Pygmy Rabbit
Encyclopedia
The Pygmy Rabbit is a North America
n 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.
Although it is listed as an endangered species
in the Columbia Basin
of the Pacific Northwest
in the United States
, the International Union for Conservation of Nature lists the species as lower risk. This is because the Columbia Basin population is a genetically distinct isolated relict
population well on its way to evolving into a distinct subspecies
, whereas the IUCN only considers species as a whole.
The Pygmy Rabbit is the world's smallest leporid, with mean adult weights from 375 to about 500 grams (about 13 ounces – 1 pound), and a body length from 23.5 to 29.5 centimeters (9¼ to 11½ inches); 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.
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).
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. 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.
are about 1 year old.
The breeding season of pygmy rabbits is very short. In Idaho it lasts from March through May; in Utah, from February through March. 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. In Idaho the third litter is generally produced in June. It is unlikely that litters are produced in the fall.
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.
The mortality of adults is highest in late winter and early spring. Green and Flinders reported a maximum estimated annual adult mortality of 88% in Idaho. Juvenile mortality was highest from birth to 5 weeks of age.
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.
stands of big sagebrush along streams, roads, and fencerows provide dispersal corridors for pygmy rabbits.
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. 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.
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. 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. 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).
Some researchers have found that pygmy rabbits never venture further than 60 feet (21.3 m) from their burrows. However, Bradfield observed pygmy rabbits range up to 328 feet (100 m) 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. Aboveground movement during the winter months is restricted to these tunnel systems.
Pygmy rabbits are seldom found in areas of sparse vegetative cover and seem to be reluctant to cross open space. 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.
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.
In southeastern Idaho, Green and Flinders 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.
(Vulpes vulpes), badger, bobcat (Felis rufus), great horned owl (Bubo virginianus) and marsh hawk (Circus cyaneus) also prey on pygmy rabbits.
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
.
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n rabbit
Rabbit
Rabbits are small mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world...
, 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
Hares and jackrabbits are leporids belonging to the genus Lepus. Hares less than one year old are called leverets. Four species commonly known as types of hare are classified outside of Lepus: the hispid hare , and three species known as red rock hares .Hares are very fast-moving...
(hare) or Sylvilagus
Cottontail rabbit
The cottontail rabbits are among the 16 lagomorph species in the genus Sylvilagus, found in the Americas.In appearance, most cottontail rabbits closely resemble the wild European Rabbit...
(cottontail) genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
and is generally considered to be within the monotypic genus Brachylagus.
Although it is listed as an endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
in the Columbia Basin
Columbia Basin
The Columbia Basin, the drainage basin of the Columbia River, occupies a large area–about —of the Pacific Northwest region of North America. In common usage, the term often refers to a smaller area, generally the portion of the drainage basin that lies within eastern Washington.Usage of the term...
of the Pacific Northwest
Pacific Northwest
The Pacific Northwest is a region in northwestern North America, bounded by the Pacific Ocean to the west and, loosely, by the Rocky Mountains on the east. Definitions of the region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common concept of the...
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, the International Union for Conservation of Nature lists the species as lower risk. This is because the Columbia Basin population is a genetically distinct isolated relict
Relict
A relict is a surviving remnant of a natural phenomenon.* In biology a relict is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas....
population well on its way to evolving into a distinct subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
, whereas the IUCN only considers species as a whole.
The Pygmy Rabbit is the world's smallest leporid, with mean adult weights from 375 to about 500 grams (about 13 ounces – 1 pound), and a body length from 23.5 to 29.5 centimeters (9¼ to 11½ inches); 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
The range of the pygmy rabbit includes most of the Great Basin and some of the adjacent intermountain areas of the western United States. Pygmy rabbits are found in southwestern Montana from the extreme southwest corner near the Idaho border north to Dillon and Bannack in Beaverhead County. 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 and Wyoming.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).
The last male purebred Columbia Basin Pygmy Rabbit
Columbia Basin Pygmy Rabbit
Columbia Basin Pygmy Rabbits are the world's smallest and among the rarest. Native only to a single area of Washington State called the Columbia Basin, this once isolated population of pygmy rabbits usually weighs less than a pound in adulthood and was declared extinct in the wild in the 1990s,...
, found only in the Columbia Basin
Columbia Basin
The Columbia Basin, the drainage basin of the Columbia River, occupies a large area–about —of the Pacific Northwest region of North America. In common usage, the term often refers to a smaller area, generally the portion of the drainage basin that lies within eastern Washington.Usage of the term...
of Washington State, died March 30, 2006, at the Oregon Zoo
Oregon Zoo
The Oregon Zoo, formerly the Washington Park Zoo, is a zoo in Portland, the largest city in the U.S. state of Oregon. Located southwest of Downtown Portland, the zoo is inside Portland's Washington Park, and includes a narrow-gauge railway that connects to the International Rose Test Garden inside...
in Portland
Portland, Oregon
Portland is a city located in the Pacific Northwest, near the confluence of the Willamette and Columbia rivers in the U.S. state of Oregon. As of the 2010 Census, it had a population of 583,776, making it the 29th most populous city in the United States...
