Cooperative Fish and Wildlife Research Units Program: Virginia
Education, Research and Technical Assistance for Managing Our Natural Resources

Fission-fusion dynamics of maternity colonies of tree-roosting bats result in roost and social networks. An improved understanding of these networks, as well as how they occur on the landscape, has the potential to improve bat conservation and management efforts. We radio-tracked five maternity colonies of northern bats (Myotis septentrionalis) at Fort Knox, Kentucky, and calculated roost and social network metrics for each colony. We used bivariate normal fixed kernel utilization distributions and compared overlap to evaluate space use by maternity colonies. Additionally, we performed simulations of randomized roost removal for the largest network we delineated. We found that roost and social network structure differed by reproductive status of the maternity colonies, with gestating bats using roosts and forming associations no different than would be expected by chance. Conversely, lactating bats exhibited closer social association and greater concentration of roost use than would be expected by chance. Maternity colony roosting areas existed in close spatial proximity, but occupied separate areas on the landscape with little overlap relative to their utilization distributions. In our simulations, roost removal was linearly related to network fragmentation. Removal of approximately 20% or more of the roosts was required to split the network into two fragments, whereas a 50% roost removal was required to generate three network fragments. Our results suggest that northern bat maternity colonies are distinct entities on the landscape, and as such may be individually manageable units.