Species Spotlight: Beaver

May 25, 2010, 11:18 am

The beaver is a lumberjack, wildlife conservationist and architect and a keystone species in many environments. Weighing 40 to 60 pounds and growing three to four feet from nose to tail, beavers are the largest rodent in North America. They are easily identified by their flat, black, scaly tail, which acts like a rudder when they are swimming. Beavers are specially equipped to live in and around water—they can hold their breath for 15 minutes and have translucent eyelids that act like underwater goggles, allowing beavers to see underwater, as well as on land.

Like all rodents, beavers have continuously growing incisors, which they trim by gnawing on wood.  They are herbivores, eating twigs, leaves, tree bark and water plants. Some of their favorite trees include aspen, alder, willow, poplar, maple, birch, and cottonwood. As a snack, beavers sometimes will eat the bark off of a tree while working; rotating it like eating corn on the cob.

Beavers topple trees in order to construct dams and lodges. A good indicator that beavers are living nearby is the prevalence of gnawed tree stumps. Beaver teeth have a hard orange enamel on the front and a softer enamel on the back, which wears away faster. This creates a chisel-like point to make gnawing through tree trunks extremely efficient.  A beaver can gnaw through a five-inch diameter tree in five minutes.

Their dams may reach a height of seven feet and a length of 1,000 yards. In fact, the world’s largest known beaver dam was recently discovered in Wood Buffalo National Park in Canada. It stretches for nearly half a mile, and is visible from outer space. Researchers believe it was built by several generations of beavers.

The pond created by the beaver dam protects the beavers from predators and also provides a good habitat for a variety of other wildlife. In the long-term a beaver dam’s pond may become a meadow and even one day the meadow may become a forest.

Beavers are nocturnal animals, and are mostly active at night. Look for them near ponds and marshes around dusk and dawn.