Anti-bat tiger moth sounds: Form and function

摘要

The night sky is the venue of an ancient acoustic battle between echolocating bats and their insect prey. Many tigermoths (Lepidoptera: Arctiidae) answer the attack calls of bats with a barrage of high frequency clicks. Some moth species usethese clicks for acoustic aposematism and mimicry, and others for sonar jamming, however, most of the work on these defensivefunctions has been done on individual moth species. We here analyze the diversity of structure in tiger moth sounds from 26 speciescollected at three locations in North and South America. A principal components analysis of the anti-bat tiger moth soundsreveals that they vary markedly along three axes: (1) frequency, (2) duty cycle (sound production per unit time) and frequencymodulation, and (3) modulation cycle (clicks produced during flexion and relaxation of the sound producing tymbal) structure.Tiger moth species appear to cluster into two distinct groups: one with low duty cycle and few clicks per modulation cycle thatsupports an acoustic aposematism function, and a second with high duty cycle and many clicks per modulation cycle that is consistentwith a sonar jamming function. This is the first evidence from a community-level analysis to support multiple functions fortiger moth sounds. We also provide evidence supporting an evolutionary history for the development of these strategies. Furthermore,cross-correlation and spectrogram correlation measurements failed to support a 'phantom echo' mechanism underlyingsonar jamming, and instead point towards echo interference [Current Zoology 56 (3): 358-369, 2010].