ABSTRACT
Urbanization exposes wild animals to increased light. Nocturnal animals in particular are affected by artificial light. Under its influence, the balance of predator-prey interactions may shift. In the interaction between echolocating bats and eared moths, bats often benefit from the effects of light because moths exposed to light resort less often to last-ditch manoeuvres in response to attacking nearby bats. To what extent increased light affects moths’ ability to engage in negative phonotaxis, a response to distant bats, is unknown. To quantify the overall effect of light on both last-ditch manoeuvres and negative phonotaxis, we counted the moths caught by two light traps over several nights. Traps were alternately equipped with speakers playing back ultrasonic simulations of hunting bats. The playback did not affect moth counts, indicating that light not only reduces the last-ditch manoeuvres of moths but also influences whether moths rely on negative phonotaxis. Increasing light pollution, therefore, interferes with different aspects of anti-predator behaviour in moths and, possibly, other eared insects. Our study demonstrates the negative effect of light on insects, clarifies the behavioural changes that result from light exposure and highlights the need for future research to uncover the mechanism(s) underlying these behavioural changes.