Mountain beaver

Mountain beaver, or sewellel (Aplodontia rufa), nocturnal, burrowing rodent of western North America. Perhaps the oldest rodent species on earth still in existence, the mountain beaver has lived in North America at least 60 million years. Unrelated to the beaver, it looks like a vole, with a stout body about 1 ft (30 cm) long, short legs, and very short tail. Colonies of mountain beavers live in burrow systems dug in stream banks.