations where they were observed historically within the Grand Teton National Park (NPS 2009, p. 10). The WGFD will add the American pika to their 2010 State Wildlife Action Plan (WAP) (WGFD 2009, p. 1). They propose to treat the subspecies as having an Unknown Native Species Status because population and distribution trends are unknown and limiting factors are poorly understood (WGFD 2009, p. 1).
In Idaho, the subspecies is broadly distributed and occupies a substantial number of sites throughout much of the State (Idaho Department of Fish and Game (IDFG) 2009, p. 1). The IDFG has no information to suggest threats exist to the subspecies. Pikas are not identified as a Species of Greatest Conservation Need in the Idaho Comprehensive Wildlife Conservation Strategy (CWCS) and pikas are considered to be secure, common, and widespread based on NatureServe's conservation status (IDFG 2005, App. A, p. 18). O. p. princeps was studied at Craters of the Moon National Monument in Idaho (Beever 2002, p. 25; NPS 2009, pp. 23), but reports did not reveal any information related to the status of pika populations there.
Ochotona princeps princeps in Utah currently have a high occupancy rate (96 percent) in suitable habitat (UDWR 2009, p. 7). Although there is no historical population information, UDWR believes that the high occupancy rate reflects stable populations (UDWR 2009, p. 11).
In Colorado, Ochotona princeps princeps is found only in the northern part of the State. Colorado Division of Wildlife (CDOW) (2009, p. 19) documented greater than 40 occupied sites based on historic and recent site surveys. Reports on O. p. princeps in Colorado do not provide any information on status (NPS 2009, p. 1012; Ray 2009, pp. 1 4).
Nevada and Washington have little information on the subspecies status. American pika records collected from 1969 to 2008 from the Ruby Mountain chain in northeast Nevada identify at least 33 pika locations (Nevada Department of Wildlife (NDOW) 2009, pp. 23); however, we have no information on the status of populations from those locations. We have no information on the status of O. p. princeps in Washington.
As previously stated, Beever and Smith (2008, p. 3) considered populations of O. p. goldmani, O. p. nevadensis, and O. p obscura, which represent a portion of the range of O. p. princeps (Hafner and Smith 2009, pp. 1819), as vulnerable (i.e., facing a high risk of extinction in the wild). Additionally, NatureServe (2009, p. 2) assigned Utah pikas, which contains populations representing all subspecies except O. p. fenisex, a status of vulnerable (i.e., a restricted range, relatively few populations, recent and widespread declines, or other factors making it vulnerable to extirpation).
In summary, most States and provinces that contain populations of O. p. princeps have not determined the subspecies' status and do not have information on population trends. Some populations within central Idaho (O. p. goldmani), northwestern Nevada (O. p. nevadensis), north central Wyoming (O. p. obscura), and northcentral Utah may be vulnerable (Beever and Smith 2008, p. 3; NatureServe 2009, p. 2). Outside of these areas, we do not have adequate information to determine the status of O. p. princeps populations.
Sierra Nevada Subspecies (Ochotona princeps schisticeps)
The Sierra Nevada subspecies (Ochotona princeps schisticeps) occurs primarily in California, Nevada, and Oregon with a small portion of occupied habitat in Utah. This subspecies has received more scientific study than any other American pika subspecies (Grayson 2005, p. 2104). Pikas are designated as a vulnerable species as well as a species of conservation priority in Nevada's WAP, with a declining population (WAP Team 2006, pp. 291, 405). O. p. schisticeps status appears to be declining within the interior Great Basin, primarily in southern Oregon and northwestern Nevada, and some places along the eastern Sierra Nevada Mountain Range (Beever et al. 2003, p. 44; Wilkening 2007, p. 58); however, outside of these areas there is no indication that the subspecies is in decline (Millar and Westfall 2009, p. 25). As identified by Beever et al. (2003, pp. 39, 44), the interior Great Basin refers to the hydrographic definition of the Great Basin (Grayson 1993, cited in Beever et al. 2003, p. 39).
As previously mentioned, some isolated populations of O. p. schisticeps have been extirpated in the interior Great Basin. Beever et al. (2003, p. 43) did not detect pikas at 6 of 25 historical (dating back to the early to mid1900s) populations during surveys from 1994 to 1999 and later documented three extirpations during 2000 to 2007 (Wilkening 2007, pp. 2527; Beever et al. 2009, p. 15).
