Size Effect on Call Properties of Japanese Tree Frogs Revealed by Audio-Processing Technique.

Sensing the external environment is a core function of robots and autonomous mechanics. This function is useful for monitoring and analyzing the ecosystem for our deeper understanding of the nature and accomplishing the sustainable ecosystem. Here, we investigate calling behavior of male frogs by applying audio-processing technique on multiple audio data. In general, male frogs call from their breeding site, and a female frog approaches one of the males by hearing their calls. First, we conducted an indoor experiment to record spontaneous calling behavior of three male Japanese tree frogs, and then separated their call signals according to independent component analysis. The analysis of separated signals shows that chorus size (i. e., the number of calling frogs) has a positive effect on call number, inter-call intervals, and chorus duration. We speculate that a competition in a large chorus encourages the male frogs to make their call properties more attractive to conspecific females.