Federal Register: September 30, 2010 (Volume 75, Number 189)
DOCID: fr30se10-27 FR Doc 2010-24349
DEPARTMENT OF THE INTERIOR
CFR Citation: 50 CFR Part 17
Docket ID: [Docket No. FWS-R8-ES-2007-0022]
MO ID: [MO 92210-0-0008-B2]
NOTICE: Part II
DOCUMENT ACTION: Notice of a 12-month petition finding.
Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition to List the Pygmy Rabbit as Endangered or Threatened
DATES: The finding announced in the document was made on September 30, 2010.
We, the U.S. Fish and Wildlife Service (Service), announce a 12month finding on a petition to list the pygmy rabbit (Brachylagus idahoensis) as endangered or threatened under the Endangered Species Act of 1973, as amended. After review of all available scientific and commercial information, we find the listing of the pygmy rabbit 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 pygmy rabbit 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 List of Endangered and Threatened Wildlife and Plants that contains substantial scientific or commercial information that the listing may be warranted, we make a finding within 12 months of the date of the receipt of the petition. In this finding, we will 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 endangered or threatened , and expeditious progress is being made to add or remove qualified species from the 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 November 21, 1991, we added the pygmy rabbit to our list of candidate species as a category 2 candidate species (56 FR 58804). A category 2 candidate species was a species for which we had information indicating that a proposal to list it as threatened or endangered under the Act may be appropriate, but for which additional information on biological vulnerability and threat was needed to support the preparation of a proposed rule. In the February 28, 1996, Candidate Notice of Review (CNOR) (61 FR 7595), we adopted a single category of candidate species defined as follows: ``Those species for which the Service has on file sufficient information on biological vulnerability and threat(s) to support issuance of a proposed rule to list but issuance of the proposed rule is precluded.'' In previous CNORs, species matching this definition were known as category 1 candidates for listing. Thus, the Service no longer considered category 2 species as candidates and did not include them in the 1996 or any subsequent CNORs. The decision to stop considering category 2 species as candidates was designed to reduce confusion about the status of these species and to clarify that we no longer regarded these species as candidates for listing.
On April 21, 2003, we received a petition dated April 1, 2003, from the Committee for the High Desert, Western Watersheds Project, American Lands Alliance, Oregon Natural Desert Association, Biodiversity Conservation Alliance, Center for Native Ecosystems, and Mr. Craig Criddle requesting the pygmy rabbit found in Oregon, Idaho, Montana, Wyoming, California, Nevada, and Utah be listed as endangered or threatened in accordance with section 4 of the Act (Committee for the High Desert et al. 2003, entirety). The petition was clearly identified as a petition and contained the names, signatures, and addresses of the requesting parties. The petitioners requested designation of critical habitat concurrent with the listing. Included in the petition was supporting information regarding the species' taxonomy and ecology, historical and current distribution, and perceived threats to the pygmy rabbit.
On June 10, 2003, we acknowledged in a letter the receipt of the petition and stated we determined an emergency listing was not warranted for the pygmy rabbit. We also stated if our ongoing status review of the species indicates that an emergency listing is warranted, we would act accordingly. In addition, we advised the petitioners that we would not be able to process the petition in a timely manner. On May 3, 2004, we received a 60day notice of intent to sue, and on September 1, 2004, we received a complaint regarding our failure to carry out the 90day and 12month findings on the status of the pygmy rabbit. On March 2, 2005, we reached an agreement with the plaintiffs to submit to the Federal Register a completed 90day finding by May 16, 2005, and to complete, if applicable, a 12month finding by February 15, 2006 (Western Watersheds Project et al. v. U.S. Fish and Wildlife Service (CV040440NBLW) (D. Idaho).
On May 20, 2005, we published a 90day finding in the Federal Register (70 FR 29253) stating that the petition did not present substantial information indicating that listing the pygmy rabbit may be warranted. On March 28, 2006, we received a complaint regarding alleged violations of the Act and the Administrative Procedure Act with regard to our May 20, 2005, 90day finding (Western Watersheds Project et al. v. Gale Norton and U.S. Fish and Wildlife Service (CV 06CV00127S EJL) (D. Idaho)). On September 26, 2007, the court issued an order remanding our May 20, 2005, 90day finding and required the Service to issue a new 90day finding on or before December 26, 2007. On January 8, 2008, we published a new 90day finding (73 FR 1312), and determined that the petition presented substantial information indicating that the petitioned action may be warranted. Additionally in that notice, we indicated that we would be initiating a status review of the pygmy rabbit and opening a 60day public comment period.
This finding does not address our prior listing of the Columbia Basin distinct population segment (DPS) of the pygmy rabbit which occurs in the State of Washington. On November 30, 2001, we published an emergency listing and concurrent proposed rule to list this DPS of the pygmy rabbit as endangered (66 FR 59734 and 66 FR 59769, respectively). We listed the Columbia Basin DPS of the pygmy rabbit as endangered in our final rule dated March 5, 2003 (68 FR 10388). This finding addresses the petitioned action that requests listing of the pygmy rabbit as endangered or threatened in the remainder of its range in Oregon, Idaho, Montana, Wyoming, California, Nevada, and Utah. Species Information
The pygmy rabbit is the smallest North American Leporid. Adult weights range from 0.54 to 1.2 pounds (245 to 553 grams); adult lengths range from 9.1 to 12.1 inches (in) (23.1 to 30.7 centimeters (cm)) (Dice 1926, p. 28; Grinnell et al. 1930, p. 554; Bailey 1936, p. 110; Orr 1940, p. 194; Janson 1946, pp. 21, 23; Durrant 1952, p. 88; Ingles 1965, p. 143; Bradfield 1974, pp. 1011; Holt 1975, pp. 125126; Campbell et al. 1982, p. 100). Adult females are generally larger than adult males. The species can be distinguished from other rabbits by its small size, gray color, short rounded ears, small hind legs, and the absence of white on the tail (66 FR 59734).
The pygmy rabbit is a member of the family Leporidae, which includes rabbits and hares. This species has been placed in various genera positions since its type specimen was described in 1891 by Merriam (1891, pp. 7678), who classified the ``Idaho pygmy rabbit'' as Lepus idahoensis. Currently, the pygmy rabbit is generally placed within the monotypic genus Brachylagus and classified as B. idahoensis (Green and Flinders 1980a, p. 1; Washington Department of Fish and Wildlife (WDFW) 1995, p. 1); this is the taxonomy accepted by the Service. The analysis of blood proteins (Johnson 1968, cited in WDFW 1995, p. 1) suggests that the pygmy rabbit differs greatly from species within both the Lepus and Sylvilagus genera. Halanych and Robinson (1997, p. 301) supported the separate generic status as Brachylagus for the pygmy rabbit based on phylogenetic position and sequence divergence values. The pygmy rabbit has no recognized subspecies (Grinnell et al. 1930, p. 555; Davis 1939, p. 364; Larrison 1967, p. 64; Green and Flinders 1980a, p. 1; Janson 2002, p. 4).
Ecology and Life History
Pygmy rabbits are typically found in areas of tall, dense Artemisia spp. (sagebrush) cover and are considered a sagebrush obligate species because they are highly dependent on sagebrush to provide both food and shelter throughout the year (Dice 1926, p. 27; Grinnell et al. 1930, p. 553; Orr 1940, pp. 194197; Hall 1946, p. 615; Janson 1946, pp. 3940, 53; Wilde 1978, p. 46; Green and Flinders 1980a, pp. 13 and b, pp. 137141; Weiss and Verts 1984, pp. 569570; Katzner et al. 1997, p. 1,053). Anthony (1913, p. 22) also mentioned he found pygmy rabbits in ``little draws and flats'' in Oregon, where the tall sagebrush was thick and where Chrysothamnus spp. (rabbit brush) grew in extensive patches, and occasionally they were found on ``sparsely brushed flats and hills.''
