Ecological Distribution of Six Species of Shrews and Comparison of Sampling Methods in the Central Rocky Mountains

Abstract

The ecological distribution of six species of shrews was studied using sunken cans in 14 montane and intermontane habitats in southern Wyoming. The vagrant shrew ( Sorex vagrans ) and masked shrew ( Sorex cinereus ) were cosmopolitan in distribution. Sorex cinereus was slightly more abundant in moist plant communities, whereas Sorex vagrans predominated in slightly drier communities. Merriam's shrew ( Sorex merriami ) occurred only in arid portions of the plains and foothills, and in short-grass prairie was the only shrew taken. The water shrew ( Sorex palustris ) occurred only along or near cold mountain streams and ponds. The dwarf shrew ( Sorex nanus ) and pigmy shrew ( Microsorex hoxji ) occupied restricted mountain habitats. The dwarf shrew was abundant in rocky locations in both alpine and subalpine plant communities; the pigmy shrew was taken only in peat-moss bogs in the spruce-fir zone. A comparison of snap traps and sunken cans as methods of collecting shrews revealed that snap traps failed to demonstrate the presence of Sorex nanus and Microsorex hoyi in areas where they were abundant. Also, densities of Sorex vagrans and Sorex cinereus indicated by snap traps were considerably below those indicated by sunken cans.