INTERACTIONS BETWEEN BATS AND ARCTIID MOTHS

Many arctiid moths emit trains of ultrasonic clicks upon tactile stimulation and when exposed to trains of ultrasonic pulses like those emitted by bats. We observed the responses of captive big brown bats (Eptesicus fuscus) and free-foraging red bats (Lasiurus borealis) to arctiid moths and similar-sized moths of other families, and the responses of free-flying moths to trains of ultrasonic pulses like those of bats. Both the big brown bats and the red bats ate significantly fewer arctiids than were available to them, but the captive bats were more likely to kill arctiids than were the free-flying ones. The captive bats ate fewer of the arctiids they killed than moths of other families. Muted arctiid moths were caught by the red bats more than intact conspecifics but usually were dropped without being eaten. Free-flying arctiid moths changed their flight paths less in response to trains of ultrasonic pulses than did moths of other families similarly capable of hearing these signals. These results suggest that arctiid moths use their clicks and chemical defenses to protect them from the bats that prey upon them, and that these clicks are aposematic signals that warn bats of unpalatable prey.