The winter diet of pygmy rabbits is composed of up to 99 percent sagebrush (Wilde 1978, p. 46; Green and Flinders 1980b, p. 138), which is unique among leporids (rabbits and hares) (White et al. 1982, p. 107). During spring and summer in Idaho, their diet consists of approximately 51 percent sagebrush, 39 percent grasses (particularly native bunchgrasses, such as Agropyron spp. and Poa spp.), and 10 percent forbs (Green and Flinders 1980b, p. 138). There is evidence that pygmy rabbits preferentially select native grasses as forage over other available foods during this period. In addition, total grass cover relative to forbs and shrubs may be reduced within the immediate areas occupied by pygmy rabbits as a result of their use during spring and summer (Green and Flinders 1980b, pp. 138141). The specific diets of pygmy rabbit likely vary by region (68 FR 10388).
Pygmy rabbits may be active at any time of the day or night, and
appear to be most active during midmorning (Anthony 1913, p. 23; Bailey 1936, p. 111; Bradfield 1974, pp. 1415; Green and
Flinders1980a, p. 3; Gahr 1993, pp. 4546). Flinders et al. (2005, p. 27) found pygmy rabbits to be 72 percent more active during twilight. Larrucea (2007, p. 79) found pygmy rabbits were most active during dawn and dusk (a bimodal diel activity pattern). Activity at dawn was greatest except for during winter when dusk activity was higher. Lee (2008, p. 33) found pygmy rabbits were active during all time periods of the day, but the greatest activity occurred at night.
Pygmy rabbits maintain a low stance, have a deliberate gait, and are relatively slow and vulnerable in more open areas. They can evade predators by maneuvering through the dense shrub cover of their preferred habitats, often along established trails, or by escaping among their burrows (Anthony 1913, pp. 2223; Bailey 1936, p. 111; Severaid 1950, p. 3; Bradfield 1974, pp. 2627). Due to their small size, behavior, and habitat, these small rabbits can be easily overlooked (Merriam 1891, p. 75; Grinnell et al. 1930, p. 553; Janson 1940, p. 1; Severaid 1950, p. 3; Holt 1975, p. 135; Janson 2003, p. 71).
The pygmy rabbit is one of only two rabbits in North America that digs its own burrows (Nelson 1909, p. 22; Bailey 1936, p. 111; Hall 1946, p. 617; Janson 1946, p. 43; Bradfield 1974, p. 28; Wilde 1978, p. 17). Pygmy rabbit burrows are typically found in relatively deep, loose soils of windborne or waterborne (e.g., alluvial fan) origin. Pygmy rabbits, especially juveniles, likely use their burrows as protection from predators and inclement weather (Bailey 1936, p. 111; Bradfield 1974, pp. 2627). Some burrows have only one entrance. Others have multiple entrances, some of which are concealed at the base of larger sagebrush plants (Dice 1926, p. 27). A single entrance burrow may be referred to as a ``burrow'' while single entrance burrows, multi entrance burrows, or an entire site may be referred to as a ``burrow system''. Burrows are relatively simple and shallow, often no more than 2.2 yards (yd) (2 meters (m)) in length and usually less than 1.1 yd (1 m) deep with no distinct chambers (Bailey 1936, p. 111; Bradfield 1974, pp. 2930; Green and Flinders 1980a, p. 2; Gahr 1993, p. 63). Burrows are typically dug into gentle slopes or mound or intermound areas of more level or dissected topography (Wilde 1978, p. 26; Gahr 1993, pp. 7780).
In general, the number of active burrows in an area increases over the summer as the number of juveniles increase. However, the number of active burrows may not be directly related to the number of individuals in a given area because some individual pygmy rabbits appear to maintain multiple burrows and some individual burrows are used by multiple individuals (Janson 1940, p. 21; Janson 1946, p. 44; Gahr 1993, pp. 66, 68; Heady 1998, p. 25).
Pygmy rabbits may also be using more than one burrow or burrow
system at a specific time or during different times of the year
(Purcell 2006, p. 96). In Idaho, Sanchez and Rachlow (2008, p. 1306)
found the number of burrows used by individuals increased with home
range size. Patterns of burrow system use varied by study area, sex, and season (Sanchez and Rachlow 2008, pp. 1306
1307). Larrucea (2007, pp. 9697) found annual and intraannual changes at three study sites during a 3year period in the Reese River Valley, Nevada. During two of the three years, one site showed lack of activity during winter and spring. Pygmy rabbits returned to this site in June and many new burrows were found. This site may have been marginal habitat and rabbits using the area in June may have been dispersing juveniles from other areas. At the other two sites where pygmy rabbits were observed yearround, the fewest active burrows were found from July to October. With the return of cooler weather in the fall, the number of active burrows again increased. Many of these new active burrows were ones that had previously been inactive or collapsed.
Flinders et al. (2005, p. 25) reported distances between burrow systems. They found burrow systems with multiple entrances averaged 124.6 yd (114.0 m) away from the next nearest multiple entrance system, while distances between systems with multiple entrances to single entrance burrows averaged 57.1 yd (52.2 m) away. Single entrance burrow systems averaged 14 yd (12.8 m) away from the nearest single entrance system.
Pygmy rabbits occasionally make use of burrows abandoned by other species, such as the yellowbellied marmot (Marmota flaviventris), badger (Taxida taxus), or Utah prairie dog (Cynomys parvidens) (Borell and Ellis 1934, p. 41; Hall 1946, p. 617; Bradfield 1974, p. 28; Green and Flinders 1980a, p. 2; Flinders et al. 2005, p. 30). As a result, they may occur in areas of shallower or more compact soils that support sufficient shrub cover (Bradfield 1974, p. 29). Natural cavities (such as holes in volcanic rock), rock piles, stone walls, and areas around abandoned buildings may also be used (Janson 1946, pp. 4446). During winter, pygmy rabbits make extensive use of snow burrows, possibly for access to sagebrush forage (Bradfield 1974, p. 17; Katzner and Parker 1997, p. 1,069), as travel corridors among their underground burrows, for protection from predators, and/or as thermal cover (Katzner and Parker 1997, pp. 1,063, 1,0691,070).
