Effects of anthropogenic noise on male signalling behaviour and female phonotaxis in Oecanthus tree crickets

Communication is vital to the survival and reproductive success of organisms. There is growing evidence that anthropogenic noise interferes with acoustic communication. While recent studies have tested whether signallers behaviourally modify their signals to prevent masking from noise, studies have only recently begun to test whether noise in fact interferes with the perception of acoustic signals. In this study, we investigated how road noise affects both male signalling and female phonotaxis in Oecanthus tree crickets. Acoustic signals of tree crickets, which are relatively low amplitude and composed primarily of low frequencies, are likely to be masked by road noise. To determine whether males alter their calls in the presence of road noise, we assessed how a playback of recorded road noise changed four male calling characteristics: dominant frequency, call amplitude, total time spent calling and latency to begin calling. We then used response trials to test the ability of females to localize and respond to male calls in the presence of road noise. Unlike studies in other organisms, which detected quantifiable differences in male signal characteristics, male tree crickets were less likely to call but did not change signal characteristics. Surprisingly, female response to male signals was not affected by the presence of road noise, despite the potential masking effects of road noise. Because tree crickets often communicate in environments with many species of calling insects, tree crickets may be adapted to tolerate novel sources of acoustic interference. This study presents a case where male signals and female responses are not affected by road noise. Since species are differentially affected by noise, detailed understanding of behaviour and sensory systems may be necessary for predicting the effect of acoustic interference on trophic interactions and population dynamics.