Endangered and Threatened Wildlife and Plants; 90-Day Finding on
a Petition To List the Pygmy Rabbit as Threatened or Endangered
[Federal Register: May 20, 2005 (Volume 70, Number 97)]
[Proposed Rules]
[Page 29253-29265]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr20my05-22]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
Endangered and Threatened Wildlife and Plants; 90-Day Finding on
a Petition To List the Pygmy Rabbit as Threatened or Endangered
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Notice of 90-day petition finding.
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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a
90-day finding on a petition to list the pygmy rabbit (Brachylagus
idahoensis) as threatened or endangered under the Endangered Species
Act of 1973, as amended. We find the petition does not provide
substantial information indicating that listing the pygmy rabbit may be
warranted. Therefore, we will not be initiating a further status review
in response to this petition. We ask the public to submit to us any new
information that becomes available concerning the status of the species
or threats to it.
DATES: The finding announced in this document was made May 20, 2005.
You may submit new information concerning this species for our
consideration at any time.
ADDRESSES: The complete file for this finding is available for public
inspection, by appointment, during normal business hours at the Nevada
Fish and Wildlife Office, U.S. Fish and Wildlife Service, 1340
Financial Boulevard, Suite 234, Reno, NV 89502. Submit new information,
materials, comments, or questions concerning this species to us at the
above address.
FOR FURTHER INFORMATION CONTACT: Robert D. Williams, Field Supervisor,
Nevada Fish and Wildlife Office (see ADDRESSES) (telephone 775/861-
6300; facsimile 775/861-6301).
SUPPLEMENTARY INFORMATION:
Background
Section 4(b)(3)(A) of the Endangered Species Act of 1973, as
amended (16 U.S.C. 1531 et seq.), requires that we make a finding on
whether a petition to list, delist, or reclassify a species presents
substantial scientific or commercial information to indicate that the
petitioned action may be warranted. We are to base this finding on
information provided in the petition. To the maximum extent
practicable, we are to make this finding within 90 days of our receipt
of the petition, and publish our notice of this finding promptly in the
Federal Register.
Our standard for substantial information within the Code of Federal
Regulations (CFR) with regard to a 90-day petition finding is ``that
amount of information that would lead a reasonable person to believe
that the measure proposed in the petition may be warranted'' (50 CFR
424.14(b)). If we find that substantial information was presented, we
are required to promptly commence a review of the status of the
species, if one has not already been initiated under our internal
candidate assessment process.
In making this finding, we relied on information provided by the
petitioners and evaluated that information in accordance with 50 CFR
424.14(b). Our process of coming to a 90-day finding under section
4(b)(3)(A) of the Act and section 424.14(b) of our regulations is
limited to a determination of whether the information in the petition
meets the ``substantial information'' threshold.
On April 21, 2003, we received a formal 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 that the pygmy rabbit (Brachylagus
idahoensis) found in California, Idaho, Montana, Nevada, Oregon, Utah,
and Wyoming be listed as threatened or endangered in accordance with
section 4 of the Act.
Action on this petition was precluded by court orders and
settlement agreements for other listing actions that required nearly
all of our listing funds for fiscal year 2003. On May 3, 2004, we
received a 60-day notice of intent to sue, and on September 1, 2004, we
received a complaint regarding our failure to carry out the 90-day and
12-month 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 90-day finding by May 16, 2005, and to complete,
if applicable, a 12-month finding by February 15, 2006 (Western
Watersheds Project et al. v. U.S. Fish and Wildlife Service (CV-04-
0440-N-BLW)).
This finding does not address our prior listing of the Columbia
Basin distinct population segment (DPS) of the pygmy rabbit. 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).
Species Information
The pygmy rabbit is a member of the family Leporidae, which
includes rabbits and hares. This species has been placed in various
genera since its type specimen was described in 1891 by Merriam (1891),
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; WDFW 1995); this is the taxonomy accepted by the Service. The
analysis of blood proteins (Johnson 1968, cited in Washington
Department of Fish and Wildlife (WDFW) 1995) suggests that the pygmy
rabbit differs greatly from species within both the Lepus or Sylvilagus
genera. Halanych and Robinson (1997) supported the
[[Page 29254]]
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; Davis 1939;
Larrison 1967; Green and Flinders 1980a; Janson 2002).
The pygmy rabbit is the smallest North American rabbit. 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) (Dice
1926; Grinnell et al. 1930; Bailey 1936; Orr 1940; Janson 1946; Durrant
1952; Ingles 1965; Bradfield 1974; Holt 1975; Campbell et al. 1982).
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).
Pygmy rabbits typically occur in areas of tall, dense sagebrush
(Artemisia spp.) cover, and are highly dependent on sagebrush to
provide both food and shelter throughout the year (Dice 1926, Grinnell
et al. 1930; Orr 1940; Green and Flinders 1980a, b; Janson 1946; Wilde
1978; Katzner et al. 1997). The winter diet of pygmy rabbits is
comprised of up to 99 percent sagebrush (Wilde 1978; Green and Flinders
1980b), which is unique among rabbits (White et al. 1982). During
spring and summer in Idaho, their diet consists of roughly 51 percent
sagebrush, 39 percent grasses (particularly native bunch-grasses, such
as Agropyron spp. and Poa spp.), and 10 percent forbs (Green and
Flinders 1980b). 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 its use during spring and summer (Green and Flinders 1980b).
The specific diets of pygmy rabbit likely vary by region (68 FR 10388).
The pygmy rabbit is one of only two rabbits in North America that
digs its own burrows (Nelson 1909; Bailey 1936; Janson 1946; Bradfield
1974; Wilde 1978). Pygmy rabbit burrows are typically found in
relatively deep, loose soils of wind-borne or water-borne (e.g.,
alluvial fan) origin. Pygmy rabbits, especially juveniles, likely use
their burrows as protection from predators and inclement weather
(Bailey 1936; Bradfield 1974). The burrows frequently have multiple
entrances, some of which are concealed at the base of larger sagebrush
plants (Dice 1926). Burrows are relatively simple and shallow, often no
more than 6.6 feet (ft) (2 meters (m)) in length and usually less than
3.3 ft (1 m) deep with no distinct chambers (Bailey 1936; Bradfield
1974; Green and Flinders 1980a; Gahr 1993). Burrows are typically dug
into gentle slopes or mound/inter-mound areas of more level or
dissected topography (Wilde 1978; Gahr 1993). In general, the number of
active burrows in a colony increases over the summer as the number of
juveniles increases. 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,
while some individual burrows are used by multiple individuals (Janson
1946; Gahr 1993; Heady 1998).
Pygmy rabbits occasionally make use of burrows abandoned by other
species, such as the yellow-bellied marmot (Marmota flaviventris) or
badger (Taxida taxus) (Borell and Ellis 1934; Bradfield 1974; Wilde
1978; Green and Flinders 1980a). As a result, they may occur in areas
of shallower or more compact soils that support sufficient shrub cover
(Bradfield 1974). Natural cavities (such as holes in volcanic rock),
rock piles, stone walls and around abandoned buildings may also be used
(Janson 1946). During winter pygmy rabbits make extensive use of snow
burrows, possibly as access to sagebrush forage (Bradfield 1974;
Katzner and Parker 1997), as travel corridors among their underground
burrows, for protection from predators, and/or as thermal cover
(Katzner and Parker 1997).
Pygmy rabbits begin breeding their second year (Wilde 1978; Fisher
1979). In some parts of the species' range, females may have up to
three litters per year and average six young per litter (Davis 1939;
Janson 1946; Green 1978; Wilde 1978). Breeding appears to be highly
synchronous in a given area and juveniles are often identifiable to
cohorts (Wilde 1978). No evidence of nests, nesting material, or
lactating females with young has been found in burrows (Janson 1946;
Bradfield 1974; Gahr 1993). Individual juveniles have been found under
clumps of sagebrush, although it is not known precisely where the young
are born in the wild, nor is it known if they may be routinely hidden
at the bases of scattered shrubs or within burrows (Wilde 1978).
Current information on captive pygmy rabbits indicates females may
excavate specialized natal burrows for their litters in the vicinity of
their regular burrows (68 FR 10388).
Pygmy rabbits may be active at any time of the day or night, and
appear to be most active during mid-morning (Bradfield 1974; Green and
Flinders 1980a; Gahr 1993). 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 (Bailey 1936; Severaid 1950; Bradfield
1974).
Pygmy rabbits tend to have relatively small home ranges during
winter, remaining within 98 ft (30 m) of their burrows (Janson 1946).
Bradfield (1974), Katzner and Parker (1997), and Flath and Rauscher
(1995) 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; Gahr 1993). 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). These home range
estimates in Washington are considerably larger than for pygmy rabbit
populations in other areas of their historic range (Katzner and Parker
1997). Pygmy rabbits are known to travel up to 0.75 mile (mi) (1.2
kilometers (km)) from their burrows (Gahr 1993), and there are a few
records of individuals moving up to 2.2 mi (3.5 km) (Green and Flinders
1979; Katzner and Parker 1998).
A wide range of pygmy rabbit population densities has been
reported. Janson (1946) reported an estimated pygmy rabbit density of
0.75 to 1.75 per ac (1.9 and 4.3 per ha) in Utah. In another area in
Utah, he estimated 3.5 pygmy rabbits per ac (8.6 per ha). Green (1978)
reported an estimate of 18.2 pygmy rabbits per ac (45 per ha) in Idaho.