Pygmy rabbits tend to have relatively small home ranges during winter, remaining within 98 ft (30 m) of their burrows (Janson 1946, p. 75). Bradfield (1974, p. 20), Katzner and Parker (1997, p. 1,066), and Flath and Rauscher (1995, p. 3) found pygmy rabbit tracks in snow indicating movements of 262 to 328 ft (80 to 100 m) or more from their burrows. They have larger home ranges during spring and summer (Janson 1946, p. 75; Gahr 1993, pp. 103105). During the breeding season in Washington, females tend to make relatively short movements within a small core area and have home ranges covering roughly 6.7 acres (ac) (2.7 hectares (ha)); males tend to make longer movements, traveling among a number of females, resulting in home ranges covering roughly 49.9 ac (20.2 ha) (Gahr 1993, p. 118). Katzner (1994, pp. 1415) found home range size extremely variable in Wyoming; home ranges were from 0.12 to 0.86 ac (0.05 to 0.35 ha) for females and 0.82 to 4.4 ac (0.33 to 1.8 ha) for males. Burak (2006, p. 22) found in Owyhee County, Idaho, that pygmy rabbit home range sizes based on Minimum Convex Polygons differed between the sexes and ranged from 49.9 to 69.7 ac (20.2 to 28.2 ha) for males and from 4 to 5.4 ac (1.6 to 2.2 ha) for females during the breeding season. Crawford (2008, p. 47) found that pygmy rabbit annual home ranges in southeastern Oregon and northwestern Nevada differed between the sexes and ranged from 1.2 to 25.8 ac (0.49 to 10.46 ha) for males and 0.27 to 18.7 ac (0.11 to 7.55 ha) for females. During the breeding season, home ranges for males ranged from 0.27 to 18.5 ac (0.11 to 7.49 ha) and from 0.15 to 17.5 ac (0.06 to 7.10 ha) for females.
Sanchez and Rachlow (2008, p. 1307) in Idaho found range use between consecutive seasons and between seasons over 2 years was highly variable; some pygmy rabbits shifted seasonal ranges markedly, but most ranges showed overlap between seasons and years. One male shifted his range center by 8,013.9 yd (7,332 m), but other males shifted their range centers between 33 and 122 yd (30 and 112 m). Females shifted their range centers between 58 and 144 yd (53 and 132 m) (Sanchez and Rachlow 2008, p. 1307). Distances shifted between like seasons over the 2 years were similar to those observed between consecutive seasons. Males showed a distance shift of between 47 and 269 yd (43 and 246 m) and females showed a shift of between 0 and 150 yd (0 and 137 m) (Sanchez and Rachlow 2008, p. 1307).
Earlier reports indicated pygmy rabbits were known to have traveled up to 0.75 mile (mi) (1.2 kilometers (km)) from their burrows (Gahr 1993, p. 108), and there are a few records of individuals moving up to 2.17 mi (3.5 km) (Green and Flinders 1979, p. 88; Katzner and Parker 1998, p. 73). Rauscher (1997, p. 5) reported that pygmy rabbits crossed 500 yd (457.2 m) of relatively open grassland habitat to reach a sagebrush stringer in Montana. Katzner (1994, p. 105) accounted for all the rabbits within a range of 0.62 mi (1 km) of his study area. When pygmy rabbits not previously observed appeared, he concluded these individuals must have traveled a ``considerable distance.'' More recently, EstesZumpf and Rachlow (2009, p. 367) radiotagged juvenile pygmy rabbits in Idaho and found median dispersal movements of 0.93 mi (1.5 km) and 3.9 mi (6.2 km) and maximum dispersal movements of 4.0 mi (6.5 km) and 7.4 mi (11.9 km) by male and female rabbits, respectively. Burak (2006, p. 27) indicated the maximum distance a male pygmy rabbit moved was 1,662.5 yd (1,521 m) and 1,112.7 yd (1,018 m) for a female. Crawford (2008, p. 54) in Nevada and Oregon reported that 24 radio marked rabbits moved greater than 0.3 mi (0.5 km) with a maximum long distance movement of 5.3 mi (8.5 km) recorded by a juvenile female. Twentyone of the individuals that traveled greater than 0.3 mi (0.5 km) were juveniles.
Pygmy rabbits may begin breeding the year following their birth
(Wilde 1978, pp. 6466, 127; Fisher 1979, p. 13). In some parts of the
species' range, females may have up to three litters per year and
average six young per litter (Davis 1939, p. 365; Hall 1946, p. 618;
Janson 1946, pp. 6769; Green 1978, pp. 3536; Wilde 1978, p. 69).
Breeding appears to be highly synchronous in a given area and juveniles
are often identifiable to cohorts (Wilde 1978, pp. 6970). Prior to
publication of a study in 2005, no evidence of nests, nesting material,
or lactating females with young had been found in burrows (Bailey 1936,
p. 111; Janson 1940, p. 23; Janson 1946, p. 69; Bradfield 1974, p. 29;
Gahr 1993, p. 82 Rauscher 1997, p. 11). Recent studies have found that
natal burrows are constructed by pygmy rabbits. Rachlow et al. (2005,
pp. 137138) provide information on seven natal burrows found in Lemhi
Valley, Idaho. Females were observed digging and subsequently back
filling burrows with soil. Fine grasses, shredded sagebrush bark, and
hair were the primary components used in the nesting material. Larrucea
(2007, pp. 8990) found three natal burrows in Reese River Valley,
Nevada, but did not describe them. Burak (2006, p. 29) found female
pygmy rabbits construct natal burrows outside of their original home
range core area. Three of the four natal burrows he found were located
outside of the core area; the fourth female stayed within a second core
area that included the natal burrow and when the burrow became
inactive, she returned to her original core area (Burak 2006, p. 29).
Individual juveniles have been found under clumps of sagebrush, although it is not known if they are
routinely hidden at the bases of scattered shrubs or within burrows (Wilde 1978, p. 115).
A wide range of pygmy rabbit population densities has been reported. Janson (1946, p. 84) reported estimated pygmy rabbit densities of 0.75 to 1.75 per ac (1.9 to 4.3 per ha) and 3.5 pygmy rabbits per ac (8.6 per ha) in Utah. Flinders et al. (2005, p. 16) reported 0.3 rabbits per ac (0.79 rabbits per ha) in Grass Valley, Utah. Green (1978, p. 62) reported an estimate of 18.2 pygmy rabbits per ac (45 per ha) in Idaho. In Montana, Rauscher (1997, p. 10) estimated pygmy rabbit density as 0.67 rabbits per burrow or 1.2 per ac (3.0 per ha). Based on fecal dropping counts, Larsen et al. (2006, pp. 2627) estimated rabbit density in Deep Creek watershed, Utah, as 0.07 per ac (0.17 rabbits per ha). Using line transects in Wyoming, Purcell (2006, pp. 100, 105) reported a range of burrow systems per mi (km) for systematic transects (1.7 to 18.2 per mi, 2.7 to 29.3 per km) and random transects (0.8 to 7.4 per mi, 1.33 to 11.97 per km) in 10 study areas. Larrucea (2007, p. 89) estimated, using transect counts, that the relative density at five study areas in California and Nevada ranged from 0.4 to 1.7 rabbits per ac (0.9 to 4.2 rabbits per ha).
The annual mortality rate of adult pygmy rabbits may be as high as 88 percent, and more than 50 percent of juveniles can die within roughly 5 weeks of their emergence (Wilde 1978, pp. 139140). Estes Zumpf and Rachlow (2009, p. 367) found mortality rates were 69.2 percent and 88.5 percent for male and female juvenile pygmy rabbits, respectively, in their study area in eastcentral Idaho. The mortality rate was highest within two months of emerging from the natal burrow. However, the mortality rates of adult and juvenile pygmy rabbits can vary considerably between years, and even between juvenile cohorts within years (Wilde 1978, pp. 8595, 138140). Predation is the main cause of pygmy rabbit mortality (Green 1979, p. 25). Sanchez (2007, pp. 9091) attributed 42 percent of natural mortalities to mammalian and avian predation. She was unable to determine the cause of death in 58 percent of the mortalities.
