The North American beaver is one of two extant beaver species. It is native to North America and introduced to Patagonia in South America and some European Countries. In the United States and Canada, the species is often referred to simply as “beaver”, though this causes some confusion because another distantly related rodent, Aplodontia rufa, is often called the “mountain beaver”. Other vernacular names, includingAmerican beaver and Canadian beaver, distinguish this species from the other extant beaver species, Castor fiber, which is native to Eurasia. The North American beaver is the national animal of Canada.
Beavers are famously busy, and they turn their talents to reengineering the landscape as few other animals can. When sites are available, beavers burrow in the banks of rivers and lakes. But they also transform less suitable habitats by building dams. Felling and gnawing trees with their strong teeth and powerful jaws, they create massive log, branch, and mud structures to block streams and turn fields and forests into the large ponds that beavers love.
Most of the beaver’s diet is made up of tree bark and cambium, the soft tissue that grows under the bark of a tree. They especially like the bark of willow, maple, birch, aspen, cottonwood, beech, poplar, and alder trees. Beavers also eat other vegetation like roots and buds and other water plants. The beaver has a specialized digestive system that helps it digest tree bark.
Although North American beavers are superficially similar to the European beaver (Castor fiber), there are several important differences between the two species. North American beavers tend to be slightly smaller, with smaller, more rounded heads; shorter, wider muzzles; thicker, longer and darker underfur; wider, more oval-shaped tails and longer shin bones, allowing them a greater range of bipedal locomotion than the European species. North American beavers have shorter nasal bones than their European cousins, with the widest point being at the middle of the snout for the former, and in the tip for the latter. The nasal opening for the North American species is square, unlike that of the European race which is triangular. The foramen magnum is triangular in the North American beaver, and rounded in the European.
The beaver was trapped out and almost extirpated in North America because its fur and castoreum were highly sought after. The beaver furs were used to make clothing and beaver hats. In the United States extensive trapping began in the early 17th century with more than 10,000 beaver per year taken for the fur trade in Connecticut and Massachusetts between 1620 and 1630. From 1630 to 1640, approximately 80,000 beaver were taken annually from the Hudson River and western New York. From 1670 onwards, the Hudson’s Bay Company sent two or three trading ships into the bay every year to take furs to England from Canada. Archaeological and historical evidence suggests that beaver ponds created “moth-hole like” habitats in the deciduous forest that dominated eastern North America. This non-forest habitat attracted both Native American and early colonial hunters to the abundant fish, waterfowl and large game attracted to the riparian clearings created by the aquatic mammal. The first colonial farmers were also attracted to the fertile flat bottomlands created by the accumulated silt and organic matter in beaver ponds.