Washington is the heartland of the mountain beaver, and its 770 records show it. King County leads with 274, and nearly all the rest, Clallam, Pierce, Grays Harbor, Pacific, Kitsap, and Snohomish among them, sit in the wet lowlands and foothills west of the Cascade crest, the narrow coastal belt where this primitive rodent makes nearly its entire world range.
Neither mountain animal nor beaver
Despite the name, the mountain beaver is no beaver at all but the most primitive living rodent, a stocky, short-limbed burrower about the size of a small groundhog. It digs long tunnel systems in soft, damp soil and feeds on ferns, salal, nettles, and other understory plants, clipping stems and sometimes hauling them back to the burrow mouth. Its record runs through the Daniel J. Evans Wilderness Area, Olympic and Mount Rainier national parks, and the Olympic and Snoqualmie national forests, all country with the moist ground it requires.
Underground but never dormant
Mountain beavers do not hibernate, and Washington’s record shows animals at work in every month of the year, rising modestly through summer as new young begin foraging above ground. Most sightings come at dawn, dusk, or on dark, wet days, since the animal prefers to stay close to its tunnels.
Status in Washington
NatureServe ranks the mountain beaver S5, Secure, in Washington, and the species is native to the state. USGS NAS does not list it as nonindigenous here.
Full species profile
