The fur has dense, soft underfur that provides warmth. Beavers range in color from yellowish brown to black, with reddish brown the most common color. Beavers have broad, flat tails. The tail is almost hairless. It is used as a prop while the beaver is sitting upright and for a rudder when swimming.
Beavers also use their tail to warn others of danger by slapping the surface of the water.
Beaver store fat in their tail for winter survival. These teeth are beveled so that they are continuously sharpened as the beaver gnaws and chews while feeding, girdling, and cutting trees. Beavers build dams to change their environment more to their liking. Besides humans, only beaver create their own habitat by building dams. Beavers use whatever materials are available to build dams.