Researchers have not systematically searched all potential pika habitat within the Great Basin and acknowledge that other sites with pikas may exist (Beever et al. 2009, pp. 31), particularly the Toiyabe Mountain Range, White Mountains, Toquima Mountain Range, and the Warner Mountains (Meredith 2002, p. 11; Beever 2009a, pers. comm.). In fact, two new sites were discovered in the Great Basin in northwestern Nevada from 2008 to 2009: Hays Canyon (Beever et al. 2008, p. 9) and Sheldon Hart National Wildlife Refuge (Collins 2009, pers. comm.). However, the subspecies is rare in the Great Basin, and likely has been relatively rare in the Great Basin for the past several thousand years. It is unlikely that many additional occupied sites will be found (Beever et al. 2008, p. 11).
Trends of pika status are mixed in other locations within the subspecies range. Pikas occur within Sequoia and Kings Canyon National Parks in California along the eastern edge of the Sierra Nevada Mountain Range, however, the population status is unknown (NPS 2009, p. 6). Pikas are widely distributed throughout Lava Beds National Monument (Ray and Beever 2007, p. 2) and populations appear to persist in warmer and drier sites, which is contrary to expectations because pikas are generally restricted to cool, moist habitats on higher peaks (Hafner 1993, p. 375). The lower elevation range limit of pikas in Yosemite National Park has contracted and moved upslope by 153 m (502 ft) (Moritz et al. 2008, p. 263), and at least one historic pika site has been extirpated within the Park (Moritz 2007, p. 37). Despite this extirpation, we do not know the status of the entire Yosemite National Park pika population. Pika populations near Bodie, California, have experienced decline as well, but not in the largest portion of the population which contains more suitable habitat and subsequently more pikas (Moilanen et al. 1998, p. 531; Nichols 2009, pp. 2, 5; Smith 2009, pers. comm.).
The relative number of unoccupied sites increased from the Sierra Nevada eastward into the Great Basin ranges (Millar and Westfall 2009, pp. 9, 11). Millar and Westfall (2009, p. 25) concluded that pika populations in the Sierra Nevada and southwestern Great Basin are thriving and show little evidence of extirpation or decline. Central Great Basin populations, on the other hand, appear less viable and more subject to disturbance from random events (Millar and Westfall 2009, p. 25).
In Utah, a population of pikas at Cedar Breaks National Monument was extirpated sometime between 1974 and 2006 (Oliver 2007, p. 5). As of 2009, the site still does not contain pikas (NPS 2009, p. 9). Pikas may have disappeared from sites near Lava Point in Zion National Park (NPS 2009, p. 13; Oliver 2007, pp. 78). However, pikas occur in other nearby locations (NPS 2009, p. 9; UDWR 2009, p. 20), demonstrating that suitable habitat capable of supporting a pika population still exists in southern Utah. Eightyfour percent of Ochotona princeps schisticeps suitable habitats in Utah are occupied (UDWR 2009, p. 7).
In summary, despite some of the uncertainty in trends across the
current range of O. p. schisticeps populations, it is clear that some
interior Great Basin pika populations (Beever et al. 2003, pp. 44, 53
54; Beever et al. 2009, p. 6) are being extirpated and moving upslope
in elevation. The recent loss of lowelevation historical pika
populations near the southern edge of historical range within the Great
Basin appears to track the fossil record (see section on Historic
Distribution and Habitat). The recent rate of population loss is more
rapid than that suggested by paleontological records (Beever et al.
2003, p. 48). The majority of suitable habitat for O. p. schisticeps
occurs outside of the Great Basin in the Sierra Nevada Mountain Range
and a large study area in the Sierra Nevada Mountain Range shows the status appears to be stable.
Southern Rocky Mountain Subspecies (Ochotona princeps saxatilis)
Even in the absence of survey data for portions of the range of the Southern Rocky Mountain subspecies, Ochotona princeps saxatilis, available information suggests that the subspecies is stable across the majority of its range. Survey data are lacking for portions of the subspecies' range.