Gahr (1993) estimated 0.09 pygmy rabbits per ac (0.22 per ha) in a
grazed area and 0.11 per ac (0.27 per ha) in an ungrazed area in
Sagebrush Flat, Washington. In Montana, Rauscher (1997) estimated pygmy
rabbit density as 1.2 per ac (3.0 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). However, the mortality
rates of adult and juvenile pygmy rabbits can vary considerably between
years, and even between juvenile cohorts within years (Wilde 1978).
Predation is the main cause of pygmy rabbit mortality (Green
[[Page 29255]]
1979). Predators of the pygmy rabbit include badgers, long-tailed
weasels (Mustela frenata), coyotes (Canis latrans), bobcats (Felis
rufus), great horned owls (Bubo virginianus), long-eared owls (Asio
otus), ferruginous hawks (Buteo regalis), northern harriers (Circus
cyaneus), and common ravens (Corvus corax) (Borell and Ellis 1934;
Janson 1946; Gashwiler et al. 1960; Green 1978; Wilde 1978; Johnson and
Hanson 1979; WDFW 1995).
Population cycles are not known in pygmy rabbits, although local,
relatively rapid population declines have been noted in some States
(Janson 1946; Bradfield 1974; Weiss and Verts 1984). 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; Green and Flinders 1980b; WDFW 1995). No study
has documented rapid increases in pygmy rabbit numbers in response to
environmental conditions (Gabler 1997).
The pygmy rabbit's 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). The northern boundary extends into southeastern Oregon and
southern Idaho. The eastern boundary extends into southwestern Montana
and southwestern Wyoming. The southeastern boundary extends into
southwestern Utah. Central Nevada and eastern California provide the
southern and western boundaries (Merriam 1891; Nelson 1909; Grinnell et
al. 1930; Bailey 1936; Janson 1946; Campbell et al. 1982; WDFW 1995).
Literature indicates that pygmy rabbits were never evenly
distributed across their range. Rather, 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; Green and Flinders 1980a; Weiss and Verts 1984;
WDFW 1995). 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 appropriate use areas (Green and Flinders 1980a; Weiss
and Verts 1984; WDFW 1995). Since European settlement of the western
United States, dense vegetation associated with human activities (e.g.,
fence rows, roadway shoulders, crop margins, abandoned fields) may have
also acted as avenues of dispersal between local populations of pygmy
rabbits (Green and Flinders 1980a; Pritchett et al. 1987).
Previous Federal Action
We added the pygmy rabbit to our list of candidate species on
November 21, 1991, 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 was
needed to support the preparation of a proposed rule. In the February
28, 1996, Notice of Review (61 FR 7595), we discontinued the use of
multiple candidate categories and considered the former category 1
candidates as simply ``candidates'' for listing purposes. The pygmy
rabbit was removed from the candidate list at that time. This species
has no Federal regulatory status.
As stated above, this finding does not address our prior listing
with regard to the Columbia Basin DPS of the pygmy rabbit that was
listed as endangered on March 5, 2003 (68 FR 10388).
Threats Analysis
Pursuant to section (4) of the Act, we may list a species,
subspecies, or DPS of vertebrate taxa on the basis of any of the
following five factors: (A) present or threatened destruction,
modification, or curtailment of habitat or range; (B) overutilization
for commercial, recreational, scientific, or educational purposes; (C)
disease or predation; (D) inadequacy of existing regulatory mechanisms;
or (E) other natural or manmade factors affecting its continued
existence. In making this finding, we evaluated whether threats to the
pygmy rabbit presented in the petition and other information may pose a
concern with respect to its survival. The Act identifies the five
factors to be considered, either singly or in combination, to determine
whether a species may be threatened or endangered. Our evaluation of
these threats, based on information provided in the petition and
available in our files, is presented below.
A. Present or Threatened Destruction, Modification, or Curtailment of
the Species' Habitat or Range
Geographic Range
The petition estimates that the historic range of the pygmy rabbit
encompassed 100 million ac (40 million ha) or more of sagebrush habitat
in the Great Basin and Intermountain West, and that populations may
currently exist in portions of 7 to 8 million ac (2.8 to 3.2 million
ha) (Committee for the High Desert et al. 2003). It appears these
estimates were determined by visually comparing the historic geographic
range map presented in previous Service Federal Register documents (66
FR 59734, 68 FR 10388), and a current range map presented in White and
Bartels (2002). However beyond apparently making a visual comparison of
these two maps to reach their conclusion the petitioners did not
provide any data to substantiate this supposed reduction in pygmy
rabbit range. We are unaware of any estimates from the scientific
literature in our files regarding a reduction in range for the species.
Therefore, we conclude that this map comparison is not substantial
information demonstrating a significant reduction in the range of the
pygmy rabbit.
The petition states that there have been rangewide declines in
pygmy rabbit populations and provides the following State-by-State
information to support this claim.
Idaho. According to the petition, Bradfield (1974) speculated that
the pygmy rabbit population was declining in his study area in Bingham
County, Idaho, because of the number of abandoned burrows, number of
skulls indicating death by predation or other means, and fewer observed
rabbits. In her Idaho study area, Gabler (1997) found 101 burrow sites,
of which 26 were active. Gabler also revisited Wilde's (1978) three
study areas, and found two collapsed burrows with no sign of occupancy,
four active burrows that were abandoned 10 months later, and 34
abandoned burrows, respectively. Roberts (2001) covered 583,600 ac
(236,175 ha) in three main river drainages during his 1997-98 survey in
Idaho and found pygmy rabbits widely scattered in all three of these
areas. Occupied habitat areas were interrupted by cultivation and burn
areas. He classified habitat value in his study area as being high
(2,000 ac (809 ha)), medium (365,200 ac (147,792 ha)), low (175,400 ac
(70,982 ha)), and nonuse (41,000 ac (16,592 ha)) for pygmy rabbits. All
of the high-value habitat was located in one of the drainages.
As included in the petition, Austin (2002) reported that all nine
of his study areas in Idaho showed past presence of pygmy rabbit use.
Recent or current signs of occupancy were found at five individual
sites within three of the nine study areas in 2001 and 2002. Austin
(2002) states that though it is recognized
[[Page 29256]]
that pygmy rabbits occur in widely scattered and/or isolated clumps
across the landscape, the large unoccupied areas of lands historically
used by pygmy rabbits within research areas of Idaho appear to indicate
a decline in populations and numbers. He reported some level of current
land use and disturbance in all of his study areas from the following:
grazing, fire, crested wheatgrass (Agropyron cristatum) seedings, weed
infestation, residential construction, communication sites, agriculture
and pasture conversion, fragmentation, gas pipelines, water
impoundments, off-highway-vehicle (OHV)/off-road vehicle (ORV) use,
trails, hunting, gravel pit, utility lines, dumping activities, and
other human influences.
The petition states that White and Bartels (2002) attempted to
check 31 historic locations for pygmy rabbits in Cassia, Minidoka,
Blaine, Power, and Oneida Counties, Idaho. Eighteen sites were too
vague to relocate, eight were disturbed due to agriculture, urban
development, wildfire and reseeding efforts, and five were potentially
suitable habitat. No active pygmy rabbit burrows were found on any of
the 13 sites visited. Roberts (2003) investigated 42,000 square mi
(108,800 square km) of southern Idaho, including lands drained by the
Snake River (southern Idaho) and Bear River (southeastern Idaho). He
found only nine currently active pygmy rabbit burrow systems. Roberts
(2003) states that the pygmy rabbit in Idaho are slowly declining based
solely on the annual loss of habitat.
Montana. The petition states that in Montana, Rauscher (1997)
reported that several previously occupied sites west of Dillon (near
Dutchman, Montana; Frying Pan Basin) were now vacant. He stated that
there was no evidence to indicate a significant range decrease had
occurred. Janson (2002) wrote that the historical range in Montana
continues to support pygmy rabbits, with some exceptions based on
limited observations in Beaverhead County, Montana, in 2001.
Oregon. The petitioners cite Olterman and Verts (1972) as stating
that pygmy rabbits appeared to occur over the same area in Oregon as
they did in past collections. However, Weiss and Verts (1984) found
that of 211 sites suspected of supporting pygmy rabbits in eastern
Oregon based on records, aerial photographs, soil maps, and interviews,
only 51 sites showed evidence of occupancy in 1982. In 1983, only 5 of
15 sites showed recent pygmy rabbit activity. Of 51 burrows found at 5
sites in 1982, 19 burrows were found open in 1983 and only 8 had fresh
signs of occupancy (Weiss and Verts 1984). Bradfield (1974) also spent
time at Ironside, in Malheur County, Oregon. He found evidence of
previous pygmy rabbit use, but no fresh signs of use or rabbits,
supporting his belief that they were in decline on a larger geographic
scale. Bartels (2003) visited 54 previously known pygmy rabbit sites in
2000 and 2001 in Harney, Malheur, Lake, and Deschutes Counties, Oregon.
Results from these visits were: Pygmy rabbit occupancy at 12 sites, no
occupancy at 34 sites, and undetermined presence at 8 sites (Bartels
2003). Impacts to unoccupied sites included fire, grazing, flooding,
agriculture, development, and seeding. Of the 69,945 ac (28,306 ha)
surveyed, 57,485 ac (23,263 ha) were classified as unoccupied. A total
of 9,589 ac (3,881 ha) were classified as occupied and 2,871 ac (1,162
ha) were classified as undetermined presence (Bartels 2003). Some of
these sites included those visited by Weiss and Verts (1984).
