Prey Consumption of Insectivorous Bats in Coniferous Forests of North-Central Idaho

A considerable body of work has emerged on the ecology of insectivorous bats in forests of the Pacific Northwest, including dietary studies. Existing research in the Pacific Northwest on bat diets and prey consumption has emphasized populations of bats in Oregon. There are limited data for species inhabiting forests elsewhere in the region. We collected fecal samples from bats captured in mist nets set during May through August, 2004-05, in two watersheds in north-central Idaho that supported forests which were actively managed for timber production. We analyzed fecal samples of 183 bats of five species and compared the results to previously published data for these same species inhabiting forest habitats in the Pacific Northwest. Remains of 12 orders or classes of prey, along with 18 taxonomic families of insects, were identified in the diet of these bats. Prey items included Acari, Arachnida, Coleoptera, Diptera, Hemiptera, Homoptera, Hymenoptera, Isoptera, Lepidoptera, Neuroptera, Orthoptera, and Trichoptera. Based on the percent volume of contents in fecal samples examined, Lepidoptera were the dominant prey of four of the five species of bats examined, with Coleoptera the dominant prey of big brown bats (Eptesicus fuscus). Evidence of moderate dietary specialization (> 40% volume of a specific taxonomic grouping) was observed in California myotis (Myotis califomicus: Lepidoptera), long-legged myotis (M. volans: Lepidoptera), and big brown bat (Coleoptera). Comparisons with data for bats in western and eastern Oregon showed major dietary shifts across geographic regions for some species of bats, likely associated with changes in moisture regimes and concomitant shifts in the availability of insect prey. Our data indicate that assemblages of bats living in managed, coniferous forests in Idaho consume a wide range of prey, suggesting that guidelines for management of these habitats should consider the importance of sustaining diverse insect communities to ensure the long-term health of bat populations inhabiting these forests.