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Overview

Brief Summary

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.

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Description

"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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  • Original description: Merriam, C.H., 1891.  Results of a biological reconnaissance of south-central Idaho, p. 76.  North American Fauna, 5:1-416.
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Distribution

Range Description

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).
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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].
  • 2. Bradfield, Terry D. 1975. Aon the behavior and ecology of the pygmy rabbit. Pocatello, ID: Idaho State University. 43 p. Thesis. [23639]
  • 4. Flath, Dennis. 1994. Bunnies by the bunch. Montana Outdoors. 25(3): 8-13. [23637]
  • 8. Green, Jeffrey S.; Flinders, Jerran T. 1980. Brachylagus idahoensis. Mammalian Species. 125: 1-4. [23631]
  • 21. Campbell, Thomas M., III; Clark, Tim W.; Groves, Craig R. 1982. Firest record of pygmy rabbits (Brachylagus idahoensis) in Wyoming. Great Basin Naturalist. 42(1): 100. [23638]

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Regional Distribution in the Western United States

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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

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Occurrence in North America

CA ID MT NV OR WA WY

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Geographic Range

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 )

  • Lyman, R. 1991. Late Quaternary Biogeography of the Pygmy Rabbit (Brachylaus idahoensis) in Eastern Washington. Journal of Mammals, 72: 110-117.
  • Sayler, R., L. Shipley, R. Westra. 2001. "Behavior, Dispersal and survival of captive-raised Idaho pygmy rabbits (Brachylagus idahoensis) released onto the INEEL in Idaho." (On-line). Accessed October 15, 2005 at http://www.stoller-eser.com/NERP/pygmy.htm.
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occurs (regularly, as a native taxon) in multiple nations

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National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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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).

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

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Physical Description

Morphology

Physical Description

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.

  • Chapman, J., G. Feldhamer. 1982. Wild Mammals of North America, Biology, Management, Economics. Baltimore, Maryland: The Johns Hopkins University Press.
  • Green, J., J. Flinders. 1980. Brachylagus idahoensis. Mammalian Species, 125: 1-4.
  • Pacific Biodiversity Institute. 2004. "Information from Pacific Biodiversity Institute's Endangered Species Information Network" (On-line). Endangered Species Information Network. Accessed October 15, 2005 at http://www.pacificbio.org/ESIN/Mammals/PygmyRabbit/pygmyrabbit.html.
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Size

Length: 29 cm

Weight: 458 grams

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Size in North America

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
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Type Information

Type for Brachylagus idahoensis
Catalog Number: USNM 24045
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Mammals
Sex/Stage: Male; Adult
Preparation: Skin; Skull
Collector(s): V. Bailey & B. Dutcher
Year Collected: 1890
Locality: Pahsimeroi Valley, near head of Pahsimeroi River, [near Goldburg (see Davis 1939:363)], Custer County, Idaho, United States, North America
Elevation (m): 2134
  • Type: Merriam, C. H. 1891 Jul 30. North American Fauna. 5: 76.
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
General: B. idahoensis mainly occupies big sagebrush (Artemisia tridentata), especially where the vegetation is very dense. It forms burrows in soft, deep soils, in areas such as alluvial fans, often burrowing into a slope or rise in land elevation (Dobler and Dixon 1990).

As observed in captivity, free-ranging females construct natal burrows that are separate from residential burrow systems. The natal burrows have a single entrance leading to a nest chamber. Entrances to natal burrows are backfilled with soil and often are located at the base of shrubs (Rachlow et al. in prep). Preliminary observations based on radio-telemetry in the Lemhi Valley, Idaho, suggest that B. idahoensis moves longer distances than previously documented (more than 7 km for adults, and more than 6 km for juvenile rabbits) (Rachlow et al. in prep).

B. idahoensis is preyed upon by coyotes (Canis latrans), badgers (Taxidea taxus), weasels (Mustela frenata), bobcats (Lynx rufus), great horned owls (Bubo virginianus), long-eared owls (Asio otus), northern harriers (Circus cyaneus) (Dobler and Dixon 1990) and red foxes (Vulpes vulpes) (Green and Flinders 1980).

Wyoming: In Wyoming, B. idahoensis appears to follow the general accepted patterns of habitat use: an affinity for tall and dense sagebrush growing on friable soils. A few documented observations are from areas with only short and sparse sagebrush; there is some speculation (and only speculation) that B. idahoensis can occupy this type of habitat when wind is persistent enough to keep even short sagebrush exposed in the winter (i.e. the true habitat requirement is sagebrush exposed in winter, which in most areas is tall sagebrush, but in a few windy sites may be otherwise). Alternatively, these observations may represent juveniles dispersing through non-typical environments. In landscapes where short and sparse sagebrush is the matrix surrounding island patches of tall and dense sagebrush, B. idahoensis can be reliably found in the islands. Several field workers in south-west Wyoming have independently remarked that B. idahoensis tends to be most frequently found in an elevation band from approximately 6,500-7,500 ft (Beauvais 2004).