Utah. Janson (1946) reported that in the winter of 1946, pygmy
rabbits appeared more scarce than in 1941 based on two study areas in
Utah (near Cedar City, Iron County; near Tremonton, Box Elder County).
Areas where he considered pygmy rabbits common in Utah in 1941 were
found to have no pygmy rabbits occupying them in 1946. Based on the two
previous study areas in Utah between 1938 and 1946, and limited
observations in Utah (near Clarkston, Cache County; near Snowville and
Grouse Creek, Box Elder County) in 2001, Janson (2002) wrote that
recent information indicated pygmy rabbit populations had declined in
some areas where they were previously more abundant, mostly as a result
of human actions. He states that residential and commercial
development, farming, and range improvements for grazing, especially
near Cedar City, had impacted the sagebrush habitat. He found no recent
sign of occupancy near Cedar City, Utah. Pritchett et al. (1987) were
unable to locate a population studied by Holt (1975) near Otter Creek
Reservoir.
Other States. The petition does not provide specific information on
population declines for pygmy rabbits in California, Nevada, or Wyoming.
Evaluation of Information in the Petition
The data and information presented in the petition has limited use
in determining rangewide distribution and abundance of the species.
Little detail is available from records prior to 1950. These records
may not accurately reflect the species' historic distribution because
they were not collected in a systematic, comprehensive manner with the
goal of determining species distribution and abundance. They represent
a collection of sightings documented through various methods by
different individuals over time. Recent surveys (post-1950) have not
been comprehensive in any State within the pygmy rabbit's range.
Consistent methodologies were not used for those previous surveys.
Definitions for historic sites versus previously known sites, methods
for determining occupancy, and definitions that would clearly
distinguish occupied from unoccupied areas, unoccupied suitable
habitat, and the extent of occupied or formerly occupied population
sites, are inconsistent.
Surveys identified in the petition have reported occupancy at
different landscape scales, ranging from the individual burrow to the
broader population level. In many cases, survey areas were not clearly
identified, and there is a lack of information on the distances between
adjacent populations, and therefore, on what defines a population. The
petition does not provide substantial scientific information to
document the historic or current range of pygmy rabbits within
sagebrush ecosystems. Although limited data are provided on local
population declines, particularly in Idaho, the petition does not
present substantial scientific information that there is a downward
trend in geographic range or abundance to a level that threatens the
survival of the pygmy rabbit across all or a significant portion of its
range. Nor does the petition present substantial information to
correlate the changes in geographic range and abundance of the species
to the actual threats to the survival of the species.
The Service has worked with the States, other Federal agencies, and
research institutions involved with pygmy rabbit work to create a
rangewide communication network to coordinate information and
activities relating to this species. We are aware of continuing survey
efforts to improve the current knowledge of pygmy rabbit distribution
across its range, as well as the development of draft survey guidelines
(Ulmschneider 2004). However, we are unaware of any accurate,
comprehensive inventories of currently occupied pygmy rabbit habitat
for any State within the range of the species. Such information is
critical to any analysis of range and/or population reductions.
Consequently, we conclude that the petitioners do not present
substantial information indicating that a reduction in the species'
numbers or range warrants a status review.
[[Page 29257]]
Habitat
The petition claims the pygmy rabbit has been subject to population
losses and declines due to various land management practices such as
conversion of sagebrush habitat to agricultural purposes, sagebrush
eradication to increase forage for livestock, livestock grazing, weed
invasions, prescribed burns and wildfires, urban and rural development,
mining and energy exploration and development, power lines, fences and
roads, military facilities, and recreational activities. The petition
states that sagebrush once covered approximately 270 million ac (109
million ha) in western North America. Today, because of various land
uses, about 150 million ac (61 million ha) of sagebrush habitat remain
(American Lands Alliance 2001). However, pygmy rabbits do not occur in
Arizona, Colorado, North or South Dakota, or New Mexico, and only in
the southwest portions of Montana and Wyoming. So the amount of
suitable sagebrush habitat for pygmy rabbits is considerably less than
the 150 million ac (61 million ha) of sagebrush currently distributed
across western North America. The petitioners claim that pygmy rabbit
populations may occur over 7 to 8 million acres within the sagebrush
ecosystem but do not present substantial information to substantiate
this estimate, nor are we aware of any such estimates in the scientific
literature.
Agriculture
The petition cites the following general information on threats of
agriculture to sagebrush habitat. Large-scale conversions of western
rangelands to agricultural lands began under the Homestead Acts of the
1800s (Todd and Elmore 1997, cited in Braun 1998). More than 70 percent
of the sagebrush shrub-steppe habitat has been converted to
agricultural crops in some States (Braun 1998). Across the Interior
Columbia Basin of southern Idaho, northern Utah, northern Nevada,
eastern Oregon and Washington, about 15 million ac (6 million ha) of
shrub-steppe habitat has been converted to agricultural cropland
(Quigley and Arbelbide 1997, cited in Committee for the High Desert et
al. 2003). Development of irrigation projects to support agricultural
production also resulted in sagebrush habitat loss (Braun 1998).
Reservoirs have been constructed to facilitate these irrigation
projects, impacting native shrub-steppe habitat adjacent to rivers, as
well as supporting the conversion of more upland shrub-steppe to
agriculture. As irrigation techniques have improved, additional land
has been irrigated, and more big sagebrush (Artemisia tridentata)
cleared. Shrub-steppe habitat continues to be converted to dry land and
irrigated cropland but at a much lower rate (Braun 1998).
Pritchett et al. (1987) reported that a portion of the Sevier River
Valley between Kingston and Otter Creek, Utah, containing one of the
last large patches of sagebrush, had been plowed. The authors
speculated this may have been a dispersal route for pygmy rabbits from
Iron County to Wayne County, Utah. Rauscher (1997) thought conversion
of sagebrush to agriculture was minimal in southwest Montana because of
the large expanses of public land. He documented that the suspected
location for one historic record had been converted to irrigated
farmland. Williams (1986) indicated that loss of sagebrush habitat in
California to agriculture was less of a concern than loss of habitat
from overgrazing. Bartels and Hays (2001) indicated that large portions
of the pygmy rabbit range in Oregon and Idaho had been converted to
agricultural use; they found that burning, plowing, and other
undetermined causes continue to result in loss of pygmy rabbit habitat.
White and Bartels (2002) believe that the pygmy rabbit historically was
impacted by sagebrush removal for agricultural purposes in Idaho; they
found that 8 of 13 locatable historic pygmy rabbit sites in Twin Falls
and Cassio Counties, Idaho, were disturbed due to agriculture, urban
development, wildfire, and seeding efforts. Of the 583,600 ac (236,175
ha) Roberts (1998) inventoried in Idaho for pygmy rabbit occupancy,
122,300 ac (49,493 ha) had been permanently removed due to agriculture
conversion.
Evaluation of Information in the Petition
The information in the petition suggests that agricultural
production has been responsible for a loss of sagebrush habitat,
including some used by pygmy rabbits, particularly in certain areas and
in Idaho. However pygmy rabbits are not distributed uniformly across
the full range of the sagebrush ecosystem in western North America. In
large areas of the sagebrush ecosystem, the pygmy rabbit does not occur
at all, and in those areas where it does occur it is patchily
distributed (Green and Flinders 1980a; Weiss and Verts 1984). The
species only occurs in areas of the sagebrush ecosystem where, at a
minimum, the habitat has sufficiently dense sagebrush and deep, loose
soils (Green and Flinders 1980a; Weiss and Verts 1984). The petitioners
only provide general characterizations of sagebrush habitat loss, or
cite specific examples of losses in specific areas, particularly in
Idaho and Oregon. However, they do not provide substantial information
that clearly documents that the areas where these habitat losses have
occurred are also the areas where pygmy rabbits are found. Also, the
petition does not present substantial information on the magnitude and
the extent of degradation and loss of habitat to agriculture such that
we can conclude that the continued existence of the pygmy rabbit
throughout all or a significant portion of its range may be threatened.
Conversion of Sagebrush
The petition identifies the conversion of sagebrush by mechanical
and chemical methods (herbicide) primarily for rangeland improvement
and grazing management as a negative impact to pygmy rabbit habitat,
and cites the following information to support this claim. Large
expanses of sagebrush have been removed and seeded with nonnative
grasses, such as crested wheatgrass, to increase forage production for
domestic and wild ungulates. This practice results in the elimination
of many native grasses and forbs that were present before the seedings.
Olterman and Verts (1972) and Wilde (1978) cautioned that the practice
of sagebrush removal from some livestock ranges in Oregon and Idaho,
respectively, could be a threat to the pygmy rabbit in the future. They
note that land changes should be closely monitored and adequate
``safeguards'' implemented to reduce excessive clearing of large areas.
Roberts (1998) calculated that of the 583,600 ac (236,175 ha) he
inventoried for pygmy rabbit occupancy in Idaho, 49,000 ac (19,830 ha)
were lost due to sagebrush eradication. Rauscher (1997) reported that
sagebrush removal was a ``popular'' rangeland improvement practice in
southwestern Montana. Sagebrush in the Coyote Creek area of the Big
Sheep Creek basin has been extensively treated, and only one active
burrow was located. In lower Badger Gulch, Bureau of Land Management
(BLM) lands border private lands. Pygmy rabbits are found on public
lands but absent on private lands where sagebrush had been removed.
