Ontogeny of an interactive call-and-response system in Spix's disc-winged bats

We investigated the ontogenetic changes of two call types, the inquiry call and the response call, which comprise an interactive communication system in Spix's disc-winged bats, Thyroptera tricolor. We documented structural changes on both inquiry and response calls during ontogeny by recording single individual vocalizations in a flight cage and triggering response calls with playbacks of adult inquiry calls. Most ontogenetic changes in response calls were sex dependent. In addition, individuality was high for both call types across age categories. Despite the observed changes during development, both call types resembled the structure of adult calls from early ontogenetic stages, suggesting little influence of social learning in call development. Finally, we found sex dependent ontogenetic changes and high levels of individuality of calls early in life, which may indicate additional functionality in sex and pup recognition. Overall, the findings bring novel insight into the complex developmental process of the call types comprising the communication systems of Spix's disc-winged bats, and contribute to a better understanding of signal development in complex social communication systems. (C) 2020 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.