The Eager Beaver

By Georgia Busch, JRA Intern

The North American Beaver (Castor canadensis) is probably best known for its tree-trimming and pond flooding abilities. But these large, “destructive” rodents have a long history in fresh water ecosystems just like the James River.

It is well-known that beavers instinctually gnaw on trees to cut them down in order to create dams. Beavers follow the sound of rushing water up small streams and even large rivers to find a specific spot to start dam construction. Using their enormous front incisor teeth, beavers will carve into the base of a tree until it falls. These trees, combined with twigs and mud, create a stable, concrete-like consistency to keep the beaver dam in place. Once a beaver dam is erected, up-stream flooding will occur, making a beaver pond. These ponds provide sheltered habitat for the beavers where they continue constructing lodges and borrows. Beavers are very smart when building their lodges and most make a two-level platform; one for sleeping and one for drying their fur. It’s a lot of work to make a beaver home!

     Once a dam, pond and lodge are constructed, beavers will sometimes vacate the area, but most stay to maintain their homes. Beaver dams are not permanent and would most likely collapse without upkeep. These dams have a secondary purpose to control water levels, ensuring the ponds are deep enough to prevent them from fully freezing in the winter. Beavers will also temporarily breach the dam to lower the water level to create more breathing room beneath the ice if the pond does freeze.

     In these beaver communities, males and females gather to reproduce. Beaver pairs are monogamous, mating together for many seasons. Baby beavers, or kits, are born two to six at a time after approximately 128 days of gestation. They grow up inside the lodge, venturing out into their protected ponds with their mother. Kits learn to use their webbed hind feet as flippers to propel them through the water. They also learn how to recognize danger from their mother’s signal. She will slap her flat, leathery tail against the surface of the water, warning the kits to dive below.  

    Some people would say that beavers’ natural activities are a destructive nuisance. However, studies have shown that beaver dams and ponds provide many benefits to freshwater ecosystems. Large beaver ponds provide stop-over habitat for migrating water fowl and nursery habitat for freshwater fish. Beavers also enhance riparian habitat by cutting smaller trees, providing room in the forest understory for shrubs and diversifying the composition. Indirectly, they also create wetlands habitat from flood water collection. Beaver ponds even increase stream flow during dry seasons by seeping stored rain water. All of these effects categorize beavers as a keystone species because their activities bring diversity to the area. The next time you are paddling, boating, biking or hiking near the James, keep an eye out for some eager beavers working to enhance the ecosystem.