US researchers have found that canny moths impersonate the sounds made by their bad-tasting relatives to ward of bat-attacks.
Writing in this week's PNAS, Jessie Barber, from Wake Forest University, trained two species of bats to hunt for moths within sight of two infra-red enabled video cameras. At the same time he recorded the sounds produced by moth prey and the hunting bats. In response to hearing the sonar emitted by bats to locate their meals, some unpalatable tiger moths use a pair of structures called tymbals to broadcast ultrasonic clicks of their own, which are designed to warn the hunter that they taste bad. The bats then duly avoid them. But other tastier moths appear to have muscled in on the trick to avoid being eaten and mimic the bat-repelling sounds with good effect: "we found that bats do not eat the good-tasting moths that make the similar sounds," said Barber. Moths that exercised the right to remain silent, on the other hand, fared less well and were instantly gobbled up.