Predators of the pygmy rabbit include badgers, longtailed weasels (Mustela frenata), coyotes (Canis latrans), bobcats (Felis rufus), great horned owls (Bubo virginianus), longeared owls (Asio otus), ferruginous hawks (Buteo regalis), northern harriers (Circus cyaneus), and common ravens (Corvus corax) (Borell and Ellis 1934, p. 42; Janson 1946, pp. 8990; Gashwiler et al. 1960, p. 227; Green 1978, p. 37; Wilde 1978, pp. 96, 141143; Johnson and Hanson 1979, p. 952; WDFW 1995, p. 6).
Sanchez (2007, p. 92) estimated that for knownaged rabbits, the average lifespan was 1.16 years. For rabbits captured as adults, assuming a birth date of May 1 of the previous year, estimated average life expectancy was 1.7 years, and the maximum lifespan achieved was 3.3 years.
Population cycles are not known in pygmy rabbits, although local, relatively rapid population declines have been noted in some States (Janson 1946, p. 84; Bradfield 1974, p. 39; Weiss and Verts 1984, p. 569). Janson (2003, p. 71) remarked that pygmy rabbits likely undergo local, if not regional, fluctuations. After initial declines, pygmy rabbit populations may not have the same capacity for rapid increases in numbers in response to favorable environmental conditions as compared to other rabbit species. This may be due to their close association with specific components of sagebrush ecosystems, and the relatively limited availability of their preferred habitats (Wilde 1978, p. 145; Green and Flinders 1980b, p. 141; WDFW 1995, p. 13). No study has documented rapid increases in pygmy rabbit numbers in response to environmental conditions (Gabler 1997, p. 95). Longterm population monitoring studies are not available indicating whether population fluctuations or cycles occur for pygmy rabbits or if seasonal or other habitat shifts or movements have been misinterpreted as declines.
Literature indicates that pygmy rabbits have never been evenly distributed across their range (Bailey 1936, p. 111; Janson 1940 p. 5; Holt 1975, pp. 133134). While the species occurs throughout most of the Great Basin, they exhibit extremely specialized habitat requirements, and thus occupy only a small subset of locations within this range (Larrucea 2007, p. 2). They are found in areas within their broader distribution where sagebrush cover is sufficiently tall and dense, and where soils are sufficiently deep and loose to allow burrowing (Bailey 1936, p. 111; Green and Flinders 1980a, p. 2; Campbell et al. 1982, p. 100; Weiss and Verts 1984, p. 563; WDFW 1995, p. 15). Sagebrush dominated communities are naturally subject to disturbances of various kinds resulting in a heterogeneous distribution of different stand sizes and age classes, and on the landscape scale, pygmy rabbit distribution is naturally disjunct (Himes and Drohan 2007, p. 380). Local distribution of this habitat and thus pygmy rabbit populations likely shift over time due to natural and human disturbances including fire, agriculture production, flooding, grazing, and weather patterns (Keinath and McGee 2004, p. 5). In the past, dense vegetation along permanent and intermittent stream corridors, alluvial fans, and sagebrush plains probably provided travel corridors and dispersal habitat for pygmy rabbits between suitable use areas (Green and Flinders 1980a, p. 1; Weiss and Verts 1984, p. 570; WDFW 1995, p. 15). Since European settlement of the western United States, dense vegetation associated with human activities (fence rows, roadway shoulders, borrow ditches, crop margins, abandoned fields) may have also acted as avenues of dispersal between local populations of pygmy rabbits (Green and Flinders 1980a, p. 1; Rauscher 1997, p. 16). Distribution, Abundance, and Trends
The pygmy rabbit's general historical and current geographic range, excluding the Columbia Basin DPS, includes most of the Great Basin and some of the adjacent intermountain areas of the western United States (Green and Flinders 1980a, p. 1), and the boundaries can be described as follows: the northern boundary extends into southeastern Oregon and southern Idaho. The eastern boundary extends into southwestern Montana and south central Wyoming. The southeastern boundary extends into southwestern Utah. Central Nevada and eastern California provide the southern and western boundaries (Merriam 1891, p. 75; Nelson 1909, p. 275; Grinnell et al. 1930, pp. 553, 558; Bailey 1936, pp. 110111; Janson 1946, pp. 3233; Campbell et al. 1982, p. 100; WDFW 1995, pp. 1 2, Purcell 2006, pp. 1, 711, 30). Based on available information, the current distribution of the pygmy rabbit indicates a possible range contraction in northern California (Larrucea and Brussard 2008a, p. 696). Because uncertainty remains about whether this possible range contraction has occurred due to limited survey efforts in northern California both historically and recently, it is not shown in Figure 1. Figure 1 illustrates the approximate historical and current range of the pygmy rabbit in the seven States discussed in this finding. [[Page 60520]]
[GRAPHIC] [TIFF OMITTED] TP30SE10.008
Figure 1. Approximate historical and current range (based on data from 1877 to 2008) of the pygmy rabbit (Brachylagus idahoensis) not including the Columbia Basin DPS in Washington State.
To determine the historical and current distribution and trend analysis for pygmy rabbits across the seven States discussed in this finding, we reviewed published scientific peerreviewed literature; unpublished agency documents; dissertations; theses; databases maintained by State heritage programs, State wildlife agencies, and Federal agencies; survey data sheets; museum records; electronic mail records; and agency notes to the files. Older published literature (prior to the mid to late 1990's) generally focused on the species' life history, behavior, and some habitat relationships and provided location information of study areas. More recent unpublished literature (since the mid to late 1990's to 2008) has been primarily related to surveys conducted by government agencies or their consultants and universities to determine pygmy rabbit occurrence within portions of a State and some information regarding species' life history, behavior, and habitat relationships. Survey efforts have focused on location of pygmy rabbit signs rather than on documenting known or perceived threats to the species at these sites. Rarely has revisiting of sites occurred with the purpose of monitoring populations over time. While we consider this information of limited use to our finding due to its local, shortterm nature, it is the best scientific information available to conduct our analysis.
We compiled a database of records (location points) of various
pygmy rabbit signs for each State from these various data sources
listed above. Some records were not entered into a State database if adequate information was
not provided (e.g., we could not determine a location point because the source map did not indicate location or survey data sheet location point information was unreadable). Once each State database was compiled, we reviewed each location point and eliminated its database record if it was not determined to be a reliable data point as discussed below. The final databases combined contain approximately 68 percent of all the location points compiled. We consider the location point data retained in these seven State databases to be the best scientific information available. We will refer to these created State databases as the Service's databases.
We are aware of concerns related to the use of anecdotal occurrence records to determine distribution of species (McKelvey et al. 2008, pp. 549554). We are also aware of confidence levels related specifically to pygmy rabbit presence and level of activity at particular sites due to various factors (e.g., sighting of targeted species vs. only targeted species sign or potential targeted species sign observed; if burrow activity is uncertain, the site should be revisited; uncertainties due to other species or other rabbit species using burrows; pellets being misidentified) (Bartels 2003, pp. 4749; Keinath and McGee 2004, pp. 3234).
As a result of these concerns, we have based our analysis on what we considered to be the more reliable records indicating pygmy rabbit presence and activity level. The following types of records were not included in the Service's databases for our analysis: database records that showed some level of uncertainty for the information being provided (e.g., other leporid species data included; uncertainty about whether pygmy rabbit was observed or other leporid species; using words such as ``possible'', ``potential'', ``maybe'', ``unsure''); records that only provided location data or indicated pygmy rabbit sign with no additional information indicating what type of sign (e.g., burrow, pellet, track, sighting of animal as relates to reliability) had been observed; records related to telemetry locations (while informative in determining an individual's distribution within its home range, this provides little information at the larger landscape scale used here; we did include the capture location of any individual pygmy rabbit trapped and fitted with a tradio collar); records based solely on pellets or tracks due to concerns with species misidentification; those lacking key information (e.g., year which is needed for trend analysis) and duplicate records.
