Tiger Moth Jams Bat Sonar

Abstract

Moths Battling Bats Many night-flying insects hear the sonar sounds of attacking bats and take evasive action. Among moths, evasive flight is often accompanied by the production of ultrasonic sounds. Three functions of these sounds have been proposed: to startle the bat, to warn of distastefulness, or to “jam” the bat's sonar system. Corcoran et al. (p. 325 ) studied a species of tiger moth ( Bertholdia trigona ) that emits a particularly dense series of ultrasonic clicks and the interception behavior of big brown bats ( Eptesicus fuscus ) presented with silenced or sound-producing tethered moths. If the moth sounds evoke startle, naïve bats should initially break off their attacks, but then the bats should habituate to the sounds and complete subsequent attacks. In contrast, if the moth sounds have a warning effect, naïve bats should initially complete their attacks on sound-emitting moths, discover that the moths are distasteful, and refuse to capture them in future trials. Most of the bats in the tests reliably caught the silenced moths but avoided completing attacks on sound-producing moths, with no evidence of increasing or decreasing probability of capture from the first to the last trial, which suggests that the moths effectively jammed the bats' sonar.