Gradual emergence of temporal structures depending on the distance between neighboring callers in natural habitat of male treefrogs

Abstract

Acoustic animals (e.g., insects and frogs) aggregate and produce sounds for mating. Well-organized chorus structures like call alternation and call synchrony indicate the importance of the precise control of call timing by individual males. However, the stable monitoring of multiple acoustic features in natural environments, especially the variation in call frequency, call timing and caller position, lacked in previous studies because of technical difficulties originating from the intense background noise, the existence of multiple sound sources and the wide area for monitoring. Here we have examined the spatio-temporal frequency structure in the choruses of wild treefrogs. First, we have performed field recordings by combining the sound-imaging system (25-66 units of sound-imaging devices) and microphone-array system (16-24ch of microphones) between 2021 and 2023. Second, we have analyzed the video and audio data and quantified the call frequency, call timing and caller position of each male, for 11 choruses with 66 males in total. Based on this large datasets, we have shown that synchronized behavior (call alternation) gradually emerges between neighboring callers depending on their distances even when the call frequency and chorus density moderately vary.