Beaver

beaver, either of two large aquatic rodents, Castor fiber and Castor canadensis, known for their engineering feats. They were once widespread in N and central Eurasia except E Siberia, and in North America from the arctic tree line to the S United States. The mountain beaver of W North America is not a true beaver, but a nonaquatic rodent of a different family.

The beaver is the largest living rodent except the capybara, and is distinguished by its extremely broad, horizontally flattened tail. Beavers are 3 to 4 ft (91–120 cm) long, including the tail (12 in./30.5 cm long, 6 in./15.2 cm wide), and about 15 in. (38 cm) high at the shoulder; they usually weigh about 60 lb (27 kg). Their long, dense fur is reddish brown to nearly black; the naked, scaly tail is black. Both sexes have scent glands located in a pouch in the anal region. The musky secretion, castoreum, which may function as a sexual attractant, was once believed to have medicinal properties, and the glands, or castors, were of commercial value. Beavers have been extensively trapped for their pelts, once considered the most valuable of furs, and were exterminated over a large part of their range. Because of their great importance in maintaining the natural environment, they have been reintroduced in many areas of North America and Russia and are now increasing in numbers.

Beavers build lodges up to 3 ft (91 cm) high and 5 ft (1.5 m) wide of sticks and mud; the entrances are below water level, with ramps leading to the living quarters, located on a platform above water level. They may also build burrows in banks with underwater entrances. They create deep ponds, or maintain the water level in old ones, by building dams across streams. These are made of sticks and logs, and the upper surfaces are reinforced with stones and mud. Materials are gathered by collecting wood and felling small trees by gnawing; often the beavers dig canals for floating these to the right spot. Most, if not all, of these activities are done mechanically, as a result of instinct; captive animals persist in building useless dams, and even in the wild beavers will attempt to reinforce solid, manmade dams with sticks.

Although they form monogamous families and live in colonies, there is little social contact among beavers and they work independently. A colony consists of a cluster of lodges, each occupied by a family of the parents and their last two litters. The beavers sleep by day and spend the night foraging for food and building or repairing their structures. They feed on a variety of aquatic and shore plants, surviving in winter largely on bark. Sticks for winter food are stored in the lodges and underwater. Excellent swimmers, they can stay underwater for up to fifteen minutes. When alarmed, a beaver slaps the water with its tail, making a loud noise that sends other beavers hurrying to the safety of deep water. Females give birth to two to eight young in the spring; these mature in two years. Beavers are responsible for creating many of the woodland ponds that support lush vegetation and eventually become meadows.

Classification

Beavers are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Rodentia, family Castoridae.

Bibliography

See L. Wilsson, My Beaver Colony (tr. 1968), Grey Owl, Pilgrims of the Wild (1935, repr. 1971).

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beaver

Beaver (Castor canadensis).

(credit: Karl Maslowski)

Either species of the aquatic rodent family Castoridae (genus Castor), both of which are well known for building dams. Beavers are heavyset and have short legs and large, webbed hind feet. They grow as large as 4 ft (1.3 m) long, including the 1-ft (30-cm) tail, and as heavy as 66 lb (30 kg). Beavers build their dams of sticks, stones, and mud in small rivers, streams, and lakes, often producing sizable ponds. With their powerful jaws and large teeth, they can fell medium-size trees, whose branches they use in their dams and whose tender bark and buds they eat. One or more family groups share a dome-shaped stick-and-mud lodge built in the water, with tunnel entrances below water level. American beavers (C. canadensis) range from northern Mexico to the Arctic. Their prized pelts stimulated the exploration of western North America, and by 1900 beavers were trapped to near extinction. Eurasian beavers (C. fiber) are now found in only a few locations, including the Elbe and Rhône drainages of Europe. The mountain beaver of the Pacific Northwest is unrelated.

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beaver

1. a large amphibious rodent, Castor fiber, of Europe, Asia, and North America: family Castoridae. It has soft brown fur, a broad flat hairless tail, and webbed hind feet, and constructs complex dams and houses (lodges) in rivers

2. the fur of this animal

3. mountain beaver a burrowing rodent, Aplodontia rufa, of W North America: family Aplodontidae

4. a woollen napped cloth resembling beaver fur, formerly much used for overcoats, etc

5. a greyish- or yellowish-brown

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beaver [′bē·vər]

(vertebrate zoology)

The common name for two different and unrelated species of rodents, the mountain beaver (Aplodontia rufa) and the true or common beaver (Castor canadensis).

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beaver

perpetually and eagerly active. [Western Folklore: Jobes, 192]

See : Industriousness

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Beaver

mischievous ten-year-old beset by trivial troubles. [TV: “Leave It to Beaver” in Terrace, II, 18–19]

See : Mischievousness

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Beaver

(Castor fiber), a mammal of the order of rodents. The beaver is well adapted to a semiaquatic way of life. Its body measures as much as 100 cm in length, its tail 30 cm in length, and its weight 30 kg. The tail, thickened from the top down, is up to 15 cm wide and almost hairless, but covered with large horny scutes. The toes on the hind legs are joined by a wide swimming membrane. The beaver has a valuable pelt, consisting of shiny coarse awn hairs and a very thick silky undercoat. The color ranges from light chestnut to dark brown or sometimes black (melanism).

In prehistoric times beavers were distributed throughout most of Europe, southern Siberia, and parts of Middle Asia, as well as through almost all of North America. (The American beaver is apparently a special type of C. canadensis.) As a result of rapacious trapping, only defined settlements of beavers are preserved in Europe and Asia; in North America beavers are quite numerous. Until 1917 there were only a few hundred beavers in the USSR. Because of preservation and reclamation the population of beavers in the USSR grows every year and had reached 50,000 by the 1960’s. Beavers are encountered in most of the oblasts of the European part of the USSR and in some raions of Siberia. (There the range of beavers is increasing slowly.) Beavers live along quiet forest rivers with banks overgrown by willows, pines, birch, poplars, and other trees, the sprouts and bark of which the beavers feed on most of the year. In the summer they eat grass. They are able to cut down thick trees. They live in earthen dens and in “lodges”—heaps of twigs, silt, and earth (up to 2.5 m high and 12 m at the base), with several internal chambers and underwater entrances. On small rivers they build dams and cut canals to float the branches and stumps of the trees they fell. They are monogamous and have a gestation period of 105–107 days. The young (three or four to a litter) are born half-blind and well covered. They can swim after a day or two. Beavers live up to 35 years (in captivity). They are valued for their beautiful, warm, and very durable fur. In the USA there is severely limited hunting of the animals. In the USSR beaver preserves have been created (the Voronezh, Byelorussian, and Kondo-Sos’vin preserves). Because of the growth of the population in the USSR, severely limited trapping of beavers for their pelts was begun in places in the 1960’s.

REFERENCES

Ognev, S. I. Zveri SSSR i prilezhashchikh stran, vol. 5. Moscow, 1947.
Kolosov, A. M., and N. P. Lavrov. Obogashchenie promyslovoi fauny SSSR. Moscow, 1968.

V. G. GEPTNER