Evidence of resource-defense polygyny in an endangered subtropical bat, Eumops floridanus

Abstract

Understanding sociality and animal behavior is critical for developing effective conservation strategies. Many tropical bat species form harems, where dominant males play key social roles by defending groups of females directly (female-defense polygyny) and/or the resources that females need (resource-defense polygyny). The Florida bonneted bat (Eumops floridanus) is an endangered subtropical species suspected to form harems, but our understanding of its social structure, reproduction, and behavior is rudimentary. In this study, we evaluated demographic variation in morphological and behavioral characteristics of Florida bonneted bats to test the hypothesis that this species forms harem groups and exhibits resource-defense polygyny at roost sites. We used a 4-year dataset of 341 individuals uniquely marked with passive integrated transponders (PIT tags), coupled with tri-annual capture records, to track activity patterns of bats at five roosts fitted with PIT tag readers. We identified the likely dominant males and other demographic groups in each roost using morphometric characteristics and reproductive status. We assessed differences between sexes and among status categories in three primary metrics: amount of activity at the roost, time of emergence, and initial foray duration per night. Dominant males consistently were the most active individuals at roosts and spent the least amount of time away from roosts during forays, relative to females and other males. Females spent more time away from roosts than males and shared similar foraging activity patterns regardless of status. Our findings suggest that Florida bonneted bats form small harem groups that are active year round. Male bats exhibit characteristics of resource-defense polygyny at roost sites and a size-biased hierarchy, with the largest reproductively active males appearing to defend the roost at the expense of time spent foraging. We suggest that the roost site represents a critical, limited and defendable resource for male Florida bonneted bats to gain access to females, which has important implications for the conservation and enhancement of roost sites. Our study highlights the importance of accounting for differences in behavior across demographic groups and social roles when considering resource needs for imperiled species.