Feeding Behavior of Myotis lucifugus and Eptesicus fuscus Holt,J.,G. Basinsky, T. Floria, R. Friesen, A. Page, and J. Paula. Department of Biology, Fitchburg State College Introduction Little brown bats, Myotis lucifugus, and big brown bats, Eptesicus fuscus, (Figure 1), are common insectivores in the Eastern United States. Big brown bats feed primarily on beetles (Carter et. al. 2003; Whitaker, 1972) and are considered beetle specialists (Freeman, 1981). Little brown bats also consume beetles but appear to be feeding generalists (Carter et. al. 2003; Whitaker, 1972). Because fireflies are common beetles and represent an abundant potential food source, we hypothesized that they would occur in the diet of both species. However, data describing the diets of big brown and little brown bats in New England were limited. The goals of this research were to increase understanding of bat diets in New England and to determine if fireflies are eaten by bats. Methods Bats were captured at Pisgah State Park (Figure 2), N.H. between May and June Bats were captured in a mist net, identified, and placed in cloth bags for 15 min. to collect feces. Bats were identified to species, banded, and weighed. Age, sex, reproductive condition, and length of forearm were recorded, and bats were released. Fecal pellets from each specimen were placed in water and teased apart so that insect parts could be identified. Results Fecal samples from 71 little brown bats and 15 big brown bats were analyzed. Diets of males and females were similar for both species. Little brown bats ate a variety of insects including members of at least 19 families from 12 orders. However, most of the diet was represented by 7 orders (Figure 3). Big brown bats consumed members of at least 11 families from 8 orders (Figure 4a). Both species of bats also consumed unidentified insects and plant remains. No fireflies were found in the diets. Discussion Little brown bats primarily fed on soft bodied aquatic insects with Diptera, Trichoptera, and Neuroptera constituting 40% of the total dietary volume. Big brown bats preferred large hard bodied insects (eg. Coleoptera; Figure 4). Both species in general, and big brown bats in particular, may actively avoid fireflies as potential prey while consuming other insects of similar size and shape. Detailed behavioral studies of bat feeding will be needed to investigate possible reasons for the absence of fireflies in bat diets. Literature Cited Freeman, P.W Correspondence of food habits and morphology in insectivorous bats. Journal of Mammalogy, 62: Whitaker, J.O., Jr Food habits of bats from Indiana, Canadian Journal of Zoology, 50: Hamilton, W. J The insect food of the big brown bat. Journal of Mammalogy, 15: Carter et. al., Food habits of seven species of bats in the Allegheny plateau and ridge and valley of West Virginia. Northeastern Naturalist, 10: Acknowledgments We thank Kevin Austin, Christopher Cratsley, Paul Moosman, Stephanie Poisson, Howard Thomas, Jacques Veilleux, Matthew Zanghi, New Hampshire Department of Parks, New Hampshire Department of Fish and Game Figure 1. Little brown 1a (Myotis lucifugus) and big brown 1b (Eptesicus fuscus) bats. 1a1b Analysis consisted of percent frequency of occurrence and mean percent abundance for each prey item. Figure 2. Location of Pisgah State Park, Cheshire County, New Hampshire. Figure 3. Eight most common food items eaten by little brown bats (Myotis lucifugus) at Pisgah State Park, New Hampshire Figure 4. Eight most common food items eaten by big brown bats (Eptesicus fuscus) at Pisgah State Park, NH (4a), and within order percentages of Coleoptera eaten by Eptesicus fuscus. 4a. 4b.