Monthly Archives: February 2016

Busy beavers help themselves and their ecosystems

By Tracie Hornung

Beaver

American Beaver (Castor canadensis), Oregon’s official state animal. Courtesy ODFW

If you’ve ever seen a beaver in the wild, you’re one of the lucky ones.

These mammals, North America’s largest rodent, are most active in the evening or at night. Beavers may weigh up to 65 pounds and average about four feet long. Their habitat consists of ponds, marshes and streams, and their bodies have evolved to fit perfectly within that environment. Thanks to webbed hind feet, a broad paddle-like tail, and membranes that cover the eyes when the animal is underwater, beavers are supreme swimmers. (But that evolutionary design makes them rather clumsy on land.) They can remain underwater for at least 15 minutes by slowing their heart rate. And their large teeth — their upper incisors can grow up to an inch long — contribute greatly to their well-known logging abilities.

Beaver tree

Results of beaver activity.
Tracie Hornung photo

But it is their thick luxurious fur, ranging from reddish brown to black, that defined their destiny after European settlers invaded North America. In fact, Oregon’s early economy was built on beaver pelts. During the 1800s, when European and U.S. East Coast demand for beaver hats and coats was at its peak, fur trappers nearly eliminated the species through unregulated trapping.

With proper management, however, beavers have become re-established and are now common throughout their range. But habitat destruction has become their most recent threat, and the improvement of wetlands and riparian areas is necessary for beavers, as well as a myriad of other species — which are helped by beavers’ aquatic activities.

Beavers build dams to create deep water that protects them from predators, helps them access their food supply and provides underwater entrances to their dens. And the ponds that beavers create expand wetlands and enhance habitat for many other fish and wildlife species, such as juvenile coho salmon.

Beaver Dam

Beaver dam
Courtesy USFWS

It’s no wonder the phrase “busy as a beaver” exists because beavers are industrious and skilled loggers and carpenters. They can fell a tree up to five-and-a-half feet in diameter. They cut down trees to construct their dens, dams, and for food. They enjoy eating the leaves, inner bark, and twigs of aspen (a favorite food), alder, birch, cottonwood, willow and other deciduous trees.

The dens they build (also known as lodges) are waterproofed with mud, and serve as a place to rest, stay warm, give birth and raise young — an average of four kits per litter. Beavers live in colonies that may contain up to 12 individuals. The colony is usually made up of the adult breeding pair and their offspring. Most kits remain with the adults until they are almost two years old. The kits then go off on their own in search of mates and suitable spots to begin colonies, which may be several miles away.

If you’re interested in learning how to help beavers and create sustainable habitat for them, read “Living with Wildlife: American Beaver” at the Oregon Dept. of Fish and Wildlife web site: http://www.dfw.state.or.us/wildlife/living_with/docs/beaver.pdf


Sadly, beavers’ logging and dam-building that sometimes results in flooding or in damaging property inspire humans to remove them. In Oregon, landowners are allowed to trap beavers. However, the Oregon Dept. of Fish and Wildlife states on its web site, “Removing beavers is often a short-term solution as other beavers will move into the area if suitable habitat is present.”

To learn about recent research at Boston University related to this issue, see “Why Monogamous Beavers Would Be Good News.”