Habitat occurrence and prey distribution of a multi-species community of shrews in the Siberian taiga

The habitat occurrence and invertebrate prey distribution of nine species of shrew in the mid-taiga of central Siberia were investigated. Species richness ranged from 4-9 shrews per habitat. Sorer araneus and S. caecutiens were numerically dominant in all seven habitats (44 and 36% of the total catch, respectively) while So, ex minutus, S. tundrensis, S. isodon, and S. roboratus each constituted 4-6% and Sorex minutissimus, S. daphaenodon, and Neomys fodiens were rare (< 1% each). There was no overall correlation between abundance of shrews and invertebrate prey, but hood-plain habitats supported the greatest abundance and species richness of shrews, and high density and biomass of prey. Oligochaete-eating shrews were twice as numerous here as in other habitats, coincident with high abundance of oligochaetes. The large, earthworm-feeding Sorer roboratus occurred only here. The more acid, typical taiga habitats had lower adundance and species richness of shrews. They had the lowest density and biomass of prey, particularly oligochaetes, and far fewer oligochaete-eating shrews. The relative paucity of shrews in bush-meadow habitats, despite abundant prey, implied that habitat structure influences shrew distribution. Differential numbers of certain species in the presence or absence of larger congeners also suggested that interspecific competitive effects influence habitat selection by shrews. The high species richness of shrews here in the mid-taiga may be accounted for by the heterogeneous nature of the constituent habitats which provide niches for small and large species of shrew with a range of feeding habits.