Short-Term Effects of Shrew Predation Upon Invertebrate Prey Sets in Prairie Ecosystem

During August of 1971, the effects of different densities of shrews (Sorex cinereus) upon the density and species composition of invertebrate prey sets on two prairies in northwestern Iowa were studied. Invertebrates were sampled using pitfall traps set on areas containing known shrew densities. In general, different levels of shrew predation produced certain differences in the prey sets. Increased shrew density was associated with the following prey set characteristics: 1) decreased numerical densities, but not the total biomass of prey sets; 2) decreased species dominance of prey sets; and 3) increased species diversity of the largest prey size subsets of the total prey set. These observed effects of shrew predation are short-term effects which are typical of keystone predators