Evaluation of Information in the Petition
Information in the petition indicates that some pygmy rabbit
habitat has been lost to sagebrush eradication for rangeland and
grazing management. However, as mentioned under agriculture in the
previous section, the pygmy rabbit is not distributed uniformly across
the full range of the
[[Page 29258]]
sagebrush ecosystem in western North America. It is absent from large
areas of the sagebrush ecosystem, and in those areas of the sagebrush
ecosystem where it does occur it is patchily distributed (Green and
Flinders 1980a; Weiss and Verts 1984), in areas where, at a minimum,
there is sufficiently dense sagebrush and deep, loose soils. The
petitioners only provide general characterizations of sagebrush habitat
loss due to conversion, or cite examples of losses in specific areas.
They do not provide substantial information that clearly documents that
the areas where these habitat losses have occurred are also the areas
where pygmy rabbits are found. Also, the petition does not present
substantial information on the magnitude and the extent of loss of
habitat due to sagebrush conversion such that we can conclude that the
continued existence of the pygmy rabbit throughout all or a significant
portion of its range may be threatened.
Livestock Grazing
The petition identifies livestock grazing as an important factor in
sagebrush habitat destruction and alteration in pygmy rabbit habitat.
The petition mentions not only the direct loss of vegetation, but
habitat degradation due to associated facilities or actions such as the
construction of fences, wells, water tanks, and pipelines which can
concentrate livestock or redistribute livestock and predators; seeding
of crested wheatgrass to increase livestock forage; and weed
infestations. The petition also claims that grazing disturbs pygmy
rabbits, increases their vulnerability to predation, and increases
stress during winter or harsh weather periods. In addition, the petition
claims trampling of burrows may cause injury or death of pygmy rabbits.
The petition cites the following information to support these claims.
The pygmy rabbit likely did not evolve with intensive grazing by
large native herbivores such as bison (Bison bison), elk (Cervus
canadensis), pronghorn (Antilocapra americana), and mule deer
(Odocoileus hemionus) (Mack and Thompson 1982, cited in Connelly et al.
2000; Belsky and Gelbard 2000). Belsky and Gelbard (2000) and Paige and
Ritter (1999) discuss impacts of livestock grazing on the arid west.
These impacts can include selective grazing for native species,
trampling of plants and soil, damage to soil crusts, reduction of
mycorrhizal fungi, increases in soil nitrogen, increases in fire
frequency, and contribution to nonnative plant introductions. When the
sagebrush-grass vegetation is overgrazed, native perennial grasses can
be eliminated, and shrubs, such as big sagebrush, tend to form dense
monotypic (single species) stands when the sagebrush-grass vegetation
is overgrazed (Blaisdell 1949, cited in Yensen 1982; Tisdale and
Hironaka 1981, cited in Paige and Ritter 1999). In addition, the
understory becomes sparse with unpalatable perennials (Tisdale and
Hironaka 1981, cited in Paige and Ritter 1999), and invasions of annual
species like cheatgrass (Bromus tectorum) can occur (Gabler 1997;
Rauscher 1997).
The magnitude of grazing effects is determined by season, timing,
duration, and intensity of the event, in addition to other factors.
Overgrazing can break down individual sagebrush plants, which opens up
interstitial (small, narrow) spaces, allowing invasion of annual
grasses and forbs (Daubenmire 1970, cited in Rauscher 1997). Livestock
grazing can result in sagebrush seedling trampling and mortality
(Connelly et al. 2000). Water developments also influence livestock
distribution in sagebrush habitat that would otherwise not be used.
While water developments may provide a more uniform livestock
distribution over the landscape, they may also distribute habitat
impacts over a larger area. The associated facilities (tanks,
pipelines, roads) may also allow predators (Braun 1998), OHV/ORV users,
and hunters to access new terrain.
Livestock can physically damage sagebrush by rubbing, battering,
breaking, and trampling seedlings. Katzner and Parker (1997) state that
the apparent dependence of pygmy rabbits on a dense understory,
provided in part by dead shrubs and extensive canopies, may explain
population declines in the pygmy rabbit in grazed sagebrush-steppe
habitat in the western United States. Lands grazed intensively by
domestic herbivores often have relatively low plant structural
complexity and may not support pygmy rabbit populations adequately. For
a species that eludes predators in sagebrush habitat, a reduction in
canopy cover would increase the vulnerability of pygmy rabbits to
predation (Bailey 1936; Orr 1940; Wilde 1978; Katzner 1994; Siegel 2002).
The physical destruction of dense, structurally-diverse patches of
sagebrush, and the corridors that connect them, result in fragmented,
unsuitable big sagebrush habitat for pygmy rabbits (Katzner and Parker
1997). Siegel (2002) found more active burrows in ungrazed areas than
grazed areas. Gahr (1993) found male pygmy rabbits had longer movements
in a grazed area in Washington during the breeding season compared with
an ungrazed area. Rauscher (1997) and Janson (2002) found that areas of
tall, dense sagebrush inhabited by pygmy rabbits were typically located
along streams. Livestock can impact these areas disproportionately by
concentrating in riparian areas where trampling and vegetation removal
can occur (Austin 2002).
Trampling of burrows by livestock has been reported in Montana by
Rauscher (1997), in Idaho by Austin (2002), and in Washington by Siegel
(2002) and Herman (2002). This could cause the death of young rabbits
in natal burrows or injury or mortality of adults. Austin (2002)
reported a burrow system in Idaho that was subjected to cattle trailing
on at least two separate occasions within a period of 2 months or less.
After the initial event, only 2 of 10 active burrows were still open. A
second visit showed additional trailing activities, and no open burrows
or recent sign were found, indicating ``that domestic livestock can have
an immediate and detrimental effect upon burrow systems'' (Austin 2002).
Evaluation of Information in the Petition
The petition describes various impacts associated with livestock
and grazing management that could affect pygmy rabbits, and cite
specific cases in isolated areas where impacts to the species have
resulted from these practices. However, the petitioners did not provide
substantial information that clearly documents that areas impacted by
grazing management practices are regularly also the areas where pygmy
rabbits are found. Also, the petition does not present substantial
information on the magnitude and the extent of degradation and loss of
habitat to livestock grazing such that we could conclude that the
continued existence of the pygmy rabbit throughout all or a significant
portion of its range may be threatened.
Invasive Plants
The petition claims weed invasions pose a threat to pygmy rabbits
throughout their range and provides the following information to
support this claim. The spread of weeds by several factors
(recreationists, ORV/OHV users, trucks, logging, road construction,
wildfire, wild animals, wind, and floods, livestock and associated
facilities, among others) (Belsky and Gelbard 2000) across the range of
the pygmy rabbit results in nonnative plants replacing native grasses
and shrubs used by pygmy rabbits. Weed infestations can also hinder
pygmy rabbit movement and increase predator detection. Quigley and
[[Page 29259]]
Arbelbide (1997, cited in Committee for the High Desert et al. 2003)
describe the effects of weeds in the Interior Columbia River Basin as
able to alter ecosystem processes, including productivity, nutrient
cycling, decomposition, and natural disturbance patterns such as
frequency and intensity of wild fires. Altering these processes can
result in the displacement of native plant species, eventually
impacting wildlife and native plant habitats.
Paige and Ritter (1999) suggest that the most harmful change to
sagebrush shrub lands has been the invasion of the nonnative grasses
and forbs, especially cheatgrass. Cheatgrass is a rapid colonizer of
disturbed areas and persistent in replacing native species (Mack 1981,
Yensen 1981, and Whisenant 1990, cited in Paige and Ritter 1999).
Cheatgrass alters fire and vegetation patterns in sagebrush habitats as
it creates a continuous fine fuel that easily carries fire (Paige and
Ritter 1999). Where it dominates, it can carry fires over large
distances, and burns more frequently than native vegetation (Paige and
Ritter 1999). It also matures and dries earlier than native vegetation,
increasing the likelihood of a fire earlier in the season (Young and
Evans 1978, Whisenant 1990, and Knick and Rotenberry 1997, cited in
Paige and Ritter 1999). Pellant and Hall (1994) reported on the 1992
distribution of cheatgrass and medusahead wild rye (Taeniatherum
asperum), the primary alien grass invaders of disturbed and fire-
altered rangelands in the Intermountain area of the western United
States. Data indicated that 3.3 million ac (1.3 million ha) of
rangeland administered by the BLM in Nevada, Oregon, Utah, Washington,
and Idaho were dominated by these two species. Another 76.1 million ac
(30.8 million ha) of public rangeland were classified as infested or
susceptible to infestation by these two species. The petition states
that this distribution corresponds to areas of the pygmy rabbit's range.
The petition provides the following specific information on the
threat of invasive weeds to pygmy rabbits and their habitat. In Oregon,
2 of 51 sites occupied by pygmy rabbits in 1982 contained appreciable
stands of cheatgrass (Weiss and Verts 1984). This led the authors to
suspect that pygmy rabbits avoid areas containing annual grasses
because it can restrict their movements or vision, especially when they
are attempting to escape predators. Weeds were reported for all nine
study areas investigated by Austin (2002) in Idaho. Gabler (1997)
predicted 10 sites on Idaho National Environmental Engineering
Laboratory (INEEL) lands would be used by pygmy rabbits, but later
found large patches of invasive cheatgrass on 8 of those sites, and
that the species did not use these sites. Other factors, such as large
amounts of dead sagebrush, and/or sparse, short sagebrush, and thick
grass cover, may have contributed to their nonuse.
