Muskrat, large aquatic rodent (a type of vole) native to North America. The name comes from the musk secreted from two glands at the base of the tail. It is a good swimmer, with partly webbed hind feet and a long, scaly tail. Its commercially valuable fur (musquash) is glossy brown and durable. Muskrats inhabit tunnels or nests by a lake or stream. Length, including tail: to 53.5cm; weight: to 1.8kg. Family Cricetidae; species Ondatra zibethicus.