Range overlap and association patterns in the tent-making bat Artibeus watsoni

Abstract

Space use and ranging patterns of individuals have traditionally been used to identify social systems, and the amount of overlap in the home ranges of individuals can provide indirect information about the likelihood of social interactions. We compared data on foraging and roosting range overlap of the tent-roosting bat Artibeus watsoni to assess how environmental and demographic factors may affect movement patterns and social interactions. We estimated the overlap of foraging and roosting ranges among simultaneously radiotagged dyads and calculated a simple association index among these individuals. We then used these data to determine whether relative population and roost abundance, as well as sex class, affected spatial and social patterns. Our results show that range overlap in A. watsoni significantly determines the degree to which individuals interact with each other. We also found that roosting range overlap may be a greater determinant of daytime social interactions than foraging range overlap, because roosting range overlap showed a stronger correlation with association patterns. In addition, the differences that we observed in roosting range overlap and association among dyads were a consequence of the effects of population and roost density. Bats sampled in areas of high-population abundance had significantly higher roosting range overlap than bats in areas of low-population abundance, and roosting ranges of bats sampled at sites with few roosting resources (i.e. tents) overlapped more than those of bats living in areas with more tents. Finally, we observed no overlap in roosting range and no association among adult males, supporting the hypothesis that males defend tents or roosting areas against other males to gain exclusive mating access to females using these structures.