“The beavers are now living in these lakes, and fresh signs are abundant. There are numerous tracks in the snow leading from the lakes to the thickets of alder, elder, and willow which they are eating. There is no typical beaver house in the lakes, but the under-water entrance to their house can be seen leading under the roots of a fir tree about four feet in diameter that stands on the edge of the upper lake.”
It is in this immediate vicinity that fairly extensive beaver workings were observed in November, 1947, including newly repaired small dams and fresh cuttings.
The house or burrow in the stream bank studied by Mr. Toll appears typical of the beaver in this area. In other sections, notably Rocky Mountain National Park, Colorado, where beavers are abundant, an extensive system of dams and canals is frequently developed on the smaller streams, with a large house completely surrounded by the impounded water a central feature of the colony. No such elaborate workings have been found here. Since the beavers habitually reside in burrows along the margins of streams they are referred to as “bank-beavers.” A plausible explanation for this habit is the constant and ample flow of water, which eliminates the necessity for large dams, and is adequate to cover at all times the underwater entrances to the burrows.
A small stream, bordered by cottonwood, alder, and willow, tracing its course through swampy places or meadow lands at intervals, is the preferred habitat of the beaver. The bulk of its food is made up of the bark of the tree species mentioned above, although coniferous trees are sometimes used, perhaps as an appetizer. The roots of aquatic plants are eaten also, as well as the smaller roots of tree species. In an active beaver colony, freshly peeled twigs and branches will be found lodged against the upstream side of the dam, as well as along the stream and pond margins.
Much has been written concerning the sagacity, engineering ability, and industry of the beaver. Certainly “busy as a beaver” is an apt comparison for the industrious. The amount of tree-felling, food harvesting, and construction and repair which a colony of beavers will accomplish overnight is remarkable.