The pocket gophers in Washington are economically important. In truck and flower gardens they are a pest, especially if the crop be bulb plants. In grain fields they are a pest because their mounds cover considerable grain and are apt to clog or dull the knife of the mower. In fields of young alfalfa they are apt to crop back the plant more rapidly than it can grow. Once the alfalfa plant is well established, however, the cultivation resulting from activities of gophers, some persons believe, stimulates the plant to such an extent that it grows larger and healthier in spite of the gopher's feeding on it. In the White Salmon Valley, Klickitat County, I examined numerous alfalfa fields. The most luxuriant growth was invariably in fields where gophers were common. In these fields, the largest plants were those in the immediate vicinity of gopher activity. The commensal relation between the gopher and alfalfa was understood by many farmers, who forbade us to take gophers for specimens from their fields. Several told us that they always trapped the gophers from the fields of young alfalfa and from hay meadows but encouraged their presence in fields of older alfalfa. [Illustration: FIG. 97. Food cache of northern pocket gopher (_Thomomys talpoides tacomensis_), from chamber four inches below surface of ground, Tacoma, Washington, December 1, 1940. Contents 575 grams (about 2 liters) of roots, principally quackgrass, _Agropyron repens_. (Fish and Wildlife Service photo by Victor B. Scheffer, No. 1119.)] Another economic factor is the gopher's removal of certain weeds from grazing land. A number of introduced weeds form dense rosettes that prevent the growth of grass from several square inches of ground and themselves lie so close to the ground as to be unavailable as food to grazing stock. These weeds seem to be favored food of gophers which cut not only the rosettes but the roots of the weeds as well. In irrigated parts of eastern Washington the gopher is a serious pest. It burrows in the banks of the main ditches, causing cave-ins and occasional breaks with resultant water loss. The mounds of gophers fill in the smaller channels and divert the streams. Constant attention is necessary to keep the ditches free of gopher mounds. In uncultivated land the gopher is a distinct asset unless the land is near enough to cultivated land to serve as a reservoir of pests. In the mountains and on the desert the gopher cultivates and keeps the soil soft and stimulates the growth of water-retaining vegetation, thus preventing rapid run-off and erosion and keeping the flow of springs and streams constant. Boulders, logs, and other obstructions are undermined and, as a result of gopher activity, in time sink under the surface of the ground. Thus a larger surface is available for plant growth. Lastly the gopher furnishes an important food source for certain fur-bearing mammals and eases the predator pressure on game species.