For our analysis, we mapped records of ``active'' sites or burrows defined as those database records that indicated an activity level (at the time of the survey) of current, present, occupied, active, or recently active burrows; burrows in combination with fresh pellets; a visual sighting; photographic evidence; fecal DNA confirmation; specimen collected; trapping effort; in combination with tracks; or any combination thereof. All sighting records were included in our analysis even if no other information was provided, unless uncertainty was expressed about whether it had been a pygmy rabbit observed or another leporid species.
We also mapped records of ``inactive'' sites or burrows defined as those database records that indicated an activity level (at the time of the survey) of inactive, not recent, old, very old, collapsed, or burrow plus old pellets. In addition, we assumed ``inactive'' for site or burrow records that did not provide a status and did not provide information to support a determination of active, those with an ``undetermined'' activity status, or were unclear. We reviewed the mapped distribution for the ``active'' and ``inactive'' site categories across each State.
In addition, we mapped database records of ``absent'' areas defined as points where no sign of pygmy rabbit occupancy was evident. Most databases do not include records of areas surveyed but where no pygmy rabbit sign was observed. We believe this type of information can be valuable; however, we do not assume that pygmy rabbits were or should have been present in areas where they were determined to be absent. It is possible that an area is unsuitable for pygmy rabbits while appearing suitable to surveyors. Conversely, it is possible an area that appears unsuitable to surveyors for pygmy rabbits may actually be so (Ulmschneider et al. 2004, pp. 23). On the ground surveying is necessary to positively indicate pygmy rabbit occupancy (Bartels 2003, pp. 9294; Lenard et al. 2005, p. 1; Meisel 2006, pp. 26, 48). The ``absent'' information indicates locations where survey efforts were conducted but pygmy rabbit sign was not evident. Limited ``absent'' information was obtained for the States of Oregon, California, Nevada, and Wyoming.
During our analysis we encountered some difficulties in adapting data collected for another's purpose for our species' status review, and there were several limitations. Overall, survey information collected over the years reflects different surveyors, different survey methods, different levels of survey intensity, and different amounts and types of information recorded. We generally accepted the information indicated in a report, data sheet, or database and tried to do as little interpretation as possible. For some locations, we replaced locational descriptions (Township, Range and Section or a narrative description) with Universal Transverse Mercator (UTM) coordinates or a center point for a section surveyed or a point was buffered to indicate an approximate location. For a portion of records from Oregon, we created a point representing the center of a study area and ``active'' and ``inactive'' burrows were separated.
We encountered some difficulties with interpreting data provided under different reporting techniques. In general, most surveys for pygmy rabbits report location information in terms of point data (i.e., legal description or Global Positioning System (GPS)) with qualifiers or descriptions for sign, such as burrows (present, absent), activity level (occupied, unoccupied, active, inactive, current, recent, old, very old), pellets (fresh, old), sightings (actual sightings of pygmy rabbits, specimen collection, capture, photographic record), and tracks. Some surveyors developed their own rating system or confidence level for burrow or site activity (Purcell 2006, p. 38; Himes and Drohan 2007, p. 375; Flinders et al. 2005, pp. 89). Some efforts reported only those sites that were considered positive (confirmed with photographic evidence), active, or occupied sites and did not include information for areas considered inactive or unoccupied. Location data may represent a burrow, a burrow system, or an entire site that was surveyed which represents one or more burrows or burrow systems.
Various techniques have been used to detect pygmy rabbit evidence
on the landscape. Techniques may include driving and walking transects
in perceived suitable habitat, winter aerial flights over potential
habitat with subsequent selection of areas for further ground surveys
(Rachlow and Witham 2006, pp. 48), random searches in perceived
suitable habitat, or spot lighting at night. Survey efforts have been
made during all times of the year. It is advised that sites that
indicate pygmy rabbit sign should be confirmed through sightings or
photographic evidence; this may or may not have occurred. The Service
has recommended using draft survey guidelines developed by Ulmschneider et al. (2004, entire) in conducting
pygmy rabbit surveys, but it has not always been used since its availability.
Larrucea (2007, p. 3) tested pellet, sighting, burrow, and camera survey methods at 20 locations in 4 known, active pygmy rabbit populations in California and Nevada. She also assessed road transect surveys for detecting and determining relative abundance in an area (Larrucea 2007, p. 3). Results indicated that pellets were found at all sites, but pellets determined to be fresh were found at only 70 percent of the sites. Sighting individual rabbits provided positive results 30 percent of the time. Burrows were located at 85 percent of the sites, but burrows determined to be active were found at only 55 percent of the sites. Cameras provided positive results 95 percent of the time (Larrucea 2007, p. 6). Photographs were taken of pygmy rabbits at all types of active sites including those with only burrows determined to be inactive and with pellets determined to be old (Larrucea 2007, p. 7). During the 10 transect counts, different rabbit and hare species were observed 569 times and 545 were identified to genus (Larrucea 2007, p. 7). Lepus was observed 491 times (90.1 percent); Sylvilagus 44 times (8.1 percent) and Brachylagus 10 times (1.8 percent) (Larrucea 2007, p. 7). Photographs taken from the camera locations provided 409 photos of rabbit and hare species; the number of photographs of Lepus was 199 (48.7 percent), Brachylagus 195 (47.7 percent), and Sylvilagus 15 (3.7 percent) (Larrucea 2007, p. 7).
Camera surveys are more effective than burrow, pellet, sightings, or road transect surveys for determining current pygmy rabbit activity at a site (Larrucea 2007, p. 7). Burrows are a good indicator that pygmy rabbits may be present, but locating one does not mean pygmy rabbits are currently using the site (Larrucea 2007, p. 8). Lack of active burrows may not mean that there are no pygmy rabbits in the area. Burrows may be used seasonally, may be difficult to locate, or may be lacking in dispersal areas (Larrucea 2007, pp. 89). Old pellets do not confirm current use of a site and pellets may be misidentified due to young rabbits of other species cohabiting a site. Not finding fresh pellets does not mean pygmy rabbits are not currently using a site as environmental conditions can influence how rapidly pellets dry and change color (Larrucea 2007, p. 9). Sightings of individual pygmy rabbits do confirm current activity, but observers should be experienced as the young of cottontails (Sylvilagus spp.) and jackrabbits (Lepus spp.) can be confused with pygmy rabbits. Sightings of pygmy rabbits are difficult and do not occur often due to the dense vegetation inhabited, limited home ranges, and their elusive nature (Larrucea 2007, p. 10). Road transect surveys are inefficient for pygmy rabbits due to their reluctance to cross open areas and roads (Bradfield 1975, p. 3). Pygmy rabbits are more likely to run a short distance, sit tight, or disappear into a burrow than to run for a long distance making detection more difficult (Larrucea 2007, p. 10).
