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The Mountain Beaver

The mountain beaver (Aplodontia rufa, family Aplodontidae) occurs in the Cascade Mountains from east-central California north through Oregon and Washington to southwestern British Columbia. Other than being a large rodent, the mountain beaver is not particularly closely related to the true beavers, which are in the family Castoridae. In fact, mountain beavers are the only species in their family, and they not closely related to any other rodents. Because of their ancient evolutionary history, mountain beavers are sometimes considered to be living fossils. In body form, the mountain beaver looks like a tailless muskrat or large vole, with small ears, short legs, and grizzled, brownish fur. Mountain beavers are terrestrial animals, digging long, complex burrows in moist, workable soil near streams, with numerous entrances and exits located in concealed places. These animals live in loose colonies, but they are not very social animals, preferring to avoid frequent, direct contact with each other. Mountain beavers eat a wide range of plant foods, including herbaceous plants and fruits, young twigs of woody plants, and conifer foliage and shoots in the wintertime. Mountain beavers store food for the winter in underground haystacks.



Banfield, A.W.F. The Mammals of Canada. Toronto: University of Toronto Press, 1974.

Grzimek, B., ed. Grzimek's Encyclopedia of Mammals. London: McGraw-Hill, 1990.

Hall, E.R. The Mammals of North America. 2nd ed. New York: Wiley & Sons, 1981.

Nowak, R.M., ed. Walker's Mammals of the World. 5th ed. Baltimore: John Hopkins University Press, 1991.

Ryden, H. The Beaver. London: Lyons & Burford, 1992.

Wilson, D.E., and D. Reeder. Mammal Species of the World. 2nd ed. Washington, DC: Smithsonian Institution Press, 1993.

Bill Freedman


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—Refers to animals that are most active in the dim light of dawn and dusk, and sometimes at night as well.


—The unsustainable exploitation of a potentially renewable natural resource, such as hunted animals or trees. Overharvesting eventually leads to a collapse in the abundance of the resource.

Additional topics

Science EncyclopediaScience & Philosophy: Ballistic galvanometer to Big–bang theoryBeavers - The American Beaver, Beavers And The Fur Trade, The Eurasian Beaver, The Mountain Beaver