Brachylagus idahoensis

The pygmy rabbit (Sylvilagus idahoensis) is markedly smaller (22 to 28 cm; 0.2 to 0.5 kg) than the eastern cottontail (Sylvilagus floridanus), lacks a conspicuous tail, and is considered by some to be a distinct genus (Brachylagus). Its range is limited to several western states, where it inhabits clumps of tall sagebrush. It is mostly nocturnal.

"Pygmy Rabbits dig extensive burrow systems, which are also used by other animals. Loss of habitat is a direct threat to this species, which depends on big sagebrush, particularly mature stands of it. Both birds and mammals prey on pygmy Rabbits, which are an important food for many of the other animals in its range. The rabbit's habitat has become increasingly fragmented by development, agriculture, rangeland ""improvements""—for example, projects that replace big sagebrush with bunchgrasses—and by fire. There is reason to be concerned about the future of this smallest North American member of the rabbit family."

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The range of the pygmy rabbit includes most of the Great Basin and some
of the adjacent intermountain areas of the western United States [8].
Pygmy rabbits are found in southwestern Montana from the extreme
southwest corner near the Idaho border north to Dillon and Bannack in
Beaverhead County [4]. Distribution continues east to southern Idaho
and southern Oregon and south to northern Utah, northern Nevada, and
eastern California. Isolated populations occur in east-central
Washington [2] and Wyoming [21].

The elevational range of pygmy rabbits in Nevada extends from 4,494 to
over 7,004 feet (1,370-2,135 m) and in California from 4,986 to 5,298
feet (1,520-1,615 m) [8].

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This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

2 Cascade Mountains
4 Sierra Mountains
5 Columbia Plateau
6 Upper Basin and Range
7 Lower Basin and Range
8 Northern Rocky Mountains

CA ID MT NV OR WA WY

General: B. idahoensis occurs throughout the Great Basin and neighbouring intermountain areas, in sagebrush habitat from southwestern Montana and western Wyoming in the east to southwestern Utah in the southeast and an isolated population in central Washington. The range also includes central Nevada to northeastern California, to the north in eastern Oregon and southern Idaho (Dobler and Dixon 1990). Within this wide range, it occurs in patches correlating positively to the density of sagebrush (Dobler and Dixon 1990).

Washington: B. idahoensis historically occurred in many areas of the Columbia Basin, but the sagebrush habitat has been heavily overgrazed and cleared completely for agriculture in many places. The population in Washington is now isolated from other populations (Dobler and Dixon 1990).

Idaho: Known populations of B. idahoensis are patchy but locally abundant in some areas within the valleys of the east-central region (Lemhi, Birch Creek, Big and Little Lost, and Pahsimeroi Valleys). Recently, isolated populations have been located in Owyhee County in the southwest of the state. Isolated populations also have been documented in the south-central region on the Camas Prairie (Rachlow 2004a).

An understanding of the current status and distribution of populations is limited by sampling effort; intensive surveys for populations have not been conducted in most areas. Within Idaho, agricultural and urban development of the Snake River Plains likely represents a significant barrier dividing populations north and south of the Snake River. Some populations north of the Snake River connect to those in southwestern Montana (including populations on the Continental Divide). South of the Snake River, populations likely connect to those in neighboring states (Oregon, Nevada, and Wyoming). The Idaho Conservation Data Center (IDCDC) has approximately 180 records of the species in the program's geospatial database, comprising both recent and historical records of occurrence. The World Conservation Union (IUCN) recommends that the area of occupancy be computed by overlaying the distribution of known occurrences with a uniform grid and tallying the area of occupied grid cells. Using a 2-km grid, we calculated the area of occupancy to be 748 km² using IDCDC records. Two important sites are the Idaho National Environmental and Engineering Laboratory (INEEL) and the Lemhi Valley, BLM lands south of Salmon, Idaho. Both areas have received significant research currently or in the past, and both support large populations of pygmy rabbits (Dixon and Bosworth 2004).

