Instantaneous song modification in response to fluctuating traffic noise in the tree cricket Oecanthus pellucens

Abstract

Noise pollution is a world-wide phenomenon and its effects on animal behaviour have been investigated by numerous studies focusing mostly on vertebrate taxa. However, studying how insects are impacted by human-made noise is indispensable, because of their ecological importance and in order to gain a more comprehensive knowledge of how animals can cope with this new challenge. The few studies that have examined the effects of noise pollution on the acoustic signalling of insects have characterized noise over long timescales. In this study we examined whether males of the tree cricket Oecanthus pellucens modify their calling song in response to the fluctuation in traffic noise over a short timescale. To examine this question we carried out (1) noise level measurements over a short time window (200 ms) paired with song parameter measurements on sound recordings of males singing in their noise-polluted habitats and (2) laboratory playback experiments in which each singing male was recorded during a silent control period and during noise playback. Our results show that males shortened their calls (echemes) and paused singing with a higher probability with increasing noise level. However, males did not modify the fundamental frequency of their song and did not adjust the duration of the interecheme interval in response to noise. These results suggest that crickets decrease signalling effort during high levels of noise and, at least for the song parameters we examined, do not modify their signals, as do birds and frogs, to reduce masking by anthropogenic noise.