Group size and environmental obstacles drive acoustic call properties for gray bats in flight: A data-driven analysis

Unlike schools of fish or flocks of birds, social bats who use echolocation for navigation are faced with the complex challenge of signal processing while living and flying in groups. Interference between an individual’s calls and those of its conspecifics can be confused, making these signals difficult to study and interpret for both animals and researchers. Moreover, it is not necessarily clear from the literature what form models that seek to predict bat echolocation behaviour should take. For example, we know that bats change their calls when flying in groups, but the literature is not consistent on what specific changes are implemented. Here, we collect and analyse data from a colony of wild gray bats, Myotis grisescens , to explore whether the number of bats emerging from the roost at a given time and the physical geometry of their environment influences their echolocation calls. Specifically, we explore whether the number of calls and their acoustic power are influenced by the group size and presence of obstacles using a time-series analysis tool called transfer entropy (TE). We further apply a data-driven algorithm called sparse identification of non-linear dynamics (SINDy) to describe a model for this phenomenon. Our findings reveal significant TE values, indicating that call properties are influenced by both social and environmental factors, without assuming a form for this influence. Additionally, SINDy-based models suggest how bats adjust their echolocation behaviour in response to the presence of conspecifics and environmental obstacles. These results provide new insights into the role of sociality and physical surroundings in shaping echolocation dynamics in gray bats.