Changes in roosting decisions and group structure following parturition in little brown myotis (Myotis lucifugus)

In many temperate animals, reproductive cycles coincide with seasonal weather changes resulting in behaviour changes such as movement and habitat selection. In social species, these physiological and environmental changes can alter the costs and benefits of social interactions, impacting the structure of animal groups. In little brown myotis (Myotis lucifugus), a gregarious bat occupying much of North America, the pregnancy and lactation phases present different challenges to energy balance and maternal movement, and reduced forage distance has been observed during the lactation period. As such, we hypothesized that differences between reproductive phases alter the roost switching decisions of individual bats and therefore the overall group structure of little brown myotis maternity colonies. We observed that adult females were less likely to switch roosts during the lactation period even when accounting for changing weather conditions. This shift in roost switching behaviour may be the source of observed differences in group structure between reproductive periods. We reported a decline in network cohesiveness, but no meaningful variation in individual roost fidelity and association strengths of dyads between reproductive phases. These results support the contention that reproductive processes in female little brown myotis influence sociality and overall roosting patterns within maternity groups.