Index of Species Information

WILDLIFE SPECIES:  Brachylagus idahoensis

Introductory

WILDLIFE SPECIES: Brachylagus idahoensis
AUTHORSHIP AND CITATION : Tesky, Julie L. 1994. Brachylagus idahoensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [].
ABBREVIATION : BRID COMMON NAMES : pygmy rabbit 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]. ORDER : Lagomorpha CLASS : Mammal FEDERAL LEGAL STATUS : Populations in the Columbia River Basin area of the Pacific Region are Endangered [25]. OTHER STATUS : 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.


WILDLIFE DISTRIBUTION AND OCCURRENCE

WILDLIFE SPECIES: Brachylagus idahoensis
GENERAL DISTRIBUTION : 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]. ECOSYSTEMS : FRES29 Sagebrush FRES30 Desert shrub STATES :
CA ID MT NV OR WA WY
BLM PHYSIOGRAPHIC REGIONS : 2 Cascade Mountains 4 Sierra Mountains 5 Columbia Plateau 6 Upper Basin and Range 7 Lower Basin and Range 8 Northern Rocky Mountains KUCHLER PLANT ASSOCIATIONS : K038 Great Basin sagebrush K040 Saltbush - greasewood K055 Sagebrush steppe K056 Wheatgrass - needlegrass shrubsteppe SAF COVER TYPES : NO-ENTRY SRM (RANGELAND) COVER TYPES : NO-ENTRY PLANT COMMUNITIES : 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].

BIOLOGICAL DATA AND HABITAT REQUIREMENTS

WILDLIFE SPECIES: Brachylagus idahoensis
TIMING OF MAJOR LIFE HISTORY EVENTS : 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]. PREFERRED HABITAT : 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]. COVER REQUIREMENTS : 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<0.01) greater on sites occupied by pygmy rabbits than on other sites in the same area [7]. FOOD HABITS : 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]. PREDATORS : 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]. MANAGEMENT CONSIDERATIONS : 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.

FIRE EFFECTS AND USE

WILDLIFE SPECIES: Brachylagus idahoensis
DIRECT FIRE EFFECTS ON ANIMALS : Pygmy rabbits probably are capable of escaping slow moving fires; however, they may be burned or die of asphyxiation in some fires. During a prescribed burn of a big sagebrush-grassland community in Idaho, several pygmy rabbits died in an area where the fire advanced rapidly. Although pygmy rabbits use burrows, the burrows evidently do not always provide them with effective protection from fire [6]. HABITAT RELATED FIRE EFFECTS : 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]. FIRE USE : 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].

REFERENCES

WILDLIFE SPECIES: Brachylagus idahoensis
REFERENCES : 1. Bernard, Stephen R.; Brown, Kenneth F. 1977. Distribution of mammals, reptiles, and amphibians by BLM physiographic regions and A.W. Kuchler's associations for the eleven western states. Tech. Note 301. Denver, CO: U.S. Department of the Interior, Bureau of Land Management. 169 p. [434] 2. Bradfield, Terry D. 1975. Aon the behavior and ecology of the pygmy rabbit. Pocatello, ID: Idaho State University. 43 p. Thesis. [23639] 3. Eyre, F. H., ed. 1980. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters. 148 p. [905] 4. Flath, Dennis. 1994. Bunnies by the bunch. Montana Outdoors. 25(3): 8-13. [23637] 5. Garrison, George A.; Bjugstad, Ardell J.; Duncan, Don A.; [and others]. 1977. Vegetation and environmental features of forest and range ecosystems. Agric. Handb. 475. Washington, DC: U.S. Department of Agriculture, Forest Service. 68 p. [998] 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] 9. Hall, E. Raymond; Kelson, Keith R. 1959. The mammals of North America, Volume II. New York: The Ronald Press Company. 79 p. [21460] 10. Holechek, Jerry L. 1981. Brush control impacts on rangeland wildlife. Journal of Soil and Water Conservation. 36(5): 265-269. [1182] 11. Jones, Fred L. 1957. Southern extension of the range of the pigmy rabbit in California. Journal of Mammalogy. 38(2): 274. [23632] 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] 13. Kuchler, A. W. 1964. Manual to accompany the map of potential vegetation of the conterminous United States. Special Publication No. 36. New York: American Geographical Society. 77 p. [1384] 14. Orr, R. T. 1940. The rabbits of California. Occassional Papers of the California Academy of Sciences. 19: 1-227. [23641] 15. Pritchett, C. L.; Nilsen, J. A.; Coffeen, M. P.; Smith, H. D. 1987. Pygmy rabbits in the Colorado River drainage. Great Basin Naturalist. 47(2): 231-233. [23633] 16. Severaid, Joye Harold. 1950. The pigmy rabbit (Sylvilagus idahoensis) in Mono County, California. Journal of Mammalogy. 31(1): 1-4. [23634] 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] 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] 19. White, Susan M.; Flinders, Jerran T.; Welch, Bruce L. 1982. Preference of pygmy rabbits (Brachylagus idahoensis) for various populations of big sagebrush (Artemisia tridentata). Journal of Range Management. 35(6): 724-726. [23636] 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] 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] 22. Chapman, Joseph A.; Feldhamer, George A., eds. 1982. Wild mammals of North America. Baltimore, MD: The Johns Hopkins University Press. 1147 p. [21085] 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] 25. U.S. Department of the Interior, Fish and Wildlife Service. 2013. Endangered Species Program, [Online]. Available: http://www.fws.gov/endangered/. [86564] 26. Washington Department of Wildlife. 1994. Species of special concern in Washington - state and federal status. Olympia, WA: Washington Department of Wildlife. 41 p. [25414]


FEIS Home Page