Feeding ecology and niche separation in some native and domestic ungulates on the shortgrass prairie

(1) Using the results of diet selection studies and two wild and two domestic species, we compare some aspects of ecology in relation to body size, the recent evolutionary history of the species and current forage conditions. (2) Food niche breadth and mter-species diet overlap seemed dependent upon recent evolutionary history as well as upon body size, but values were strongly influenced by forage quantity and quality. (3) Dietary selectivity appears especially sensitive to seasonal changes in forage quality, e.g. large as well as small animals pursued relatively selective strategies when forage conditions permitted, but body size and related nutritional-energetic demands appeared to set the limits where switches from selective to non-selective tactics took place. (4) Sensitivity to diet composition and quality increased with decreasing size except in the domestic sheep. It is likely that anatomical-physiological adaptations, including a relatively large rumeno-reticulum allow domestic sheep to utilize more forage plant species and mhabit a wider variety of niches and ecosystems than most ungulates. Human selection has made the sheep food and habitat generalists despite their relatively small size.