Movements and Behavior of Bighorn Sheep on Summer Ranges in Yellowstone National Park

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The ecology of bighorn sheep (Ovis canadensis) was studied in Yellowstone National Park, Wyoming, during the summers of 1966 and 1967. Ewe groups often included rams up to 2 years old, but rams older than 2 years remained in their own groups. With few exceptions, the sexes remained separated on summer ranges. Group composition was unstable, and bands often dispersed or formed again. Other than a separation of sexes, distinct groups were not found in areas of bighorn concentration. Adults generally led groups, but there were no established leaders. Bighorns were observed feeding long after sunset, and movements as far as M mile occurred after dark. Mills (1937) conducted a preliminary study of bighorn sheep in Yellowstone Park, and Davis (1938) studied the summer activities of a bighorn herd on Mount Washburn. Other workers (Greer 1931, Murie 1940, Gammill 1941) reported on summer observations of bighorns in the Park. Buechner (1960) summarized the status of bighorns in Yellowstone, but no recent studies provide information about the sheep on summer ranges in the Park. This study was possible because of the cooperation of the National Park Service and the staff of Yellowstone National Park. Funds were provided by Rachelwood Wildlife Research Preserve, the Yellowstone Library and Museum Association, the National Park Service, and the Wildlife Management Institute. D. R. Smith, Colorado State University, provided invaluable assistance in the planning and conduct of the study, and W. Barmore, National Park Service, offered suggestions during the study and reviewed the manuscript.