In this paper, the realized trophic niche overlaps and breadths were calculated a mong Microtus brandti, Ochotona daurica, Citeilus dauricus and Lepus capensis respectively,according to the diet compositions under free-ling circumstances. Fundamental trophic niche breadths and overlaps of Microtus brandti, Ochotona daurica and Citellus dauricus were also measured based on the results of food selection tirals. Owing to the restriction of food availabil ity in the habitats, the realized trophic niche breadth...