DIET OF CALIFORNIA BIGHORN SHEEP, OVIS-CANADENSIS-CALIFORNIANA, IN BRITISH-COLUMBIA - ASSESSING OPTIMAL FORAGING HABITAT

Monthly, seasonal, and annual food habits of California Bighorn Sheep (Ovis canadensis californiana) were related to forage quality, plant f requency, and foliar cover from May 1977 to April 1979, on a study sit e 10 km south of Penticton. British Columbia. During the two years, 14 grasses and sedges, 47 forbs and bryophytes, and 18 browse species av eraged 66.6, 19.0, and 14.6% of the diet, respectively. Each forage gr oup was selected by the sheep in proportions similar to average freque ncy on the site: grasses - 68.2%; forbs - 16.4%; browse - 15.2%. Blueb unch Wheatgrass (Agropyron spicatum) comprised the most common diet co mponent (20.5%), followed by Prairie Junegrass (Koeleria cristata) (13 .9%), Needle-and-thread (Stipa comata) (10.6%), Rough Fescue (Festuca scabrella) (8.0%), Cheatgrass (Bromus tectorum) (4.6%), and Arrowleaf Balsamroot (Balsamorhiza sagittata) (4.0%). Based on selection indices , most forage species were ingested randomly by the bighorn sheep. Hig h (> 2.5) selection indices for Rough Fescue, Prairie Junegrass, Needl e-and-thread, Kentucky Bluegrass (Poa pratensis), Thompson's Paintbrus h (Castilleja thompsonii), Silky Lupine (Lupinus sericeus), Pasture Sa ge (Artemisia frigida), Snow Buckwheat (Eriogonum niveum), and Wyeth B uckwheat (E. heracleoides) were associated with a combination of pheno logical patterns, plant morphology, environmental site characteristics . and grazing preferences. Bluebunch Wheatgrass was generally selected in proportions less than available on the study site. Bighorn sheep d iet correlated only poorly with crude protein, acid detergent fibre, c alcium, and phosphorus. Diet frequency correlated most consistently wi th plant cover, suggesting that California Bighorn Sheep selected fora ges based primarily on plant availability.