Photo Courtesy of North Dakota Game and Fisheries Department

Habitat:

Beavers live much of their life in water and settle along the banks of streams, rivers, and lakes (Col 1998, Grzimek 1975, Jackson 1997). They also need a riparian zone with thick underbrush to provide them with construction material for their dams, lodges, and bank dens. (Grzimek 1975, Halley 2002)) Their habitat requirements include a predictable water store that provides a depth of at least 2-3 ft. The water supplies the beaver with a hiding place from predators, a way to transport logs for food and construction, and a place to store food for the icy winters. Beavers may construct a dam if the water level needed is not present or merely to increase the size of their habitat (Shepherd 1994). They gain access to more food as the pond gets bigger. (NYSDC 2002) The marshlands created by dams supply the beaver’s surroundings with an abundance of food that is easily accessible. Some of their favorite foods (water lilies, cottonwood, willow, and alder) grow best in these soggy habitats. Beavers also prefer fertile valleys with flat terrain to steep slopes, so they can create small ponds with their dams. (Jackson 1997)

Food and Winter Preparation:

Beavers are vegetarians. In the summer, their diet consists of aquatic plants- such as pondweeds, water lilies, and cattails- and the shoots, twigs, leaves, roots, and bark of woody plants (Col 1998, Caras 1967, NYSDC 2002). In the winter, the inner bark of trees and shrubs provides an important seasonal source of food. Beavers are able to digest cellulose, unlike humans (Matz 2003), and can therefore feed on the cambium of hardwoods, which is the soft tissue underneath the bark where new wood grows (Col 1998) Their favorite terrestrial trees include Aspen, birch, alder, and willow. (Jackson 1997) A 0.5-hectare plot of land will supply a beaver colony with food for one to one and a half years. (Grzimek 1975)

In the winter, beavers do not hibernate like other rodents, but do become much less active. In areas where the water of the river or lake freezes over, beavers turn to their storage of sticks and twigs cached in the bottom of the pond for winter provisions. (Grzimek 1975) For this reason, food gathering is busiest in autumn in preparation for winter. (Cahalane 1947) Beavers hoard food underwater by anchoring logs and sticks to the riverbed (Walker 1964, Jackson 1997) Their underwater supply remains accessible to the colony because the surface layer of water is the only portion of the aquatic habitat to freeze over.

Predators:

Most of the beaver's predators live on land. (Jackson 1997) These predators include the wolf, coyote, bear, cougar, lynx, fox, and bobcat (Caras 1967, Cahalane 1947, Shepherd 1994, Matz 2003). Arial predators include the hawk, eagle, and owl (Col 1998). The young are more susceptible to predators and are preyed upon mainly by predaceous mammals such as the otter and the mink. . The adult beaver, on the other hand, is seldom susceptible to predators because they rarely travel far from the water (NYSDC 2002). Dispersal is the time when beavers are most vulnerable to predators. (Caras 1967) Man is also a predator of the beaver (Walker 1964).

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This page was completed in partial fulfillment of the requirements for Biology 323, Animal Behavior, at Davidson College in the Spring Semester 2003.