American Beaver Castor canadensis

Large rodent covered in thick brown fur with a large paddle-shaped tail and webbed feet.

Length: Body: 2-4 ft. Tail: 8-12 in.

Weight: 30-70 lbs.

Range: much of North America outside of the Desert Southwest and the northern reaches of the Arctic

Diet: tree bark and cambium (soft tissue under tree bark)

Mating: Mate in winter, gestation period of about 100 days. Mate for life.

Life Expectancy: ~10 years

Like humans, beavers are engineers on the landscapes they inhabit. They fell aspens, willows, birches, and other trees, damming streams and rivers to create ponds. There, they build their homes, in the form of lodges or burrows. The tree bark and cambium in these building materials also serve as a primary food source, available even in winter under snow and ice.

The action of beaver colonies create habitat for other wildlife, particularly waterfowl, amphibians, mink, and otter. While none of the wetlands in the Arb have been entirely created by beavers, they have built a lodge on Turtle Pond and dammed a number of small streams. A colony of beavers appear to be living there, and possibly another colony living in a bank burrow along the Cannon River. The twigs and branches they have dragged to the burrow form a conspicuous mass along the bank. The beavers drag logs into the river beside trees that beaver teeth have obviously chiseled. A few times beavers have tried to build dams on Spring Creek, which runs through the Carleton campus! You’ll have no trouble finding their sign around, but if you want to see one, they are crepuscular, meaning that they are most active at dawn and dusk. Sometimes if you walk along the banks of a waterway, you might hear a surprising splash.