March 24, 2017


The American Beaver
(Castor canadensis) can be found throughout most of Maine and is the largest rodent in North America. A large adult beaver may measure 4.5 feet long, including its foot-long tail.

Compact and round,with short legs, beavers are ungainly and slow on land. In the water, however, the beaver is a strong and graceful swimmer. They have many adaptations to their aquatic habitat: their eyes are able to see well under water thanks to a specialized transparent membrane that can be drawn over the eye for protection while diving. Nostrils are small and can be closed for underwater swimming, and their ears too, can be closed under water.

The beaver’s tail is covered with leathery scales and sparse, coarse hairs. In the water, they can use this tail as a four-way rudder. Although fat, the tail is flexible and muscular. When diving after being frightened, a beaver slaps the water with its tail, making a noise like a pistol shot, which warns all beavers in the vicinity that danger is near and may serve to drive away potential predators. On land, the tail acts as a prop when the beaver is sitting or standing upright. It also serves as a counterbalance and support when the animal is walking on its hind legs while carrying building materials like mud, stones, or branches with its front paws.

The beaver’s hind feet are very large, with five long blunt-clawed toes which are fully webbed for swimming. In the water, a beaver uses only its hind feed to propel itself, with occasional aid from its tail. Its forepaws are small, without webs, and the toes end in long sharp claws suited to digging. These delicate paws are very dextrous almost like hands and with them the beaver can hold and carry sticks, stones, and mud and perform a variety of complex construction tasks.

Dams are built by beavers that need to enlarge the underwater habitat open to them in winte–the goal is to create a pond deep enough that it won’t freeze to the bottom.

Like many rodents, beavers construct nesting dens for shelter and for protection against predators. These may merely be burrows in a river bank or the more familiar lodges built in the water or on the shore. However, the basic interior design varies little and consists of one or more underwater entrances, a feeding chamber, a dry nest den, and a source of fresh air.

A beaver takes only one mate, which it keeps for life. One litter, averaging three or four kits, is born each year in May or June following a 100-day gestation period. Although kits are well-furred, have teeth already cut, and can see, walk, and swim when born, they generally don’t move out of the lodge for at least one month. The young stay with their parents until they are two and sometimes three years old.

Beavers were trapped aggressively in the nineteenth century. At the peak of the fur trade era some 200,000 pelts a year were sold to the European market, most being used to make hats. A large adult beaver skin yielded enough fur for 18 hats.

After the turn of this century, the trade in beaver declined, partly with the decline of the beaver hat as fashionable headwear, and partly because the beavers themselves were becoming scarce all over North America. Many large regions were completely without beaver during most of the first half of this century.