Noctuid moths show neural and behavioural responses to sounds made by somebat-marking rings

Coloured rings are often used for marking bats so that specific individuals can be recognized. We noticed that the rings of mouse-eared bats, Myotis m yotis and Myotis blythii, in a combination of one plastic-split and one met allic ring on the same forearm, emitted sounds that were largely ultrasonic each time the rings met in flight. We recorded the ring sounds and the ech olocation calls produced by the bats, and played them back to neural prepar ations of lesser yellow underwing moths, Noctua comes, while making extrace llular recordings from the moths' Al auditory receptors. The peak energy of the ring sounds occurred much closer in frequency to the moth's best audit ory frequency (the frequency at which the moth has the lowest auditory thre shold) than the peak energy of the calls, for both bat species, and the rin g sounds were detected at a threshold 5-6 dB peSPL lower than the calls. Mo ths performed evasive manoeuvres to playbacks of ring sounds more frequentl y than they did to control (tape noise) sequences. These neural and behavio ural responses imply that certain bats should not be marked with two rings on one wing, as this may make the bat more apparent to tympanate insects, a nd may therefore reduce its foraging success. (C) 1999 The Association for the Study of Animal Behaviour.