Wyoming: B. idahoensis in Wyoming appears to be widespread throughout the sagebrush-dominated portions of the Bear and Green River Basins. In the Bear River, B. idahoensis is consistently found in good numbers at Fossil Butte National Monument. In the Green River, B. idahoensis is consistently found to the south and west of the towns of Pinedale and Boulder. B. idahoensis appears to be widespread in the western quarter of the Great Divide Basin as well. The Jack Morrow Hills are known to support several occurrences. There is a single occurrence in the Sweetwater River Basin, just across the divide from the Great Divide Basin, documented in 2003; this signals the need for more sampling in the Sweetwater to determine the actual distribution there. This is the only known occurrence of the species on the east side of the Continental Divide in Wyoming (Beauvais 2004).

Oregon: The range of B. idahoensis in Oregon has not been determined. Recent surveys have found rabbits in Lake, Harney, Malheur, and Deschutes counties. Known areas include Foster Flat, Warner Valley, and north of Sheldon National Wildlife Refuge (NWR) (Carey et al. 2004).

Utah: Occurrences of B. idahoensis in Utah listed in Oliver (2004) have been augmented since the document's printing. Initial survey efforts have focused on the determining of presence or absence, but systematic searches in suitable habitat over large geographic ranges have given us a measure of relative densities. The top three most populous areas include the Western Box Elder County, Northern Rich County, and the Piute/North-western Garfield County. Within these areas, B. idahoensis is considered relatively common. The most notable absence of rabbits occurs throughout the central portion of Utah's Great Basin, which was included in historical estimates of the rabbit's statewide range (Kozlowski 2004).

California: They occur in Mono County California and are abundant from the Bodie Hills to south of Mono Lake. No pygmy rabbits have been relocated to northern California but surveys are on going (Sequin 2004). A recent survey found B. idahoensis present throughout the southern portion of its historic range in California, but did not find active sites in Modoc and Lassen counties in northern California (Larrucea and Brussard 2008).

Nevada: B. idahoensis is found from the state border in the north to the northern end of Nye and Lincoln Counties in the south and from the state border in the east to Vya, Nevada in the west. The pygmy rabbit is still found in most of the higher intermountain regions in the Great Basin Desert of Nevada (Sequin 2004). A recent survey found B. idahoensis present throughout the entire extent of its historic range in Nevada (Larrucea and Brussard 2008).

Montana: They are known from the extreme southwest corner of Montana (Dillon south to Idaho border) (Hays 2004).

Pygmy rabbits live throughout most of the Great Basin area and, to a lesser extent, in nearby intermountain areas of the western United States. They are found from the southwest corner of Montana north and east through southern Idaho and southern Oregon. Distribution also extends south to northern Utah, northern Nevada, and Eastern California. There are also populations in east-central Washington and Wyoming that are genetically isolated.

There is some evidence that the geographic range of pygmy rabbits has diminished within the last 3000 years. Fossil evidence and the constant reduction of sagebrush habitat, the habitat type that is necessary for pygmy rabbit survival, provide strong evidence that the prehistoric range was much larger than it is currently.

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (20,000-2,500,000 square km (about 8000-1,000,000 square miles)) Oregon (Verts and Carraway 1998) to east-central California, east to western Utah, western Wyoming (Campbell et al. 1982), and southwestern Montana; isolated population in east-central Washington. Range apparently decreased in eastern Washington during the last 3,000 years as the extent of sagebrush-dominated steppe diminished (Lyman 1991). Within its range the distribution is not continuous but patchy, primarily in areas of Great Basin big sagebrush (Artemisia tridentata)-dominated plains and alluvial fans where plants occur in tall and dense clumps, and the soil is relatively deep and friable (Orr 1940; Green and Flinders 1980a,b; Weiss and Verts 1984). Also reported to frequent areas in Idaho supporting greasewood (Sarcobatus spp.) (Davis 1939).

Historic Range:
U.S.A. (CA, ID, MT, NV, OR, UT, WA, WY)

Brachylagus idahoensis is the smallest rabbit species in North America and fit easily in the palm of a hand. They weigh between 246 to 462 grams, averaging 398 to 436 g. They are 23.5 to 29.5 cm long, with a tail length of 15 to 24 mm and hind foot length of 67 to 76 mm. Their fur color varies from brown to dark grey with white around the margins of their short, round ears. Their ears and feet are densely covered in hair and they have a very short tail. Rabbits in general show some sexual size dimorphism, in that females are 1 to 10 percent larger than males.

