Comparative Nutritional Ecology of Montane Ungulates during Winter

Abstract

Comparisons of botanical and nutritional characteristics of winter diets of elk (Cervus elaphus nelsoni), mule deer (Odocoileus hemionus hemionus) and mountain sheep (Ovis canadensis canadensis) revealed sharp divergence in food niches. Deer diets contained the most browse and lignin, were intermediate in crude protein, and contained the least in vitro digestible dry matter (IVDDM). Mountain sheep diets were dominated by forbs and were consistently highest in protein and IVDDM. Cell solubles were higher and nonlignified cell wall lower in mule deer and mountain sheep diets compared with the elk diets. Elk diets contained the most grass, were intermediate in IVDDM, and were lowest in crude protein. Protein and cell soluble content of diets were correlated with diet selectivity. These species ate less grass and more dicots when the crude protein and cell soluble content of grasses declined. The findings are discussed in the context of current theory on trophic ecology of wild ungulates. Mule deer seem to fit some aspects of this theory poorly; recent findings on their digestive physiology may explain this inconsistency.