FOOD NICHE OVERLAP AND ECOLOGICAL SEPARATION IN A MULTISPECIES COMMUNITY OF SHREWS IN THE SIBERIAN TAIGA

An investigation of the feeding habits and prey availability in a comm unity of seven species of shrew (Insectivora: Soricidae) inhabiting th e taiga of Central Siberia was carried out with the aim of quantifying levels of niche overlap and elucidating modes of ecological separatio n amongst these coexisting species. All species took a wide range of i nvertebrate prey, and overlap in the numbers of shared prey taxa was h igh, but differences in dietary composition of certain taxa reduced ov erlap between most species. Small species fed almost exclusively on sm all arthropods, mostly Araneae, Chilopoda and Coleoptera, while medium and large-sized species took high proportions of oligochaetes. Prey w ere mostly taken in proportions approximately equal to their availabil ity, although certain prey appeared to be selected. All shrews took pr ey in a range of sizes, and the high dietary occurrence of small inver tebrates reflected their availability and high encounter rate in field samples. Dietary occurrence of small prey was negatively correlated, and large prey positively correlated, with body size of shrew. Smaller shrews were predominantly ground-surface foragers while larger specie s were more subterranean, with body size and dietary occurrence of soi l prey being positively correlated. Differences in prey size and forag ing mode reduced niche overlap between shrew species of widely differi ng sizes. Each shrew species did not occupy a separate, well-defined f ood niche. Instead, the community was sub-divided into three functiona l groups: large and small species which tended towards specialization with relatively low levels of overlap, and intermediate, generalist sp ecies with higher levels of overlap.