Dynamics of autumn swarming and population structure of little brown and northern Myotis bats (Myotis lucifugus and M. septentrionalis)

Abstract

As a fundamental unit in evolutionary ecology and the base unit for management, the population is of immense interest in understanding a species’ ecology. Individuals are the foundation of populations where their diversity in behaviours can scale up to variation in other traits that characterize population dynamics. Understanding the variation of individuals in their behaviours and traits within a population (i.e., their structure) is therefore of great importance in characterizing populations. Bats are highly vagile and gregarious animals that show variation among sex and age classes in many stages of their annual cycle that are best understood during the summer and winter seasons. In this thesis I explored the dynamics in activity of two temperate bats, little brown Myotis (M. lucifugus) and northern Myotis (M. septentrionalis) during swarming in autumn to characterize aspects of their population structures. To examine intersexual differences in swarming activities bats were captured and tagged at multiple swarming sites to characterize intersexual differences in the frequency and extent of re-use of swarming sites. I explored the associations among sex and age classes of each species to test predictions of hypotheses on the functions of swarming of gene flow and information transfer from mother bats to offspring. Lastly, I characterized population genetic structure of M. lucifugus to study the reproductive cohesion of bats - gene flow- among swarming sites. Male bats were found to have higher swarming activity compared to females which may reflect males spending more time devoted to swarming to maximize mating opportunities. Predictable age and sex class groups were found during swarming where young-of-the-year were found to have the highest associations with other bats and most preferentially with other young-of-the-year. Adult male and female bats were most often captured alone, but when males were captured they showed preference for grouping with other males, including male M. lucifugus having preferred male associates across nights. Genetic data for M. lucifugus were suggestive of high gene flow and thus a high degree of reproductive connectivity among swarming sites. Together these results provide information of how variation among individuals contributes to population structure.