Range mass: 0.4 to 0.46 kg.

Range length: 23.5 to 29.5 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: female larger

Average basal metabolic rate: 2.145 W.

Length: 29 cm

Weight: 458 grams

Sexual Dimorphism: Females are larger than males.

Length:
Average: 275 mm males; 283 mm females
Range: 252-285 mm males; 230-302 mm females

Weight:
Average: 411 g males; 432 g females
Range: 373-435 g males; 415-458 g females

Comments: This rabbit generally occurs in dense stands of big sagebrush growing in deep loose soils. It is highly dependent on sagebrush for food and shelter throughout the year. Unlike most other rabbits, it digs burrows, which are around 3 inches in diameter; a burrow may have multiple entrances. Pygmy rabbits occasionally use of burrows abandoned by other species and may occur in areas of shallower or more compact soils if these sites support sufficient shrub cover (USFWS). Microhabitat for nesting is poorly known; burrows have been excavated, but no nests have been found (Green and Flinders 1980).

In southwestern Wyoming, pygmy rabbits selectively used dense and structurally diverse stands of sagebrush that accumulated a relatively large amount of snow; the subnivean environment provided access to a relatively constant supply of food and provided protection from predators and thermal extremes (Katzner and Parker 1997).

More info for the terms: cover, shrub

Pygmy rabbits are restricted to areas with heavy shrub cover [4,8].
Pygmy rabbits are seldom found in areas of sparse vegetative cover and
seem to be reluctant to cross open space [2]. In southeastern Idaho,
woody cover and shrub heights were significantly (P less than 0.01) greater on
sites occupied by pygmy rabbits than on other sites in the same area
[7].

More info for the term: cover

Pygmy rabbits are generally limited to areas on deep soils with tall,
dense sagebrush which they use for cover and food [4,8]. Individual
sagebrush plants in areas inhabited by pygmy rabbits are often 6 feet
(1.8 m) or more in height [4]. Extensive, well-used runways interlace
the sage thickets and provide travel and escape routes [8]. Dense
stands of big sagebrush along streams, roads, and fencerows provide
dispersal corridors for pygmy rabbits [17].

Burrows - The pygmy rabbit is the only native leporid that digs burrows.
Juveniles use burrows more than other age groups. Early reproductive
activities of adults may be concentrated at burrows [8]. When pygmy
rabbits can utilize sagebrush cover, burrow use is decreased. Pygmy
rabbits use burrows more in the winter for thermal cover than at other
times of the year [20].

Burrows are usually located on slopes at the base of sagebrush plants,
and face north to east. Tunnels widen below the surface, forming
chambers, and extend to a maximum depth of about 3.3 feet (1 m).
Burrows typically have 4 or 5 entrances but may have as few as 2 or as
many as 10 [8]. In Oregon, pygmy rabbits inhabited areas where soils
were significantly deeper and looser than soils at adjacent sites. Site
selection was probably related to ease of excavation of burrows [17].
In areas where soil is shallow pygmy rabbits live in holes among
volcanic rocks, in stone walls, around abandoned buildings, and in
burrows made by badgers (Taxidea taxus) and marmots (Marmota
flaviventris) [2,8].

Some researchers have found that pygmy rabbits never venture further
than 60 feet (21.3 m) from their burrows [2]. However, Bradfield [2]
observed pygmy rabbits range up to 328 feet (100 m) from their burrows.

Winter - Some areas inhabited by pygmy rabbits are covered with several
feet of snow for up to 2 or more months during the winter. During
periods when the snow has covered most of the sagebrush, pygmy rabbits
tunnel beneath the snow to find food. Snow tunnels are approximately
the same height and width as underground burrows. They are quite
extensive and extend from one sagebrush to another [2,8]. Aboveground
movement during the winter months is restricted to these tunnel systems
[2].

