Why do caterpillars whistle at birds? Insect defence sounds startle avian predators

Dookie, Amanda L.; Young, Clyde T.; Lamothe, Gilles; Schoenle, Laura A.; Yack, Jayne E.

doi:10.1016/j.beproc.2017.02.002

Cited by 23 publications

(39 citation statements)

References 41 publications

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“…Bombycoidea caterpillar sounds are believed to function in defence against vertebrate predators. However, the specific effects that these and most other insect defence sounds have on predators remains poorly understood (Conner, 2014;Dookie et al, 2017). It has been recently proposed that different sound characteristics may communicate different meanings to predators (Bura et al, 2016).…”

Section: Function and Evolutionmentioning

confidence: 99%

“…It is unlikely that these sounds function to warn of a chemical defence as A. floridensis lacks chemical-releasing spines or scoli, and regurgitation is not coupled to sound production. Compared with visual defensive ecology in insects, little is known about the functional significance of signal variation in defence sounds (Conner, 2014), and future studies should employ live predators and comparative analyses to test hypotheses (Bura et al, 2016;Dookie et al, 2017).…”

Section: Function and Evolutionmentioning

confidence: 99%

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Vocalization in caterpillars: a novel sound-producing mechanism for insects

Rosi-Denadai

Scallion

Merrett

et al. 2018

Journal of Experimental Biology

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Insects have evolved a great diversity of sound-producing mechanisms largely attributable to their hardened exoskeleton, which can be rubbed, vibrated or tapped against different substrates to produce acoustic signals. However, sound production by forced air, while common in vertebrates, is poorly understood in insects. We report on a caterpillar that 'vocalizes' by forcing air into and out of its gut. When disturbed, larvae of the Nessus sphinx hawkmoth (Sphingidae: ) produce sound trains comprising a stereotyped pattern of long (370 ms) followed by multiple short-duration (23 ms) units. Sounds are emitted from the oral cavity, as confirmed by close-up videos and comparing sound amplitudes at different body regions. Numerical models using measurements of the caterpillar foregut were constructed to test hypotheses explaining sound production. We propose that sound is generated by ring vortices created as air flows through the orifice between two foregut chambers (crop and oesophagus), a mechanism analogous to a whistling kettle. As air flows past the orifice, certain sound frequencies are amplified by a Helmholtz resonator effect of the oesophagus chamber. Long sound units occur during inflation, while short sound units occur during deflation. Several other insects have been reported to produce sounds by forced air, but the aeroacoustic mechanisms of such sounds remain elusive. Our results provide evidence for this mechanism by showing that caterpillars employ mechanisms similar to rocket engines to produce sounds.

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Section: Function and Evolutionmentioning

confidence: 99%

Section: Function and Evolutionmentioning

confidence: 99%

Vocalization in caterpillars: a novel sound-producing mechanism for insects

Rosi-Denadai

Scallion

Merrett

et al. 2018

Journal of Experimental Biology

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“…; Dookie et al . ). Recent studies suggest that these acoustic signals are directed primarily to vertebrate predators (Bura et al .…”

Section: Introductionmentioning

confidence: 97%

“…; Dookie et al . ). Despite the diversity of defensive sounds, their functions and the significance of their varied characteristics are poorly understood (Dookie et al .…”

Section: Introductionmentioning

confidence: 97%

Acoustic stimuli from predators trigger behavioural responses in aggregate caterpillars

Breviglieri

Romero

2019

Austral Ecology

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Prey detect their predators through predator signals and cues and, consequently, respond with antipredatory behaviours to inhibit the action of their aggressors. Lepidopterans can intercept signals emitted by predators and may defend themselves through chemical, morphological or behavioural responses. In this study, we investigated the effect of acoustic stimuli of different predators on defensive behaviour of gregarious caterpillars. Our results demonstrated that Hylesia nigricans (Lepidoptera, Saturniidae) caterpillars alter their behaviour (i.e. abruptly raising the head) in response to the acoustic stimulus of the predators (i.e. predation risk signals from birds and wasps). The magnitude of this response depended on predator identity and caterpillar body size. Larger caterpillars responded more strongly to predatory stimuli than smaller caterpillars. However, regardless of the size of the caterpillars, they responded more strongly to the stimuli of wasps. In addition, we identified that H. nigricans caterpillars emit ultrasonic noise after detecting the stimuli of the predatorsthis noise seems to function as an alert about the risk of predation during the early stages of development (second and fifth instars). The duration of ultrasonic emission (i.e. milliseconds) increases with the number of repetitions of the stimuli (i.e. wing-beat sounds of the wasps and insectivorous birds). These results provide novel information about predation risk in interactions among caterpillars and their predators, and indicate possible communication among invertebrates mediated by the risk of predation.

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“…Eyespots are also found in a variety of other taxa (Skelhorn, Holmes, Hossie, et al 2016), and other forms of deimatic display are also found in insects (Maldonado 1970;Kang et al 2016;Umbers and Mappes 2015), molluscs (Staudinger et al 2011), amphibians, fishes, etc. (Edmunds 1974), including deimatic displays in non-visual sensory modalities (Dookie et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Two Models of Predator Decision Making Under Uncertainty

Dewan¹

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Predators are faced with an uncertain world. The presence of anti-predator defences, means that any potential prey item may actually be unpalatable, outright toxic, difficult to catch, or cause harm. In order to deal with this uncertainty regarding profitability, predators need strategies to make good decisions on what to attack based on the information about potential prey available to them. I develop two models of optimal decision making for predators. The first deals with generalizing from experience to novel prey types: I develop a Bayesian model framework that treats generalization as a process of learning about the distribution of prey in the environment, and apply it to a problem in generalization. The second deals with startle displays: I develop an extension of signal detection theory to cases where continued examination is possible, and apply it to predators faced with startle displays. ii ACKNOWLEDGEMENTS Firstly, I would like to thank my supervisor, Tom Sherratt for all his support and assistance over the course of my MSc. Every time I come out of a meeting with him, I feel better about the work I've done, and more optimistic about and better prepared for the next steps of my project. I've learned a great deal over the past two years, and I've had a great time doing it. I'm very grateful to have had the opportunity to work with Tom.

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Why do caterpillars whistle at birds? Insect defence sounds startle avian predators

Cited by 23 publications

References 41 publications

Vocalization in caterpillars: a novel sound-producing mechanism for insects

Vocalization in caterpillars: a novel sound-producing mechanism for insects

Acoustic stimuli from predators trigger behavioural responses in aggregate caterpillars

Two Models of Predator Decision Making Under Uncertainty

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