Risks of calling by the field cricket Teleogryllus oceanicus; potential predation by Australian long-eared bats

Abstract

Male Teleogryllus oceanicus prefer to call from refuges and from these protected sites produce signals that contain more trill elements than produced by males calling without the protection of refuges. We tested the vulnerability of male crickets to predation from two species of gleaning bats, Nyctophilus major and N. geoffroyi. Crickets called from the floor of darkened fly-ways where bats preyed on calling rather than silent males. Both species of bat used passive listening to locate their prey rather than echolocation. Those crickets calling from refuges avoided predation. By counting the number of passes each bat made over paired speakers emitting different digitized songs, we tested the bat's preference for different call elements or the total number of sound elements in the song per unit time. When the total number of sound elements of each signal was balanced, bats preferred trills to chirps, and when call length differed, bats preferred those signals with more total sound elements. We discuss the possibility that predation by bats is a form of counter-selection on calling in T. oceanicus.