Fighting and flirting: the vocal repertoire of the greater mouse-eared bat in mating roosts and its seasonal variation

Vocalizations are crucial for communication in many taxa, including bats, where they serve both echolocation and social functions. This study provides an in-depth analysis of the vocal repertoire of the greater mouse-eared bat, Myotis myotis , in mating roosts, focusing on male courtship vocalizations and their potential role in individual recognition and mate choice. We found a broad vocal repertoire with 14 distinct vocalization types. Further, male M. myotis produce complex trill vocalizations that encode individual signatures. These vocalizations are likely important for both male competition and female mate choice. Our observations showed distinct seasonal patterns in the production of different vocalization types, marked by peaks in aggressive vocalizations and trills, reflecting the phenology of territorial and courtship behaviours. Through bioacoustic monitoring within mating roosts over several months, we identified vocalizations as valuable indicators for assessing bat social dynamics and territory establishment and for identifying mating roosts. Overall, our results enhance the understanding of the social system of this common European bat species and provide new insights into the behavioural significance of vocalizations in M. myotis . These insights have potential applications in conservation and population monitoring efforts by providing a new approach for identifying mating roosts and determining critical periods during the season, allowing renovation activities to be carefully planned in alignment with the protection needs of mating roosts. Our results can contribute to effective wildlife management, ensuring both efficiency and minimal disturbance for bats. • Male Myotis myotis produce 14 vocalization types during the mating season. • Complex trill vocalizations facilitate male competition and female mate choice. • Courtship vocalizations of males encode individual signatures. • Seasonal patterns of vocal output reflect the phenology of male behaviours. • Acoustic monitoring can inform protection practices of bat mating roosts.