Nevada: B. idahoensis in Nevada seems to have similar habitat preferences as rabbits found in other states. They require loamy soils with big sagebrush. They can be located throughout entire valleys, but when not, they generally tend to be found in the largest, most dense clumps of sagebrush on appropriate soils. They have been located in areas with practically no understory (example: Reese Valley) as well as in areas with a heavy understory of forbs and bunch grasses (Sheldon Preserve). There may be competition between B. idahoensis and cottontail rabbits. Areas with high understory often have both rabbit types while areas with moderate understory only have cottontails. These cottontails have been found to be living in burrows that may have originally been made by B. idahoensis. In areas with practically no understory, B. idahoensis has been found with no cottontails (Sequin 2004).

California: B. idahoensis in California has similar habitat requirements to those in Nevada. However, the rabbits around Mono Lake are found in soils that have a higher sand content than populations found in Nevada. They are often found in "loamier" inclusions in stabilized sand dunes. Also, the rabbits in the Bodie area live at very high elevations (8,400+ ft). These rabbits are found in loamy soils in relatively low sagebrush (about 2-3 ft). They are still more likely to be found in the largest and densest sagebrush in the area (Sequin 2004).

Utah: Habitat use by B. idahoensis as inferred from burrow placement and distribution of pellets indicates preferential use of the densest patches of sagebrush available on the landscape. Use of sagebrush species (Artemisia tridentata tridentata, A. t.vaseyana, A. t. wyomingensis, and Artemisia arbuscula) and heights (30 -160 cm) varies considerably with elevation and latitude. It should also be noted that numerous sites considered by range specialists to be "overgrazed" (maintains its sagebrush over story, but exhibits substantial loss of grass and forb understory) contained large numbers of B. idahoensis. This, combined with their use of roadsides and disturbed edge, indicated that rabbits in Utah seem relatively flexible in their use of habitat, given sagebrush maintains proper canopy cover. Extensive snow tracking has been conducted in populations of the Wyoming Basin (Rich County). Initial analysis of non-dispersal movements indicated regular movements of 0.5-1.0 km within the first six hours after a fresh snowfall (Kozlowski 2004).

Systems
  • Terrestrial
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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).

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Cover Requirements

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].
  • 2. Bradfield, Terry D. 1975. Aon the behavior and ecology of the pygmy rabbit. Pocatello, ID: Idaho State University. 43 p. Thesis. [23639]
  • 4. Flath, Dennis. 1994. Bunnies by the bunch. Montana Outdoors. 25(3): 8-13. [23637]
  • 7. Green, Jeffery, S.; Flinders, Jerran T. 1980. Habitat and dietary relationships of the pygmy rabbit. Journal of Range Management. 33(2): 136-142. [6257]
  • 8. Green, Jeffrey S.; Flinders, Jerran T. 1980. Brachylagus idahoensis. Mammalian Species. 125: 1-4. [23631]

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Preferred Habitat

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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].
  • 2. Bradfield, Terry D. 1975. Aon the behavior and ecology of the pygmy rabbit. Pocatello, ID: Idaho State University. 43 p. Thesis. [23639]
  • 4. Flath, Dennis. 1994. Bunnies by the bunch. Montana Outdoors. 25(3): 8-13. [23637]
  • 8. Green, Jeffrey S.; Flinders, Jerran T. 1980. Brachylagus idahoensis. Mammalian Species. 125: 1-4. [23631]
  • 17. Weiss, Nondor T.; Verts, B. J. 1984. Habitat and distribution of pygmy rabbits (Sylvilagus idahoensis) in Oregon. Great Basin Naturalist. 44(4): 563-571. [23635]
  • 20. Wilde, Douglas B.; Keller, Barry L. 1978. An analysis of pygmy rabbit populations on the Idaho National Engineering Laboratory site. In: Markham, O. D., ed. Ecological studies on the Idaho National Engineering Laboratory site. 1978 Progress Report IDO-12087. Idaho Falls, ID: U.S. Department of Energy, Environmental Sciences Branch, Radiological and Environmental Sciences Lab: 305-316. [2561]

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Associated Plant Communities

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].
  • 2. Bradfield, Terry D. 1975. Aon the behavior and ecology of the pygmy rabbit. Pocatello, ID: Idaho State University. 43 p. Thesis. [23639]
  • 7. Green, Jeffery, S.; Flinders, Jerran T. 1980. Habitat and dietary relationships of the pygmy rabbit. Journal of Range Management. 33(2): 136-142. [6257]
  • 16. Severaid, Joye Harold. 1950. The pigmy rabbit (Sylvilagus idahoensis) in Mono County, California. Journal of Mammalogy. 31(1): 1-4. [23634]
  • 18. Welch, Bruce L.; Wagstaff, Fred J.; Roberson, Jay A. 1991. Preference of wintering sage grouse for big sagebrush. Journal of Range Management. 44(5): 462-465. [16608]

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Habitat: Plant Associations

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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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Habitat: Ecosystem

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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

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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

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Migration

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).

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Trophic Strategy

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).