We are also aware of difficulties in interpreting site activity during surveys. For example, in Montana, Lenard et al. (2005, p. 9) commented that comparisons of active to inactive burrows may be complicated, stating that burrows exhibiting current rabbit activity were easier to locate because tracks in the snow made them very apparent. The relative difference in abundance between currently active and recently active should not be interpreted to indicate any level of past versus current activity. Flinders et al. (2005, p. 33), in Utah, commented that single burrow systems are harder to detect than multiple entrance burrow systems. The Bureau of Land Management (BLM) (2007a, p. 1) used the Ulmschneider et al. (2004, entire) method and noted that this type of inventory covered large expanses and typically found the larger pygmy rabbit populations and a small subset of the actual burrow systems on a particular site. However, when sites were reinventoried intensively, BLM found numerous additional burrow systems. Lee et al. (2008, pp. 45), in Utah, commented that using criteria from Rachlow and Witham (2004b, pp. 67) or Ulmschneider et al. (2004, entire) is somewhat inaccurate in predicting current pygmy rabbit burrow utilization. Lee et al. (2008, p. 5) used remote cameras to verify the presence or absence of pygmy rabbits in comparison to burrow classification. By using both burrow classifications methods along with remote cameras, refinement of burrow classifications and census techniques may be possible in the future.
Bartels (undated) compared active and passive survey methods for detecting pygmy rabbit burrow occupancy at what she considered isolated and low density sites. She compared the use of an active survey method (peeper probe) and a passive survey method (surface classification of burrows using sign (burrows, pellets) to determine occupancy by pygmy rabbits (Bartels undated, pp. 34). A total of 233 burrows were compared on 27 sites in Oregon and Idaho. Under the passive method, all 233 burrows were considered occupied (Bartels undated, p. 5). Under the active survey method, 122 (52.4 percent) of the burrows were classified as occupied and as recently occupied, and 111 (47.6 percent) were classified as unoccupied (Bartels undated, p. 5). Bartels (undated, p. 7) recommended use of an active survey method in areas where pygmy rabbit numbers appear to be low and isolated sites are found. Viewing the internal attributes of burrows and establishing a standard for occupancy increases survey accuracy and could lead to greater accuracy when monitoring pygmy rabbit occupancy over time.
We must also take into consideration complicating factors when interpreting current distribution and/or status as we do not have a complete understanding of pygmy rabbit habitat use. For example, it appears that some habitat use may be seasonal and pygmy rabbits may be somewhat migratory as some burrow systems appear occupied during certain times of the year and inactive during others, or from year to year (Flinders et al. 2005 p. 35; Bockting 2007 p. 2; Larrucea 2007, pp. 9697). Flinders et al. (2005 p. 35) reported that areas where pygmy rabbits were relatively abundant in Utah suddenly became sparse after the juveniles dispersed. Other areas then appeared to indicate an increase in the numbers of pygmy rabbits. In Utah, Flinders et al. (2005, p. 32) found active burrows were more common than the other activity classifications (i.e., recent, old, very old), and thus support statements that pygmy rabbits use more than one burrow system. He thought inactive burrows likely play an important role in providing escape cover. Cameras placed on burrows classified as old or very old documented use by pygmy rabbits. Larrucea (2007, p. 7) also photographed pygmy rabbits at sites where burrows were determined to be inactive.
After reviewing the available information, we consider our approach
in using information to determine the status of the pygmy rabbit to be
conservative. We have used these data to compare historical (1999 and
earlier) to current (2000 and later) distribution patterns. We have
used the data to compare activity levels (active; inactive) of sites or
burrows during these two time periods. Questions have been raised
regarding surveyors' abilities to accurately determine activity level
due to possible detection differences, absence of longterm site
monitoring, and our incomplete understanding of the pygmy rabbit's life
history requirements (e.g., possible seasonal use of some areas or periods of burrow nonuse). We are also aware that some
survey techniques provide better data than others. Though these data are limited in their usefulness for our purposes due to their local, shortterm nature, they are understood, by the Service to be the best available information. This data does provide baseline information that could be the foundation for future survey and monitoring efforts. Models
To facilitate pygmy rabbit surveys in recent years, models of potential habitat have been developed for some States or study areas. Eliminating areas in these models that are unsuitable can be important as it can concentrate efforts and resources in areas that are more likely to support pygmy rabbits (Gabler et al. 2000, p. 763). Large areas that seem to be appropriate pygmy rabbit habitat may not be suitable based on the specific habitat characteristics needed for pygmy rabbits (Gabler et al. 2000, p. 763). To aid pygmy rabbit research in Oregon, modeling efforts have been conducted by the following researchers: Bartels (2003, p. 35) for the BLM Burns District using GIS; Meisel (2006, p. 4) for the Hart Mountain National Antelope Refuge; and Hager and Lienkaemper (2007, pp. 12) for large blocks of State land.
In Idaho, modeling efforts have been conducted by Rachlow and Svancara (2006, p. 828); Bartels (2003, pp. 3538), and Gabler et al. (2000, pp. 762763; 2001 entirety). In Montana, Lenard et al. (2005, p. 1) reported on the development of four predictive models in Montana. In Wyoming, Purcell (2006, p. 28) used a probabilistic distribution map developed by Keinath and Thurston (2005, cited in Purcell 2006, p. 28) using the combination of two models, DOMAIN (environmental similarity method) and CART (classification and regression tree analysis). Based on data collected during Purcell's study, a new predictive distribution model was created (Purcell 2006, p. 31).
In Nevada, a predictive equation was produced based on habitat data collected and used as a model to characterize habitat where pygmy rabbits or sign occurred. The model explained the occurrence of pygmy rabbits or their sign on 56.7 percent of transects (Himes and Drohan 2007, p. 376). Larrucea and Brussard (2008a, p. 693) used GIS coverages. In Utah, Lee et al. (2008, p. 3) used vegetation data from the 2004 Southwestern Regional Gap Analysis Project. In general, these models are helpful in focusing survey efforts over a large area; however, researchers also recognize that due to scale and available data for particular attributes such as soils and vegetation, only on the ground surveying can positively indicate pygmy rabbit presence (Bartels 2003, pp. 9294; Meisel 2006, pp. 26, 48; Lenard et al. 2005, p. 1).
We believe our largescale, rangewide analysis, based on the Service's databases, represents the best scientific and commercial information available on the distribution of pygmy rabbits. As mentioned above, many individual records were considered but not included in the Service's databases for the following reasons: database records showing some level of uncertainty for the information being provided (e.g., other leporid species data included; uncertainty about whether pygmy rabbit was observed or other leporid species; using words such as ``possible'', ``potential'', ``maybe'', ``unsure''); records that only provided location data or indicated pygmy rabbit sign with no additional information indicating what type of sign (e.g., burrow, pellet, track, sighting of animal as relates to reliability) had been observed; records related to telemetry locations (while informative in determining an individual's distribution within its home range, this provides little information at the larger landscape scale used here; we did include the capture location of any individual pygmy rabbit trapped and fitted with a radio collar); records based solely on pellets or tracks due to concerns with species misidentification; those lacking key information (e.g., year which is needed for trend analysis); and duplicate records.
Eliminating records with these types of concerns provides for a more accurate representation of pygmy rabbit rangewide distribution rather than including all records without considering some level of reliability of the data. While pygmy rabbits likely occur in additional unsurveyed areas and even in some areas that have been surveyed (pygmy rabbit sign can be easily overlooked), we have made our finding based on our review of these databases, which represent the best scientific and commercial information available.
Distribution by State
The following distribution and trend discussion is based on information obtained from published and unpublished literature and an interpretation of the survey location point data compiled in the Service's databases. The following review does not discuss every document from the various information sources due to the volume, but a selection of literature that provides substantive historical information and survey information on a large scale. The literature is generally, but not entirely, associated with records included in the Service's databases. This is because not all reports provided specific location points and not all location points are associated with a report, and as stated earlier, some records are not included in the Service's databases. This analysis compares our understanding of the historical and current ranges of the pygmy rabbit discussed in this finding.