Pikas are well distributed in highelevation areas of Colorado, which contains the majority of the subspecies' habitat. Fiftyeight of 62 historical sites surveyed had O. p. saxatilis populations persisting even at relatively lowelevation 2,743 to 3,048 m (9,000 to 10,000 ft) sites (CDOW 2009, p. 22; Peterson 2009, pers. comm.). Pika habitat is extensive in Colorado, and connectivity between pika habitat and populations appears sufficient to maintain a healthy population structure (CDOW 2009, p. 22).
In Utah, 92 percent of surveyed suitable pika habitat in the La Sal Mountains of eastern Utah was occupied (UDWR 2009, p. 7). There is no evidence of declines of American pika populations from historical levels in Utah (UDWR 2009, p. 11).
Density and trend data are not available for Ochotona princeps saxatilis populations in New Mexico (New Mexico Department of Game and Fish (NMDGF) 2009, p. 2; U.S. Forest Service (USFS) 2009, p. 1). New Mexico's CWCS lists the Goat Peak pika (was Ochotona princeps nigrescens, now included in O. p. saxatilis) as a subspecies of greatest conservation need as well as vulnerable and State sensitive (NMDGF 2006, pp. 55, 57). However, based on limited field observation, persistence of O. p saxatilis populations within New Mexico does not appear to reflect the pattern of recent extirpation observed within the interior Great Basin (NMDGF 2009, p. 3). Beever and Smith (2008, p. 3) have assigned O. p. lasalensis and O. p. nigrescens, which now belong to the O. p. saxatilis subspecies (see Table 1; Hafner and Smith 2009, p. 21), a status of vulnerable.
Despite some of the uncertainty in status across the range of O. p. saxatilis in New Mexico, the subspecies appears to be well distributed throughout the available habitat, especially in Colorado and Utah (CDOW 2009, p. 22; UDWR 2009, p. 11). There is no evidence indicating that the subspecies is in decline across its range in Utah and Colorado. Based on other status reviews (Beever and Smith 2008; NatureServe 2009b, p. 2), further monitoring may be warranted for O. p. saxatilis populations in the Jemez Mountains of New Mexico and La Sal Mountains of Utah to obtain a current status characterization of this portion of the subspecies range.
Cascade Mountain Subspecies (Ochotona princeps fenisex)
We have no trend data available for Ochotona princeps fenisex populations. In many locations where recent pika surveys have been conducted, no historical information exists for purposes of comparison. NatureServe has assigned the American pika a status of apparently secure (i.e., uncommon but not rare; some cause for longterm concern due to declines or other factors) in Oregon; secure (i.e., common; widespread and abundant) in the State of Washington; and secure in the Canadian province of British Columbia.
All eight survey locations in the Three Sisters Mountains and at McKenzie Pass, (located in the Cascade Mountain Range) have evidence of recent pika activity (Millar and Westfall 2009, p. 9). O. p. fenisex populations also occur in lowelevation (range of 121 to 255 m (397 to 837 ft)) habitat in the Columbia River Gorge, Oregon (Simpson 2009, p. 244). We have population estimates of O. p. fenisex from Mt. St. Helens from 1992 to 1994 (Bevers 1998, p. 42), but no information on the population status.
Survey data are lacking for a large portion of O. p. fenisex range, and no reports indicate population status. Based on the current pattern of known occupancy and the NatureServe (2009b, pp. 12) assessment, the subspecies is apparently secure.
Uinta Mountain Subspecies (Ochotona princeps uinta)
The Uinta Mountain subspecies, Ochotona princeps uinta, occurs solely within the State of Utah. The species is believed to have a relatively high occupancy rate (63 percent) with no evidence of declines from historical levels (UDWR 2009, pp. 7, 9, 11, 20). Based on available information, O. p. uinta populations appear stable. Summary of American Pika Population Status
Most States and provinces that contain populations of O. p. princeps and O. p. fenisex have not determined the subspecies' status and do not have information on population trends. Information presented above suggests that O. p. schisticeps populations in some areas, primarily in the interior Great Basin, may be in decline. O. p. saxatilis populations appear to be well distributed throughout the majority of available habitat and O. p. uinta populations appear stable. Recent observed trends for O. p. princeps, O. p. saxatilis, O. p. fenisex, and O. p. uinta subspecies do not seem to mirror the loss of occupied pika sites and upward range contraction that has been reported for interior Great Basin populations. There is discrepancy among reported population trends within California, southern Utah, and New Mexico. Some information suggests that the species is vulnerable within some areas of California, southern Utah, and New Mexico (Beever and Smith 2008; NatureServe 2009b); however, other reports discussed above suggest that the O. p. schisticeps subspecies is stable or not in decline (Millar and Westfall 2009, p. 25; NMDGF 2009, p. 3; UDWR 2009, p. 11).