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Food Habits

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].
  • 2. Bradfield, Terry D. 1975. Aon the behavior and ecology of the pygmy rabbit. Pocatello, ID: Idaho State University. 43 p. Thesis. [23639]
  • 6. Gates, Robert J.; Eng, Robert L. 1984. Sage grouse, pronghorn, and lagomorph use of a sagebrush-grassland burn site on the Idaho National Engineering Laboratory. In: Markham, O. Doyle, ed. Idaho National Engineering Laboratory radio ecology and ecology programs: 1983 progress reports. Idaho Falls, ID: U.S. Department of Energy, Radiological and Environmental Sciences Laboratory: 220-235. [1005]
  • 7. Green, Jeffery, S.; Flinders, Jerran T. 1980. Habitat and dietary relationships of the pygmy rabbit. Journal of Range Management. 33(2): 136-142. [6257]
  • 8. Green, Jeffrey S.; Flinders, Jerran T. 1980. Brachylagus idahoensis. Mammalian Species. 125: 1-4. [23631]

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Food Habits

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)

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Associations

Predators

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].
  • 2. Bradfield, Terry D. 1975. Aon the behavior and ecology of the pygmy rabbit. Pocatello, ID: Idaho State University. 43 p. Thesis. [23639]
  • 8. Green, Jeffrey S.; Flinders, Jerran T. 1980. Brachylagus idahoensis. Mammalian Species. 125: 1-4. [23631]
  • 20. Wilde, Douglas B.; Keller, Barry L. 1978. An analysis of pygmy rabbit populations on the Idaho National Engineering Laboratory site. In: Markham, O. D., ed. Ecological studies on the Idaho National Engineering Laboratory site. 1978 Progress Report IDO-12087. Idaho Falls, ID: U.S. Department of Energy, Environmental Sciences Branch, Radiological and Environmental Sciences Lab: 305-316. [2561]

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Ecosystem Roles

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

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Predation

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:

Anti-predator Adaptations: cryptic

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Population Biology

Number of Occurrences

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.

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Global Abundance

2500 to >1,000,000 individuals

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

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General Ecology

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

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Habitat-related Fire Effects

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].
  • 6. Gates, Robert J.; Eng, Robert L. 1984. Sage grouse, pronghorn, and lagomorph use of a sagebrush-grassland burn site on the Idaho National Engineering Laboratory. In: Markham, O. Doyle, ed. Idaho National Engineering Laboratory radio ecology and ecology programs: 1983 progress reports. Idaho Falls, ID: U.S. Department of Energy, Radiological and Environmental Sciences Laboratory: 220-235. [1005]
  • 23. Harniss, Roy O.; Murray, Robert B. 1973. 30 years of vegetal change following burning of sagebrush-grass range. Journal of Range Management. 26(5): 322-325. [1086]
  • 24. Rosentreter, Roger; Jorgensen, Ray. 1986. Restoring winter game ranges in southern Idaho. Tech. Bull. 86-3. Boise, ID: U.S. Department of the Interior, Bureau of Land Management, Idaho State Office. 26 p. [5295]

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Timing of Major Life History Events

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].
  • 8. Green, Jeffrey S.; Flinders, Jerran T. 1980. Brachylagus idahoensis. Mammalian Species. 125: 1-4. [23631]
  • 20. Wilde, Douglas B.; Keller, Barry L. 1978. An analysis of pygmy rabbit populations on the Idaho National Engineering Laboratory site. In: Markham, O. D., ed. Ecological studies on the Idaho National Engineering Laboratory site. 1978 Progress Report IDO-12087. Idaho Falls, ID: U.S. Department of Energy, Environmental Sciences Branch, Radiological and Environmental Sciences Lab: 305-316. [2561]
  • 22. Chapman, Joseph A.; Feldhamer, George A., eds. 1982. Wild mammals of North America. Baltimore, MD: The Johns Hopkins University Press. 1147 p. [21085]

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Life History and Behavior

Behavior

Communication and Perception

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

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Cyclicity

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

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Life Expectancy

Lifespan/Longevity

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.

  • Conaway, C., H. Wight. 1962. Journal of Wildlife Management. Onset of Reproductive Seasonand First Pregnancy of the Season in Cottontails, 26: 278-290.
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Lifespan, longevity, and ageing

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).
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Reproduction

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).

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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)

  • Chapman, J., G. Feldhamer. 1982. Wild Mammals of North America, Biology, Management, Economics. Baltimore, Maryland: The Johns Hopkins University Press.
  • Green, J., J. Flinders. 1980. Brachylagus idahoensis. Mammalian Species, 125: 1-4.
  • 2004. "
    Information from Pacific Biodiversity Institute's Endangered Species Information Network
    " (On-line image). Endangered Species Information Network. Accessed October 15, 2005 at http://www.pacificbio.org/ESIN/Mammals/PygmyRabbit/pygmyrabbit.html.
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
Beauvais, G.P., Sequin, E., Rachlow, J., Dixon, R., Bosworth, B., Kozlowski, A., Carey, C., Bartels, P., Obradovitch, M., Forbes, T. & Hays, D.

Reviewer/s
Smith, A.T. & Boyer, A.F. (Lagomorph Red List Authority)

Contributor/s

Justification
The population status of Brachylagus idahoensis is extremely varied across its discontinuous range, and its dependence on big sagebrush makes it particularly vulnerable to habitat loss from rangeland conversion and fire, and the resulting fragmentation often leads to decreased genetic diversity within populations (Dobler and Dixon 1990). Some populations, such as the extirpated Columbia Basin population, have declined drastically. However, there are several robust populations in less disturbed areas, and suitable habitat still exists in many areas.

