In the dark corners of old church attics, a remarkable natural drama unfolds: males of the Greater Mouse-Eared Bat (Myotis myotis), Germany’s largest bat species, gather to compete for the attention of females. With complex vocal displays and impressive persistence, these bats engage in a mating strategy that has now been scientifically confirmed to be a lek mating system – a behaviour rarely documented in bats.
As part of her PhD research, Lisa Printz observed more than 70 male bats across six church attics in Bavaria. The males occupied small, repeatedly used roosting spots, which they defended vigorously while producing elaborate trilling calls. These vocalisations serve a dual purpose: deterring rival males and attracting females. During the mating season, which peaks in August, males travel specifically to these lek sites and often return to the same location year after year.
The findings are striking: female bats appear to choose a mate even before landing, flying directly to a specific calling male. After landing, mating may not begin immediately – instead, the pair often rests quietly side by side. Some mating events last for more than 34 hours, with the male wrapping his wings around the female afterwards. This prolonged contact may represent a form of mate guarding, ensuring reproductive success.
The study has clear implications for bat conservation: male bats display strong site fidelity to their mating roosts. Renovations or structural changes to buildings such as churches or monasteries could severely disrupt these critical behaviours.
“Traditionally, conservation efforts have focused on maternity and hibernation roosts, while male roosts have been overlooked,” says Lisa Printz. “But our results show that male mating roosts are seasonally important and consistently used over many years – they deserve the same level of protection.”
The German Bat Observatory supports the call for better protection of mating roosts and encourages conservationists and building caretakers to factor these sites into preservation plans.
Study details:
Printz, L., Lustig, A., Nagy, M., Knörnschild, M. (2025): Mating system and copulatory behavior of the greater mouse-eared bat (Myotis myotis). Annals of the New York Academy of Sciences 2025, 1–14. https://doi.org/10.1111/nyas.15390