Identification | Biology | Damage ID| Management | Handling
Identification
The mountain beaver (Aplodontia rufa) is a medium-sized rodent in the family Aplodontiadae. There are no other species in the family. The mountain beaver is more closely related to squirrels than to beavers.
Legal Status
Mountain beavers are generally considered unprotected nongame species, although one subspecies found in Mendocino County, California is listed as endangered by the US Fish and Wildlife Service. Individuals wanting to control mountain beavers should consult their state fish and game agency to determine current regulations.
Physical Description
Average adults weigh 2.3 pounds (1,050 g) and range from 1.8 to 3.5 pounds (800 to 1,600 g). Average overall length is 13.5 inches (34 cm), including a rudimentary tail about 1 inch (2.5 cm) long. The body is stout and compact. The head is relatively large and wide and blends into a large neck with no depression where it joins the shoulders. The eyes and ears are relatively small and the cheeks have long silver “whiskers.” The hind feet are about 2 inches (5 cm) long and slightly longer than the front feet. Mountain beavers often balance on their hind feet while feeding. The front feet are developed for grasping and climbing.
Adults are grayish brown or reddish brown. The underfur on the back and sides is charcoal with brown tips; guard hair is dark brown or black with silver tips. Ventrally, the underfur is gray with few guard hairs. A whitish spot of bare skin is present at the base of the ears. The feet are lightly furred on top and bare on the soles. Young animals are generally darker than adults. Males have a baculum (a bone about 1 inch [2.5 cm] long in the penis). Mature females generally have a patch of dark-colored underfur around each of the six nipples.
Species Range
Mountain beavers are found in the Pacific coastal region from southern British Columbia to northern California. They range westward from the Cascade Mountains and southward into the Sierras. Numbers are higher and populations are more continuous in the coastal Olympic Mountains and in the coast range of Washington and Oregon than elsewhere. In the southern limit of its range, populations are more scattered but sometimes locally abundant.
Voices and Sounds
A mountain beaver grinds or clicks its teeth as a defense, or when foraging for food. It squeals or gives sharp whistle when defending its burrow.
Tracks and Signs
Mountain beaver feet are developed for burrowing and climbing. Hind feet are about 2 inches long, slightly longer than the front feet.
Acknowledgements
Information on this species is based on the chapter in Prevention and Control of Wildlife Damage (Hygnstrom, Larson, Timm, ed. 1994), written by Dan Campbell (USDA-APHIS-Animal Damage Control, Olympia Field Station).