Summary of Information Pertaining to the Five Factors
Section 4 of the Act and implementing regulations (50 CFR part 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 endangered or threatened based on any of the following
five factors: (1) The present or threatened destruction, modification,
or curtailment of its habitat or range; (2) overutilization for
commercial, recreational, scientific, or educational purposes; (3)
disease or predation; (4) the inadequacy of existing regulatory
mechanisms; or (5) other natural or manmade factors affecting its
continued existence. In making this finding, information pertaining to
the American pika in relation to the five factors provided in section
4(a)(1) of the Act is discussed below. In making our 12month finding
on a petition to list the American pika or any of the five subspecies
of pika, we considered and evaluated the best available scientific and
commercial information. Below, we provide a summary of our analysis of
threats to the five recognized subspecies of the American pika and to the species as a whole.
A. The Present or Threatened Destruction, Modification, or Curtailment of its Habitat or Range
The following potential factors that may affect the habitat or range of American pika are discussed in this section: (1) Climate change; (2) livestock grazing; (3) native plant succession; (4) invasive plant species; and (5) fire suppression.
Climate change is a potential threat to the longterm survival of the American pika. Thermal and precipitation regime modifications may cause direct adverse effects to individuals or populations. Climate change has the potential to contribute to the loss of and change in pika habitat and enhance negative ecological and anthropogenic effects. The Science of Climate Change
The Intergovernmental Panel on Climate Change (IPCC) concluded that global climate change is occurring and is caused by human activities, such as the burning of fossil fuels and clearing of forests (Forster et al. 2007, pp. 135136). The IPCC is a scientific intergovernmental body established by the World Meteorological Organization and the United Nations Environment Programme ``to assess scientific information related to climate change, to evaluate the environmental and socio economic consequences of climate change, and to formulate realistic response strategies'' (IPCC 2007, p. iii). The publications of the IPCC, specifically the fourvolume IPCC Fourth Assessment Report: Climate Change 2007, constitute the best available science on global climate change. The IPCC Fourth Assessment Report: Climate Change 2007 included the findings of three working groups composed of more than 500 lead authors and 2,000 expert reviewers and provided objective scientific guidance to policymakers on the topic of climate change (IPCC 2007, p. iii). We believe the IPCC information is the best available scientific information on global climate change at a broad scale.
Historical records analyzed by the IPCC demonstrate that global surface temperatures have risen (with regional variations) during the past 157 years, most strongly after the 1970s (Trenberth et al. 2007, p. 252). Globally, average surface temperatures have risen by 0.074 [deg]C plus or minus 0.018 [deg]C (0.13 [deg]F plus or minus 0.03 [deg]F) per decade during the past century (1906 through 2005) and by 0.177 [deg]C plus or minus 0.052 [deg]C (0.32 [deg]F plus or minus 0.09 [deg]F) per decade during the past quartercentury (1981 through 2005) (Trenberth et al. 2007, p. 253).
Changes in the amount, intensity, frequency, and type of precipitation have been summarized by the IPCC (Trenberth et al. 2007, p. 262). The warming of global temperatures has increased the probability of precipitation falling as rain rather than snow, especially in nearfreezing situations, such as the beginning and end of the snow season (Trenberth et al. 2007, p. 263). In many Northern Hemisphere regions, this has caused a reduced snowpack, which can greatly alter water resources throughout the year (Trenberth et al. 2007, p. 263). As a result of thermal and precipitation regime changes, the IPCC expects the snowline (the lower elevation of yearround snow) in mountainous regions to rise 150 m (492 ft) for every 1 [deg]C (1.8 [deg]F) increase in temperature (Christenson et al. 2007, p. 886). These predictions are consistent with regional predictions for the Sierra Nevada in California that calculate that yearround snow will be virtually absent below 1,000 m (3,280 ft) by the end of the 21st century under a high emissions scenario (Cayan et al. 2006, p. 32).
