Page:The New International Encyclopædia 1st ed. v. 02.djvu/740

BEAVER. drive stakes into the ground, has no foundation in fact; and some of the other particulars which passed current along with it were equally fabulous. They dwell normally in colonies along streams, which may have been inhabited for scores of generations, and whose improvements represent the combined labor of thousands of individuals past and present. Such a colony begins by the settlement in the spring upon some sluggish, moderately deep woodland stream or pond of a pair of young beavers, who have emigrated thither from some old colony. Their first labor is to dig a burrow in the bank, the entrance to which is at a safe depth beneath the water, and the interior chamber at a safe height above its normal rise. In this burrow they make their home the first year, or perhaps two years; and such burrows, more or less in use and serving as refuges in danger, are common always in beaver settlements. It is essential that a sufficient depth of water be maintained before the door of this burrow to give clear ingress and egress under the winter's ice, and to afford room for storage of winter provisions; and in most places chosen by the animals this can be arranged only by damming the stream. As the droughts and low water of summer begin, therefore, the beavers seek a place in the stream a little below their residence, where it is narrow, not more than 2½ feet deep, and has a firm bottom, and begin a dam. Gnawing down saplings 10 or 12 feet long, they drag and float them to the spot, and sink them lengthwise, side by side, across the current, beginning at the centre of the channel and loading them with stones, sods, and mud, to keep them in place. They will handle remarkably large stones for this purpose. The work is gradually extended until it reaches the bank on each side, and in doing so a convex outline upstream is usually given; but this probably is an accident of the increasing pressure of the obstructed current on the progressing wings of the new dam rather than an engineering design, for reverse (or weak) curves are frequently seen. Such a dam grows constantly by the addition of all sorts of material—not only the logs and sticks from which the bark has been gnawed for food, but others cut for the purpose, and a constant intermixture of roots and branches with stones, moss, grasses, and mud.

Additions, as well as constant repairs, are made on the upper side, which comes to present a low slope and comparative solidity, while the lower front of the dam is a more abrupt tangle of sticks and branches. The beavers work at the dam only at night, except in an emergency, and each one does what it thinks proper in a quite independent way, though the result is for common benefit. After many years such dams may be 4 or 5 feet high at the channel, and stretch to the right and left across low ground for 50 yards or more, converting the space above it into a broad, grassy pond, having a network of clear channels. Morgan describes dams 600 feet long in northern Wisconsin, with many acres of flooded ground. The water does not flow over the tops of these dams, but percolates through them, though some of them become seemingly solid barriers of earth. “In places,” says Hearne, “which have been long frequented by beavers undisturbed, their dams, by frequent repairing, become a solid bank, capable of resisting a great force, both of water and ice; and as the willow,

poplar, and birch generally take root and shoot up, they by degrees form a kind of regular planted hedge, which I have seen in some places so tall that birds have built their nests among the branches.” A large proportion of the marshy ponds and peat-bogs of the country have had this origin.

Meanwhile, from the first summer onward, the gradually increasing number of beaver families have built each for itself permanent homes, known from their resemblance to the Algonkian wigwam as ‘lodges.’ The sites chosen are along the banks of the stream or canal, and several houses may be so close together as to touch, or they may be widely scattered. The larger lodges are, in the interior, about 7 feet in diameter, and between 2 and 3 feet high, with the floor and inner walls made smooth by gnawing and wear. The entrances are always two, both leading down into the water, and in northerly regions there is no opening into the air—a needful precaution against the cold of mid-winter, as well as against such insidious foes as weasels and blacksnakes. This structure, like the dam, is formed of branches of trees, matted with mud, grass, moss, and other material. The walls are very thick, and the entire structure not only secures much warmth, but is an efficient protection from wolves, wolverines, and other beasts of prey, especially when solidly frozen in winter. Each family builds, maintains, and occupies its own lodge, the current belief that several families live together arising from the fact that the young beavers usually continue to live with their parents until the third year. Single ‘bachelors’ dwelling remote and alone are occasionally seen.

Food and Winter Provision.—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 the beavers 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 the stream 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 burrow, 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 beaver colony, and perhaps the most important service of the dam and its pond is to provide against this contingency. 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 intelligently supplemented by the animals, who dig deep canals, 2 or 3 feet wide, which penetrate