Warning signals are an effective defence strategy for aposematic prey, but only if they are recognized by potential predators. If predators must eat prey to associate novel warning signals with unpalatability, how can aposematic prey ever evolve? Using experiments with great tits (Parus major) as predators, we show that social transmission enhances the acquisition of avoidance by a predator population. Observing another predator’s disgust towards tasting one novel conspicuous prey item led to fewer aposematic than cryptic prey being eaten for the predator population to learn. Despite reduced personal encounters with unpalatable prey, avoidance persisted and increased over subsequent trials. Next we use a mathematical model to show that social transmission can shift the evolutionary trajectory of prey populations from fixation of crypsis to fixation of aposematism more easily than was previously thought. Therefore, social information use by predators has the potential to have evolutionary consequences across ecological communities.
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We are grateful to N. Boogert for suggesting the video playback method, D. Abondano Almeida, S. Burdillat and M. Brain for help with the experiments, J. Valkonen for valuable technical help, V. Franks for providing illustrations, and H. Nisu and staff at the Konnevesi Research Station for hosting the experiments and caring for the birds. P. Klopfer provided helpful discussion and the manuscript was improved by comments from N. Boogert, L. Hämäläinen and M. Puurtinen. R.T. was funded by an Independent Research Fellowship from the Natural Environment Research Council (NE/K00929X/1). J.M. and H.K. were supported by the Academy of Finland Centre of Excellence in Biological Interactions (project number 252411) and H.K. was additionally supported by the Swiss National Foundation.
Supplementary Methods, Supplementary References, Supplementary Figures 1–3, and Supplementary Tables 1–2.
Example of social information treatment from validation experiment.
Example of control from validation experiment.
Example of social information treatment from predation experiment.
Example of control from predation experiment.