Food Habits and Interspecific Relationships in Two Red-backed Voles, Clethrionomys in Hokkaido

Abstract

For a study of coexistence system in two red-backed voles, Clethrionomys rufocanus bedfordiae (THOMAS) andC. rutilus mikado (THOMAS), seasonal changes of food habits, biomass of plants, population density and microhabitat selection were examined. Food habits of these two species were similar from May to October, when plant biomass was richest. In the season when the common available foods decreased, C. rufocanusobviously changed its staple food item to the other one, whereasC. rutilusprincipally kept its food habits unchanged. These tendencies were not influenced by population density or microhabitat selection of the two species. In conclusion, C. rufocanushas a wider food niche than doesC. rutilus, and this condition may partly explain the frequent coexistence of the two species.