Resource Utilization: Temporal and Spatial Components of Bat Activity in Central Iowa

Foraging activity of insectivorous bats was studied from April through October in central Iowa. Temporal activity was quantified by recording capture times throughout feeding periods, and spatial patterns were examined by measuring the abundance and diversity of species in three contrasting habitats. Six species, Myotis lucifugus, Myotis keenii, Lasionycteris noctimgans, Eptesicus fuscus, Lasiurus borealis, and Lasiurus cinereus, were characterized by initial periods of foraging occurring within 5 hours after sunset. Myotis keenii and L. noctivagans had distinct secondary periods of activity, but other species showed only minor secondary periods, or complete cessation of activity, following the initial foraging period. The modes of initial and secondary activity of L. noctivagans, L. borealis and L. cinereus showed almost complete displacement and corresponded to peak periods of nocturnal insect activity, suggesting a mechanism by which some insectivorous bats may partition environmental resources. Those species showing overlap in temporal foraging (M. keenii and L. noctivagans on the one hand, and M. lucifugus, E. fuscus, and L. borealis on the other) may have evolved spatial strategies to reduce competition for resources. Intraspecific foraging patterns of three species examined may reflect resource partitioning or, alternatively, secondary foraging activity owing to different energy demands of young and lactating females.