BEAVER

Beaver is a furry animal with a wide, flat tail that looks like a paddle. Beavers are known for their skill at cutting down trees with their strong front teeth. They eat the bark and use the branches to build dams and lodges (homes) in the water. Beavers almost always seem to be busy working. For this reason, we often call a hard-working person an "eager beaver" or say that the person is "busy as a beaver."

Beavers live in rivers, streams, and freshwater lakes near woodlands. They are excellent swimmers and divers. A beaver can swim underwater for 1/2 mile (0.8 kilometer), and can hold its breath for 15 minutes.

There are more beavers in the United States and Canada than anywhere else in the world. Beavers are also found in Asia and Europe. In the 1980's, trappers in the United States and Canada captured about a million beavers a year. Beaver fur is soft and shiny, and it wears well. Clothing manufacturers use it to make fur coats and to trim the collars and cuffs of cloth coats. Beaver fur is also squeezed together with other kinds of fur to make a cloth called felt.

Beavers were probably the most hunted animals in North America from the late 1500's through the 1800's. The pioneers and Indians ate beaver meat, and traded the furs for things they needed. In the late 1600's, a person could trade 12 beaver skins for a rifle. One beaver skin would buy four pounds of shot, or a kettle, or a pound of tobacco. Trading companies shipped beaver fur throughout the world to be made into coats or hats. Hunters killed so many beavers that hardly any were left in North America by the late 1800's. The U.S. and Canadian governments passed laws to protect the animals. Today, beavers, like many other wild animals, can be trapped only at certain times of the year.

The body of a beaver

North American beavers are 3 to 4 feet (91 to 120 centimeters) long, including the tail, and weigh from 40 to 95 pounds (18 to 43 kilograms). They are the largest rodents (gnawing animals) in the world except for the capybara of South America. Unlike most other kinds of mammals, beavers keep growing throughout their lives. Most beavers look larger than they really are because of their humped backs and thick fur. Thousands of years ago, some beavers of North America were about 7 1/2 feet (2.3 meters) long, including the tail--almost as long as the grizzly bears. No one knows why these huge beavers disappeared.

Head. The beaver has a broad head, with large and powerful jaws. Its rounded ears and small nostrils can close tightly to keep water out. A beaver has three eyelids on each eye. Two outer eyelids, one upper and one lower, fit around the eye. A transparent inner eyelid slides down over the eye and lets the animal see under water. On land, it protects the eye from sharp twigs when the animal cuts trees. The beaver cannot see well, and depends on its keen hearing and smell to warn it of danger.

Teeth. A beaver has 20 teeth--4 strong, curved front teeth for gnawing, and 16 back teeth for chewing. The front teeth, called incisors, have a bright orange outer covering that is very hard. The back part of the incisors is made of a much softer substance. When a beaver gnaws, the back part of its incisors wears down much faster than the front part. As a result, these teeth have a sharp, chisel-like edge. The incisors never wear out because they keep growing throughout the animal's life. The back teeth have flat, rough edges and stop growing when the beaver is about 2 years old.

There are large gaps between the beaver's incisors and its back teeth. Flaps of skin, one on each side of the mouth, fold inward and meet behind the incisors. These skin flaps seal off the back of the mouth. They let the animal gnaw wood on land or in the water without getting splinters or water in its mouth. The flaps open when the beaver wants to eat or drink.

Tail of a beaver is one of the animal's most interesting features. The stiff, flat tail looks like a paddle. It is about 12 inches (30 centimeters) long, 6 to 7 inches (15 to 18 centimeters) wide, and 3/4 inch (19 millimeters) thick. A small part of the tail nearest the beaver's body has the same kind of fur as the body. The rest is covered with black, scaly skin and has only a few stiff hairs. The beaver uses its tail to steer when it swims. The tail is used as a prop when the animal stands on its hind legs to eat or to cut down trees. A beaver slaps its tail on the water to make a loud noise to warn other beavers of danger.

Fur. Beaver fur varies from shiny dark brown to yellowish brown. It looks black when wet. A beaver's coat consists of two kinds of fur: (1) short, soft underfur; and (2) long, heavy guard hairs. The guard hairs lie over the underfur and protect it. The underfur helps keep a beaver comfortable in the water. This fur traps air and holds it close to the animal's skin. The trapped air acts as a protective blanket that keeps the beaver warm, even in icy water.

