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Paper: The contingencies of group size and vigilance

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  • Stephan Pickering
    S.B. Ale & J.S. Brown, 2007/8. The contingencies of group size and vigilance. Evolutionary Ecology Research IN PRESS. ABSTRACT. BACKGROUND: Predation risk
    Message 1 of 1 , Nov 2, 2007
      S.B. Ale & J.S. Brown, 2007/8. The contingencies of group size and vigilance. Evolutionary Ecology Research IN PRESS. ABSTRACT.
      BACKGROUND: Predation risk declines non-linearly with one's own vigilance and the vigilance of others in the group (the many-eyes effect). Furthermore, as group size increases, the individual's risk of predation may delince through dilution with more potential victims, but may increase if larger groups attract more predators. These are known, respectively, as the dilution effect and the attraction effect.
      ASSUMPTIONS: Feeding animals use vigilance to trade-off food and safety. Net feeding rate declines linearly with vigilance.
      QUESTION: How do the many-eyes, dilution, and attraction effects interact to influence the relationship between group size and vigilance behavior?
      MATHEMATICAL METHODS: We use game theory and the fitness generating function to determine the ESS level of vigilance of an individual within a group.
      PREDICTIONS: Vigilance decreases with group size as a consequence of the many-eyes and dilution effects, but increases with group size from the attraction effect, when they act independent of each other. Their synergetic effects on vigilance depend upon the relative strengths of each and their interactions. Regardless, the influence of other factors on vigilance -- such as encounter rate with predators, predator lethality, marginal value of energy and value of vigilance -- decline with group size.
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      STEPHAN PICKERING / Chofetz Chayim ben-Avraham
      The Dinosaur Fractals Project
      2333 Portola Drive # 4
      Santa Cruz, California 95062-4250
      stephanpickering@...
      website: http://groups.yahoo.com/group/paleo_bio_dinosaur_ontology
      theropod research summarized: < www.dinodata.net > see PICKERING under their
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      IN PROGRESS; Mutanda Dinosaurologica: in memory of Samuel Paul Welles
      (9  November 1909--6 August 1997)
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