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ABSTRACT - We used fecal analysis to describe the diet of Eptesicus fuscus in Pennsylvania and western Maryland. We examined spatial variation in diet composition among three populations and temporal variation within a maternity colony. Temporal patterns of prey use were compared with similar data collected previously from a maternity colony in Indiana. Overall, Coleoptera (58-82%), especially Scarabaeidae (14-31%), were the dominant prey items. Hemiptera, primarily Acrosternum hilare (5-19%), were also major prey, and Tettigoniidae (not previously reported) were prey of two populations (6%, 17%). Significant spatial and temporal variation existed in diet composition among populations and use of major prey types, respectively. Comparison of temporal data collected in this study and in Indiana indicated a nearly identical pattern in the use of Scarabaeidae. These insects are abundant in the spring, and the data suggest widespread specialization on Scarabaeidae in April and May. Several insects preyed on by E. fuscus in this study are serious agricultural pests.
INTRODUCTION
The big brown bat, Eptesicus fuscus, is a common insectivorous species found throughout much of North America (Barbour and Davis 1969, Kurta and Baker 1990). This bat often roosts in buildings (Barbour and Davis 1969, Whitaker and Gummer 2000) and readily takes advantage of insect concentrations near street lights (Furlonger et al. 1987; Geggie and Fenton 1985). E. fuscus is an important species in many North American ecosystems because it is widespread and abundant and, therefore, potentially has a significant impact on insect populations (Agosta 2002, Pierson 1998). Understanding the natural history of species and developing hypotheses about foraging strategies, competitive interactions, and the effects of predation on prey communities requires basic information on food habits (Litvaitis 2000).
Numerous studies have documented the food habits of E. fuscus (reviewed in Agosta 2002). In New Mexico, Black (1974) classified this bat as a beetle (Coleoptera) "strategist." Most studies have supported Black's classification (but see Brigham 1990 and Verts et al. 1999). However, this is probably too broad a generalization because many other prey types are eaten and the foraging behavior of this species appears to be flexible (Agosta et al. in press a, Brigham 1991, Brigham and Saunders 1990). In general, its relatively large size (14-30 g; Nowak 1999) and robust skull morphology (Freeman 1981) probably allow,...