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Social transmission of avoidance among predators facilitates the spread of novel prey


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.

Author information

R.T. conceived the project and designed and conducted the experiments and analyses. J.M. designed the experiments and assisted with the analyses. H.K. conceived and conducted the modelling. All authors wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Correspondence to Rose Thorogood.

Supplementary information

  1. Supplementary Information

    Supplementary Methods, Supplementary References, Supplementary Figures 1–3, and Supplementary Tables 1–2.

  2. Life Sciences Reporting Summary

  3. Supplementary Video 1

    Example of social information treatment from validation experiment.

  4. Supplementary Video 2

    Example of control from validation experiment.

  5. Supplementary Video 3

    Example of social information treatment from predation experiment.

  6. Supplementary Video 4

    Example of control from predation experiment.

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Fig. 1: Latency to forage and initial prey choices.
Fig. 2: Relative predation risk for novel conspicuous prey versus the cryptic phenotype.
Fig. 3: An example of the temporal dynamics predicted if social information is available.
Fig. 4: Threshold frequency of aposematic prey necessary for the phenotype to reach fixation.
Fig. 5: Effect of social transmission on the initial population size required for aposematic prey to reach fixation.