AN EXPERIMENTAL TEST OF CLUTTER TOLERANCE IN BATS

Abstract

To examine the effects of spatially complex habitat (i.e., cluttered) and prey availability on habitat selection by bats, we constructed 3-dimensional “clutter cones” and monitored activity of free-ranging bats in them. Cones were paired with cones of equal clutter density and size in which we placed ultraviolet (UV) light sources to attract nocturnal insects and hence increase prey availability. We tested predictions arising from resource-partitioning experiments in previous works from laboratories and the field. Activity by bats of all sizes was unaffected by density of clutter, and activity by small-sized bats at all UV-illuminated sites increased significantly, whereas activity by large-sized bats was unaffected. Also, Myotis lucifugus did not negotiate clutter densities as complex as those in previous laboratory work. This suggests that habitat complexity is likely one means by which foraging areas are partitioned between those bats that can exploit them (i.e., smaller species) and those that cannot and that cluttered habitats are avoided except when they may serve a purpose such as an energetic benefit. Although behavioral studies conducted in the laboratory serve to obtain data on ultimate capabilities, differences between results from the laboratory and the field suggest that an animal's behavior may be specific to its present environment.