Behavioural State Determines Male Response to Conspecific Male Calls in a Tree Cricket

In this study, we tested whether male tree crickets show behavioural state-dependent responses to louder conspecific male calls, which are known to trigger competitive behaviour. Furthermore, we tested whether males change their call characteristics upon hearing the loud, conspecific playback. To answer such questions, we build a t-maze inside an anechoic chamber with a speaker randomised to play a conspecific loud playback from either side of the maze. Thus, our study gathered behavioural data from a controlled semi-natural laboratory setup. We had two experimental setups, one where males heard a loud conspecific call before they initiated acoustic signalling and another where males heard a loud conspecific call after they began calling themselves.

Our data shows that males who heard the playback before signalling themselves remained silent and moved towards the playback. The males who called first and then heard the louder playback maintained their acoustic state (calling) and did not move toward the speaker. Moreover, we did not find any change in acoustic parameters (e.g., sound pressure level, calling effort) in males who called first and then heard to playback, which indicated tree crickets do not compete acoustically using these call characteristics. However, we found that chirp rate increased with time but not with exposure to louder, conspecific call, suggesting that, naturally, males called faster with time. Furthermore, males who heard the playback before signalling and those who initiated calling before hearing the signalling had similar acoustic call properties (sound pressure level, chirp rate, calling effort), indicating that the decision to call was not affected by the conspecific playback.