Body size matters for aposematic prey during predator aversion learning

Karen E Smith,Christina G Halpin,Candy Rowe

doi:10.1016/j.beproc.2014.09.026

Karen E Smith, Christina G Halpin + Show 1 more

Open Access

https://doi.org/10.1016/j.beproc.2014.09.026

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Journal: Behavioural Processes	Publication Date: Sep 23, 2014
Citations: 20	License type: cc-by

Affiliation: University of Newcastle Australia

Abstract

Aposematic prey advertise their toxicity to predators using conspicuous warning signals, which predators learn to use to reduce their intake of toxic prey. Like other types of prey, aposematic prey often differ in body size, both within and between species. Increasing body size can increase signal size, which make larger aposematic prey more detectable but also gives them a more effective and salient deterrent. However, increasing body size also increases the nutritional value of prey, and larger aposematic prey may make a more profitable meal to predators that are trading off the costs of eating toxins with the benefits of ingesting nutrients. We tested if body size, independent of signal size, affected predation of toxic prey as predators learn to reduce their attacks on them. European starlings (Sturnus vulgaris) learned to discriminate between defended (quinine-injected) and undefended (water-injected) mealworm prey (Tenebrio molitor) using visual signals. During this process, we found that birds attacked and ate more defended prey the larger they were. Body size does affect the probability that toxic prey are attacked and eaten, which has implications for the evolutionary dynamics of aposematism and mimicry (where species share the same warning pattern).

Highlights

Aposematic insects advertise their defensive toxins to predators using a variety of conspicuous warning signals (Poulton, 1890; Rowe & Guilford, 2001; Mappes et al, 2005; Rowe & Halpin, 2013)
Defended prey were attacked and eaten more often across the seven learning sessions with increasing body size, differences could not be detected in the final session
This shows that body size per se, independent of colour signal, can alter predatory behaviour and increase the costs to larger-bodied aposematic prey during the learning process

Summary

Introduction

Aposematic insects advertise their defensive toxins to predators using a variety of conspicuous warning signals (Poulton, 1890; Rowe & Guilford, 2001; Mappes et al, 2005; Rowe & Halpin, 2013). Hunting predators, including many birds and insect species, learn to associate a conspicuous visual signal with toxicity and the probability that they will attack an aposematic prey declines with repeated encounters Birds learn about the nutritional qualities as well as the toxin content of aposematic prey, and are more likely to include toxic prey in their diets when they are nutritionally enriched (Halpin et al, 2014). We do not know whether the nutrient content of aposematic prey affects mortality during the learning process

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