More info for the term: forbs

Pygmy rabbits are found primarily in big sagebrush (Artemisia
tridentata) and rabbitbrush (Chrysothamnus spp.) dominated communities
[2,7,16,18]. Pygmy rabbits are also found in areas where greasewood
(Sarcobatus spp.) is abundant [7]. Some woody species found on sites
inhabited by pygmy rabbits in southeastern Idaho include big sagebrush,
antelope bitterbrush (Purshia tridentata), threetip sagebrush (A.
tripartita), low rabbitbrush (C. viscidiflorus), gray horsebrush
(Tetradymia canescens), and prickly phlox (Leptodactylon pungens).
Grasses and forbs include thick spike wheatgrass (Elymus lanceolatus),
plains reedgrass (Calamagrostis montanensis), sedges (Carex spp.),
prairie junegrass (Koeleria macrantha), Sandberg bluegrass (Poa
secunda), bluegrass (Poa spp.), needle-and-thread grass (Stipa comata),
western yarrow (Achillea millefolium), rosy pussytoes (Antennaria
microphylla), milkvetch (Astragalus spp.), arrowleaf balsamroot
(Balsamorhiza sagittata), buckwheat (Eriogonum spp.), tailcup lupine
(Lupinus caudatus), and phlox (Phlox spp.) [7]. In the Upper Sonoran
Desert pygmy rabbits occur in desert sagebrush associations dominated by
big sagebrush and rabbitbrush with bitterbrush and sulphurflower
(Eriogonum umbellatum var. stellatum) [16].

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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

K038 Great Basin sagebrush
K040 Saltbush - greasewood
K055 Sagebrush steppe
K056 Wheatgrass - needlegrass shrubsteppe

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

FRES29 Sagebrush
FRES30 Desert shrub

Habitat and Ecology

Systems

• Terrestrial

Brachylagus idahoensis are found primarily in big sagebrush (Artemisia tridentata) habitat and secondarily in communities dominated by rabbitbrush (Chrysothamnus spp.). More rarely they are found in areas of abundant greasewood (Sarcobatus spp.). They have also been found in areas with the woody plants antelope bitterbrush (Purshia tridentate), threetip sagebrush (Artemisia tripartita), gray horsebrush (Tetradymia canecens), and prickly phlox (Leptodactylon pungens). Grasses they are associated with include thick spike wheatgrass (Elymus lanceolatus), palins reedgrass (Calamagrostis montanensis), sedges (Carex spp.), prairie junegrass (Koeleria macratha), and several others.

Pygmy rabbits can be found from 4,494 to more than 7,004 feet (1,370 to 2,135 meters) in Nevada and from 4,986 to 5,298 feet (1,520 to 1,615 meters) in California.

Range elevation: 1370 to 2135 m.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: savanna or grassland ; scrub forest

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

In southwestern Wyoming, winter home range size was 548-18,464 sq m (mean 2568 sq m and 10,204 sq m in two different years) (Katzner and Parker 1997).

In Washington, mean home range size was 0.7 hectares in males. 0.3 hectares in females; a small number had much larger home ranges; 95 percent of males had home ranges smaller than or equal to 20.2 hectares (Gahr 1993).

Comments: Big sagebrush is the primary food source, particularly in winter, but grasses (particularly native bunch-grasses, such as Agropyron spp. and Poa spp.) and forbs also are eaten in spring and summer (Green and Flinders 1980, Lyman 1991).

More info for the terms: forb, forbs, shrub, shrubs

The primary food of pygmy rabbits is big sagebrush, which may comprise
up to 99 percent of the food eaten in the winter. Grasses and forbs are
also eaten from mid- to late summer [2,6,7,8]. In Idaho, Gates and Eng
[6] found that shrubs contributed 85.2 percent (unweighted mean) of
pygmy rabbit diets from July to December. Shrub use was lowest in
August (73.1%) and highest in December (97.9%). Big sagebrush was the
most important shrub in the July to December diet (54.2%), followed by
rubber rabbitbrush (Chrysothamnus nauseosus) (25.8%) and winterfat
(Krascheninnikovia lananta) (4.6%). Grasses comprised 10 percent of the
July to December diet and were consumed mostly during July and August.
Indian ricegrass (Oryzopsis hymenoides) and needlegrass (Stipa spp.)
were the most important grasses consumed. Forbs contributed 4.9 percent
of the July to December diet [6].

