MASKED SHREW (SOREX CINEREUS) ABUNDANCE, DIET AND PREY SELECTION IN AN IRRIGATED FOREST

Moisture has been proposed as the primary factor affecting local abund ance of shrews. We studied invertebrate availability and masked shrew (Sorer cinereus) diet in wastewater-irrigated and nonirrigated forests in central Pennsylvania to better understand the relationships among moisture, invertebrate abundance and shrew diet. Earthworms, gastropod s, isopods, millipedes, larval beetles and larval flies were more abun dant in irrigated than nonirrigated plots during both spring and autum n, indicating greater availability of certain foods. Larval beetles an d larval flies composed a greater portion of the masked shrew diet in irrigated plots during autumn (P < 0.05). Spiders, which were less abu ndant in irrigated than in nonirrigated plots during spring and autumn , made up a smaller portion of the masked shrew diet in irrigated plot s during autumn (P < 0.01). Masked shrews rarely ate millipedes and is opods, although these invertebrates were very abundant in irrigated pl ots. Shrews did not feed on invertebrates in proportion to their abund ance (P < 0.05), but selected some taxa (e.g., insect larvae) and avoi ded others (e.g., millipedes). Our study suggests that increased popul ations of invertebrates in moist forests, especially those selected by shrews, affected the diet of shrews and may be a mechanism for the in creased abundance of shrews in moist environments.