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Amazing Facts About Beaver The Large Aquatic Rodent

Beaver, The Amazing Animals

Beaver is a large aquatic rodent of the Northern Hemisphere. Beavers are characterized by their adaptation to an aquatic life and by their commercially valuable fur. The American beaver (Castor canadensis) and the Eurasian beaver (C. fiber) are the sole living representatives of the family Castoridae, in the order Rodentia, class Mammalia.

Physical Characteristics and Habitat

Beavers have large, fully webbed hind feet, which are used for swimming. The animals are also known for their broad, scaly tail. The beaver's coat, which is usually brownish, has exceedingly close, fine hairs. When freed from the long hairs that are scattered through it and that overlie the undercoat, the fur is considered to be among the most valuable, commercially.

Large beavers have a head-and-body length of about 2.5 feet (76 cm), a tail length of about 1.5 feet (46 cm), and a weight of 60 to 70 pounds (27 to 31 kg). Usually found along a sluggish woodland stream or a small lake, the species tend to inhabit low, level ground.

Fossil beavers from far back into the Tertiary period have been recovered, with small-sized species bearing some distinctive peculiarities appearing in rocks of the Oligocene epoch, in the western United States. A huge beaver (Trogonotherium) lived in Eurasia during the Pliocene and Pleistocene epochs, and an even larger form (Castoroides) existed in North America during the Pleistocene.

Behavior and Diet

Beavers dwell in colonies, which under favorable circumstances may persist for centuries, and exist primarily on a diet of bark from hardwood trees, such as maple, linden, birch, and poplar. The species never eat the bark of coniferous trees and so do not inhabit forests composed entirely of conifers.

Although beavers sometimes live in burrows dug into the bank of a pond or stream, frequently they erect a conical house or lodge for themselves. The interior of the house is a chamber 6 or 7 feet (1.8 to 2.1 meters) wide and 2 feet (0.6 meters) high, with the entire lodge having a basal diameter of as much as 40 feet (12 meters).

The structure has no opening to the outside air but is instead entered from beneath the water by two channels, one being the usual entrance and the other providing a means of escape in case of attack by a mink or other aquatic predator. The beaver's home is solidly constructed, becoming so strong when frozen in winter that nothing less than a bear can break into it. The houses are largest and strongest in cold northern regions.

In order to maintain a water level that will hide the entrance to their home, beavers also build a dam, which stretches across the stream at a place below their settlement. The stream bottom must be firm at the chosen spot, and the water can be no more than 2.5 feet deep. Beginning in the center of the channel, beavers place a number of long sticks parallel to the current and hold them down with a pile of mud and stones. Extensions are then built to each shore.

The poles used in building the dam are cut with the beavers' very large and strong front teeth, which are faced with a hard, yellow enamel. The back part of these teeth is made of a softer material, which wears away with use, ultimately leaving the tooth with a sharp, chisellike edge. Consequently, beavers can fell trees with a diameter of as much as 42 inches (107 cm).

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Young beavers that have matured and left their family's home construct a new dwelling close to their old one. As a result, a considerable colony can arise within just a few years. All through this period work progresses on the dam, with each beaver gathering driftwood, branches, logs, stones, mud, pieces of sod, and any other available materials, which are worked into the dam's structure.

Ultimately the dam becomes a tangled heap with a long slope, a comparatively tight surface on the upper side, and many channels running through it, being strong enough in some cases to hold back a large pond. Beaver dams have proven valuable to humans by holding back spring floods and by helping to maintain a steady supply of water to localities below the dam during dry summers.

During the summer beavers go ashore to feed on the roots and stems of aquatic plants and to gather bark for food. The bark, some of which is stored for winter, is obtained by felling large trees near the water's edge and cutting them up into pieces that can be carried to a spot close to the beavers' home.

When beavers exhaust the supply of nearby trees, they excavate canals that gradually are extended farther and farther into the woods, so that they can float materials from a new supply of trees back to the colony. In some of the swampy forests of the upper Mississippi Valley, these canals have been known to extend several hundred feet, being the product of beaver colonies that have existed for more than 200 years. Channels are kept free from weeds, with the dam serving to maintain a proper water level in the canals.

It appears that the architectural work of the American beaver is often more complex than that of European beavers. There are few records of structures as elaborate as those described above having been made in central Europe, and the beavers now inhabiting the streams of Germany and France make few attempts to construct either dams or houses, usually living instead in bank burrows. Beavers survive well in confinement, and colonies exist in the zoological gardens of several large cities.


The beaver, especially the female, is generally monogamous. Mating occurs in January and February, and the litter, normally comprising two to four young, is born in April or May. The offspring remain with the family until maturity is reached in two or three years. Beavers in captivity have been known to live as long as 50 years.

Environmental Status

Originally beavers were widespread throughout Europe and northern Asia; they became extinct in the British Isles in the 12th century. In continental Europe they remain in only a few of the wilder streams of Norway, Poland, and Russia and in some of the tributaries of the Rhône and Elbe rivers, where the animals are officially protected. In some instances colonies made up of formerly captive beavers have reestablished themselves under protection. The beaver still exists in Siberia and Mongolia.

When Europeans first entered North America, the beaver inhabited almost all of the continent's woodland streams, from the Arctic Circle down to northern Mexico. However, because it was extensively hunted for its valuable fur and pushed from its habitats by encroaching human populations, the animal vanished from much of its range.

Beavers now are rarely found south of the rivers that flow into Hudson Bay, except in the Rocky Mountains, the Sierra Nevada, and the Coast Ranges and in a few remote and scattered places, such as the forests of Maine and the Lake Superior region, where beavers are more or less protected by law.

A few also survive in the wilder ranges of the southern Appalachian Mountains and along the borders of Mexico. In some places, chiefly in the northeastern United States, the beaver has been reintroduced for its value in water conservation.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

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