In southeastern Idaho, Green and Flinders [7] found that pygmy rabbits
ate big sagebrush throughout the year but in lesser amounts in summer
(51% of diet) than in winter (99% of diet). Other shrubs in the area
were consumed infrequently. Grass and forb consumption was relatively
constant throughout the summer (39% and 10% of diet respectively) and
decreased to a trace amount through fall and winter. Thickspike
wheatgrass, bluebunch wheatgrass (Pseudoroegneria spicata), and Sandberg
bluegrass were preferred foods in the summer [7].

Pygmy rabbits are herbivorous grazers that eat mostly sagebrush (Artemisia spp.). During winter months their diet consists of up to 98% sagebrush. In the summer and spring months their diet becomes more varied, including more grass and new foliage.

Plant Foods: leaves; roots and tubers; wood, bark, or stems; seeds, grains, and nuts

Primary Diet: herbivore (Folivore , Lignivore)

More info for the term: marsh

Weasels (Mustela spp.) are the principal predators of pygmy rabbits.
Coyote (Canis latrans), red fox (Vulpes vulpes), badger, bobcat (Felis
rufus), great horned owl (Bubo virginianus) and marsh hawk (Circus
cyaneus) also prey on pygmy rabbits [2,8,20].

Brachylagus idahoensis is a prey source for many predators (listed above) but dwindling populations make them scarce game. It is possible that the burrowing and grazing habits of these rabbits have an advantageous effect on at least one species of sagebrush plants (Artemisia tridentate), which are their primary food source.

Ecosystem Impact: creates habitat

Pygmy rabbits are preyed upon by weasels (Mustela), coyotes (Canis latrans), badgers (Taxidea taxus), bobcats (Lynx rufus), diurnal birds of prey (Falconiformes), owls (Strigiformes), foxes (Vulpes and Urocyon cinereoargenteus), and sometimes humans (pygmy rabbits are sometimes difficult for hunters to distinguish from other rabbit species). Predation is the primary cause of mortality among both adults and juveniles and can be as high as 50% in the first five weeks of life. Like other rabbits, pygmy rabbits mainly try to stay hidden and are cryptically colored to avoid predation. They are also capable of short bursts of speed to try and escape predators.

Known Predators:

• weasels (Mustela)
• coyotes (Canis latrans)
• badgers (Taxidea taxus)
• bobcats (Lynx rufus)
• diurnal birds of prey (Falconiformes)
• owls (Strigiformes)
• foxes (Vulpes and Urocyon cinereoargenteus)
• humans (Homo sapiens)

Anti-predator Adaptations: cryptic

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 21 - 80

Comments: Number of occurrences not known, but all states tracking the species have ranks of S1 to S3. In Oregon, Weiss and Verts (1984) found only 51 occupied sites among 211 potentially suitable sites.

2500 to >1,000,000 individuals

Comments: Washington population estimated at fewer than 30 animals (USFWS 2003); no population estimates available from other states.

Predators include: weasels, coyotes, owls, and likely other carnivorous mammals and birds.

More info for the term: cover

Loss of big sagebrush as a result of a fire may decrease both food and
cover for pygmy rabbits. Big sagebrush is often completely killed by
fire and is slow to reestablish on burned sites. On the Upper Snake
River Plains in Idaho, big sagebrush did not recover to prefire
densities until 30 years after an August fire [23]. Big sagebrush may
be eliminated from some areas due to repeated fire [24]. Fires that
eliminate much of the big sagebrush would have an adverse effect on the
pygmy rabbit population in that area. Two months following an August
prescribed fire in a big sagebrush-grassland community in Idaho, only 3
of 11 located radio-collared pygmy rabbits were still alive. Predation
was a cause of death for seven of the eight pygmy rabbits. The loss of
big sagebrush cover from their home ranges probably increased their
vulnerability to predation. Some of the surviving pygmy rabbits
abandoned their home ranges and established new home ranges on adjacent
unburned sites. Of the six pygmy rabbits that remained on the burn
site, only one survived through winter [6].

More info for the term: litter

Age at sexual maturity - Pygmy rabbits are capable of breeding when they
are about 1 year old [8,20].

Breeding season - The breeding season of pygmy rabbits is very short.
In Idaho it lasts from March through May; in Utah, from February through
March [22].