Evaluation of Information in the Petition
The petitioners provide information about weed invasions within the
sagebrush ecosystem in general, and provide a few specific cases where
the presence of weeds may have been the reason why pygmy rabbits were
absent from an area. However, petitioners did not provide substantial
information that clearly documents that areas impacted by invasive
species are regularly also the areas where pygmy rabbits are found.
Furthermore, the petitioners do not provide substantial information on
the magnitude and the extent of habitat impacts by invasive weeds such
that we might conclude that they may threaten the continued existence
of the pygmy rabbit throughout all or a significant portion of its range.
Fire
The petition contends that fire, either wild or prescribed, can
result in long-term habitat loss and fragmentation of pygmy rabbit
habitat across its range. Fire can result in death, increased
predation, or home range abandonment. The petition cites the following
information to support this claim.
Fire intervals during presettlement times have been estimated at 20
to 25 years in wetter regions, where fuels (vegetation) are more
abundant. In the arid sagebrush steppe of Idaho, intervals have been
estimated at 60 to 110 years because fuels are less abundant (Tisdale
and Hironaka 1981 and Whisenant 1990, cited in Paige and Ritter 1999).
Burning typically kills big sagebrush (Artemisia tridentata tridentata,
A. t. vaseyana, A. t. wyomingensis) (Pechanec et al. 1954, cited in
Yensen 1982), fire it and does not resprout after burning (Wright et
al. 1979, cited in Braun 1998; Paige and Ritter 1999). As a result, big
sagebrush habitat takes a long time to recover following burns.
Depending on the species, sagebrush can reestablish itself within 5
years of a burn, but it may take 15 to 30 years to return to preburn
densities (Bunting 1984; Britton and Clark 1984, cited in Paige and
Ritter 1999). Billings (1994) documented slow shrub succession
following a burn in western Nevada, with little sagebrush recovery
after 45 years.
Burning can also damage perennial grasses, allowing cheatgrass to
increase (Stewart and Hull 1949; Wright and Britton 1976, cited in
Yensen 1982). The presence of cheatgrass extends the fire season and
can carry a fire into areas where burning would not normally occur
(Yensen 1982; Billings 1994). Though it is not known when cheatgrass
became so abundant in the sagebrush ecosystem as to allow extensive
fires in the western Great Basin, these fires were common as early as
the mid-1930s (Billings 1994). Range fire intervals on the Snake River
Plain in Idaho may have been 50 to 100 years (Whisenant 1990, cited in
Gabler 1997). Whisenant (1990, cited in Gabler 1997) indicates this
interval currently occurs at 3 to 5 years, and that the burns are more
extensive and leave fewer patches of unburned habitat within the burned
areas. With cheatgrass cover, fire frequency increases and sagebrush
are unable to reestablish (Whisenant 1990, cited in Gabler 1997).
The petition states that numerous and extensive fires have occurred
in States where pygmy rabbits occur. Wildfires have reduced more than
50 percent of sagebrush acreage in some areas in Idaho and Nevada (BLM
2000). In Idaho a number of fires have occurred during the last decade
that have exceeded 100,000 ac (40,469 ha) (Roberts 2003). In Nevada,
1,277 fires in 2001, impacted 654,253 ac (264,768 ha) on public and
private lands (BLM 2001a). In 2002, BLM reported 771 fires that
impacted 77,551 ac (31,384 ha) on public and private lands in Nevada
(BLM 2002).
According to Gabler (1997), range fires may be a more serious
threat to pygmy rabbit populations now than in the past. Roberts (1998)
stated that of the 583,600 ac (236,175 ha) he inventoried in Idaho,
about 2,500 ac (1,012 ha) had been temporarily removed due to fire (a
loss of 0.4 percent). White and Bartels (2002) indicated that of the
133,067 ac (53,851 ha) surveyed, 23,660 ac (9,575 ha) had been affected
by wildfire within the last 15 years. Gabler (1997) mentions that 12.5
percent of her predicted pygmy rabbit habitat in Idaho was destroyed by
fires during 1994-1996.
The petition cites several instances of fire impacting pygmy rabbit
populations locally across its range. In Idaho, Austin (2002) indicated
a burrow system was no longer occupied by pygmy rabbits following an
escaped BLM controlled burn. White and Bartels (2002) discuss that
wildfires in the 1990s at INEEL severely affected the pygmy rabbit
population, though some individuals remained. Gates and Eng (1984,
cited in Tesky 1994) reported that 2 months following a fire in big
sagebrush-grassland community in Idaho, only 3 of
[[Page 29260]]
11 located radio-collared pygmy rabbits were alive. Of the eight lost,
seven were due to predation. They speculated that the loss of big
sagebrush from their home ranges probably increased vulnerability to
predation. Some of the surviving pygmy rabbits abandoned their home
ranges and moved to new home ranges in adjacent unburned sites. Of the
six rabbits remaining on the burn site, only one survived the winter.
Pygmy rabbit habitat in Benton County, Washington, was destroyed by
fire soon after its discovery in 1979 (WDFW 1995). The population at
the Coyote Canyon site in Washington showed a dramatic decline in 1999
following a fire (WDFW 2001).
Roberts (2003) suggests that sagebrush habitat can be regenerated
within 30 to 50 years but how long it takes for pygmy rabbits to
recolonize is unknown. Roberts (2001) mentions a 1966 burn near Gilmore
Summit, Idaho, that has not regenerated to suitable habitat and which
pygmy rabbits have not recolonized. White and Bartels (2002) state that
after the removal of sagebrush habitat along the Snake River Plain, the
area from Jerome to Idaho Falls, Idaho, became important pygmy rabbit
habitat. This area was recently burned and reseeded with crested
wheatgrass. Rauscher (1997) reported that a prescribed burn in 1980
near Badger Pass, Montana, had been recolonized by pygmy rabbits. He
did not know how long this process had taken or if pygmy rabbit
densities had reached pre-burn levels. White and Bartels (2002) suggest
that the current low abundance and populations of the species is likely
due to recent wildfires and slow rate of habitat recovery.
Evaluation of Information in the Petition
The information in the petition indicates that fire has impacted
sagebrush ecosystems, that there have been increased numbers of fires
in this system, and that pygmy rabbits have been negatively affected in
some local areas within their range due to fire. But pygmy rabbits are
not distributed uniformly across the full range of the sagebrush
ecosystem in the western United States, and only occur in areas where,
at a minimum, dense sagebrush and deep, loose soils are found (Green
and Flinders 1980a; Weiss and Verts 1984). The petitioners did not
provide substantial information that demonstrates that the areas of the
sagebrush ecosystem impacted by fires, and those subject to increased
fire frequency, are also the areas occupied by pygmy rabbits, with the
exception of a limited number of cases, mostly from Idaho. Also, the
petition does not provide substantial information to document how much
of the sagebrush ecosystem where pygmy rabbits occur has been impacted
by fire. Therefore, we conclude that the petition has not presented
substantial information that fire in the sagebrush ecosystem is a
factor that may threaten the continued existence of the pygmy rabbit
throughout all or a significant portion of its range.
Urban and Suburban Development
The petition identifies habitat loss from rural and urban
development as a negative impact to pygmy rabbits and their habitat.
This includes the infrastructure that accompanies such development.
(i.e., roads, powerlines, pipelines). Historic destruction of sagebrush
habitat for urban development has occurred (Braun 1998). More recent
expansion into rural areas is resulting in additional sagebrush habitat
loss (Braun 1998), as well as introducing nonnative predators such as
domestic pets to these areas (Connelly et al. 2000). Janson (2002)
discovered that one of his 1940s pygmy rabbit study areas was impacted
by residential and commercial development near Cedar City, Utah, when
revisited in 2001. White and Bartels (2002) also found that urban
development had impacted historic pygmy rabbit locations in Idaho.
Evaluation of Information in the Petition
The petition indicates that some sagebrush habitat has been lost
due to development, and that in some specific instances pygmy rabbits
have been impacted locally. With the exception of these few local
examples, the petitioners do not provide substantial information to
document that the areas impacted by development are the same as those
where the pygmy rabbit occurs, nor do they provide any documentation
that indicates how much pygmy rabbit habitat has been lost to urban and
suburban development across its range. Therefore, we conclude that the
petition has not presented substantial information that urban and
suburban development in the sagebrush ecosystem is a factor that may
threaten the continued existence of the pygmy rabbit throughout all or
a significant portion of its range.
Mining
The petition contends that mining and associated facilities
threaten sagebrush habitats, thereby negatively impacting pygmy
rabbits. The petition provides the following information to support
this claim. Sagebrush habitat throughout the west has been impacted by
gold, coal, and uranium mining (Braun 1998). Immediate impacts include
direct loss from mining and construction of associated facilities,
roads, and power lines (Braun 1998). In western North America,
development of mines and energy resources began before 1900 (Robbins
and Wolf 1994, cited in Braun 1998). Mining occurs across large areas
in northern Nevada where pygmy rabbits are known to occur (Nevada
Natural Heritage Program 2002). In California, pygmy rabbits have been
observed in the area around Bodie, a mining town that was abandoned in
the mid-1930s (Severaid 1950).
Evaluation of Information in the Petition
Though the petition provides general information on mining
activities where pygmy rabbit habitat may occur, it does not present
substantial information that correlates mining activities with the
direct loss of pygmy rabbits or their habitat, nor does it quantify the
extent of this effect across the range of the species.