Scientists at climate research institutions in the United States and in over a dozen countries worldwide, have
generated projections of future climatic conditions both globally and in the United States, which includes the range of the American pika. These projections were assessed and synthesized in the Fourth Assessment Report of the IPCC. The United States Global Change Research Program (USGCRP) coordinates climate change research from 13 departments and agencies and was mandated by Congress in the Global Change Research Act of 1990 to, ``assist the Nation and the world to understand, assess, predict, and respond to humaninduced and natural processes of global change.'' The IPCC has predicted global average surface warming during the 21st century is likely between 1.1 and 6.4 [deg]C (2.0 and 11.5 [deg]F), depending on the emissions scenario, and taking into account other sources of uncertainty in the projections (Solomon et al. 2007, p. 70, Table TS. 6). The recent USGCRP assessment of climate impacts (Karl et al., 2009, pp. 129, 135) also adopts the IPCC range of temperature projections for different United States regions.
On a regional scale, North America is likely to exceed the global mean warming in most areas (Christenson et al. 2007, p. 850). Specifically, warming is likely to be largest in winter in northern regions of North America, with minimum winter temperatures likely rising more than the global average (Christenson et al. 2007, p. 850). Across 21 global climate models using a midlevel emissions scenario, the IPCC predicted that the average annual temperature in western North America (covering the entire range of the American pika) will increase between 2.1 and 5.7 [deg]C (median 3.4 [deg]C) (3.8 and 10.3 [deg]F (median 6.1 [deg]F)) during the 21st century (Christenson et al. 2007, p. 856). The 2009 USGCRP impacts report projects the Southwest to warm 2 to 6 [deg]C (4 to 10 [deg]F) relative to the 19601979 baseline (Karl et al. 2009, p. 129) and the Northwest to warm by ``another 2 to 6 [deg]C (3 to 10 [deg]F)'' by the end of the century (Karl et al. 2009, p. 135).
In the 20th century, the Pacific Northwest and western United States experienced annual average temperature increases of 0.6 to 1.7 [deg]C (1.1 to 3.1 [deg]F) and 1.1 to 2.8 [deg]C (2.0 to 5.0 [deg]F), respectively (Parson et al. 2001, p. 248; Smith et al. 2001, p. 220). Temperature increases are expected to affect precipitation, snowpack, and snowmelt in the range of the American pika. Climate warming corresponds with a reduced mountain snowpack (Mote et al. 2005 and Regonda et al. 2005 cited in Vicuna and Dracup 2007, p. 330; Trenberth et al. 2007, p. 310) and a trend toward earlier snowmelt in western North America (Stewart et al. 2004, pp. 217, 219, 223). The IPCC concluded that snowseason length and depth of snowpack are very likely to decrease in most of North America (Christenson et al. 2007, p. 850). Leung et al. (2004, p. 75) concluded that future warming increases in the western United States will cause increased rainfall and decreased snowfall, resulting in reduced snow accumulation or earlier snowmelt. Similarly, Rauscher et al. (2008, p. 4) concluded that increased temperatures in the late 21st century could cause earlyseason snowmeltdriven runoff to occur as much as 2 months earlier than presently in the western United States.
The above information applies at large, general scales. To understand the changes likely to occur in pika habitat, we worked with the National Oceanic and Atmospheric Administration (NOAA) to assess the best available climate science across the range of the American pika (NOAA 2009, p. 4). The NOAA study reviewed historical climate observations and climate projections of surface temperatures for 20 year periods centered on 2025, 2050, and 2100 in alpine and subalpine mountain areas that are habitat for the American pika. Because model projections for precipitation are less reliable than for temperature in this region, their report focused primarily on temperature (NOAA 2009, pp. 10, 15). We primarily relied on this report to perform deterministic risk assessments of increased temperature in the foreseeable future to American pika populations throughout their range in the western United States. In addition, we used information on historical climate observations to supplement previous peerreviewed publications and other reports from the literature to assess how temperature increases may have affected pikas in recent decades.
