The North American beaver is one of two extant beaver species.
It is native to North America and introduced in South America and Europe.
North American beavers live in rivers, ponds, streams, and small lakes.
They usually live between 10 and 20 years in the wild, but may live up to 30 years in captivity.
This beaver is the largest rodent in North America and competes with its Eurasian counterpart, the European beaver, for being the second-largest in the world, both following the South American capybara. The European species is slightly larger on average but the American has a larger known maximum size.
The head-and-body length of North American beavers is from 74 to 90 cm (29–35 in), with the tail adding a further 20 to 35 cm (7.9–13.8 in) and they usually weigh from 11 to 32 kg (24 to 71 lb), with 20 kg (44 lb) being typical.
The beaver’s fur consists of long, coarse outer hairs and short, fine inner hairs. The fur has a range of colors, but usually is dark brown.
The North American beaver is semiaquatic and has many traits suited to this lifestyle. It has a large, flat, paddle-shaped tail and large, webbed hind feet.
They swim at a speed of 3.2 km/h (2 mph), but if they are getting chased they can go up to 9.6 km/h (6 mph).
Beavers are best known for building lodges of sticks and mud. Lodges are an oven-shaped houses of sticks, grass, and moss, woven together and plastered with mud. They may be surrounded by water, or touching land, including burrows dug into river banks.
They are also well known for building dams. The purpose of dams is to create deepwater refugia enabling the beaver to escape from predators. When deep water is already present in lakes, rivers, or larger streams, the beaver may dwell in a bank burrow and bank lodge with an underwater entrance. The beaver dam is constructed using branches from trees the beavers cut down, as well as rocks, grass, and mud.
North American Beavers are active mainly at night. They are excellent swimmers and may remain submerged up to 15 minutes. More vulnerable on land, they tend to remain in the water as much as possible. They use their flat, scaly tail both to signal danger by slapping the surface of the water and as a location for fat storage.