History
  • 1994
    Vulnerable
    (Groombridge 1994)
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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

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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.

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U.S. Federal Legal Status

Populations in the Columbia River Basin area of the Pacific Region are
Endangered [25].
  • 25. U.S. Department of the Interior, Fish and Wildlife Service. 2013. Endangered Species Program, [Online]

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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

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National NatureServe Conservation Status

United States

Rounded National Status Rank: N4 - Apparently Secure

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NatureServe Conservation Status

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).

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Status

Near Threatened.
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Population

Population
Washington: The Columbia Basin population of B. idahoensis was extirpated as of 2004 (Sayler et al. 2007), and is federally listed as endangered. A captive population exists with 21 Columbia Basin specimens of B. idahoensis and 26 rabbits crossed and backcrossed with B. idahoensis from Idaho (Hays 2004). Specimens taken to establish founding population for reintroduction had low reproductivity and high disease susceptibility, probably as a result of inbreeding depression. Intercrossing with B. idahoensis from Idaho was successful in restoring genetic diversity and increasing reproductive levels (Sayler et al. 2007). In March 2007, 20 rabbits were released as part of a reintroduction program in Douglas County, Washington (Oregon Zoo 2007).

Wyoming: The Wyoming Natural Diversity Database (WYNDD; University of Wyoming) has on file 93 records of B. idahoensis observations documented in Wyoming. Very few populations have been studied enough to draw reliable conclusions as to size or trend. The population at Fossil Butte National Monument as been studied at various times in the past, and appears to be rather abundant and persistent. In general, field biologists with good knowledge of B. idahoensis habitat can find individuals with relative ease within the known range of the species in Wyoming. In 2003, WYNDD biologists surveyed two areas outside of known range in the state; B. idahoensis was documented at one of these sites (Sweetwater River watershed, described above). Appropriate habitat is rather abundant and contiguous in southwest Wyoming; cheatgrass has not impacted this area to any great degree (yet) (Beauvais 2004).

Nevada and California: Sizes of populations and abundances of B. idahoensis in an area vary. Certain populations in Nevada are composed of vast expanses of burrows. Other populations may include only one burrow system with only about two rabbits photographed at the site. However, we do not know how far these rabbits can disperse and so do not know what constitutes a single population. Once an area is found to contain B. idahoensis, they are often located throughout the valley in reasonable numbers. Fragmentation of populations is largely unknown since we do not know much about dispersal potential. I have photographed juvenile rabbits in areas with no burrows, a long way from any known burrow sites. These rabbits may potentially be able to travel farther than we think as long as cover is provided. Fragmentation is a serious issue when fires or agricultural fields remove cover from vast areas (Sequin 2004).

Oregon: In 2000, a survey was conducted at 17 historical sites active in 1995 in southeast Oregon and only three sites contained evidence of current use by B. idahoensis. A 2001-2002 survey of 38 historical sites found evidence of recent use at only one location. However, recent surveys at new sites with habitat attributes preferred by B. idahoensis found evidence of rabbit use. On the Burns BLM district, 54 sites were surveyed and 12 sites showed signs of occupied rabbit use and undetermined use at 8 sites (Carey et al. 2004).

Utah: The more surveys that are conducted, the more rabbits are found. Populations of B. idahoensis in the Wyoming Basin, Great Basin, Colorado Basin, and Wasatch Mountains all appear to sustain habitat with robust numbers. It should be noted that to date, little to no attention has been paid to analyzing the density, genetic isolation, or trends of these populations (although surveys to increase our knowledge of these three issues are currently underway). It appears that the habitat that has remained intact since the last statewide examination of B. idahoensis in the 1940s also continues to maintain populations. Although it is clear that significant populations of B. idahoensis (both in terms of area and numbers) still inhabit Utah, overall loss of habitat has occurred since the 1950s, rendering large portions of their historical range unsuitable (Eastern Box Elder County, Central Great Basin, Southwestern Utah) (Kozlowski 2004).

Montana: Rauscher (1997) includes Horse Prairie, Big Sheep Creek, Sage Creek, Centennial Valley, the Sweetwater Basin, The Blacktail Wildlife Management Area, Antelope Flats, and the White Rocks as B. idahoensis range.

Idaho: In Idaho, known populations of B. idahoensis are highly fragmented, with the exception of the east-central valley region (Rachlow 2004b).

Population Trend
Unknown
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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).

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Threats

Major Threats
General: B. idahoensis is dependent on big sagebrush (Artemisia tridentata), it is particularly sensitive to habitat loss. Fires that are more frequent due to the increase of invasive cheatgrass, conversion to cropland and rangeland are contributors to loss of sagebrush habitat. Isolation of populations due to fragmentation of suitable habitat cause bottlenecks that threaten subpopulations. Dispersal is limited in fragmented populations, because B. idahoensis will not cross large open areas (Dobler and Dixon 1990).

Washington: In Washington, B. idahoensis is threatened by loss of deep soil shrub-steppe habitat, increase in fire frequencies due to cheatgrass invasion. Fires have the potential to remove sagebrush from vast areas. A recent fire in Washington State burned 66,000 hectares just outside the historic range of B. idahoensis. There are 417,000 hectares within the historic range of B. idahoensis in Washington with soil types where rabbits have been located. Of that amount, 27,000 acres remain in shrub-steppe today, and much of that has been degraded through fire and agricultural practices. Change in abundance and foraging of native predators due to habitat change are potential threats range wide that are largely unstudied (Hays 2004).