The NOAA's analysis (NOAA 2009, p. 9) revealed an evident warming trend between 1950 and 2007 in the western United States. Strong warming trends occurred across 89 percent of the western United States and 37 to 42 percent of western United States mountain ranges (Das et al. 2009, cited in NOAA 2009, p. 9). Within the western United States, warming was documented and is attributable to anthropogenic climate change (Bonfils et al. 2008, cited in NOAA 2009, p. 11). Some studies (Barnett et al. 2008, p. 1080; Pierce et al. 2008, p. 6436) have estimated that up to about half of the trends in temperature and associated hydrologic variables can be attributed to anthropogenic causes. Natural climate variability may account for the remainder of the observed climate change in the western United States, and will likely play a role in the future climate of that region.
Changes in the hydrologic cycle, including timing of snowmelt runoff, amount of precipitation falling as snow versus rain, and spring snow water equivalent, have been documented in the mountains of western North American and attributed to anthropogenic causes (multiple references cited in NOAA 2009, p. 8), with the exception of some high elevation areas, especially in the Rocky Mountains. Most of the reduction in snowpack in the western United States has occurred below about 2,500 m (8,200 ft) (Regonda et al. 2005, cited in NOAA 2009, p. 9). This elevation is near the lower limit of American pikas' elevation range (Smith and Weston 1990, p. 2); therefore, it can be inferred that the majority of pika habitat in mountainous areas has not experienced the large changes in the hydrologic cycle seen at lower elevations. Climate Change and Pika Biology
Several climate variables are relevant to persistence of American pika populations because past and present trends in climate have been identified as having important physiological, ecological, and demographic consequences. These climate variables include, but may not be limited to, number of extremely hot or cold days, average summer temperatures, and duration of snow cover (Beever et al. 2009, pp. 5, 10, 1618).
In general, pika biologists agree that temperatures below the habitat surface, such as in talus crevices, better approximate the conditions experienced by individual pikas because pikas rely on subsurface refugia to escape hotter summer daytime temperatures and obtain insulation in the colder winter months (Beever et al. 2009, p. 9). Therefore, surface temperature variables may not be as useful as subsurface temperatures for predicting persistence or extirpations of pika populations in the face of climate change. However, data on subsurface temperatures within pika habitat vary depending on site specific conditions and are largely unavailable.
Beever et al. (2009, p. 18) found that average summer (JuneJuly
August (JJA)) belowtalus temperature was the best predictor of pika
extirpation. They also discovered two other patterns: (1) The number of
extremely cold and hot days based on estimates of belowtalus
temperatures was useful in predicting patterns of pika extirpations
(Beever et al. 2009, p. 18); and (2) the majority of pikaextirpated sites were covered with
snow for only 2 weeks or less; whereas, the majority of pikaextant sites had continuous snow cover for greater than 2 weeks and as long as 8.2 months (Beever et al. 2009, p. 16). Because American pikas are small and do not hibernate, reduced snowpack can mean a lack of insulation from cold winter temperatures (Morrison and Hik 2008, p. 905). Exposure to colder temperatures could have an adverse effect on pika individuals and populations as a result of increased energy expenditure during a time of year where food resources are limited (Smith et al. 2004, p. 5). However, pika biologists have not determined the actual effects of acute coldstress on pikas (Beever et al. 2009, p. 29).
The population collapse of a closely related pika species, the collared pika (Ochotona collaris), was related to warmer winters that resulted in low snow accumulation (and, therefore, poor insulation value), increased frequency of freezethaw events, icing following winter rains, and late winter snowfalls that delay the start of the growing season (Morrison and Hik 2008, pp. 104105, 110). Following a decline in population abundance, populations recovered in subsequent years, in some cases to near predecline levels (Morrison and Hik 2007, pp. 902903). Declines in snowpack and earlier montane snowmelt are predicted to occur within the next century, and winter survival of the American pika may consequently decrease. Alternatively, earlier snowmelt could improve pika survival and positively affect American pika populations (Morrison and Hik 2007, p. 905). Based on the available information there does not appear to be a direct line of evidence linking reduced snowpack to reductions in American pika populations.
Several lines of evidence have been used to suggest that thermal stress will adversely impact the American pika. Wolf et al. (2007, p. 43) pointed out that increasing temperatures will eliminate cool, moist refugia in talus habitat, causing individuals to be unable to thermoregulate in summer months. However, Millar and Westfall (2009, p. 25) stated that nonrockice features will likely become warmer and more marginal for pikas, but environments with rockice features are highly likely to remain buffered against temperature change due to the insulation of rock features. Millar and Westfall (2009, p. 10) documented that 83 percent of over 400 surveyed pika sites in the Sierra Nevada and Great Basin occurred in rockice landforms, indicating that pikas have a preference for these types of environments. Therefore, we expect pika habitat that contains rockice features or features that are similar to rockice (i.e., talus or taluslike environments) to be buffered from rising surface temperatures. We are not aware of any studies that have identified the distribution of these types of features, and thus we are not able to use that type of information to help us increase the sensitivity of our climate change threats analysis.
