Food and Trinter Prorision.—The food of beavers is almost wholly the bark of deciduous trees, especially poplar, birch, willow, linden, and maple; they never eat 'evergreen' bark, and are absent from forests exclusively coniferous. In the summer they gnaw at fresh bark day by day, and also eat more or less of lily-roots and other green vegetables, berries. and leaves. The impossibility of obtaining this food in winter, when the waters and woods are clogged with ice • and snow, compels them to prepare a supply. For this purpose time heavers become very active in the autumn, each family cutting down large trees and gnawing their limbs and trunks into sections small enough to be dragged to the water and floated to the neighborhood of their lodge. There this material is sunk to the bottom and firmly anchored (in a manner not comprehended), • until a sufficient supply has been acquired. The dams are also especially repaired in autumn. The freezing of puts an end to their labors, whereupon the beavers retire to their lodges and remain there, subsisting upon their store, pieces of which are daily taken into the house, or into some bank and the bark is eaten.
It will readily be seen that the supply of edible wood within a manageable distance from the water would soon be exhausted by a heaver col ony, and perhaps the most important service of the damn and its pond is to provide against this In a flat country the mere raising of the water by flooding spaces of woods answers the purpose to some extent; but this is most in telligently supplemented by the animals, who dig deep canals, 2 or 3 feet wide, which penetrate the woods in various directions, sometimes for 100 yards or more, and thus render accessible a large number of trees otherwise out of reach. These canals are kept open with great pains, while the rest of the pond becomes gradually grown up with grass, and they form avenues along which lodges and burrows are placed, and where the colony may swim freely, and float their food and building materials from the woods to their lodges and dams, of which latter, on a long-tenanted and favorable stream, several may exist. This perfection of beaver economy is by no means seen everywhere, but might commonly be observed previous to 1850 in such highly favor able regions as the swampy forests about the headwaters of the Mississippi, and it is being renewed in northern Maine, where, under the protection of law, beavers are increasing and re occupying their ancient haunts.
Economic Considerations.—Beavers are closely related to the squirrels, and, like them, 'sit up' a great deal, bolding their food up to their mouths in their fore paws, which otherwise are used very dexterously. It is needless to contra diet the many foolish stories as to the use of the tail as a vehicle for carrying mud, a trowel for applying it, and so on. The animals live well in confinement, and colonies are flourishing in zoiilogical gardens and parks in New York, Washington, and other American cities, as well as abroad, where small, watered valleys, fenced with wire, are devoted to them. In closer cap tivity they betray their constructive instincts by weaving the sticks supplied them into the bars of their cages. They have usually four young at a birth, and keep them at home for two years.
The fur of the beaver, by reason of its softness and density, is one of the most valuable yielded by any animal, and in former times was the staple of the fur trade, especially in America, when the early prosperity of Canada and New York was based upon it. (For statistics see FURS AND FUR TRADE.) It is probable that only the invention of silk-plush applied to the making of hats saved the animal from extinction long ago. Beavers were obtained mainly by wasteful methods of trapping, and they are so obtained yet. and chiefly in winter. Their noc turnal habits and extreme shyness make the shooting of them impracticable. Their flesh is esteemed by the Indians and frontiersmen.
Large glandular pouches, two in number, closely connected with the organs of reproduc tion, contain the substance called castorcum (q.v.). Its uses in the animal economy are by no means well known; they are probably anal ogous to those of musk and civet, but its peculiar pungent odor is so attractive to beavers that use is made of it as a bait for beaver-traps.
The beaver family dates from the middle of the Tertiary period, a fossil species of very large size occurring in the Upper Pliocene of Europe. Fossils of a small size and some distinctive pecu liarities are found in the Miocene of the United States.