The North American beaver was the first natural resource of what eventually became Canada to be exploited by Europeans. Beaver pelts were so valued that they were once the unit of currency. The North American beaver population was almost wiped out by 1930, but conservation measures have since restored their numbers to relatively healthy levels. The species has been introduced into Europe, where viable populations have been established.
North American beavers have a well-developed social hierarchy in which the family is the basic unit. The adult female is the central figure in each family. The usual family group consists of adults, kits, and yearlings of the previous year. The average size of the family is about 10 or 12 individuals. Adult weight ranges between 15 and 35 kg (33 to 77 lb.), with the average about 20 kg (44 lb.). Both males and females attain about the same adult size.
Herbivorous, they eat leaves, twigs and bark of most tree species. They also stockpile branches and logs by sticking them into the mud at the bottom of their pools to use for food in winter.
The bear, wolf, coyote, fisher, wolverine, otter and lynx prey upon the North American beaver who is, nevertheless, a powerful adversary. Their lodges, made of tangled sticks and caked mud, offer protection that even black bears have difficulty breaking through.
The North American beaver is the animal which places second only to humans in the magnitude of change which they can effect on their environment. They do so through the dams they build. North American beaver dams are usually about 50 m (164 ft.) in length, 2 m (6.5 ft.) high, and about 3 m (10 ft.) through the base. Their dams help to maintain water levels in forest streams, thus providing habitat for themselves, fish and waterfowl. Beavers use the water to transport the logs they harvest and to provide a safe place to escape to when necessary.