American Beaver

Scientific name: Castor canadensis

American Beaver - Castor canadensis
American Beaver - Castor canadensis. Photo © Wendy Shattil and Bob Rozinski / Getty Images.

The American beaver (Castor canadensis) is one of two living species of beavers—the other species of beaver is the Eurasian beaver. The American beaver is the world's second largest rodent, only the capybara of South America is larger.

American beavers are stocky animals that have a compact body and short legs. They are aquatic rodents and have a number of adaptations that make them adept swimmers including webbed feet and a broad, flat tail that is covered with scales. They also have an extra set of eyelids which are transparent and close over their eyes enabling beavers to see while underwater.

Beavers have a pair of glands located at the base of their tail called castor glands. These glands secrete an oil that has a distinct musk odor, making it great for use in marking territory. Beavers also use the castor oil to protect and waterproof their fur.

Beavers have very large teeth in proportion to their skull. Their teeth and are super-sturdy thanks to a coating of tough enamel. This enamel is orange to chestnut brown in color. Beavers' teeth grow continuously throughout their lives. As beavers chew through tree trunks and bark, their teeth get warn down, so the continuous growth of their teeth ensures they always have a sharp set of teeth available to them. To further assist them in their chewing endeavors, beavers have strong jaw muscles and significant biting strength.

Beaver build lodges, which are dome-shaped shelters made of woven sticks, branches, and grass that are plastered together with mud. The entrance to a beaver lodge is located below the surface of the water. Lodges can be burrows built into pond banks or mounds built in the middle of a pond.

Beavers live in family units called colonies. A beaver colony commonly includes as many as 8 individuals. Members of the colony establish and defend a home territorial.

Beavers are herbivores. They feed on bark, leaves, twigs and other plant material.

American beavers inhabit a range that extends throughout most of North America. The species is only absent from the northernmost regions of Canada and Alaska as well as the deserts of the southwestern United States and Mexico.

Beavers reproduce sexually. They reach sexual maturity at about 3 years of age. Beavers breed in January or February and their gestation period is 107 days. Typically, 3 or 4 beaver kits are born in the same litter. Young beavers are weaned at about 2 months of age.

Size and Weight

About 29-35 inches long and 24-57 pounds


American beavers are classified within the following taxonomic hierarchy:

Animals > Chordates > Vertebrates > Tetrapods > Amniotes > Mammals > Rodents > American beaver


Rodents first appear in the fossil record about 65 million years ago, around the time when the non-avian dinosaurs became extinct. The ancestors of today's beavers and their relatives appear in the fossil record near the end of the Eocene. Ancient beavers include creatures such as Castoroides.