Listening for bats: pulse repetition rate as a cue for a defensive behavior inCycnia tenera (Lepidoptera:Arctiidae)

Summary The tympanate, arctiid moth,Cycnia tenera responds to pulsed, 30 kHz acoustic stimuli resembling bat echolocation signals by emitting trains of clicks. This phonoresponse was used to determine that this moth is maximally sensitive to stimulus pulse repetition rates of 30–50 pulses/s, rates typically emitted by bats shortly before they close with their targets. At rates both above and below this optimum moths exhibit higher thresholds and reduced responsiveness. These data suggest thatC. tenera is capable of using the repetition rate emitted by an approaching bat as a cue in determining the relative proximity of the bat. The use of repetition rate information should allow this moth both an unambiguous indication of a bat at very close range as well as the ability to distinguish sources of nocturnal, high-frequency sounds not emitted by predators.