Abstract
The night sky is the venue for an ancient arms race. Insectivorous bats with their ultrasonic sonar exert an enormous selective pressure on nocturnal insects. In response insects have evolved the ability to hear bat cries, to evade their hunting maneuvers, and some, the tiger moths (Arctiidae), to utter an ultrasonic reply. We here determine what it is that tiger moths “say” to bats. We chose four species of arctiid moths, Cycnia tenera, Euchaetes egle, Utetheisa ornatrix, and Apantesis nais, that naturally differ in their levels of unpalatability and their ability to produce sound. Moths were tethered and offered to free-flying naïve big brown bats, Eptesicus fuscus. The ability of the bats to capture each species was compared to their ability to capture noctuid, geometrid, and wax moth controls over a learning period of 7 days. We repeated the experiment using the single arctiid species E. egle that through diet manipulation and simple surgery could be rendered palatable or unpalatable and sound producing or mute. We again compared the capture rates of these categories of E. egle to control moths. Using both novel learning approaches we have found that the bats only respond to the sounds of arctiids when they are paired with defensive chemistry. The sounds are in essence a warning to the bats that the moth is unpalatable—an aposematic signal.
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Acknowledgements
N.I.H. collected the data, whereas W.E.C. helped design the experiments and supervised the project. We thank Mitch Masters and Amanda Lollar for helpful advice on how to maintain a healthy bat colony. We are grateful to Wake Forest undergraduates Sarah Ross, Payton Deal, Megan Clendenin, and Jason Davenport for assistance with the learning experiments. Anna Price, Rebecca Cooke, and Hugh Labusohr reared many of the insects. Jesse Barber, Susan Fahrbach, and two anonymous reviewers greatly improved a previous version of this manuscript and Jesse assisted with the bat experiments. Mindy Conner provided editorial assistance and suggested the title for this article. The research was supported in part by the Science Research Fund at Wake Forest University, the Eppley Foundation of New York, and the National Science Foundation (IBN-0135825). All experiments were carried out in compliance with current laws in the United States.
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Hristov, N.I., Conner, W.E. Sound strategy: acoustic aposematism in the bat–tiger moth arms race. Naturwissenschaften 92, 164–169 (2005). https://doi.org/10.1007/s00114-005-0611-7
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DOI: https://doi.org/10.1007/s00114-005-0611-7