Weighing an average of 40 pounds, Beavers are the largest rodents in North America. They are built to live in water with their thick fur, webbed feet, paddle-shaped tails, and ears and nostrils that close when they dive under water. Beavers also have strong, constantly growing incisor teeth that allow them to gnaw through wood. They are herbivores and prefer to eat leaves, bark, twigs, roots and aquatic plants. Although occasionally active during the day, Beavers are mostly nocturnal.
Beavers are well-known for their engineering abilities. They build dams with brush and tree trunks on a foundation of mud and stones to flood an area for their lodge, to stay safe from predators and promote growth of their favorite foods. Dams are constructed higher than the water level. Successive generations of Beavers may repair and enlarge dams made by their parents and grandparents. Beavers do not build dams if they are living in a body of water that has a constant water level, such as a lake or pond.
Lodges, built in the water that is contained by the dam, have a single chamber inside that is above water level and one or more entrances that are accessed under water. Beavers do not hibernate, but they may become less active during the winter, spending most of their time in the lodge.
Beavers live in small, compatible colonies generally made up of a mated, monogamous adult pair and their young up to 2 years old. They have a short breeding season in late winter. From April to June litters of 2 to 4 kits are born already furred and with open eyes. The young attain sexual maturity at about 2 years, at which point their parents usually force them to leave the colony.
Once one of the most widely distributed North American mammals, Beavers have suffered a sharp decline in their numbers. Unregulated trapping for Beaver pelts has decimated populations. Landowners have also killed Beavers who build dams that flood agricultural or other private lands.
On balance, Beavers do far more good than harm, creating scarce and valuable wetlands and habitat for a number of plants and animals. The population decline in Beavers has damaged both the species and the environment.
Homeowners and farmers can modify their property to prevent or discourage Beavers from dam building that damages trees or causes flooding.
It may be possible to keep out Beavers by enclosing a parcel of land in a metal fence. When metal fencing is not practical, an electric fence may work. Suspend a single wire at about 1 foot off the ground. Beavers receive a mild shock when they touch the wire, but they are not injured and will learn to avoid the area.
Be sure to consult your local zoning or electrical inspection office and search any neighborhood covenants to determine whether electric fences are permitted in your area. You also need to know what kind of electric fencing is allowed.
You can protect your trees from Beavers by wrapping the trunks in metal flashing, wire mesh, hardware cloth, or tree wrap. These materials are usually available at garden stores. Wrap the tree trunks at least 3 to 4 feet above ground, or at least 2 feet above the high water mark if the trees stand on land that occasionally floods.
Another option is to make tree trunks unpalatable to Beavers. Make a repellent by mixing 1 tablespoon of hot pepper sauce in 1 gallon of water, then paint or spray the mix on the tree trunks. You will need to reapply it regularly, especially after a heavy rain and in 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 use a flow device to keep the water level rise to a minimum.
You can find plans on how to do this in the Beaver fact sheet on the Washington Department of Fish and Wildlife website in the section called "Preventing Conflicts."
Above: An orphaned American Beaver kit at PAWS Wildlife Center