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The evolution of locomotory behavior in profitable and unprofitable simulated prey


Prey that are unprofitable to attack (for example, those containing noxious chemicals) frequently exhibit slower and more predicable movement than species that lack these defenses. Possible explanations for the phenomenon include a lack of selection pressure on unprofitable prey to avoid predators and active selection on unprofitable prey to advertise their noxiousness. We explicitly tested these and other hypotheses using a novel “artificial world” in which the locomotory characteristics (step size, waiting time, and angular direction) of artificial profitable and unprofitable computer-generated prey were subject to continued selection by humans over a number of generations. Unprofitable prey evolved significantly slower movement behavior than profitable prey when they were readily recognized as unprofitable, and also when they frequently survived predatory attacks. This difference arose primarily as a consequence of more intense selection on profitable prey to avoid capture. When unprofitable prey were very similar (but not identical) in morphological appearance to profitable prey, unprofitable prey evolved particularly slow movement behavior, presumably because when they were slow-moving they could be more readily recognized as being unprofitable. When unprofitable prey were constrained to move slowly, a morphologically identical profitable prey species evolved locomotor mimicry only when it had no more effective means of avoiding predation. Overall, our results provide some of the first empirical support for a number of earlier hypotheses for differences in movement between unprofitable and profitable prey and demonstrate that locomotor mimicry is not an inevitable outcome of selection even in morphologically similar prey.

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We thank the students of Carleton University for their participation. All volunteers gave their informed consent prior to their inclusion in the study. The research was approved by Carleton University Research Ethics Committee and conducted according to the guidelines set out in Canadian Tri-Council Policy Statement on Ethical Conduct for Research Involving Humans. Rebecca Tittler gave helpful statistical advice. We are also very grateful to our referees who made a number of constructive comments that have helped improve the clarity of our manuscript.

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Correspondence to Thomas N. Sherratt.

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Sherratt, T.N., Rashed, A. & Beatty, C.D. The evolution of locomotory behavior in profitable and unprofitable simulated prey. Oecologia 138, 143–150 (2004).

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  • Aposematism
  • Warning signals
  • Mimicry
  • Movement
  • Locomotion