American Beaver Facts

Scientific Name: Castor canadensis

American Beaver - Castor canadensis

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.

Fast Facts: Beavers

  • Scientific Name: Castor canadensis
  • Common Name(s): Beaver, North American Beaver, American Beaver
  • Basic Animal Group: Mammal
  • Size: About 29–35 inches long
  • Weight: 24–57 pounds
  • Lifespan: Up to 24 years
  • Diet: Herbivore
  • Habitat: Wetland areas of North America outside of the California and Nevada deserts and parts of Utah and Arizona.
  • Population: 6–12 million
  • Conservation Status: Least Concern

Description

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 worn 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, American Beaver, Castor canadensis, adult entering water
Stan Tekiela Author / Naturalist / Wildlife Photographer/Getty Images

Habitat and Distribution

American Beavers live in the riparian zone—along the edges of wetlands and bodies of fresh water including rivers, creeks, lakes, and ponds and, in some cases, in and around brackish estuaries.

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.

Diet

Beavers are herbivores. They feed on bark, leaves, twigs and other plant material which is plentiful in their native habitat.

Behavior

Beavers are well-known for their unusual behaviors: They use their strong teeth to fell small trees and branches which they use to build dams and lodges which have a significant impact on the path and health of waterways.

Beaver dams are structures built with logs, branches, and mud. They are used to block up flowing streams to flood grasslands and forests, thus turning them into beaver-friendly habitats. In addition to providing habitat for a wide range of animals, beaver dams also reduce waterway erosion.

Beavers build lodges, dome-shaped shelters made of woven sticks, branches, and grass that are plastered together with mud. Lodges can be burrows built into pond banks or mounds built in the middle of a pond. They can be up to 6.5 feet tall and 40 feet wide. These elaborate structures include an insulated, wood-lined lodge chamber and a ventilating shaft called a "chimney." The entrance to a beaver lodge is located below the surface of the water. Lodges are generally built during the warmer months, during which time beavers also gather food for the winter. While they do not migrate or hibernate, they do slow down during the winter months.

Reproduction and Offspring

Beavers live in family units called colonies. A beaver colony commonly includes as many as eight individuals including a monogamous breeding pair, newborn kits, and yearlings (kits from the prior season). Members of the colony establish and defend a home territory.

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

Beaver family on the lake shore
Zoran Kolundzija/Getty Images

Conservation Status

Beavers are considered to be of Least Concern, meaning that there is a large, thriving population of beavers in North America. This has not always been the case; in fact, beavers were overhunted for many years and beaver fur was the basis of many large fortunes. More recently, however, protections were put in place which allowed beavers to re-establish their population.

Beavers and Humans

Beavers are a protected species, but their behaviors can make them a nuisance in some settings. Beaver dams can cause flooding to roads and fields, or block the flow of waterways and the fish that swim in them. On the other hand, beaver dams are also important for controlling erosion and runoff during storms.

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