Bent posture improves the protective value of bird dropping masquerading by caterpillars

Animal Behaviour

Volume 105, July 2015, Pages 79–84

• Toshitaka N. Suzuki^{a, , †,} ,
• Reika Sakurai^{b, †}

• ^a Department of Evolutionary Studies of Biosystems, The Graduate University for Advanced Studies, Kanagawa, Japan
• ^b Department of Life Science, Rikkyo University, Tokyo, Japan

Received 16 January 2015, Revised 9 February 2015, Accepted 2 April 2015, Available online 16 May 2015

MS. number: 15-00040

doi:10.1016/j.anbehav.2015.04.009

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Highlights

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We tested whether a bent posture enhances bird dropping masquerade in caterpillars.

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Bent posture improved the survival of bird dropping-coloured caterpillar models.

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Bent posture did not affect the survival rate of green caterpillar models.

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We show for the first time the protective value of posture in masquerading prey.

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Masquerade describes a defence by animals that have evolved to closely resemble inedible objects such as twigs, stones or bird droppings. Animals that masquerade often match their models in size or shape, and may even adopt specific postures in order to enhance their resemblance, causing predators to misclassify them as their model objects. The caterpillars of some moth species resemble bird droppings, and bend their bodies while resting on branches or leaves. We hypothesized that such bending might enhance the caterpillars' resemblance to real bird droppings. In this study, we tested this hypothesis by pinning artificial caterpillars with green or bird dropping coloration onto tree branches in both straight and bent postures, after which we exposed them to bird predation in the wild. We found that the adoption of a bent posture resulted in a lower attack rate by birds on the artificial caterpillars with the bird dropping coloration, while green caterpillars experienced no benefit from the same treatment. This study is the first experimental demonstration of the protective value of a specific posture in masquerading prey, and highlights the importance of considering an organism's shape and posture in the study of masquerade.

Keywords

• bird dropping masquerade;
• caterpillar;
• defensive coloration;
• posture;
• predation

Correspondence: T. N. Suzuki, Department of Evolutionary Studies of Biosystems, The Graduate University for Advanced Studies, Hayama, Miura-gun, Kanagawa 240-0193, Japan.

†

The authors contributed equally to this work.

Copyright © 2015 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.