A study on the range use of sika deer was conducted in the Nemuroshibetsu district of eastern Hokkaido, Japan, from September, 1978 through November, 1979. The range varied according to the change in the amount of available plant food and the snow depth. During the snowless season the deer depended mainly on green forages, i. e., they fed on many species of forbs and grasses in the woods and on a river bank in summer, and on pasture herbages in fall. With the increase in snow depth in winter the feeding habits were changed to foraging the leaves of sasa bamboos (Sasa senanensis) or to browsing along with concentrating themselves in the wintering area of a river bank. The change in the food habits and the range use of the deer occurred parallel to the formation of“feeding groups”in the open pastures in fall and of“yard groups”in the wintering area in winter. It was assumed that the size and availability of the wintering area might be an important factor controlling the density of the deer in an area.