Beaver, Muskrat and Nutria Identification
The American beaver is a native mammal that plays an important ecological role in our watersheds. It's also a species of management concern for some landowners. This page has information aobut how to tell the difference between beavers, muskrats and nutria.
American Beaver (Castor canadensis)
Characteristics
- Broad (horizontally flattened) and almost hairless tail
- Length is between 39 and 47 inches
- They weigh between 35 and 50 pounds or more.
- Fur color appears reddish brown to black
- Each foot has five digits
- The hind feet have webbing, but the front do not
Also Look For
Girdled or felled trees, limbs with bark removed
- Beaver prefer certain tree and shrub species including aspen, cottonwood, willow, conifers, fruit trees, and ornamentals
- Dams and lodges made from limbs and mud
- Primary dam-building time is August through October
- Slides or slicked-down paths where they enter and leave water, 15 to 20 inches wide and at right angles to the shoreline
- Channels that lead to their ponds (sometimes look human made)
Muskrat (Ondatra zibethicus)
Characteristics
- Much smaller than a beaver, but not as large as a nutria
About 16 to 25 inches long
- May reach a maximum of four pounds
- Long, rat-like tail that is flattened vertically
- Dense, grayish under fur overlaid by long, glossy guard hairs that vary in color from dark brown to yellowish brown; guard hairs are long and coarse on the back and finer on the side and the belly
Also Look For
Lodges that are smaller than beaver lodges and built from marsh vegetation, not sticks
- Food consists almost entirely of aquatic and semi aquatic vegetation including grasses, rushes, sedges, cattails, etc.
Nutria (Myocastor coypus)
Characteristics
Much smaller than the beaver; much larger than the muskrat
- May reach a maximum of 20 pounds
- Mature adults are about two feet long
- Muzzle is covered by white coarse hair
- Tail is hairy and round (not compressed from side to side) and pointed at the tip
- Hind legs are much longer than the front legs, giving them a hunched appearance when on land
- Hind feet are webbed
- Large incisors are yellow to orange-red
Also Look For
- Floating platforms up to three feet high that they make from aquatic vegetation
- Burrows in vegetated banks near waterways and collapsing banks and road beds
For More Information
- Beaver Management Plan by the City of Portland, Version 2.0, January 2020
- Oregon Department of Fish and Wildlife, Living with Beaver
http://www.dfw.state.or.us/wildlife/living_with/beaver.asp - Portland State University Report on Nutria Management
http://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=1023&context=centerforlakes_pub