Wolf et al. (2007, p. 44) also state that, even if the talus refugia remain cool, ambient external temperatures may reduce an individual's ability to forage during midday. They assert that if pika individuals cannot adequately forage in the summer months, they may not have the required body mass or haypile volume needed for winter survival. However, pikas at low elevations restrict their activity when temperatures exceed their thermal tolerance but are able to obtain enough food and overwintering vegetation (hay pile) during the morning and evening so that longterm population persistence is not affected (Smith 1974a, pp. 11171118; Smith 1974b, pp. 13701372; Smith 2009, p. 4).
Warmer summer temperatures may affect the ability of juvenile pikas to successfully disperse and colonize new areas (Smith 1974a, p. 1112; Smith 1978, p. 137; Wolf et al. 2007, p. 44). Because dispersal occurs on the habitat surface, dispersing pikas are exposed to the hottest temperatures on the surface of their environment. Hotter surface temperatures may decrease the distance juveniles are able to travel in search of new habitat patches, but primarily in warmer, lowelevation habitats. A pika metapopulation range may decline if juveniles are unable to colonize new patches or immigrate to other populations.
Wilkening (2007, pp. 3637) suggested that a greater depth of
available talus should be positively associated with pika persistence,
and pika populations located in habitat with shallow talus or small
diameter rocks of similar size might be susceptible to adverse effects
of increasing temperatures. With the appropriate assemblage of talus
structural features, belowtalus microclimate might be less thermally
variable and more suitable for pikas (Millar and Westfall 2009, p. 21).
Studies from Lava Beds National Monument support this hypothesis by
demonstrating that talus depth (amount of insulation) was one of the
strongest predictors of pika occurrence (Ray and Beever 2007, p. 45).
Based on these data, it is likely that habitat with suboptimal talus
characteristics would be less likely to support pika populations under projected warming scenarios.
American Pika Responses to Climate Change
Past and Present Trends
Recent climatic change, including increased temperatures, freeze free periods, and changes in precipitation is an important driving force on ecosystems and has affected a wide variety of organisms with diverse geographic distributions (Walther et al. 2002, pp. 391392; Parmesan and Yohe 2003, p. 41). Many plant and animal species have advanced the timing of spring events (e.g., plant flowering or bird migration) and experienced a shift in latitudinal and altitudinal range (i.e., movement to higher latitudes or higher altitude) (Walther et al. 2002, pp. 391392).
The biology of the American pika makes the species a useful indicator of changing climatic conditions and useful to test extinction theory (Smith et al. 2004, p. 5; Smith 2009, p. 2). The species lives in a very narrow ecological habitat (primarily talus) that is frequently fragmented or patchily distributed. They are generally poor dispersers, and thus the narrow niche may expose some populations to negative effects associated with increasing temperatures (Smith 1974b, p. 1372; Smith 2009, p. 2). However, pikas also may exhibit considerable behavioral and physiological flexibility that may allow them to persist in environmental conditions that humans perceive to be outside of the species' ecological niche (Smith 2009, p. 4).
The distribution of American pikas from prehistoric times to the present is a result of changing climatic conditions. Pika population occurrences in the southern Rocky Mountains are closely tied to the past and present distribution of alpine permafrost conditions, with altithermal (i.e., a dry postglacial interval centered about 5,500 years ago during which temperatures were warmer than at present) warming accounting for 66.7 percent of all postWisconsinan period population extirpations (Hafner 1994, p. 375). Climate change and subsequent impacts on vegetation determined the distribution of the American pika in the Great Basin (Grayson 2005, p. 2103). The present distribution of the Am
FOR FURTHER INFORMATION CONTACT
Larry Crist, Field Supervisor, Utah
Ecological Services Field Office (see ADDRESSES); by telephone at 801 9753330; or by facsimile at 8019753331. Persons who use a
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