Article

Sonar jamming in the field: effectiveness and behavior of a unique prey defense

Wake Forest University, Department of Biology, Winston-Salem, NC 27106, USA.
Journal of Experimental Biology (Impact Factor: 3). 12/2012; 215(Pt 24):4278-87. DOI: 10.1242/jeb.076943
Source: PubMed

ABSTRACT Bats and insects provide a model system for integrating our understanding of predator-prey ecology, animal behavior and neurophysiology. Previous field studies of bat-insect interactions have been limited by the technological challenges involved with studying nocturnal, volant animals that use ultrasound and engage in battles that frequently last a fraction of a second. We overcame these challenges using a robust field methodology that included multiple infrared cameras calibrated for three-dimensional reconstruction of bat and moth flight trajectories and four ultrasonic microphones that provided a spatial component to audio recordings. Our objectives were to document bat-moth interactions in a natural setting and to test the effectiveness of a unique prey defense - sonar jamming. We tested the effect of sonar jamming by comparing the results of interactions between bats and Grote's tiger moth, Bertholdia trigona, with their sound-producing organs either intact or ablated. Jamming was highly effective, with bats capturing more than 10 times as many silenced moths as clicking moths. Moths frequently combined their acoustic defense with two separate evasive maneuvers: flying away from the bat and diving. Diving decreased bat capture success for both clicking and silenced moths, while flying away did not. The diving showed a strong directional component, a first for insect defensive maneuvers. We discuss the timing of B. trigona defensive maneuvers - which differs from that of other moths - in the context of moth auditory neuroethology. Studying bat-insect interactions in their natural environment provides valuable information that complements work conducted in more controlled settings.

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Available from: Aaron Corcoran, Jan 22, 2014
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    • "Energetic cost typically scales with sound production rate (Prestwich 1994). Therefore, our results suggest that clicking in tiger moths has little energetic consequence, whether used for sonar jamming, acoustic aposematism, acoustic mimicry, or courtship (Conner 1999; Conner and Corcoran 2012). Clicking for sonar jamming may have evolved from clicking for acoustic aposematism, which requires only a simple sound-producing organ (Hristov and Conner 2005). "
    Canadian Journal of Zoology 02/2015; 93(4):150204152504000. DOI:10.1139/cjz-2014-0231 · 1.35 Impact Factor
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    • "Palatability for a moth species was taken as the averaged percentage of the moths consumed by bats. This method provides results that are similar to releasing silenced moths and observing whether free-flying, wild bats consume or drop moths after capture (Corcoran and Conner 2012; n. Dowdy, personal communication). "
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    ABSTRACT: Bats and their insect prey rely on acoustic sensing in predator prey encounters-echolocation in bats, tympanic hearing in moths. Some insects also emit sounds for bat defense. Here, we describe a previously unknown sound-producing organ in Geometrid moths-a prothoracic tymbal in the orange beggar moth (Eubaphe unicolor) that generates bursts of ultrasonic clicks in response to tactile stimulation and playback of a bat echolocation attack sequence. Using scanning electron microscopy and high-speed videography, we demonstrate that E. unicolor and phylogenetically distant tiger moths have evolved serially homologous thoracic tymbal organs with fundamentally similar functional morphology, a striking example of convergent evolution. We compared E. unicolor clicks to that of five sympatric tiger moths and found that 9 of 13 E. unicolor clicking parameters were within the range of sympatric tiger moths. Remaining differences may result from the small size of the E. unicolor tymbal. Four of the five sympatric clicking tiger moth species were unpalatable to bats (0-20 % eaten), whereas E. unicolor was palatable to bats (86 % eaten). Based on these results, we hypothesize that E. unicolor evolved tymbal organs that mimic the sounds produced by toxic tiger moths when attacked by echolocating bats.
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    • "Several moth species are known to easily detect lower call frequencies and subsequently avoid the bats [16] [47] [48]. Other Lepidoptera species can even jam the echolocation call which makes it very difficult for the bat to detect the prey [16] [49]. Call frequency was relative strongly related to Lepidoptera content, while cranial length and bodyweight did not show any relationship with the dietary content of Lepidoptera. "
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