A study of the food habits, range use, and home range of pronghorn antelope (Antilocapra americana) with emphasis on the winter period was conducted in 1966-67 in Montana. Quantitative measurements of canopies and densities of taxa were made in five of the eight vegetation types available to antelope. The sagebrush-grassland type received most of the use by antelope, both in summer and winter. Most winter observations were in vegetation types where sagebrush was common. The winter diet, determined by plant utilization, consisted of 93 percent shrubs, 6 percent forbs, and a minor amount of grass. The diet, determined by analysis of rumen contents, consisted of 78 percent shrubs, 19 percent forbs, and a small amount of grass. Big sagebrush (Artemisia tridentata) provided 45 percent of the antelope food in winter. Results of five summer aerial censuses showed 32 male antelope per 100 females and 74 fawns per 100 females. Poor body condition of antelope and some fawn mortality in winter was possibly related to quality of sagebrush in the diet. Winter home-range size was determined for each of 16 individually marked antelope, three using telemetry. Eight of the marked antelope "shifted" their home range at least once. A yearling female had a home-range size of 5,574 acres and a yearling male, 4,160 acres. Six adult females had an average home-range size of 2,841 acres; three fawn females, 2,417 acres; and five fawn males, 1,580 acres.
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