Beavers

Once one of the most widely distributed mammals in North America, Beavers (Castor canadensis) 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.

Beavers actually do far more good than harm. They are commonly known as environmental engineers because of their ability to manipulate the environment to fit their needs, in turn creating valuable wetlands and habitat for a number of plants and animals. These wetland habitats help to alleviate both droughts and regional floods and have been rated as the land’s most beneficial ecosystem by ecologists.

The population decline in Beavers has damaged both the species and the environment. It is estimated that the North American Beaver population today is only 10 percent of what existed before the European settlement. However, with proper management they have become reestablished in much of their former range and are now common in many areas.

Did you know? The Beaver is the national animal of Canada.

 

Description

Weighing an average of 40 pounds and measuring more than 3 feet long, Beavers are the largest rodent in North America. They are built to live in water with their thick fur, webbed feet, and paddle-shaped tails. Beavers also have strong, constantly growing incisor teeth that allow them to gnaw through wood.

Did you know? A Beaver’s ears and nostrils close when they dive under water.

Ecology

Habitat

Beavers are found where their food supply is plentiful; along rivers and in small streams, lakes, marshes and even roadside ditches where there is year round water flow. In areas where there is not an adequate amount of calm, deep water, Beavers build dams to create ponds. They use brush and tree trunks to build their dams on a foundation of mud and stones. This not only keeps them safe from predators but also promotes growth of their favorite foods.

Successive generations of Beavers may repair and enlarge dams made by their parents and grandparents. Beavers can sense almost immediately when the water level drops and will busily work to repair any breaches in their dam, making it stronger each time.

Lodges

Lodges are built in the water that is contained by their dam. They 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.

Did you know? The largest Beaver dam in existence is located in Wood Buffalo National Park in Alberta, Canada. It stretches for 2,800 feet and is visible from space.

 

Development and Family Structure

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 two to four 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.

 

Foraging

Beavers are herbivores and prefer to eat leaves, bark, twigs, roots and aquatic plants.

 

Behavior

Although occasionally active during the day, Beavers are mostly nocturnal. Beavers communicate with each other using vocalizations and tail slapping. Vocalizations are used to beg for food and initiate grooming and play. The tail slap, when a Beaver forcibly strikes the water with his heavy tail, is the best-known Beaver sound. It may function to issue a warning signal to family members, drive away predators and elicit a response from the source of the disturbance.

• Beavers also use scent marking as a way of communication. They have castor glands that produce a strong-smelling, urine-based brown paste called castoreum. They dispense their scent on mounds of mud and debris to mark their territory.

Did you know? Beavers are prolific builders during the night, hence the saying “busy as a Beaver.”

 

Living with Beavers

Homeowners and farmers can modify their property to prevent or discourage Beavers from dam building that damages trees or causes flooding.

Fencing

It may be possible to keep Beavers out by enclosing a parcel of land inside 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.

Protecting Trees

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 heavy rains and in spring and summer when Beavers are most active.

Modify the Water Flow

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.”

 

References

Beavers: Wetlands & Wildlife. December 9, 2015. Beavers & Wetlands

Burke Museum. December 9, 2015. Mammals of Washington: Beavers

Feldhamer G.A., Thompson B.C. & Chapman J.A. (Eds). (2003). Wild Mammals of North America, Biology, Management, and Conservation (2nd ed.). Baltimore MD: The Johns Hopkins University Press.

Washington Department of Fish and Wildlife. December 8, 2015. Living with Wildlife: Beavers