Abstract

Anthropogenic noise exposure is widely accepted as an impediment to animal communication in nature. However, only recently has there been an interest in whether anthropogenic noise specifically affects singing insects. Orthopterans are an order of insects in which many of the members sing to attract mates and, relative to the rest of Insecta, have been well studied in the context of communication in anthropogenic noise. To date, behavioural results on how orthopterans communicate and locate each other in anthropogenic noise have been conflicting and contradictory. Investigating behaviour alone meant that previous studies have been unable to demonstrate whether the orthopterans are unable to hear in anthropogenic noise or if anthropogenic noise is changing how they respond. In this thesis, I use a combination of behavioural and neural recording techniques to test several proposed consequences of exposure to anthropogenic noise, specifically traffic noise, in two species of orthopterans, the cricket Teleogryllus oceanicus, and the katydid Neoconocephalus ensiger.

First, I examine and compare the effects of long-term and immediate exposure to traffic noise on the ability of female T. oceanicus to locate mates. I show that traffic noise affects the willingness of females to begin searching, but that long-term and short-term exposure have opposing effects, and that hearing-wise, detection of the males was unaffected. Next, I compared traffic noise to other repetitive and persistent natural sources of noise in terms of whether they impede mate localization in female T. oceanicus. I show that traffic noise is no worse than other natural noises, such as other insects or a river, in inhibiting hearing or localization. Finally, I investigated whether traffic noise affects how N. ensiger males react to both a predatory and relatively harmless bat call. I found that the presence of traffic noise changes the relative perception of threat of each bat compared to silence, but does not affect how the calls are detected at the ear. Overall, I show that the common perception that traffic noise is impeding hearing in Orthopterans is highly unlikely, but the effects of traffic noise on behaviour may be far more complex than originally thought.