Male bushcrickets show context-dependent plasticity in temporal signal features during acoustic contests

Abstract

Males of sound-communicating species typically emit acoustic signals both to attract mating partners and compete against rival males. Temporal properties of these signals convey information about the males’ condition and quality as potential mates. Previous studies on acoustic competition in bushcrickets have shown that temporal features are plastic and may vary depending on male body condition and social context, including the distance, number and quality of competitors. Prolonged acoustic contests may also prompt signalling males to modify their calling behaviour over time. To investigate context-dependent behavioural plasticity in bushcrickets, we analysed the temporal properties of Poecilimon ampliatus male signals, specifically verse duration, verse number and duty cycle, in relation to their social environment, body mass as a predictor of body condition and the time spent in signalling competition. Males from two distinct body mass classes, light and heavy, were tested at the beginning and the end of a 50 min recording period under two conditions: a playback experiment simulating competition with a strong rival and no playback. Regardless of their body mass, P. ampliatus males adjusted temporal signal features depending on the social context, promptly increasing their signalling effort under competition compared with isolation. However, behaviourally plastic responses of light males to competition also varied over time, likely due to tradeoffs imposed by prolonged competitive signalling. These findings highlight the importance of adaptive signal modifications in mediating competitive interactions in bushcrickets, with potential implications for female choice.