The earliest pygmy rabbit records for the State of Oregon include: two specimens collected in Callow Valley, Harney County, Oregon (Nelson 1909, p. 278); specimens collected near Ironsides, Malheur County, Oregon in 19111912 (Anthony 1913, pp. 2021); and 10 specimens collected near Baker, Baker County, Oregon (Dice 1926, p. 27).
Bailey (1936, pp. 110111) indicated that pygmy rabbits in Oregon extended from the southern foothills of the Blue Mountain Plateau and eastern base of the Cascade Range over the southeastern quarter of the State. He reported that they were absent from areas of open country where sagebrush and rabbit brush were not abundant. As a result, there are numerous wide gaps in their range.
Brodie and Maser (1966, pp. 1112) reported the contents from owl pellets collected in 1966 at Lower Bridge, Deschutes County, Oregon. Prey animals consisted of pygmy rabbits. This location was reported as a new location for the pygmy rabbit as the nearest previously documented location was Redmond, Oregon (Hall and Kelson 1959, cited in Brodie and Maser 1966, p. 12) about 10 miles (16.1 km) east of Lower Bridge.
Olterman and Verts (1972, p. 25) listed 37 museum records for
Oregon which occurred in general near the following areas: Baker, Baker
County; Paulina, Crook County; Redmond, Deschutes County; Beakley,
Beaties Butte, Burns, Rock Creek Ranch, Crane, Drewsey, Narrows,
Sageview, Mud Lake, Steens Mountain, Voltage, and Waverly, Harney
County; Fremont and Klamath Falls, Klamath County; Adel, Ft. Rock,
Guano Creek, Guano Valley, Rabbit Creek, andSilver Lake, Lake County;
and Cold Springs, Cow Creek Lake, Ironside, Mahogany Mountains,
Malheur, McDermitt, Riverside, and Rome, Malheur County. At the time of
their writing, Olterman and Verts (1972, p. 25) indicated recent observations by biologists demonstrated that pygmy
rabbits were occurring over the same area as in the past. Pygmy rabbits were observed near Hines, Wagontire, Lakeview, Hart Mountain National Antelope Refuge, Hampton, Ft. Rock, and Lower Bridges.
Bradfield (1974, p. 39) also spent time at Ironside, in Malheur County, Oregon. He found evidence of previous pygmy rabbit use, but no fresh sign of use or rabbits, which supported his belief that they were in decline on a larger geographic scale.
Weiss and Verts (1984, p. 563) attempted to search for pygmy rabbits in Oregon based on museum record information for sites listed in Olterman and Verts (1972, p. 25). Because of the generality of the location descriptions provided, they also reviewed aerial photography and soil maps to assist in narrowing searches in the areas described where pygmy rabbits had been collected previously (Weiss and Verts 1984, p. 564). Evidence of pygmy rabbits was found at 51 of 211 areas searched in 1982 (Weiss and Verts 1984, p. 566). In 1983, only 5 of the 15 sites that had been sampled for soil and vegetation information in 1982 showed recent pygmy rabbit activity (Weiss and Verts 1984, p. 566). Of 51 burrows found at 5 of the sites occupied in 1982, 19 burrows were found open in 1983 and 8 had fresh pellets (Weiss and Verts 1984, p. 568). Only the locations of the 15 occupied sites in Grant and Lake Counties where Weiss and Verts (1984, p. 566) recorded vegetation and soil data are provided in their document.
Since 2000, additional survey efforts have been conducted. Bartels (2003, p. 70) visited 54 previously known pygmy rabbit sites located on BLM lands in 2000 and 2001 in Harney, Malheur, Lake, and Deschutes Counties, Oregon. Results from these visits showed 12 sites were occupied, 8 were of undetermined occupancy, and 34 showed no occupancy. Three additional sites were surveyed off of BLM lands. One site was occupied, one showed no evidence of pygmy rabbit use, and one was considered undetermined and warranted further investigation (Bartels (2003, p. 86). Some of these sites included those visited by Weiss and Verts (1984, p. 564) (Bartels 2003, p. 91).
BLM conducted surveys on their Lakeview and Vale Districts in Harney and Lake Counties, Oregon in 2002 and 2003 (BLM 2003a, p. 1). Fortyfive sites were surveyed in fall of 2002 and winter 2003 on the Lakeview District with 19 sites indicating pygmy rabbit activity (10 active, 9 inactive). Twenty sites were surveyed in fall of 2002 and winter 2003 on the Vale District with two sites indicating pygmy rabbit activity (1 active, 1 inactive). The remaining sites surveyed (44) on the two districts in fall of 2002 and winter 2003 showed no evidence of pygmy rabbit use (BLM 2003a, p. 1). During the summer of 2003, 23 additional sites were surveyed and 19 showed pygmy rabbit activity (11 active, 8 inactive); 4 sites showed no evidence of pygmy rabbit use (BLM 2003a, no page number provided). BLM continued to conduct surveys on their Burns and Lakeview Districts in Harney and Lake Counties, Oregon, respectively, in 2005 and 2006 (BLM 2006a, pp. 34); active pygmy rabbit use was found at four of the seven sites surveyed. In 2006 and 2007, BLM surveyed 12 additional sites on the Lakeview District, and active pygmy rabbit use was found at 8 sites (BLM 2007b, p. 1). Various numbers of burrow systems were found at the different sites (BLM 2003a, p. 3; BLM 2006a, pp. 34; BLM 2007b, pp. 36).
Meisel (2006, p. 4), improved the known distribution of pygmy
rabbits at Hart Mountain National Antelope Refuge, Lake County, during
2004 and 2005. The sagebrush habitat on the refuge has been protected
from development and other human disturbances for at least 70 years
(Meisel 2006, p. 9). Remote infrared 35mm cameras were used to confirm occupancy by pygmy rabbits (Meisel 2006, p. 12). Habitat
characteristics were measured at 45 occupied burrows (Meisel 2006, p. 18). In 2005, refuge staff found approximately 99 occupied burrows near burrow locations that were found in 2004 by Meisel (R. Huddleston Lorton, cited in Meisel 2006, p. 27). Location information on these 99 burrows was not included in Meisel (2006). It is possible that a large population inhabits the northeast portion of the refuge (Meisel 2006, p. 27). Meisel (2006, p. 27) recommends future research be conducted in areas of Wyoming big sagebrush to locate all burrows and document the population status on the refuge which is currently unknown.
Hager and Lienkaemper (2007, p. 1) conducted surveys to determine the presence or absence of pygmy rabbits on State lands in Malheur, Harney, Lake, and Deschutes Counties. One hundred and fiftyseven sites were ground surveyed during 2004 and 2005 (Hager and Lienkaemper 2007, p. 3). Of the 157 sites, 18 were determined to be active, 14 inactive, and 125 showed no evidence of pygmy rabbit presence (Hager and Lienkaemper 2007, pp. 45).
