beaver Castor canadensis, a member of the family Castoridae. These animals have stout bodies about 1 m (40") in length with a tail of about 30 cm (12") characteristically broad and flat which serves variously as a rudder, propeller, and signal gun when the animal is in the water. Mature animals reach weights up to 30 kg (over 60 lb).
Beavers live in ‘colonies’, each ‘colony’ consisting of a family unit of up to 12. They are well known for their building of elaborate dams and ‘houses’ or lodges. The dams cause an overflow of river banks, forming a beaver-pond in which they construct their lodge.