The life of a beaver

Beavers usually live in family groups. As many as 12 beavers may make up a family, but generally there are 6 or fewer. The group includes the adult male and female, the young born the year before, and the newborn.

Beavers live as long as 12 years. Their enemies include bears, lynxes, otters, wolverines, wolves, and people. A beaver avoids these enemies by living in the water and by coming out mostly at night to eat or work.

The young. A female beaver carries her young inside her body for about three months before they are born. She has two to four babies at a time. Most young beavers, called kits or pups, are born in April or May. A newborn kit is about 15 inches (38 centimeters) long, including its tail, and weighs 1/2 to 1 1/2 pounds (0.2 to 0.68 kilogram). The tail is about 3 1/2 inches (8.9 centimeters) long. A kit has soft, fluffy fur at birth, and its eyes are open.

The young live with their parents for about two years, and then are driven from the family group. These young adults are forced out to make room for the newborn. Beavers rarely fight with each other except in spring, when the 2-year-olds are driven away.

Food. Beavers eat the inner bark, twigs, leaves, and roots of trees and shrubs. Poplar trees, especially aspens and cottonwoods, and willow trees are among their favorites. One acre (0.4 hectare) of poplars can support a family of six beavers for one to two years. Beavers also eat water plants, and especially like the roots and tender sprouts of water lilies.

Beavers store food for winter use. They anchor branches and logs in a cache under the water near their lodges. In winter, they swim under the ice and eat the bark.

Cutting down trees. A beaver uses its strong front teeth to cut down trees and to peel off the bark and the branches. To cut a tree, the beaver stands on its hind legs and uses its tail as a prop. It places its front paws on the tree trunk, and turns its head sideways. Then the beaver bites the trunk to make a cut in it. The animal makes another cut farther down on the trunk. The distance between the two cuts depends upon the size of the tree. The cuts are farther apart on large trees than on small ones. The beaver takes several bites at the cuts to make them deeper. Then the animal pulls off the piece of wood between the cuts with its teeth. It keeps cutting and tearing out pieces of wood until the tree falls. Beavers usually cut the wood away around a tree trunk, but they may cut through the trunk from only one side.

Building dams and canals. The beaver's habits of building and of storing food seem to be instinctive (unlearned). A beaver cuts down trees even if it has no place to build a dam or a lodge, and even if it has more than enough food.

A whole beaver family, and sometimes beavers from other families, may join in building a dam. Beaver dams are made of logs, branches, and rocks plastered together with mud. Beavers use mud and stones for the base of a dam. Then they add brush and log poles. They strengthen the dam by placing the poles so that the tips lean in the same direction as the water flows. The beavers plaster the tops and sides of the poles with more mud, stones, and wet plants. They do most of this work with their front teeth and front paws. They bring mud from the river bottom by holding it against their chests with their front paws.

The beavers build their dam so that the top is above the water. Some dams are more than 1,000 feet (300 meters) long. Beavers may keep their dams in good condition for many years. Most beavers that live in lakes do not build dams, but some build dams across the outlets of small lakes.

A beaver marks its territory with castors, small piles of mud mixed with the beaver's scent. The castor glands of beavers are used in making perfume.

Building lodges. A beaver lodge looks somewhat like a tepee. A family of beavers builds its lodge with the same materials and in much the same way as it builds a dam. The lodge may stand on the riverbank or in the water like an island. The tops of most lodges are 3 to 6 feet (91 to 180 centimeters) above the water. Each lodge has several underwater entrances and tunnels, all of which lead to an inside chamber. The floor of the chamber is 4 to 6 inches (10 to 15 centimeters) above the water. Here, young beavers can stay warm and dry in winter, and the adults can dry off after bringing in food. Holes between the branches in the ceiling let in fresh air.

The size of the lodge depends on the size of the family and the length of time the beavers have lived there. The animals enlarge and repair the lodge as long as they live in it. Most beavers abandon their lodge only if they have eaten all the food in the area, or if too many enemies move nearby.

Beavers that live in large lakes or in swift rivers may dig dens in the banks. These beaver dens, like the lodges, have underwater entrances and tunnels.

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