Gestation period and litter size - The gestation period of pygmy rabbits
is unknown. It is between 27 and 30 days in various species of
cottontails (Sylvilagus spp.). An average of six young are born per
litter and a maximum of three litters are produced per year [8]. In
Idaho the third litter is generally produced in June [20]. It is
unlikely that litters are produced in the fall [8].

Growth rate of juveniles - The growth rates of juveniles are dependent
on the date of birth. Young from early litters grow larger due to a
longer developmental period prior to their first winter [8].

Mortality - The mortality of adults is highest in late winter and early
spring. Green and Flinders [8] reported a maximum estimated annual
adult mortality of 88 percent in Idaho. Juvenile mortality was highest
from birth to 5 weeks of age [8].

Pygmy rabbits may be active at any time of day; however, they are
generally most active at dusk and dawn. They usually rest near or
inside their burrows during midday [8].

Brachylagus idahoensis produce several vocalizations characterized as squeals, squeaks, and chuckles. They squeal when alarmed. Male pygmy rabbits also communicate dominance through body signals. It is likely that chemical cues play a role in communication, as in other mammals, but this is poorly understood in pygmy rabbits.

Communication Channels: visual ; acoustic

Perception Channels: visual ; acoustic

Comments: Activity occurs throughout the year. Pygmy rabbits may be active at any time of day or night, but most activity is crepuscular.

Little is known about the lifespan of pygmy rabbits. Lifespans of related rabbit species vary greatly. Pygmy rabbit lifespan is primarily limited by predation, which can claim up to 88% of all individuals including adults and juveniles. Maximum mortality occurs between birth and 5 weeks old.

Observations: Knowledge regarding the longevity of these animals is limited. One wild born specimen was still alive in captivity at about 4.3 years of age (Richard Weigl 2005).

Breeding period extends from spring to early summer. Gestation lasts probably about 27-30 days (Green and Flinders 1980). Adult females produce 2-3 litters per year, with 4-8 young per litter (Reid 2006).

Mating systems in pygmy rabbits are unknown. In the related genus Sylvilagus, males maintain sexual hierarchies, with dominant individuals mating with more females.

There is little known about the reproductive habits of pygmy rabbits. The breeding season is short, compared to other rabbits, occurring from March to May in Idaho and February to March in Utah. It has been suggested that young are raised in nests inside burrows, though none have been found. Pygmy rabbits appear to synchronize breeding throughout the breeding season. Breeding time is determined by female readiness, which seems to be influenced by photoperiod and the condition of local food plants. Gestation is unknown, but lasts from 27 to 30 days in Sylvilagus species. Average litter size is 6. There is a maximum of three litters in a breeding season. Pygmy rabbits are capable of reproduction in the year following their birth.

Breeding interval: There is a maximum of three litters in each breeding season.

Breeding season: Breeding occurs from March to May in Idaho and February to March in Utah.

Range number of offspring: 4 to 8.

Range gestation period: 27 to 30 days.

Range age at sexual or reproductive maturity (female): 11 (high) months.

Range age at sexual or reproductive maturity (male): 11 (high) months.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Average number of offspring: 6.

There is little known about parental investment among pygmy rabbits. In other rabbit species females build nests for their young and care for them until they are mature.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)

Current Listing Status Summary

Status: Endangered
Date Listed: 11/30/2001
Lead Region:   Pacific Region (Region 1) 
Where Listed: Columbia Basin DPS

Population detail:

Population location: Columbia Basin DPS
Listing status: E

For most current information and documents related to the conservation status and management of Brachylagus idahoensis , see its USFWS Species Profile

Information on state- and province-level protection status of animals in the
United States and Canada is available at NatureServe, although recent changes
in status may not be included.

Populations in the Columbia River Basin area of the Pacific Region are
Endangered [25].

Year Assessed

Assessor/s

Reviewer/s

Justification

History

• 1996
  Lower Risk/near threatened
• 1994
  Vulnerable
  (Groombridge 1994)

Washington state lists B. idahoensis as an endangered species and it is believed that there are less than fifty left, maybe none left in the wild. Breeding and reintroduction programs to date have been mostly unsuccessful. Washington pygmy rabbits are a genetically distinct subspecies and, therefore, conservationists are not trying to crossbreed them with larger populations elsewhere. Pygmy rabbits are also a species of concern in Idaho.

