Habitat
Inhabits lakes, ponds, marshes, rivers, streams, and most permanent source of water from sea level to 3400 m in mountains. Prefer low gradient streams, ponds, and small mud-bottomed lakes with dimmable outlets (Slough and Sadleir 1977, Beier and Barrett 1987, Novak 1987a, McComb et al. 1990). Beavers readily occupy artificial ponds, reservoirs, and canals if food is available. They generally avoid lakes with strong wave action or fluctuating flow or water levels and fast- moving streams. One study found that 68 percent of the American beaver colonies recorded in Colorado were in valleys with a stream gradient of less than 6 percent. No beaver colonies were recorded in streams with a gradient of 15 percent or more. Valleys that were only as wide as the stream channel were unsuitable beaver habitat, while valleys wider than the stream channel were frequently occupied by beavers (Munther 1981). In larger rivers (9th order or larger streams), beavers use floodplains and backwaters. In the north, they require water that is deep enough such that it does not freeze to the bottom and allows the accumulation of a substantial food pile beneath the ice. Beavers are associated with deciduous tree and shrub communities (NatureServe 2007b), including riparian areas of mixed coniferous- deciduous forests and deciduous forests containing abundant foods and lodge building material such as quaking aspen (Populus tremuloides), willows (Salix spp.), alders (Alnus spp.), red-osier dogwood (Cornus sericea), and cottonwoods (Populus spp., Patric and Webb 1953, Allen 1983). Marshes, ponds, and lakes are often occupied by American beavers when an adequate supply of food is available. Beavers generally forage no more than about 300 feet (90 m) from water; however, foraging distances of up to 656 feet (200 m) have been reported (Allen 1983).
References
Allen, A. W. 1983. Habitat suitability index models: beaver. FWS/OBS-82/10.30 (Revised). Washington, DC: USDI, USFWS. 20 p.
Beier, P., and R. H. Barrett. 1987. Beaver habitat use and impact in Truckee River basin, California. Journal of Wildlife Management 51:794-799.
McComb, W. C., J. R. Sedell, and T. D. Buchholz. 1990. Dam-site selection by beavers in an eastern Oregon basin. Great Basin Naturalist 50:273-281.
Munther, G. L. 1981. Beaver management in grazed riparian ecosystems. In: J. M. Peek and P. D. Dalke, eds. Wildlife-livestock relationships symposium: Proceedings 10; [Date of conference unknown]; Coeur D`Alene, ID. Moscow, ID: University of Idaho, Forest, Wildlife and Range Experiment Station: 234-241.
NatureServe. 2007b. NatureServe Explorer: An online encyclopedia of life [web application]. Version 6.2. NatureServe, Arlington, Virginia. Available http://www.natureserve.org/explorer.
Novak, M. 1987a. Beaver. Pages 283-313 in M. Novak, et al. editors. Wild furbearer management and conservation in North America. Ontario Ministry of Natural Resources.
Patric, E.. F. and W. L. Webb. 1953. A preliminary report on intensive beaver management. North American Wildlife Conference. 18(33): 533-539.
Slough, B. G., and R. M. F. S. Sadleir. 1977. A land capability classification system for beaver (Castor canadensis). Canadian Journal of Zoology 55:1324-1335.
