Beavers live in streams and lakes of Washington under diverse climatic conditions. They are perhaps most abundant in the western Washington lowlands where there are numerous watercourses. In the Cascade Mountains they are found well up into the Canadian Life-zone, where the streams are swift and clear with stony bottoms. The highest altitudinal record known to us is Reflection Lake, Mt. Rainier, 4,861 feet (Brockman, 1939: 71). Farther east, in the timbered regions of the eastern Cascades and in northeastern Washington, beavers live in deeper, more sluggish streams. Abundant beaver signs were noted at the junction of the Snake and Columbia rivers where the animals were occupying one of the hottest, most desertlike portions of the state. They are found in Moses Lake, in the center of the arid Columbian Plateau. Beavers once occurred in the San Juan Islands and have recently been reintroduced there. [Illustration: FIG. 100. Beaver (_Castor canadensis_): lodge and beaver pond, Elbe, Washington, August 24, 1926. (T. H. Scheffer photo.)] The part the beaver played in man's exploration of the state of Washington is a story in itself. The establishment of Fort Vancouver and Fort Spokane and other settlements was principally due to the trade in beaver pelts. These forts served as headquarters for Douglas, Suckley, Townsend, Nuttall and other early naturalists who contributed so greatly to the knowledge of the mammalian fauna of the western United States. [Illustration: FIG. 101. Cottonwood pole carved by beaver, Lake Wenatchee, Washington, May 13, 1938. (Fish and Wildlife Service photo by Victor B. Scheffer, No. 33.)] Trapping for fur drastically reduced the number of beavers in Washington. After trapping was prohibited they were slow in recovering and, until about 1930, they were uncommon. After that date they seemed to increase rapidly, becoming abundant about 1940. The present system of removing beavers only from areas where they are doing damage, and then only under strict supervision from the State Department of Game, has held their numbers at a high level. The food of the beaver varies greatly with locality. Along the Columbia River, in eastern Washington, cottonwood (_Populus hastata_) and willow (_Salix_ sp.) seem to constitute favorite foods. Few other trees grow in this arid region. On Puget Island, near the mouth of the Columbia, willow, alder (_Alnus oregonus_) and probably other shrubs are eaten. In the many streams that run from the western Cascade Mountains to Puget Sound, various species of willow seem to be the principal food eaten. Some alder, cascara, Douglas fir, red huckleberry and salmonberry are eaten. In some streams on the eastern slope of the Cascades, coniferous trees, including Douglas fir, yellow pine (_Pinus ponderosa_), and red cedar (_Thuja plicata_) are used.