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

TL;DR

This study investigates how the temporal structure of male treefrog choruses gradually develops depending on the spatial distance between neighboring callers, using advanced field recording and analysis techniques in natural habitats.

Contribution

It introduces a comprehensive field methodology combining sound-imaging and microphone arrays to analyze natural chorus structures and reveals the spatial dependence of call synchronization.

Findings

Synchronized call alternation emerges gradually with decreasing distance between callers.

Call frequency and chorus density moderately influence the emergence of temporal structures.

The study provides detailed spatio-temporal data on natural frog choruses.

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.