Scientific Name: Castor canadensis

Description: Beavers are the largest living rodents in North America, with adults averaging 40 pounds in weight and measuring more than 3 feet in length, including the tail. These semi-aquatic mammals have webbed hind feet, large incisor teeth, and a broad, flat tail. The beaver’s incisors (front teeth) are harder on the front surface than on the back, and so the back wears faster. This creates a sharp edge that enables a beaver to easily cut through wood.

Habitat: Once among the most widely distributed mammals in North America, beavers were eliminated from much of their range in the late 1800s because of unregulated trapping. With a decline in the demand for beaver pelts, and with proper management, they became reestablished in much of their former range and are now common in many areas.

Beavers are found where their preferred foods are in good supply—along rivers, and in small streams, lakes, marshes, and even roadside ditches containing adequate year-round water flow. In areas where deep, calm water is not available, beavers that have enough building material available will create ponds by building dams across creeks or other watercourses and impounding water.

Like many rodents, beavers construct nesting dens for shelter and for protection against predators. These may be burrows in a riverbank 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 area, a dry nest den, and a source of fresh air.

Reproduction and Family Structure:

• A mated pair of beaver will live together for many years, sometimes for life.
• Beavers breed between January and March, and litters of one to eight kits (average four) are produced between April and June. The number of kits is related to the amount of food available (more food, more kits), and the female’s age.
• The female nurses the kits until they are weaned at 10 to 12 weeks of age.
• Most kits remain with the adults until they are almost two years old. (Some leave at 11 months and a few females may stay until they are three years of age.) The kits then go off on their own in search of mates and suitable spots to begin colonies, which may be several miles away.
• Beavers live in colonies that may contain 2 to 12 individuals. The colony is usually made up of the adult breeding pair, the kits of the year, and kits of the previous year or years.
• Populations are limited by habitat availability, and the density will not exceed one colony per ½ mile under the best of conditions