My Home Is Your Castle : Roost Making Is Sexually Selected in the Bat

Abstract

Shelters are important for the survival and reproduction of many animals and this is particularly true for bats. Depending on the future use and effect of shelters on the fitness of individuals, not all members of a group of animals may contribute equally to shelter making. Thus, knowledge about the identity of shelter-making individuals may teach us much about the social system and mating strategy of species. To exemplify this, we review what is known about the roost-making behavior and the social system of Lophostoma silvicolum, a neotropical bat that excavates roost cavities in active arboreal termite nests. Roosts in termite nests are highly beneficial for the bats because they offer improved microclimate and possibly are responsible for the lower parasite loads of L. silvicolum in comparison to bat species using other, more common, roost types. Examination of observational field data in combination with genetic analyses shows that roost cavities excavated by single males subsequently serve as maternity roosts for females and that this improves reproductive success of the male who excavated the roost. This suggests that roosts in termite nests serve as an extended male phenotype and roost making is a sexually selected behavior. Roost-making behavior is tightly linked to the species' social organization (single-male-multifemale associations that stay together year-round) and mating system (resource-defense polygyny). The case study of L. silvicolum shows that it is important to learn more about the implications of shelter making in bats and other animals from ongoing and future studies. However, differences in costs and benefits for each group member must be carefully evaluated before drawing conclusions about social systems and mating strategies in order to contribute to our current knowledge about the evolution of sociality in mammals.