Aspects of ecology and behaviour of the serotine bat (Eptesicus serotinus)
The aim of this study was to investigate the ecology and behaviour of the serotine bat, a widely distributed and little studied European species. The composition and social structure of maternity colonies were determined during three breeding seasons. No adult males were found in any maternity colonies. A total of 209 adult females were caught and 71 individuals were recaptured in the same and/or subsequent years. Only one female was reproductively active in all three years. Of all females caught, 66% were reproductively active and 34% were reproductively inactive. Twelve percent of the females caught were nulliparous. A total of 87 juvenile bats were caught. Births took place between the 29 June and the 6 July. There was a significant difference in body size between juvenile male and female bats and also in the body size of juveniles caught at different roosts at the same time of year. Activity patterns at a maternity roost were investigated by use of a remote monitoring system throughout a summer season. The activity patterns were unimodal during early pregnancy, bimodal during middle and late pregnancy and multimodal during lactation. The duration of the first flight decreased significantly during pregnancy as the parturition date approached and increased significantly as lactation progressed. Inclement weather inhibited or shortened the duration of flights. At weaning mothers sometimes used different day-roosts from their young. The behaviour of foraging serotines was investigated by radio-tracking. Reproductively active females were strongly philopatric to their day-roost and reproductively inactive females sometimes changed their day-roosts, moving up to 5 km. There was no movement of individuals between maternity colonies. White streetlamps were often used by foraging serotines and they were commonly found feeding close to accumulations of cattle dung in late summer. Foraging serotines were able to locate temporary concentrations of insects and they used three distinct foraging styles: hawking, flycatching and feeding on the ground.