US Federal List: endangered

CITES: no special status

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Moderately large range in the Great Basin and Intermountain region of western North America; range has decreased as shrub-steppe habitats have been lost and degraded as a result of fire, grazing, invasion of exotic annuals, and agricultural conversion.

Intrinsic Vulnerability: Highly to moderately vulnerable.

Comments: Some populations of pygmy rabbits are susceptible to rapid declines and possibly local extirpation. Some studies suggest that pygmy rabbits are a "high inertia" species with low capacity for rapid increase in density (Weiss and Verts 1984).

Near Threatened.

Population

Population Trend

Global Short Term Trend: Decline of 10-50%

Comments: Little information is available on population trend in mostt states. The trend for Great Basin shrubsteppe habitats is generally downward due to fire, grazing, invasion of exotic annuals, and agricultural conversion, which likely correlate with downward trends for sagebrush obligate species (Whisenant 1990; Knick and Rotenberry 1995, 1997).

Columbia Basin Distinct Population Segment: Has declined greatly in eastern Washington, from six colonies to probably just one, and from at least 150 individuals to fewer than 30 in the last decade (USFWS 2001, 2003).

Degree of Threat: High

Comments: The loss and degradation of habitat through fire, grazing, invasion of exotic annuals, energy development, and agricultural conservsion (Whisenant 1990; Knick and Rotenberry 1995, 1997) are probably the most significant factors contributing to pygmy rabbit population declines. Sagebrush cover is critical to pygmy rabbits; sagebrush eradication is detrimental (Holochek 1981). Fragmentation of sagebrush communities also poses a threat to populations of pygmy rabbits (Weiss and Verts 1984) because dispersal potantial is limited.

Under current climate-change projections, further invasion by Bromus tectorum into sagebrush habitat is likely to occur, as is invasion by woody species, and fire frequency (as well as extent and severity) likely will continue to increase. Climate change is thus likely to exacerbate the existing primary threats such as frequent wildfire and invasive nonnative plants, particularly B. tectorum.

Major Threats

More info for the term: cover

Some populations of pygmy rabbits are susceptible to rapid declines and
possibly local extirpation. Some studies suggest that pygmy rabbits are
a "high inertia" species with low capacity for rapid increase in density
[17]. The loss of habitat is probably the most significant factor
contributing to pygmy rabbit population declines. Sagebrush cover is
critical to pygmy rabbits and sagebrush eradication is detrimental [10].
Protection of sagebrush, particularly on floodplains and where high
water tables allow growth of tall, dense stands, is vital to the
survival of pygmy rabbits [4]. Fragmentation of sagebrush communities
also poses a threat to populations of pygmy rabbits [17] because
dispersal potential is limited.

Burned areas can be reseeded and planted with big sagebrush to help
facilitate sagebrush establishment. Seeding on 4 to 8 inches (10-20 cm)
of snow is a successful way to establish seedlings. Aerial seeding of
big sagebrush in the late fall is suitable for sites where planting seed
to is not practical. Areas planted or seeded with big sagebrush should
be protected from livestock grazing for several years [12].

Conservation Actions

Management Requirements: In 2002, an experimental reintroduction of 20 captive-reared Great Basin pygmy rabbits was conducted in Idaho. Four of the 20 rabbits survived the winter and successfully bred in the wild in 2003 (Washington Department of Fish and Wildlife).

Global Protection: Few to several (1-12) occurrences appropriately protected and managed

Comments: Idaho National Engineering and Environmental Laboratory (east of Idaho Falls) represents one of the largest remaining protected areas of shrubsteppe habitat. Some Bureau of Land Management Areas of Critical Environmental Concern also provide small areas of protected habitat.

Needs: Protection of sagebrush, particularly on floodplains and where high water tables allow growth of tall, dense stands, is vital to the survival of pygmy rabbits (Flath 1994).

Pygmy rabbits have no known negative economic impact on humans.

Pygmy rabbits are important and unique members of the ecosystems in which they live.