Most historical records (1999 and earlier) for Oregon occur in the following counties: Malheur, Harney, and Lake. A few historical records also occur in Baker, Grant, Crook, Deschutes, and Klamath Counties. There is also a 1992 database sighting record for Jefferson County. Current information (2000 and later) indicates Malheur, Harney, and Lake as well as Klamath and Deschutes Counties continue to support pygmy rabbit activity. We are unaware of information indicating any recent survey efforts have been conducted to determine pygmy rabbit activity for Baker, Grant, or Jefferson Counties. Baker County indicated some activity in 1926. Grant County indicated inactivity during 1982 and 1983. Jefferson County had some activity in 1992. The southeastern portion of Crook County was searched during 2005 by BLM, but pygmy rabbit evidence was not found. In general, pygmy rabbit activity continues to occur in southeastern Oregon in a similar distributional pattern as compared with historical information. Idaho
Merriam (1891) was the first to describe the ``Idaho pygmy rabbit (Lepus idahoensis)'' based on a specimen collected on September 16, 1890, along the upper part of the Pahsimeroi River by Basil Dutcher (Merriam 1891, pp. 7, 13, 7578). Merriam (1891, p 75) indicated that the general distribution for the pygmy rabbit was the ``Sage Plains'' along the Snake River, and in Birch Creek and Lemhi Valleys, Little Lost River Valley, Pahsimeroi Valley and Big Lost River Valley, Idaho and into northern Nevada to the south, and to the west ``probably'' into eastern Oregon and Washington.
Other early records include: six specimens collected from Big Lost
River Valley, Birch Creek, Junction, Lost River Mountain, and
Pahsimeroi Valley, Idaho (Nelson 1909, p. 278); and a report of two
pygmy rabbits collected from 1 mi (1.6 km) west of Schutt's Mine in
November 1930 (Whitlow and Hall 1933, p. 269). In May 1931, a female
was collected near Trail Creek (Whitlow and Hall 1933, p. 270). These
records extended the known range by 75 mi (120.7 km) to the southeast
(Whitlow and Hall 1933, p. 270). Observations of pygmy rabbits in Idaho
occurred near the head of the Pahsimeroi River, Idavada, Pahsimeroi
Valley, Riddle, and Pocatello (Davis 1939, p. 364). Davis lists
locations of 10 specimens examined: Owyhee County, near Riddle, 2;
Cassia County, Elba, 1; Butte County, Craters of the Moon National
Monument, 1; Power County, near Michaud, 3; Bannock County, near
Schutt's Mine, 2; Trail Creek near Pocatello, 1. Additional records mentioned included Nelson's (1909)
records of Lemhi County, Junction; Custer County, Pahsimeroi Valley. Additional locations included Minidoka County, Minidoka (Seton 1929, cited in Davis 1939, p. 366); Cassia County, Burley (Grinnell et al. 1930, cited in Davis 1939, p. 366); Clark County, Birch Creek; Butte County, Big Lost River Valley; Lost River Mountains (Lyon 1904, cited in Davis 1939, p. 366). Lyon (1904, cited in Davis 1939, p. 366) also includes a record from Ione Valley. Davis (1939, p. 366) was unable to find Ione Valley in Idaho and thought the specimen may have been from Nevada.
Bradfield (1974, p. 39) speculated that the pygmy rabbit population was declining in his study area in Bingham County, Idaho. This was based on the number of abandoned burrows, number of skulls indicating death by predation or other means, and fewer observed rabbits.
In her Idaho study area in portions of Idaho National Engineering and Environmental Laboratory (Laboratory) in Butte and Jefferson Counties, Gabler (1997, p. 42) found 101 burrow sites, of which 26 were active. Gabler (1997, p. 94) also revisited Wilde's (1978) three study areas on Laboratory lands, and found two collapsed burrows with no sign of occupancy; four active burrows which were abandoned 10 months later; and 34 abandoned burrows, respectively.
Several surveys were conducted by Roberts between 1997 and 2004. In 1997 and 1998, Roberts (2001, pp. 46) conducted surveys on BLM lands administered by the Salmon and Challis Field Offices (FO) in Lemhi and Custer Counties. The 3 areas occurred in the upper Lemhi River and upper Birch Creek Valleys; upper Pahsimeroi River and upper Little Lost River Valleys; and the upper Warm Springs Creek and upper Big Lost River Valleys. He found that pygmy rabbits were found widely scattered in all 3 of these areas (Roberts 2001, pp. 1011). In addition, Roberts (2001, p. 11) mentioned an occupied area in Railroad Canyon adjacent to Bannock Pass. This may be contiguous with habitat found in Horse Prairie Creek, Montana reported by Rauscher (1997, p. 13). Other areas of occupied rabbit habitat were found in Hawley Creek and in Bradshaw Basin (Roberts 2001, p. 11). During 2002, Roberts (2003a, pp. 3, 5) conducted surveys in the Snake River Plains area in southern Idaho. Surveys were conducted on BLM lands within Idaho Falls, Pocatello, Shoshone, Owyhee, Jarbidge, and Burley FO areas, on U.S. Forest Service (USFS) lands within Targhee, Caribou, Cache, Sawtooth, Salmon, and Challis National Forests, and the Curlew National Grasslands. Roberts (2003a, p. 6) found 9 currently active pygmy rabbit burrow systems. Four were found on the Owyhee FO, two on the Pocatello FO and one each in Idaho Falls and Jarbidge FO areas. One was found on the Curlew National Grasslands. Two systems were classified as recently active. One was found on the Owyhee FO area and the other on the Shoshone FO area.
During the summer of 2003, Roberts (2003b, p. 3) searched areas in Big Lost River Valley, Little Lost River Valley, Birch Creek, and Medicine Lodge Creek for pygmy rabbits. He found three currently and recently active burrow sites in Big Lost River Valley; seven currently and recently active burrows in Little Lost River Valley; seven currently active burrow sites in Birch Creek where five pygmy rabbits were observed; and one currently active burrow site at Medicine Lodge Creek area. Another active burrow site was found in upper Medicine Lodge Creek (Targhee National Forest 3 miles from Bannock Pass).
In 2004, Roberts (2004, p.2) continued to survey areas in Big Lost River Valley, Little Lost River Valley, Birch Creek, and Medicine Lodge Creek located in Butte and Clark Counties. He was unable to find pygmy rabbit evidence in the areas he searched in Big Lost River (Roberts 2004, pp. 34). He found 11 currently active sites in Little Lost River area. In the Birch Creek area he found 7 currently and recently used sites. He saw 6 pygmy rabbits at one of these areas. In this area, the pygmy rabbits were using cracks and crevices in and around large rocks and boulders as their burrows. In the Medicine Lodge Creek area he found 10 new burrow sites. He found 2 active burrows on the Targhee National Forest. Two additional active burrow sites were found on the U.S. Sheep Experiment Station.
White and Bartels (2002, p. 1) surveyed for pygmy rabbits on 11 grazing allotments in Twin Falls and Cassia Counties on BLM lands administered by the Burley FO. Results included 35 burrows found on 6 of the allotments (White and Bartels 2002, p. 5). Twentyfour of the burrows were revisited with a peeper probe and six burrows located on two allotments were considered occupied by pygmy rabbits (White and Bartels 2002, p. 5). In addition, White and Bartels (2002, p. 7) attempted to visit 31 historical locations for pygmy rabbits in Cassia, Minidoka,
FOR FURTHER INFORMATION CONTACT
Robert D. Williams, State Supervisor, U.S. Fish and Wildlife Service, Nevada Fish and Wildlife Office (see ADDRESSES); by telephone (775) 8616300 or by facsimile (775) 8616301. Persons who use a telecommunications device for the deaf (TDD) may call the Federal Information Relay Service (FIRS) at (800) 8778339.