Temporal structure of two call types produced by competing male cicadas
Male cicadas vocalize sounds to attract conspecific females. The acoustic traits of calls vary significantly among species and show unique temporal and spectral patterns that dynamically change, even in the same bout. While the calling behavior of a single cicada has been quantified for many species, the acoustic interaction between multiple cicadas and the usage of different call types have not been well studied. In this study, we examined the interaction between male cicadas (Meimuna opalifera) that utilize two types of calls. First, we caught two cicadas in their natural habitat and recorded their calls in the laboratory. Second, we detected the calls of each cicada and classified them into two types: Type I calls with a short duration and high repetition rate and Type II calls with a longer duration and low repetition rate. The analysis of the chorus structure demonstrated that the cicadas vocalized a Type II call immediately after another cicada vocalized a Type I call. Furthermore, we tested the hypothesis that such a timing strategy allowed the cicadas to effectively mask the calls of their competitors. Specifically, we conducted a numerical simulation randomizing the onsets of calls and compared the masking performance with empirical data, which did not support our hypothesis. This study highlights the well-organized structure of cicada calls, even in the choruses with multiple call types, and indicates these calls have a function other than male-male acoustic interaction that requires further investigation. Summary statementMale cicadas (Meimuna opalifera) produce two types of calls by synchronizing their temporal structure and switching call types when positioned close together.