Wyoming: Although cheatgrass is not yet a major problem in southwest Wyoming, it is thought to be only a matter of time before it begins to dominate here as it has in states to the west. Also petroleum exploration and development is expected to increase markedly here, with consequent increase in sagebrush removal, alteration of fire cycles, increased road density, and increased potential for cheatgrass and other noxious weed establishment. Habitat managers appear to support more prescribed burning of tall and dense sagebrush, primarily to increase forage for big game and improve habitat for sage grouse. There is only occasional attention being paid to how this might harm B. idahoensis, as well as other vertebrates with similar habitat affinities (e.g. sage thrashers, sage sparrows). Heavy livestock grazing has the potential to reduce habitat quality for B. idahoensis, but it is important to recognize that southwest Wyoming was historically grazed by bison and white-tailed prairie dogs (Cynomys leucurus) with the latter species persisting into the present. Grazing by domestic sheep, cattle, horses, and feral horses occurs today, but was probably more intense and pervasive in the early 20th century and B. idahoensis are presumed to have persisted through that period. Disturbance of habitat in the vicinity of Bear Lake (ID) may reduce the already tentative connectivity between Wyoming populations and those to the west (Beauvais 2004).

Nevada and California: The main threat to B. idahoensis in Nevada and California is fragmentation due to vast fires. (These fires have extirpated populations from entire valleys and without leaving any cover behind may not allow rabbits to repopulate the area.) This is a severe problem that will most likely become greater with increasing cheatgrass invasion across Nevada. Agricultural fields are also a threat. Not only are they usually placed on the same loamy soils the rabbits prefer, but they also create a potentially impassable barrier and may increase the habitat suitability for cottontails. Road systems may also be a larger barrier to dispersal that we may think. In nighttimes road transect surveys in areas with known ratios of jackrabbits/cottontails/ B. idahoensis, B. idahoensis was consistently significantly underrepresented. This may be due to their reluctance to cross open areas (Sequin 2004).

Oregon: Threats to B. idahoensis in Oregon include fire (natural and managed), flooding, conversion to agriculture, exotic plants, decadence and overgrazing. The accumulative effects of the threats have contributed to habitat fragmentation and the isolation of populations (Carey et al. 2004).

Utah: The primary threat to B. idahoensis at this time is habitat loss. Loss occurs as a result of human development (historic losses: Wasatch Front north of Salt Lake; current losses: southwestern portion of the state in the vicinity of Cedar City), conversion to cultivated agriculture (northwestern portion of the Great Basin), degradation of plant communities due to overgrazing (widespread), increased fire frequency due to invasive weed understory (Great Basin), and large scale range improvement projects favouring the creation of large openings in mature sagebrush (Wyoming Basin, Lower Wasatch Range). As populations get smaller and more isolated, predators and disease may play more prominent roles as threats (Kozlowski 2004).

Idaho: B. idahoensis is threatened in Idaho by loss and/or modification of habitat including agricultural and urban development, invasive weeds, and changes in fire frequencies (Rachlow 2004b).

Montana: Rauscher (1997) mentions fragmentation of B. idahoensis habitat resulting from projects to improve rangeland for cattle as a threat (sagebrush is removed). He qualified that by stating that the rabbit is somewhat resilient and has the ability to use sites that were previously disturbed.
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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.

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Management

Conservation Actions

Conservation Actions
General: Greater sage-grouse range overlaps with B. idahoensis range. Conservation of sage-grouse is a big issue and a federal listing may occur. Conservation of sage-grouse will likely benefit B. idahoensis to a significant degree. However, fire is being used to restore shrub-steppe and sage-grouse range in places, and although agencies are starting to include B. idahoensis in planning, it does not always happen (Hays 2004).

Washington: B. idahoensis from the Columbia Basin are federally listed as endangered. A recovery plan is being prepared, a captive breeding program is in place, habitat acquisition is proceeding, habitat management has changed, surveys have proceeded, reintroduction sites have been selected, and reintroduction techniques have been developed (Hays 2004). The reintroduction plan involves intercross breeding of B. idahoensis from the Columbia Basin with intraspecific rabbits from Idaho because of the bottleneck of genetic diversity caused by an extremely small population size (Sayler et al. 2007). The plan outlines reintroductions in 2007, followed by monitoring through the year for survival, dispersal, and reproductive success, and then a second reintroduction in early 2008 to augment the established population (Sayler et al. 2007). In March 2007, the first reintroduction of 20 rabbits bred by the Oregon Zoo were released in Douglas county, Washington, eight of which will be tracked by radio collar (Oregon Zoo 2007).

Wyoming: In Wyoming, B. idahoensis occurs on Fossil Butte National Monument; small population segments may extend onto Seedskadee and Bear River Meadows National Wildlife Refuges. These are all rather small and isolated protected areas. The vast majority of B. idahoensis populations in Wyoming occur on surfaces managed for multiple uses by the USDI Bureau of Land Management (BLM). A lesser amount of state and private land within the BLM matrix also supports rabbits. The USDA Forest Service may manage some small population segments at the high-elevation periphery of the species distribution. B. idahoensis is on the Sensitive Species list of the Wyoming State Office of the BLM, which requires that agency to consider the effects of management actions on B. idahoensis (Beauvais 2004).