Energy Development
The petition contends that energy development and associated
facilities threaten sagebrush habitats thereby negatively impacting
pygmy rabbits. The petition identifies habitat loss from energy
development (i.e., oil, gas, and geothermal energy) as a negative
impact to the pygmy rabbit. Millions of acres of western lands are in
production for oil and gas energy. Other western lands have been
developed for geothermal energy, but the number of acres is much lower
than for oil and gas. Energy development involves construction of well
pads, roads, pipelines, and other associated facilities. The
petitioners specifically mention concerns with oil, gas, and coal bed
methane development in Wyoming and they cite proposals for energy
production in sagebrush habitats in this State. The Jack Morrow Hills
Supplemental Draft Environmental Impact Statement (DEIS) (2002, cited
in Committee for the High Desert et al. 2003) proposes oil, gas, and
coalbed methane production in sagebrush habitats north of Rock Springs,
Wyoming. The scoping notice for the South Piney Natural Gas Development
Project (2002, cited in Committee for the High Desert et al. 2003)
proposes the possible development of 210 new natural gas wells on
31,000 ac (12,545 ha) in southwestern Wyoming. The Pinedale Anticline
DEIS (2002, cited in Committee for the High Desert et al. 2003)
indicates that large areas of Lincoln, Uinta, Sublette and Sweetwater
Counties with existing and potential oil and gas development are
planned. The Upper Green River Valley Coalition
[[Page 29261]]
(2003, cited in Committee for the High Desert et al. 2003) predicts
that the Green River Valley will be a major natural gas production
region in the United States. In addition, BLM's Kemmerer Field Office
contains a log of 100 oil, gas, and other energy related actions, and
the Rock Springs Field Office contains a register of over 70 oil, gas,
coal, and other energy related actions (Committee for the High Desert
et al. 2003).
The petition contends that wind energy and geothermal energy
development threaten sagebrush habitats and, therefore, pygmy rabbits
in Idaho and Nevada. The petition cites a proposed wind power project
to be located west of Salmon Falls Reservoir, Idaho (Jarbidge BLM
Environmental Assessment (EA) 2003, cited in Committee for the High
Desert et al. 2003). On adjacent BLM lands, along the Nevada/Idaho
border, meteorlogical towers have been installed to determine the
feasibility of these areas for wind energy development. Both White and
Bartels (2002) and Roberts (2003) found pygmy rabbit populations in
this region. The petition cites a Battle Mountain Geothermal
environmental assessment (2002, cited in Committee for the High Desert
et al. 2003) which could authorize geothermal leasing and exploration
on 4.3 million (1.7 million ha) of BLM lands in Nevada, including areas
of occupied pygmy rabbit habitat. Nielsen et al. (2002) indicates
geothermal development sites located in big sagebrush habitats in all
western states in portions of pygmy rabbit habitat except in Wyoming.
Evaluation of Information in the Petition
While the petition provides some information regarding oil, gas,
and coal bed methane production in Wyoming, it does not present
substantial information that this development has resulted in losses of
large amounts of pygmy rabbit habitat. Much of the information in the
petition identifies potential impacts rather than actual impacts. And
while information in the petition indicates that wind power and
geothermal energy development projects are occurring or planned in
areas of pygmy rabbit habitat, the petition does not present
substantial information to correlate this development with reductions
in pygmy rabbit habitat that may affect their reproduction and survival
throughout all or a significant portion of their range. Therefore, we
conclude that the petition has not presented substantial information
that habitat degradation and loss due to energy development may
threaten the continued existence of the pygmy rabbit throughout all or
a significant portion of the range.
Power Lines, Fences, and Roads
The petition contends that the construction of power lines, fences,
and roads results in direct sagebrush habitat loss, provides raptor
perches that facilitate predation, facilitates the spread of weeds,
disrupts pygmy rabbit dispersal corridors, and increases human access
for recreational activities, all of which impact pygmy rabbits and
their habitat. Sagebrush habitat contains power lines, fences, and
roads associated with urban and rural development, grazing, mining and
energy development, and recreation. Power poles and fences can provide
hunting and roosting perches, and nesting support, for many raptor
species that can prey upon pygmy rabbits. These power lines and fences
are often accompanied by maintenance roads that may serve as travel
corridors for predators, spread weeds, and offer access for hunters and
recreationists. Power lines occur throughout occupied pygmy rabbit
habitat, such as through the Big Lost Valley and INEEL lands in Idaho
(Committee for the High Desert et al. 2003).
The petition also contends roads disrupt the dispersal capabilities
of pygmy rabbits, and it provides the following information to support
this claim. Bradfield (1974) suggested that pygmy rabbits were
reluctant to cross open areas based on the lack of highway mortality
(Gordon 1932, Sperry 1933, Smith 1943, cited in Bradfield 1974). Others
(Weiss and Verts 1984; Roberts 2001) have reiterated this comment.
Rauscher (1997) reported use of a subnivian (layer between snow and
soil surface) tunnel that extended across a back country road near
Badger Pass, Montana. Jones (1957) mentions a pygmy rabbit winter road
kill in California north of Crowley Lake, Mono County. Rauscher (1997)
found pygmy rabbits crossed relatively small open areas (1,500 ft (457
m)) to reach suitable habitat in Montana. Katzner and Parker (1998)
report a pygmy rabbit traveling long distance (2.2 mi (3.5 km)) through
open habitat likely unsuitable for long-term habitation. This suggests
that fragmented populations may not be as isolated as previously
suggested and has implications for recolonization of nearby areas.
Evaluation of Information in the Petition
The petition does not provide substantial information that directly
relates the actual and potential impacts of power lines, fences, and
roads to the significant loss of pygmy rabbits or their habitat. The
information in the petition does not directly implicate that activities
related to power lines, fences, and roads are threatening pygmy
rabbits; the information provided is ``anecdotal'' and/or speculative
in nature, and not comprehensive. Therefore, we conclude that the
petition has not presented substantial information that power lines,
fences, and roads in the sagebrush ecosystem are factors that may
threaten the continued existence of the pygmy rabbit throughout all or
a significant portion of their range.
Activities on Military Facilities
Military facilities occur within the range of the pygmy rabbit. The
petition claims that impacts of military operations could involve
direct mortality to pygmy rabbits and cause loss and degradation of
sagebrush habitats. The U.S Air Force (USAF) has constructed roads and
an electronic training range site and other facilities in Owyhee
County, Idaho (USAF 1998, cited in Committee for the High Desert et al.
2003). According to the petition, one emitter site and access road is
located less than 2.0 mi (3.2 km) from occupied pygmy rabbit habitat
reported by Roberts (2003). These facilities increase pygmy rabbit
habitat degradation and fragmentation by facilitating weed invasion and
increased fire potential. Noise levels due to training exercises may
also impact pygmy rabbits.
Evaluation of Information in the Petition
The petition does not provide substantial information that
documents the actual loss of pygmy rabbits and their habitat by
military activities, and how this may threaten the survival of the
species across its range.
Recreational Activities
The petition contends that recreation, especially ORV/OHV and
snowmobile use, threatens pygmy rabbit and sagebrush habitats by
disturbing individuals, damaging sagebrush, damaging burrows or
subnivian tunnels, increasing the spread of weeds, and increasing human
presence and pets in the area. Much of the sagebrush habitat occupied
by pygmy rabbits is open to recreational use. Bradfield (1974)
suggested that the pygmy rabbit depends on its hearing for predator
detection, and may be less active during windy periods when predator
detection may be reduced. Thus, passing vehicle noise may make the
pygmy rabbit more vulnerable to predation. The petition cites a BLM
document indicating that a proposed OHV/ORV race in Idaho could
[[Page 29262]]
damage pygmy rabbit burrows (Jarbidge Field Office BLM 2003, cited in
Committee for the High Desert et al. 2003). Austin (2002) found weed
infestation highest in areas of greatest disturbance, which included
ORV use areas in his Idaho study areas.
Evaluation of Information in the Petition
As presented in the petition, the information on recreational
impacts is speculative. We conclude that the petition does not provide
substantial information that describes how recreation activities
threaten pygmy rabbits and their habitats.
Habitat Manipulations for Other Species
Connelly et al. (2000) recommend managing sagebrush canopy cover
for sage grouse habitat at 10 to 25 percent for brood-rearing, 15 to 25
percent for breeding habitat and 10 to 30 percent for winter habitat.
Pygmy rabbits, in general, prefer taller, denser sagebrush cover
relative to the surrounding landscape, which can be greater than the 10
to 30 percent range (Green and Flinders 1980b; Weiss and Verts 1984)
suggested for various sage grouse habitats. Reducing dense sagebrush
cover to benefit sage grouse may be in conflict with the needs of pygmy
rabbits.
Evaluation of Information in the Petition
While we share a concern that large scale vegetation manipulations
to benefit sage grouse may negatively impact pygmy rabbit habitat, the
petition does not provide substantial information to document the
magnitude and extent of this concern for pygmy rabbits throughout their
range.
Summary of Habitat Threats
While a variety of anthropogenic activities that affect sagebrush
(e.g., agriculture, grazing, mining) are occurring across the range of
the pygmy rabbit, the petition does not provide substantial information
that these activities, either singly or in combination with one
another, are destroying or modifying pygmy rabbit habitat over all or a
significant portion of the species' range. Also, with limited
exceptions, the petition fails to provide scientific documentation to
demonstrate that the areas where sagebrush habitat loss and degradation
are occurring are also the areas where pygmy rabbit populations occur.
Additionally, the petition does not provide substantial information to
document what the effects of these anthropogenic changes are on pygmy
rabbit population numbers across the range of the species. Based on the
preceding discussion, we do not believe that substantial information is
available indicating that the present or threatened destruction,
modification, or curtailment of habitat or range may, either singularly
or in combination with other factors, rise to the level of a threat to
the continued existence of the species throughout all or a significant
portion of the species' range.
