Beaver (Castor canadensis)

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Beaver (Castoridae: Castor canadensis)

No other mammal, except man, has such a great influence on its environment as the Beaver. The Beaver's system of dams and canals alters the landscape, turning streams into ponds, marshes, and wetlands. The Beaver is found throughout North America wherever there are streams, from the Northern Boreal Forest southward to northern Florida and northern Mexico.

Characteristic Features: The Beaver is a very large, bulky rodent 25 to 30 inches in length from the head to the base of the tail and weighing between 30 and 60 pounds. The tail is naked, flat, and shaped like a paddle. The fur is brown. The front teeth are huge and chisel-shaped.

Similar Species: There are other aquatic rodents. The River Otter is elongate and slender and the tail is slender and covered with fur. The Muskrat and the Nutria are smaller than the Beaver. The tail of the Muskrat is elongate slightly flattened in the opposite direction to that of the Beaver. The tail of the Nutria is round and covered with fur.

Habitat: The Beaver is found along streams, ponds, and lakes surrounded by trees or alders. Although the Beaver is potentially found just about everywhere, it is most common in wooded regions such as the Northern Boreal Forest. The Beaver was exterminated from much of its range by fur trappers, but is now being re-established in most of its former range, either deliberately or by the natural spread of the species.

Food: The majority of the diet of the Beaver consists of the bark and twigs of a variety of trees. Favorite food trees consist of aspen, poplar, birch, willow, and alder. Beavers cannot climb so they chop the trees down with their large, strong incisors and peal the bark from the trees. The felled trees and shrubs are also used in the construction of their dams and lodges.

Behavior: Beavers are famous for the construction of dams. Dams are constructed of a network of tree trunks and branchs and caulked with mud (see picture on the left). The dams form ponds along streams providing a living space for the Beavers and also favoring tree species the Beavers relish as food such as willows and alders. With time the ponds fill with sediment and produce meadows in the middle of the forest. Beavers also construct conical lodges of tree branches and mud (bottom picture on the left). Beavers live in the lodges during both the summer and the winter. Beavers will also constuct a network of canals to assist in moving felled trees to the pond. A dam and lodge is home to a group of Beavers consisting of the parents, one-year olds and the new born kits. Beavers are long-range dispersers and have been known to move as much as 150 miles from their birth place before setting up their own dam and lodge.

Reproduction: Young are known as kits and are born between April and July depending on location. There are usually between 2 and 4 kits in a litter. Young stay with the family for a year before moving off and overlap the birth of the next year's generation.

Notes: A couple of years ago someone started chopping down the cherry trees around the tidal basin near the Jefferson Memorial in Washington, D.C. This vandalism was considered by most to be equal to spitting on the Liberty Bell so the various police organizations of Washington such as the D.C. Police Department, The Park Police, the Capitol Police, the FBI, and maybe even the CIA, conducted an intensive stakeout of the Tidal Basin. The vandals turned out to be a male and female Beaver pair. The couple was captured, tried, and convicted of vandalism of government property and sentenced to exile at a federal wildlife refuge.