Nevada: There is increased awareness but otherwise no conservation actions for B. idahoensis in Nevada. B. idahoensis populations are located in the Sheldon National Wildlife Refuge, as well as in the Great Basin National Park (Sequin 2004).

California: B. idahoensis is located at Mono Lake and Bodie State Historic Park and receive protection in these areas (Sequin 2004).

Oregon: Surveys are being conducted throughout the historic range of B. idahoensis in Oregon and additional surveys are planned for fall 2004 and 2005. A Master's student is studying habitat at Sheldon NWR. Also, a small telemetry project is underway. The BLM and Hart Mountain National Wildlife Refuge are now surveying for B. idahoensis prior to management activities such as road work and controlled burns (Carey et al. 2004). The Oregon Zoo has provided a source population for reintroductions of B. idahoensis in the Columbia Basin, Washington (Oregon Zoo 2007).

Utah: B. idahoensis is listed in Utah as a Species of Special Concern, and has been the focus of three ambitious grants designed to assess the effects of current land treatment practices on B. idahoensis, to examine historical trends in habitat loss, and to develop a statewide habitat model to increase management efficiency of the species (Kozlowski 2004).

Idaho: Current actions include increased survey efforts to document the occurrence of B. idahoensis within its range, and research into its ecology and habitat requirements. Captive breeding has been established for the Columbian Basin DPS and experimental reintroductions have been initiated for the species. Loss and/or modification of habitat include agricultural and urban development, invasive weeds, and changes in fire frequencies (Rachlow 2004). In 2004, 42 captive-bred rabbits were released into the wild at the Idaho National Laboratory for a study intended to evaluate techniques to be used for future Columbia Basin, Washington population reintroductions. Less than half survived more than 18 days, but survival may have been more successful if release pens were more protected from predators and if the rabbits had been released farther apart (Sayler et al. 2007).

Montana: B. idahoensis is listed as a species of special concern by Montana Natural Heritage Program (Rauscher 1997).
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Management Considerations

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.
  • 4. Flath, Dennis. 1994. Bunnies by the bunch. Montana Outdoors. 25(3): 8-13. [23637]
  • 10. Holechek, Jerry L. 1981. Brush control impacts on rangeland wildlife. Journal of Soil and Water Conservation. 36(5): 265-269. [1182]
  • 17. Weiss, Nondor T.; Verts, B. J. 1984. Habitat and distribution of pygmy rabbits (Sylvilagus idahoensis) in Oregon. Great Basin Naturalist. 44(4): 563-571. [23635]

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Use of Fire in Population Management

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].
  • 12. Klott, James H.; Ketchum, Chris. 1991. The results of using "Hobble Creek" sagebrush on two fire rehabilitations. Idaho BLM Technical Bulletin 91-1. Boise, ID: U.S. Department of the Interior, Bureau of Land Management. 12 p. [19869]

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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).

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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).

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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

Pygmy rabbits have no known negative economic impact on humans.

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Economic Importance for Humans: Positive

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

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Wikipedia

Pygmy rabbit

The pygmy rabbit (Brachylagus idahoensis) is a North American rabbit, and is one of only two rabbit species in America to dig its own burrow. The pygmy rabbit differs significantly from species within either the Lepus (hare) or Sylvilagus (cottontail) genera and is generally considered to be within the monotypic genus Brachylagus. One isolated population, the Columbia Basin Pygmy Rabbit, is listed as an endangered species by the U.S. Federal government, though the International Union for Conservation of Nature lists the species as lower risk.

The pygmy rabbit is the world's smallest leporid,[3][4][5][6] with mean adult weights from 375 to about 500 grams (0.827 to about 1.102 lb), and a body length from 23.5 to 29.5 centimeters (9.3 to 11.6 in); females are slightly larger than males. The pygmy rabbit is distinguishable from other leporids by its small size, short ears, gray color, small hind legs, and lack of white fur on the tail.

Distribution[edit]

The range of the pygmy rabbit includes most of the Great Basin and some of the adjacent intermountain areas of the western United States.[7] Pygmy rabbits are found in southwestern Montana from the extreme southwest corner near the Idaho border north to Dillon and Bannack in Beaverhead County.[8] 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 [9] and Wyoming.[10]

The elevational range of pygmy rabbits in Nevada extends from 1,370–2,135 meters (4,495–7,005 ft) and in California from 1,520–1,615 meters (4,987–5,299 ft).[7]

The last male purebred Columbia Basin pygmy rabbit, found only in the Columbia Basin of Washington State, died March 30, 2006, at the Oregon Zoo in Portland. The last purebred female died in 2008.[11] A crossbreeding program conducted by the Oregon Zoo, Washington State University and Northwest Trek is attempting to preserve the genetic line by breeding surviving females with the Idaho Pygmy Rabbit.[12]

Plant communities[edit]