B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
Hunting
The petition contends that pygmy rabbit populations at low levels
could be harmed due to hunting mortality and research activities. The
petition also notes the difficulty in distinguishing pygmy rabbits from
other rabbit species, especially cottontails (Sylvilagus spp.) (Garber
and Beauchaine 1993), and claims that this difficulty could lead to
accidental shootings. The petition contends that road networks
associated with energy, pipeline, powerline, mining, and development
provide travel corridors for hunters, increasing the likelihood of
pygmy rabbit mortality.
The following information from the petition summarizes potential
impacts to the species from hunting. Williams (1986) stated that
although hunting impacts were not known in California, he thought that
hunters probably did not kill many because the species was quite
secretive and rarely left dense brush. Rauscher (1997) reported pygmy
rabbit hunting in southwestern Montana, but stated that hunting did not
appear to be a significant mortality factor. Fisher (1979) recommended
that bag limits be monitored in Idaho, especially where habitat was
declining, because with the pygmy rabbit's lower reproductive potential
as compared to other rabbits, fewer surplus animals may be available to
hunters. Pritchett et al. (1987) reported that, according to locals
near Loa, in Wayne County, Utah, pygmy rabbits have been ``extensively
hunted'' along with black-tailed jackrabbits (Lepus californicus) and
cottontails. Where he was able to access portions of his previous study
area outside Cedar City, Utah, Janson (2002) found spent shotgun
shells. He thought it was probable that some pygmy rabbits were shot
because most hunters do not distinguish between pygmy rabbits and
cottontails.
The petition also contends that shooting or poisoning likely caused
pygmy rabbit population declines in the past even though jackrabbits
were primarily taken. While we are aware that rabbit drives occurred
(Bacon et al. 1959; Jackman and Long 1965), there is little
documentation on the impacts to pygmy rabbits. Bacon et al. (1959)
collected rabbits, mostly by organized drives of hunters who shot them,
to gather ectoparasitic (parasite on outer surface of an animal)
information on wild rabbits and rodents in eastern and central
Washington between 1951 and 1956. Of the 1,040 rabbits collected,
representing four species, only one was a pygmy rabbit. It is unknown
if the single collection indicates pygmy rabbits are less vulnerable to
drives, or if numbers were reduced in that area at the time.
Currently, only three (California, Montana, and Nevada) of the
eight States where the pygmy rabbit occurs allow hunting. For those
States that allow hunting of pygmy rabbits, the State Wildlife Boards
of Commissioners set hunting regulations yearly. In California the
hunting season extends from July 1 to the last Sunday in January with a
bag limit of 5 per day and 10 in possession (Pat Lauridson, California
Department of Fish and Game, pers. comm. 2005). The 2004 pygmy rabbit
hunting season in Nevada opened October 9 and closed February 28 with a
daily limit of 10 and a possession limit of 20 (Sandy Canning, Nevada
Department of Wildlife, pers. comm. 2005). For Montana, information on
hunting seasons is more limited. Based on the Montana Fish, Wildlife
and Parks webpage pygmy rabbits can be hunted year round and there is
no bag limit. For the three States that allow hunting of this species,
harvest data are collected through hunter surveys but the various
rabbit species are not distinguished from one another so the number of
pygmy rabbits harvested in these States per year is not known.
Evaluation of Information in the Petition
The petition did not provide, nor are we aware of, any long-term
historic or recent hunting data that would clarify past or current
hunting pressure on the pygmy rabbit across its range. This includes a
lack of information related to poaching and accidental shootings. The
petition does not provide substantial information indicating that
hunting may threaten the continued existence of the species across all
or a significant portion of its range.
Research
The petition presents the following information on the threat of
research activities to pygmy rabbits. Research activities on the
species that involve trapping, handling, and holding them for a period
of time can result in mortality from exposure, injury, trap
[[Page 29263]]
predation, intraspecific fighting, and capture stress (Wilde 1978; Gahr
1993; Rauscher 1997). Mortality rates reported for captured pygmy
rabbits have been 3 percent (Gahr 1993), 5 percent (Wilde 1978), and 19
percent (Rauscher 1997). Investigations may also involve digging out of
burrows, stepping on burrows accidentally, measuring vegetation and
other site characteristics near burrows, and other general disturbance
in the study area (Janson 1946; Bradfield 1974; Green 1978; Wilde 1978;
Gahr 1993; Katzner 1994; Gabler 1997; Rauscher 1997). Katzner (1994)
reported that all of his radio-collared rabbits (10) died. He suggested
the weight of the radiocollars, and increased grooming as a result of
their presence, may have increased a rabbits' vulnerability to predation.
Evaluation of Information in the Petition
While these actions can be of concern for small populations such as
in Washington (66 FR 59734, 68 FR 10388), the petition did not
adequately describe how conducting research activities within pygmy
rabbit habitats may threaten the continued existence of the species.
Therefore, we conclude that the petition does not present substantial
information to indicate that conducting research activities within
pygmy rabbit habitat threatens the existence of pygmy rabbits
throughout all of a significant portion of their range.
C. Disease or Predation
The petition contends that disease likely poses a serious threat to
remaining pygmy rabbit populations. A lack of adequate food or an
increase in stress associated with altered sagebrush habitat throughout
its range, could increase the species' susceptibility to disease. It
also states predation may not represent a significant threat to
relatively large well-distributed populations, but may have an impact
on small pygmy rabbit populations in degraded habitats. The petition
also mentions West Nile Virus as a growing concern for all native
wildlife including pygmy rabbits. The petition cites the following
information to support these claims.
Pygmy rabbits can harbor high parasite loads (Janson 1946; Wilde
1978; Gahr 1993; WDFW 1995; 66 FR 59734). These parasites include
ticks, fleas, lice, and bot flies (Dice 1926; Janson 1946; Larrison
1967; Wilde 1978; Gahr 1993; Rauscher 1997), which can be vectors of
disease. Reports of episodes of plague and tularemia from these vectors
in populations of other leporid species indicate they often spread
rapidly and can be fatal (Quan 1993, cited in 68 FR 10388). There have
been no reports of severe disease epidemics occurring in pygmy rabbits
(68 FR 10388). Parasites and disease have not been regarded as a major
threat to pygmy rabbits (Wilde 1978; Green 1979, cited in 68 FR 10388).
Gahr (1993) found bot flies only on pygmy rabbits located in the
grazed area of her study, indicating that cattle may act as a vector
for spreading parasites and possibly disease. She only had two rabbits
with bot flies. She commented that parasitism by bot flies is not
necessarily detrimental to the rabbit, and additional study is needed
to determine if cattle presence increases the incidence of
ectoparasites for pygmy rabbits. Siegel (2002) and Austin (2002) also
expressed concern that disease transport and transmission by domestic
livestock to pygmy rabbits could be a threat. Austin (2002) raised the
concern that a calicivirus, such as Rabbit Hemorrhagic Disease, could
explain declines in pygmy rabbit populations and suggests additional
research is needed. Janson (2002) reported that no obviously diseased
pygmy rabbits were seen in his earlier work in the 1940s. He thought it
may be likely that disease reduced pygmy rabbit populations
periodically when they reached high densities.
Predation is the main cause of pygmy rabbit mortality (Wilde 1978;
Green 1979, cited in 68 FR 10388). As discussed in the background
section, pygmy rabbits have numerous predators and have adapted to
their presence (Janson 1946; Gashwiler et al. 1960; Green 1978; Wilde
1978). The petition contends that habitats degraded by grazing and its
associated facilities, or other actions can damage the structural
components of the sagebrush habitat as well as increase or redistribute
predators, thus increasing the pygmy rabbit's vulnerability to
predation. Weiss and Verts (1984) thought that use of denser and taller
sagebrush habitats by pygmy rabbits was related to predator avoidance.
Katzner (1994) documented that raptors were a cause of mortality and
denser sagebrush cover deterred these avian predators. The petition
also includes vertical structures, such as fences and powerlines, as
features providing raptor perches and possibly impacting pygmy rabbit
populations, as discussed earlier. Siegel (2002) suggested that artificial
livestock watering possibly increased coyote numbers in Washington.
Evaluation of Information in the Petition
Disease and predation may be significant threat factors to small
pygmy rabbit populations. Habitat degradation and fragmentation may
increase the effects of disease, parasites, and predation on some
populations. However, the petition does not adequately describe how the
species' continued survival over all or a significant portion of its
range is threatened by disease and predation. The information presented
indicates that these potential threats have not been evaluated, and
that further research is needed to determine actual impacts to pygmy
rabbits. Thus the petition does not provide substantial information to
indicate that disease or predation may threaten pygmy rabbits over all
or a significant portion of its range.
D. Inadequacy of Existing Regulatory Mechanisms
The petition contends that State and Federal agencies have failed
to conduct monitoring for the species in most of its range and to
protect it from numerous direct and indirect impacts associated with
livestock grazing, prescribed and wild fires, energy exploration and
development, vegetation manipulation, weed invasion, roads, and OHV/ORV
proliferation (see Factor A). The petition contends that mechanisms to
regulate and control these various activities have failed to prevent
harm to pygmy rabbit habitat in a significant portion of its range. The
petition cites the following information to support these claims.
