Beaver, the largest European aquatic representative of the mammalian order RODENTIA, easily recognized by its large trowel-like, scaly tail, which is expanded in the horizontal direction. The word is descended from the Aryan name of the animal, cf. Sanskrit babhru's, brown, the great ichneumon, Lat. fiber, Ger. Biber, Swed. bäver, Russ. bobr'; the root bhru has given “brown,” and, through Romanic, “ bronze” and “ burnish.” The true beaver (Castor fiber) is a native of Europe and northern Asia, but it is represented in North America by a closely-allied species (C. canadensis), chiefly distinguished by the form of the nasal bones of the skull.

Beavers are nearly allied to the squirrels (Sciuridae), agreeing in certain structural peculiarities of the lower jaw and skull. In the Sciuridae the two main bones (tibia and fibula) of the lower half of the leg are quite separate, the tail is round and hairy, and the habits are arboreal and terrestrial. In the beavers or Castoridae these bones are in close contact at their lower ends, the tail is depressed, expanded and scaly, and the habits are aquatic.

Beavers have webbed hind-feet, and the claw of the second hind-toe double. In length beavers—- European and American—- measure about 2 ft. exclusive of the tail, which is about 10 inches long. They are covered with a fur to which they owe their chief commercial value; this consists of two kinds of hair—the one close-set, silky and of a greyish colour, the other much coarser and longer, and of a reddish brown.

Beavers are essentially aquatic in their habits, never travelling by land unless driven by necessity. Formerly common in England, the European beaver has not only been exterminated there, but likewise in most of the countries of the continent, although a few remain on the Elbe, the Rhone and in parts of Scandinavia. The American species is also greatly diminished in numbers from incessant pursuit for the sake of its valuable fur.

Beavers are sociable animals, living in streams, where, so as to render the water of sufficient depth, they build dams of mud and of the stems and boughs of trees felled by their powerful incisor teeth. In the neighbourhood they make their “lodges,” which are roomy chambers, with the entrance beneath the water. The mud is plastered down by the fore-feet, and not, as often supposed, by the tail, which is employed solely as a rudder.

They are mainly nocturnal, and subsist chiefly on bark and twigs or the roots of water plants.

Article courtesy of the Encyclopedia Britannia 1911
Image courtesy of the US Fish and Wildlife Service