. The last purebred female died in 2008. A crossbreeding program conducted by the Oregon Zoo, Washington State University
Washington State University
Washington State University is a public research university based in Pullman, Washington, in the Palouse region of the Pacific Northwest. Founded in 1890, WSU is the state's original and largest land-grant university...
and Northwest Trek is attempting to preserve the genetic line by breeding surviving females with the Idaho Pygmy Rabbit.
Plant communities
Pygmy rabbits are found primarily in big sagebrush (Artemisia tridentata) and rabbitbrush (Chrysothamnus spp.) dominated communities. Pygmy rabbits are also found in areas where greasewood (Sarcobatus spp.) is abundant. 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.). 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).Timing of major life events
Pygmy rabbits are capable of breeding when theyare about 1 year old.
The breeding season of pygmy rabbits is very short. In Idaho it lasts from March through May; in Utah, from February through March. 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. In Idaho the third litter is generally produced in June. It is unlikely that litters are produced in the fall.
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.
The mortality of adults is highest in late winter and early spring. Green and Flinders reported a maximum estimated annual adult mortality of 88% in Idaho. Juvenile mortality was highest from birth to 5 weeks of age.
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.
Habitat
Pygmy rabbits are generally limited to areas on deep soils with tall, dense sagebrush which they use for cover and food. Individual sagebrush plants in areas inhabited by pygmy rabbits are often 6 feet (1.8 m) or more in height. Extensive, well-used runways interlace the sage thickets and provide travel and escape routes. Densestands of big sagebrush along streams, roads, and fencerows provide dispersal corridors for pygmy rabbits.
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. 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.
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. 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. 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).
Some researchers have found that pygmy rabbits never venture further than 60 feet (21.3 m) from their burrows. However, Bradfield observed pygmy rabbits range up to 328 feet (100 m) 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. Aboveground movement during the winter months is restricted to these tunnel systems.
Cover requirements
Pygmy rabbits are restricted to areas with heavy shrub cover.Pygmy rabbits are seldom found in areas of sparse vegetative cover and seem to be reluctant to cross open space. 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.
Food habits
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. In Idaho, Gates and Engfound 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.
In southeastern Idaho, Green and Flinders 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.
Predators
Weasels (Mustela spp.) are the principal predators of pygmy rabbits. Coyote (Canis latrans), red foxRed Fox
The red fox is the largest of the true foxes, as well as being the most geographically spread member of the Carnivora, being distributed across the entire northern hemisphere from the Arctic Circle to North Africa, Central America, and the steppes of Asia...
(Vulpes vulpes), badger, bobcat (Felis rufus), great horned owl (Bubo virginianus) and marsh hawk (Circus cyaneus) also prey on pygmy rabbits.
Listing status
On September 26, 2007, Judge Edward LodgeEdward Lodge
Edward Lodge is a federal judge on the United States District Court for the District of Idaho in Boise, Idaho. He is the husband of Idaho State Senator Patti Anne Lodge.- Education and Career :...
of the United States District Court for the District of Idaho
United States District Court for the District of Idaho
The United States District Court for the District of Idaho is the Federal district court whose jurisdiction comprises the state of Idaho...
granted litigant party Western Watersheds Project summary judgment
Summary judgment
In law, a summary judgment is a determination made by a court without a full trial. Such a judgment may be issued as to the merits of an entire case, or of specific issues in that case....
remanding the United States Fish and Wildlife Service
United States Fish and Wildlife Service
The United States Fish and Wildlife Service is a federal government agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats...
90-day finding denying conservationist parties' listing petition
Petition
A petition is a request to do something, most commonly addressed to a government official or public entity. Petitions to a deity are a form of prayer....
. The petition sought legal protection for Pygmy Rabbit as an endangered or threatened species
Threatened species
Threatened species are any speciesg animals, plants, fungi, etc.) which are vulnerable to endangerment in the near future.The World Conservation Union is the foremost authority on threatened species, and treats threatened species not as a single category, but as a group of three categories,...
.
External links
- Washington Department of Fish and Wildlife, Pygmy Rabbit
- Article on Washington State University's pygmy rabbit breeding and release program, with photos and videos
- Fish and Wildlife Science Magazine, article on captive breeding program for pygmy rabbits (with several photos)
- Western Watersheds Project