A large portion of pygmy rabbit habitat occurs on BLM lands. BLM
has designated the pygmy rabbit as a special status species/bureau
assessment species in five of the seven States in which it occurs
(Idaho, Montana, Nevada, Oregon, and Wyoming). Special status species
management is discussed in BLM's 6840 Manual, ``Special Status Species
Management'' (BLM 2001b). This manual provides agency policy and
guidance for the conservation of special status plants and animals and
the ecosystems on which they depend, but it is not a regulatory
document. Currently, there are no regulations requiring BLM land use
plans to address the conservation needs of special status species (BLM
2003).
According to the petition, the U.S. Forest Service (USFS) does not
include the pygmy rabbit as a Management Indicator Species in any of
the States where the pygmy rabbit occurs (Committee for the High Desert
et al. 2003) on USFS lands. Pygmy rabbit habitat also occurs on lands
managed by other Federal agencies such as the Service and National Park
Service.
Currently, hunting of pygmy rabbits is allowed in three of the
eight States within the species' range (Committee for the High Desert
et al. 2003). Hunting of pygmy rabbits is not allowed in Idaho
[[Page 29264]]
or Wyoming, where they are considered a species of special concern, or
in Utah where they are considered a sensitive species. Hunting is also
not allowed in Oregon, where the pygmy rabbit is protected from take.
In Montana, the pygmy rabbit is also considered a species of concern,
but there is no protection from take. According to the petition,
Wyoming is the only state that has a management plan for the pygmy
rabbit (Committee for the High Desert et al. 2003). In Washington, the
pygmy rabbit was listed as threatened in 1990 by the Washington
Wildlife Commission (Commission). In 1993, the Commission reclassified
the species as endangered (WDFW 1995). A recovery plan for the species
was completed in 1995, and an addendum to the plan was prepared in 2001
(WDFW 1995, 2001).
Evaluation of Information in the Petition
Based on the information in the petition, the primary concern
expressed by the petitioners regarding the inadequacy of existing
regulatory mechanisms is related to pygmy rabbit habitat conservation.
Sagebrush habitat degradation and loss, discussed under Factor A, is
due mostly to human activities as opposed to natural events. However,
the petition does not provide substantial scientific information that
quantifies impacts to pygmy rabbit habitat rangewide, or the level of
significance of these threats to pygmy rabbit populations. Thus, we
conclude that the petition does not present substantial information to
indicate that pygmy rabbits are threatened by the inadequacy of
existing regulatory mechanisms across all or a significant portion of
its range.
E. Other Natural or Manmade Factors Affecting the Species Continued
Existence
The petition contends that several other factors, not discussed
above, negatively impact pygmy rabbit populations. These include:
intra- and interspecific competition, habitat fragmentation, natural
stochastic (random) events such as floods and drought; mortality caused
by collisions with OHV/ORV, snowmobiles, and automobiles; and life
history traits. The petitioners are also concerned that habitat
manipulations taken to benefit sage grouse may negatively impact pygmy
rabbit. Lastly, the petition claims that predator control to benefit
livestock may have a negative impact on pygmy rabbits.
The petition suggests that because pygmy rabbits are extreme
habitat specialists, intraspecific competition among individuals may be
exacerbated under environmental stress such as drought. The petition
also contends interspecific competition with other herbivores for
sagebrush such as jackrabbits (Wilde 1978), pronghorn, and mule deer,
could occur. Large populations of jackrabbits from past decades are
likely gone, but as sagebrush is reduced across the range, they may
compete with pygmy rabbits at lower population levels. Conde (1982)
compared pygmy rabbit and black-tailed jackrabbit use in sagebrush-
greasewood habitat in Cassia County, Idaho. She found in summer that
pygmy rabbits selected areas with abundant grass while jackrabbits
selected areas with abundant forbs. During the fall-winter period,
shrubs played an important role for both species, but pygmy rabbits fed
on sagebrush leaves and young stems (Johnson 1979, cited in Conde 1982)
and jackrabbits on 2-year old woody stems (Currie and Goodwin 1966,
cited in Conde 1982). Spatial distribution and exploitation of
different vegetation in the summer allow a sympatric relationship to
occur between these two species (Conde 1982).
Siegel (2002) at Sagebrush Flat, Washington, found cottontails
inhabited burrows dug by pygmy rabbits, but it is unclear if
cottontails were displacing pygmy rabbits. Cottontails may use burrows
after they are abandoned by pygmy rabbits, because 60 percent of the
burrows used by cottontails had not shown pygmy rabbit use on the date
the burrow was last checked. Siegel (2002) found pygmy rabbits reused
burrows in summer that had been occupied by cottontails the previous
winter.
Grazing competition with livestock will depend on the range
conditions and grazing practices that vary across the range of the
pygmy rabbit. At Sagebrush Flat, Washington, Siegel (2002) determined
that livestock grazing seasonally reduced the quantity of preferred
vegetation by pygmy rabbits as well as reduced the nutritional quality
of the forage. By spring, fewer differences were noted, likely
reflecting the new spring growth. Other impacts of cattle grazing in
pygmy rabbit habitat have been previously discussed under Factor A. In
Montana, there is spatial overlap between big game winter range, other
sagebrush winter ranges, and the range of pygmy rabbits. Hence,
interspecific competition may result (Janson 2002). No substantial
scientific information regarding the effects of intra- and
interspecific competition on pygmy rabbits has been provided.
The petition identifies habitat fragmentation as a threat to pygmy
rabbits as it results in small, isolated populations surrounded by vast
areas of inhospitable lands (Austin 2002; White and Bartels 2002;
Roberts 2003). Habitat fragmentation can influence size, stability, and
success of pygmy rabbit populations because of their low dispersal
capabilities (Katzner and Parker 1997). Bartels (2003) suggested that
pygmy rabbit distribution may be more fragmented than previously
thought due to the limited availability of suitable habitat and their
absence from large areas of sagebrush. Bartels (2003) suggested other
disturbances, such as habitat fragmentation, seeding after wildfires,
improper range improvements, sagebrush removal, development,
agriculture, sagebrush diseases, and floods, are all contributing factors.
The petition claims that because most of the remaining pygmy rabbit
populations are small, they are vulnerable to environmental and
demographic stochasticity. Natural stochastic events can significantly
impact local populations if they result in high mortality, habitat
loss, or little or no possibility of recolonization. They are most
significant for small or fragmented populations. Small, isolated
populations are also at a greater risk to the deleterious effects of
demographic and genetic problems (Schaffer 1981). The petition cites a
concern with flooding which may cause burrow abandonment, mortality,
and erosion of deep soils. Pygmy rabbits are known to use deeper soils
found along drainages for burrows (Flath and Rauscher 1995). Bartels
and Hays (2001) state that historic pygmy rabbit habitat was lost in
Oregon and Idaho due to flooding. White and Bartels (2002) reported
that uncontrolled floods at the Sagebrush Flat site in Washington were
a major reason for loss of individuals during 1996 to 1997. Bartels
(2003) mentions a large flood event in pygmy rabbit habitat in the
Harney Basin, Oregon, in 1984. Natural stochastic events have not been
reported as types of events that have played a significant role in
population abundance and/or trends for the pygmy rabbit range wide, nor
did the petition provide substantial scientific information that
current pygmy rabbit populations are small or isolated.
Because the pygmy rabbit is a habitat specialist, and its climax-
type habitat is highly fragmented and occurs across the landscape, the
petition contends the species' life history traits could affect
population viability. Pygmy rabbits have small home ranges, are not
evenly distributed across the species' range, and appear to have poor
dispersal and low reproduction capabilities. Pygmy rabbits do not
respond to abundant spring food supply by producing
[[Page 29265]]
additional litters like other rabbits (Wilde 1978). These factors may
explain the slow recolonization of vacated habitat even under normal
conditions (Heady et al. 2001). However, though the pygmy rabbit is a
habitat specialist, the petition does not present substantial
information on how the pygmy rabbit's natural history characteristics
have limited the species across its range.
Lastly, the petition does not provide supporting documentation that
supports the claim that predator control for livestock benefits
increases predation on pygmy rabbits.
Based on the foregoing discussion, we do not believe that the
petition has presented substantial scientific information to indicate
that natural or manmade factors threaten the continued existence of pygmy
rabbits throughout all or a significant portion of the species' range.
Finding
We have reviewed the petition and literature cited in the petition,
and evaluated that information in relation to other pertinent
literature and information available in our files. After this review
and evaluation, we find the petition does not present substantial
information to indicate that listing the pygmy rabbit may be warranted
at this time. Although we will not be commencing a status review in
response to this petition, we will continue to monitor the species'
population status and trends, potential threats, and ongoing management
actions that might be important with regard to the conservation of the
pygmy rabbit across its range. We encourage interested parties to
continue to gather data that will assist with the conservation of the
species. If you wish to provide information regarding the pygmy rabbit,
you may submit your information or materials to the Field Supervisor,
Nevada Fish and Wildlife Office (see ADDRESSES section above).
References Cited
A complete list of all references cited herein is available, upon
request, from the Nevada Fish and Wildlife Office (see ADDRESSES section).
Author
The primary author of this notice is Marcy Haworth, U.S. Fish and
Wildlife Service, Nevada Fish and Wildlife Office (see ADDRESSES).
Authority
The authority for this action is section 4 of the Endangered
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).
Dated: May 12, 2005.
Marshall P. Jones, Jr.,
Acting Director, Fish and Wildlife Service.
[FR Doc. 05-10056 Filed 5-19-05; 8:45 am]
BILLING CODE 4310-55-P
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