Food niche overlap and ecological separation amongst six species of coexisting forest shrews (Insectivora : Soricidae) in the Russian Far East

The feeding habits and foraging modes of six species of shrew (Insectivora, Soricidae) coexisting in the forests of the Russian Far East were investig ated in order to quantify levels of niche overlap and elucidate the role of body size in ecological separation. Overlap in numbers of shared prey taxa was high and Lithobiomorpha, one of the most abundant macro-invertebrates in field samples, was a major prey item of all species. The composition of different prey taxa in the diet of Sorer unguiculatus and the abundance of these taxa in field samples were positively correlated. Major differences i n dietary composition and foraging mode reflected body size of shrews. Whil e the niches of individual species were not exclusive, small species fed on ly on arthropods, were epigeal, and had relatively narrow niche breadths. L arge species fed extensively on lumbricids and other soil-dwelling inverteb rates, and were hypogeal. There were significant negative correlations betw een niche overlap in terms of prey composition, prey size and prey location , and increasing body-length ratios in pair-wise comparisons. Combined nich e overlap was reduced with increasing divergence of body size. Adjacent spe cies-pairs in the size series had a mean combined niche overlap of 88% comp ared with non-adjacent pairs of 67%. The most significant areas of ecologic al separation between species as a function of body size were in the dietar y occurrence of small versus large prey and in the foraging mode (epigeal v ersus hypogeal). These findings confirm that body size has an important rol e in effecting ecological separation in multi-species communities where a h igh degree of morphological and ecological similarity occurs between member s.