Averaging forty pounds in weight, beavers are the largest rodents in North America.

With their thick fur, webbed feet, and paddle-shaped tail, they are well suited to living in aquatic environments. Beavers also have specially adapted eyes, ears, and nostrils that close when they dive under water, and strong, constantly growing incisors that enable them to gnaw through wood.

Beavers are well known for their engineering abilities. Dams, built with brush and tree trunks on a foundation of mud and stones, are constructed higher than the level of the water and may be repaired and enlarged over time by generations of beavers. Lodges, built in the water that is contained by the dam, have a single chamber inside and one or more entrances form below. Beavers do not hibernate during the winter, but may be less active, spending most of their time in the lodge.

Beavers live in small, compatible colonies generally made up of a mated, monogamous pair of adults and their young of up to two years. There is a short breeding season in late winter, and litters of two to four babies are born furred and with eyes open from April to June. The young attain sexual maturity at about two years at which point they are usually forced by their parents to leave the colony.

Once among the most widely distributed species of mammal in North America, beaver populations were threatened by unregulated trapping for their pelts. They have also been killed for building dams and flooding private or agricultural lands. On balance, beavers do far more help than harm, creating scarce and valuable wetlands.

To prevent potential damage to trees or the possibility of flooding, homeowners and farmers can modify habitat to exclude or discourage beaver activity.

It may be possible to exclude beavers by enclosing a parcel of land with a metal fence. When fencing is not practical, an electric fence may deter beavers. Suspend a single wire at about 1 foot off the ground. Beavers receive a mild shock when they touch the wire, but are not injured and will learn to avoid the area. Be sure to consult your local zoning or electrical inspection office as well as any neighborhood covenants to determine whether electric fences are permitted in your area, as well as the characteristics of allowable electric fencing.

Trees can be protected from beavers by wrapping trunks in metal flashing, wire mesh, hardware cloth, or tree wrap which is available at garden stores. Trunks should be wrapped at least 3-4 feet above ground, or at least 2 feet above the high water mark if the trees stand on land that is occasionally flooded.

Another option is to make the tree trunk aversive to beavers. A repellent can be made by mixing 1 tablespoon of hot pepper sauce in one gallon of water. This can be painted or sprayed on tree trunks, and must be reapplied regularly, especially after a heavy rain and during the spring and summer when beavers are most active.

It is pointless to destroy beaver dams because beavers begin rebuilding immediately. But it is possible to modify a dam so that water can flow through a pipe, or culvert, placed through the dam. Such a culvert can be made of plastic or metal pipe measuring 8-12 inches in diameter. It must be 10-40 feet in length. must extend beyond the dam, and should be placed at the intended depth of the water. The side facing the dam must be baffled to prevent beavers from damming the pipe. This can be done by placing a wire guard over the pipe, or by fitting the pipe with a 90 degree elbow joint that extends downward 1 foot or more below the water's surface.

Return to Wildlife Fact Sheets.