Marlena Lopez

Abstract: 

Our understanding on how roosting habits of bats influence their social organization and mating systems is scarce. Here we attempted to fill in some of these gaps by examining the social organization of the Proboscis bat at La Selva Biological Station, Costa Rica, both during the day and at night. Day roosts of these bats are very exposed and bats are visually and behaviorally cryptic during the day but not at night. We thus predicted that the social organization would differ between the day and the night roost of this species. Behavioral observations of individually banded bats show that there were 2 social groups in Cabina 5 during the day using only a small part of the potential roosting space and that virtually all members showed high fidelity to the day roost. In contrast, we found bats to be using a much larger part of the potential roosting space at night and to have much lower fidelity; only 38% of the males present in the day were regularly present at the night roost and our results provide evidence of five male territories in the night roost. Our study suggests that R. naso might have a resource-defense polygyny rather than a female-defense polygyny as previously thought. Our finding thus indicates that female choice probably plays a much larger role in Proboscis bats than previously anticipated. Observing the social structure at night allowed us to understand a major feature of the social organization of this bat species that had been missed before and has essential consequences for interpreting the mating system.