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Predators' decisions to eat defended prey depend on the size of undefended prey

Lookup NU author(s): Dr Christina Halpin, Dr John Skelhorn, Professor Candy Rowe

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

Naive predators can learn to recognise and avoid aposematic prey that have evolved conspicuous colours and/or markings to advertise their toxins. However, once predators have learned to associate the warning coloration with toxicity they may still include aposematic prey in their diets, to gain the nutrients that they contain. Prey size is widely reported to correlate with nutritional content, yet we don’t know how prey size affects predators’ decisions to eat aposematic prey. Here, we used a well-established system of wild-caught European starlings (Sturnus vulgaris) foraging on mealworms (Tenebrio molitor) to test how the size of undefended (water-injected) and defended (quinine-injected) prey affected birds’ decisions to eat toxic prey. We found that: (i) birds ate fewer defended prey and less quinine when undefended prey were large than when they were small; and (ii) the size of the defended prey did not affect the numbers eaten. The birds appeared to be carefully managing their toxin burden, providing the first empirical support for the idea that detoxification processes limit the ingestion of toxic prey. In addition, the birds did not learn to discriminate between defended and undefended prey based on size, but only on the basis of colour. This suggests that colour signals may be more salient to predators than size differences, allowing Batesian mimics to benefit from aposematic models even when they differ in size. Our findings provide an insight into the mechanisms underlying the decisions made by avian predators towards toxic prey, with implications for the evolution of prey defences.


Publication metadata

Author(s): Halpin CG, Skelhorn J, Rowe C

Publication type: Article

Publication status: Published

Journal: Animal Behaviour

Year: 2013

Volume: 85

Issue: 6

Pages: 1315-1321

Print publication date: 01/06/2013

Online publication date: 17/04/2013

Acceptance date: 05/03/2013

ISSN (print): 0003-3472

ISSN (electronic): 1095-8282

Publisher: Elsevier

URL: http://dx.doi.org/10.1016/j.anbehav.2013.03.021

DOI: 10.1016/j.anbehav.2013.03.021


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