PREY SELECTION BY BATS IN FORESTS OF WESTERN OREGON

We investigated food habits and relationships between food resource abundance and activity of bats. We identified Prey remains In guano collected from 337 individuals in the Oregon Coast Range. Guano analyses indicated that 2 species, long-legged Myotis (Myotis volans) and Townsend's big-eared bat (Corynorhinus townsendii), consumed predominantly Lepidoptera 4 species. California myotis (M. californicus), little brown myotis (M. lucifugus) Yuma myotis (M. yumanesis), and silver-haired bat (Lasionycteris noctivagants), consumed predominantly smaller insects likely of aquatic origin (Diptera and Trichoptera); and the remaining 4 species. long-eared myotis (M. evotis), fringed brown bat (Eptesicus fuscus). and fringed myotis (M. thysanodes), big brown bat (Eptesicus fuscus), and hoary bat (Lasiurus cinerens), consumed predominantly larger invertebrates of terrestrial origin (Lepidoptera, Coleoptera. Hemiptera, and Araneae). We hypothesized that bat activity in riparian areas Would be correlated with abundance of preferred insect prey and used an information-theoretic approach to determine whether variability in bat activity was more strongly associated With captures of all insects, of taxa most frequently Occurring in the diet, or of particular size classes of insects. We found strong associations between activity of small Myotis species and number of captures of small insects, but activities of larger Myotis species and of non-Myotis species were not associated with numbers of insects of any category.