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Evidence for the dilution effect in the selfish herd from fish predation on a marine insect


It has been proposed that a major factor underlying the evolution of gregarious behaviour is a reduction in the risk of being attacked by predators1–3. One way in which individuals may gain protection from predators by joining a group is through a simple ‘dilution’ effect—for any one predator attack, the larger the group of prey animals, the smaller is the chance that any particular individual will be the victim. We present here field observations of predation on a marine insect, in which it is possible, for the first time, to quantify the magnitude of the dilution effect and distinguish it from other benefits of group living.

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  1. Williams, G. C. Adaptation and Natural Selection (Princeton University Press, 1966).

    Google Scholar 

  2. Hamilton, W. D. J. theor. Biol. 31, 295–311 (1971).

    CAS  Article  Google Scholar 

  3. Alexander, R. D. A. Rev. Ecol. Syst. 5, 325–383 (1974).

    Article  Google Scholar 

  4. Bertram, B. C. R. in Behavioural Ecology (eds Krebs, J. B. & Davies, N. B.) 64–96 (Blackwell, Oxford, 1978).

    Google Scholar 

  5. Major, P. F. Anim. Behav. 26, 760–777 (1978).

    Article  Google Scholar 

  6. Calvert, W. H., Hedrick, L. E. & Brower, L. P. Science 204, 847–850 (1979).

    ADS  CAS  Article  Google Scholar 

  7. Birch, M. C., Cheng, L. & Treherne, J. E. Proc. R. Soc. B206, 33–53 (1979).

    ADS  CAS  Google Scholar 

  8. Foster, W. A. & Treherne, J. E. Proc. R. Soc. B206, 33–52 (1979).

    Google Scholar 

  9. Treherne, J. E. & Foster, W. A. Anim. Behav. 28, 1119–1122 (1980).

    Article  Google Scholar 

  10. Treherne, J. E. & Foster, W. A. Anim. Behav. 29 (in the press).

  11. Milinski, M. Z. Tierpsychol. 45, 373–388 (1977).

    Article  Google Scholar 

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Foster, W., Treherne, J. Evidence for the dilution effect in the selfish herd from fish predation on a marine insect. Nature 293, 466–467 (1981).

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