ECHOLOCATION BEHAVIOR OF VESPERTILIONID BATS (LASIURUS-CINEREUS AND LASIURUS-BOREALIS) ATTACKING AIRBORNE TARGETS INCLUDING ARCTIID MOTHS

We observed the echolocation and hunting behaviour Lasiurus borealis and Lasiurus cinereus from May to August of 1989, 1990, and 1991 to assess the role of feeding buzzes in the behaviour of echolocating bats attacking airborne prey. Feeding buzzes consist of short echolocation pulses produced at a rapid rate just before contact between a flying bat and its prey. The hypothesis that the duration of the feeding buzz reflects the size of the attacked prey was not supported by the data. The mean lengths of silent periods between the end of the feeding buzz and the next echolocation call were significantly longer after successful attacks than after unsuccessful attacks. There was, however, no threshold value unambiguously separating successful from unsuccessful attacks in either species. The responses of bats to tossed pebbles and to some insects indicated that during some feeding buzzes L. borealis and L. cinereus judged the nature and range of prey being attacked. Attacks by free-flying L. borealis on muted arctiid moths (Hypoprepia fucosa), combined with the rejection of these moths as food by captive bats, suggest that in this setting the clicks of these moths are aposematic signals, warning the bats of the moths' bad taste.