Pygmy rabbits are found primarily in big sagebrush (Artemisia tridentata) and rabbitbrush (Chrysothamnus spp.) dominated communities.[9][13][14][15][16] Pygmy rabbits are also found in areas where greasewood (Sarcobatus spp.) is abundant.[14] 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.).[14] 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).[15]

Lifecycle[edit]

Pygmy rabbits are capable of breeding when they are about 1 year old.[7][17]

The breeding season of pygmy rabbits is very short. In Idaho it lasts from March through May; in Utah, from February through March.[18] 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.[7] In Idaho the third litter is generally produced in June.[17] It is unlikely that litters are produced in the fall.[7]

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.[7]

The mortality of adults is highest in late winter and early spring. Green and Flinders [7] reported a maximum estimated annual adult mortality of 88% in Idaho. Juvenile mortality was highest from birth to 5 weeks of age.[7]

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.[7]

Habitat[edit]

Pygmy rabbits are generally limited to areas on deep soils with tall, dense sagebrush which they use for cover and food.[7][8] Individual sagebrush plants in areas inhabited by pygmy rabbits are often 6 feet (1.8 m) or more in height.[8] Extensive, well-used runways interlace the sage thickets and provide travel and escape routes.[7] Dense stands of big sagebrush along streams, roads, and fencerows provide dispersal corridors for pygmy rabbits.[19]

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.[7] 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.[17]

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 1 meter (3.3 ft). Burrows typically have 4 or 5 entrances but may have as few as 2 or as many as 10.[7] 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.[19] 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).[7][9]

Some researchers have found that pygmy rabbits never venture farther than 60 feet (18 m) from their burrows.[9] However, Bradfield [9] observed pygmy rabbits range up to 100 meters (330 ft) from their burrows.

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.[7][9] Above ground movement during the winter months is restricted to these tunnel systems.[9]

Cover requirements[edit]

Pygmy rabbits are restricted to areas with heavy shrub cover.[7][8] Pygmy rabbits are seldom found in areas of sparse vegetative cover and seem to be reluctant to cross open space.[9] In southeastern Idaho, woody cover and shrub height were significantly (P<0.01) greater on sites occupied by pygmy rabbits than on other sites in the same area.[14]

Food habits[edit]

The primary food of pygmy rabbits is big sagebrush, which may comprise up to 99% of the food eaten in the winter. Grasses and forbs are also eaten from mid- to late summer.[7][9][14][20] In Idaho, Gates and Eng [20] found that shrubs contributed 85.2% (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% 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% of the July to December diet.[20]

In southeastern Idaho, Green and Flinders [14] 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.[14]

Predators[edit]

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.[7][9][17]

Listing status[edit]

On September 26, 2007, Judge Edward Lodge of the United States District Court for the District of Idaho granted litigant party Western Watersheds Project summary judgment remanding the United States Fish and Wildlife Service 90-day finding denying conservationist parties' listing petition. The petition sought legal protection for Pygmy Rabbit as an endangered or threatened species.[21]

References[edit]

 This article incorporates public domain material from the United States Department of Agriculture document "Brachylagus idahoensis".

  1. ^ Hoffman, R. S.; Smith, A. T. (2005). "Order Lagomorpha". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 194. ISBN 978-0-8018-8221-0. OCLC 62265494. 
  2. ^ Beauvais, G.P., Sequin, E., Rachlow, J., Dixon, R., Bosworth, B., Kozlowski, A., Carey, C., Bartels, P., Obradovitch, M., Forbes, T. & Hays, D. (2008). "Brachylagus idahoensis". IUCN Red List of Threatened Species. Version 2009.2. International Union for Conservation of Nature. Retrieved 01 February 2010. 
  3. ^ George Gilbert Goodwin, Frederick Drimmer (1954). The Animal kingdom: the strange and wonderful ways of mammals, birds, reptiles, fishes, and insects; a new and authentic natural history of the wildlife of the world, Volume 1. Cornell University. p. 246. 
  4. ^ George C. Goodwin (1962). Small mammals. Cornell University. 
  5. ^ Sharon Sharth (1999). Rabbits. p. 12. ISBN 156766587X. 
  6. ^ Meet the World's Smallest Rabbit, October 14, 2009
  7. ^ a b c d e f g h i j k l m n o p q r Green, Jeffrey S.; Flinders, Jerran T. 1980. Brachylagus idahoensis. Mammalian Species. 125: 1–4
  8. ^ a b c d Flath, Dennis. 1994. Bunnies by the bunch. Montana Outdoors. 25(3): 8–13
  9. ^ a b c d e f g h i j Bradfield, Terry D. 1975. On the behavior and ecology of the pygmy rabbit. Pocatello, ID: Idaho State University. Thesis
  10. ^ Campbell, Thomas M., III; Clark, Tim W.; Groves, Craig R. 1982. First record of pygmy rabbits (Brachylagus idahoensis) in Wyoming. Great Basin Naturalist. 42(1): 100
  11. ^ National Geographic – Editor's Note – January 2009
  12. ^ Captive breeding offers hope for near-extinct pygmy rabbits
  13. ^ Larrucea, Eveline S.; Brussard, Peter F. (2008). "Habitat selection and current distribution of the pygmy rabbit in Nevada and California, USA". Journal of Mammalogy 89: 691. doi:10.1644/07-MAMM-A-199R.1. 
  14. ^ a b c d e f g Green, Jeffery, S.; Flinders, Jerran T. 1980. Habitat and dietary relationships of the pygmy rabbit. Journal of Range Management. 33(2): 136–142
  15. ^ a b Severaid, Joye Harold. 1950. The pigmy rabbit (Sylvilagus idahoensis) in Mono County, California. Journal of Mammalogy. 31(1): 1–4
  16. ^ Welch, Bruce L.; Wagstaff, Fred J.; Roberson, Jay A. 1991. Preference of wintering sage grouse for big sagebrush. Journal of Range Management. 44(5): 462–465
  17. ^ a b c d Wilde, Douglas B.; Keller, Barry L. 1978. An analysis of pygmy rabbit populations on the Idaho National Engineering Laboratory site. In: Markham, O. D., ed. Ecological studies on the Idaho National Engineering Laboratory site. 1978 Progress Report IDO-12087. Idaho Falls, ID: U.S. Department of Energy, Environmental Sciences Branch, Radiological and Environmental Sciences Lab: 305–316
  18. ^ Chapman, Joseph A.; Feldhamer, George A., eds. 1982. Wild mammals of North America. Baltimore, MD: The Johns Hopkins University Press
  19. ^ a b Weiss, Nondor T.; Verts, B. J. 1984. Habitat and distribution of pygmy rabbits (Sylvilagus idahoensis) in Oregon. Great Basin Naturalist. 44(4): 563–571
  20. ^ a b c Gates, Robert J.; Eng, Robert L. 1984. Sage grouse, pronghorn, and lagomorph use of a sagebrush-grassland burn site on the Idaho National Engineering Laboratory. In: Markham, O. Doyle, ed. Idaho National Engineering Laboratory radio ecology and ecology programs: 1983 progress reports. Idaho Falls, ID: U.S. Department of Energy, Radiological and Environmental Sciences Laboratory: 220–235
  21. ^ Standard for Listing Petitions & Evaluation of Threats to the Pygmy Rabbit


