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Aposematic prey warn predators of their toxicity using conspicuous signals. However, predators are known to include aposematic prey in their diets even when they know that they are defended and contain toxins. Eating aposematic prey allows predators to access the valuable nutrients that they contain, and it is predicted that predators should eat aposematic prey when the benefits of eating the nutrients outweigh the costs of ingesting their toxins. [GW1] One factor that should affect this trade-off is temperature, since the energetic requirements of predators should change with ambient temperature. [GW2] Although there is some observational evidence to suggest that temperature might affect predators' decisions to eat aposematic prey, there has been no experimental test of this idea. In this study, we found that European starlings (Sturnus vulgaris) increased their consumption of mealworm prey (Tenebrio molitor) containing quinine (a mild toxin) when the ambient temperature was reduced from 20°C to 6°C. This suggests that selection pressures from predators on aposematic prey in the wild will change with temperature and/or latitude, and provides an explanation for temperature-dependent expression of conspicuous warning signals and aggregation behaviours. surprisingly, we found little evidence that the birds were in a poorer energetic state at lower temperatures, although they were less active at 6°C compared to 20°C. This suggests that changes in their energy budget may have driven birds’ decisions to eat more defended prey at lower temperatures, our results highlight that changes in climate could affect the evolutionary dynamics of defensive strategies.
Author(s): Chatelain M, Halpin CG, Rowe C
Publication type: Article
Publication status: Published
Journal: Animal Behaviour
Print publication date: 01/10/2013
Online publication date: 16/08/2013
Acceptance date: 03/07/2013
Date deposited: 10/01/2014
ISSN (print): 0003-3472
ISSN (electronic): 1095-8282
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