American Beaver (Castor canadensis)


American beaver
Castor canadensis

Found near creeks, rivers, ponds and lakes, beavers are found wherever there is water in North America and in parts of Eurasia. With the exclusion of Florida and the desert region in the southwest, beavers are found everywhere in North America from pristine forests to many urban settings, so long as there is water present.

The largest rodent in North American, the average adult beaver weighs between 30-60 pounds (14-27 kg). Covered in fur that is dark brown to almost black with lighter belly, the beaver is distinguished by its trademark flattened tail and large, webbed feet, which help him swim. The beaver differs from other rodents with its large size and webbed feet. The river otter is a close cousin, but has long, slender toes and a pointed heel.

The beaver’s incisors (front teeth) are harder on the front surface than on the back, and so the back wears faster. This creates a sharp edge that enables a beaver to easily cut through wood.

According to the IUCN this species is considered LEAST CONCERN (lowest threat level).
According to the IUCN this species is considered LEAST CONCERN (lowest threat level).

up to 3 feet (91 cm)

up to 40 pounds (18 kg)

5-10 years

According to the IUCN the threat level for this species is LEAST CONCERN.

Beavers are found where their preferred foods are in good supply—along rivers, and in small streams, lakes, marshes, and even roadside ditches containing adequate year-round water flow. In areas where deep, calm water is not available, beavers that have enough building material available will create ponds by building dams across creeks or other watercourses and impounding water. Beavers dams create habitat for many other animals and plants of Washington. In winter, deer and elk frequent beaver ponds to forage on shrubby plants that grow where beavers cut down trees for food or use to make their dams and lodges. Weasels, raccoons, and herons hunt frogs and other prey along the marshy edges of beaver ponds. Migratory waterbirds use beaver ponds as nesting areas and resting stops during migration. Ducks and geese often nest on top of beaver lodges since they offer warmth and protection, especially when lodges are formed in the middle of a pond. The trees that die as a result of rising water levels attract insects, which in turn feed woodpeckers, whose holes later provide homes for other wildlife.

Beavers eat the leaves, inner bark, and twigs of aspen (a favorite food), alder, birch, cottonwood, willow, and other deciduous trees. Beavers also eat shrubs, ferns, aquatic plants, grasses, and crops, including corn and beans. Coniferous trees, such as fir and pine, are eaten occasionally; more often, beavers will girdle and kill these trees to encourage the growth of preferred food plants, or use them as dam building material. Beavers have large, sharp, upper and lower incisors, which are used to cut trees and peel bark while eating. The incisors grow their entire lives, but are worn down by grinding them together, tree cutting, and feeding. (Fig.1) Fermentation by special intestinal microorganisms allows beavers to digest 30 percent of the cellulose they ingest. When the surface of the water is frozen, beavers eat bark and stems from a food “cache” (a safe storage place) they have anchored to the bottom of the waterway for winter use. They also swim out under the ice and retrieve the thick roots and stems of aquatic plants, such as pond lilies and cattails. Food caches are not found consistently where winters are comparatively mild.

f-american-beaver-scat-4leggers-comSIGNS OF PRESENCE:
Cut-off trees, gnawed to a cone near the base are the easiest indicator of beavers being present. Debarked trees are another clear indicator. Dams and conical lodges built of twigs and sticks are the best proof of a beaver’s presence.




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U.S. Fish and Wildlife Dept.

National Park Service

International Union for the Conservation of Nature and Natural Resources

Paul Tarwell, “Camping & Wilderness Survival Second Edition” (Lebanon, New Hampshire: Paul Tarwell, 2006).

Washington Dept. of Fish & Wildlife

World Worldlife Federation