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Columbia Basin pygmy rabbit

The Columbia Basin pygmy rabbit is an isolated population of pygmy rabbit (Brachylagus idahoensis) native only to a single area of Washington state called the Columbia Basin.[1] While the IUCN considers the species as a whole to be of least concern, the US Fish & Wildlife Service considers this a distinct population segment, and as thus merits protections under the Endangered Species Act.[2]

Conservation[edit source | edit]

Unlike most rabbits, the Columbia Basin pygmy rabbit did not breed prodigiously in these environs, partially due to inbreeding within the tiny wild population. As a result they were cross bred with Idaho pygmy rabbits and subsequent breeding efforts have been more successful. In 2009, the Oregon Zoo produced 26 kits, bringing the total offspring population for the year to 73 kits among participating breeding facilities.[3] In 2010, the zoo found that pairings based on familiarity and preferences resulted in greater breeding success than pairings based only on genetic relatedness.[4]

Characteristics[edit source | edit]

Pygmy rabbits are the only North American rabbits that dig burrows and live in a sagebrush habitat. In the wild, pygmy rabbits eat sagebrush almost exclusively in the winter; during summer, they eat a more varied diet. They may have two to four litters of about two to six kits during the spring and summer breeding seasons. Population decline is widely attributed to predation and habitat loss caused by agricultural development and wildfires.

See also[edit source | edit]

References[edit source | edit]

  1. ^ B. J. Verts; Leslie N. Carraway (15 August 1998). Land Mammals of Oregon. University of California Press. p. 128. ISBN 978-0-520-21199-5. 
  2. ^ "Pygmy Rabbit (Brachylagus idahoensis)". US Fish & Wildlife Service Species Profile. 
  3. ^ Meet the World's Smallest Rabbit. ZooBorns (2009-10-14). Retrieved on 2012-12-31.
  4. ^ "Love is in the hare: Zoo explores pygmy rabbit ‘love connection’". The Oregon Zoo (KVAL). February 14, 2013. 
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Names and Taxonomy

Taxonomy

The currently accepted scientific name for the pygmy rabbit is
Brachylagus idahoensis (Merriam) [8]. Some authorities have placed the
pygmy rabbit in the genus Sylvilagus subgenus Brachylagus [9,14]. Pygmy
rabbits are in the family Leporidae. There are no recognized subspecies
or races [8].
  • 8. Green, Jeffrey S.; Flinders, Jerran T. 1980. Brachylagus idahoensis. Mammalian Species. 125: 1-4. [23631]
  • 9. Hall, E. Raymond; Kelson, Keith R. 1959. The mammals of North America, Volume II. New York: The Ronald Press Company. 79 p. [21460]
  • 14. Orr, R. T. 1940. The rabbits of California. Occassional Papers of the California Academy of Sciences. 19: 1-227. [23641]

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Common Names

pygmy rabbit

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Comments: Formerly included in genus Sylvilagus (see Diersing 1984). Included in the genus Brachylagus by Jones et al. (1992) and Hoffmann (in Wilson and Reeder 1993). Another synonym is Lepus idahoensis.

The Washington State (Columbia Basin) population is genetically distinct from the remainder of the species, and is believed to have been isolated for at least 10,00o years, perhaps much longer (USFWS 2001).

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