The effect of dominance hierarchy on the use of alternative foraging tactics: a phenotype-limited producing-scrounging game |
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Authors: | Zoltán Barta Luc-Alain Giraldeau |
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Institution: | (1) Department of Biology, Concordia University, Montréal, Quebec H3G 1M8, Canada, CA;(2) Department of Biology, Concordia University, Montréal, Quebec H3G 1M8, Canada Tel.: 1-514-848-3425; Fax: 1-514-848-2881; e-mail: giraluc@vax2.concordia.ca, CA |
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Abstract: | Group living is thought to be advantageous for animals, though it also creates opportunities for exploitation. Using food
discovered by others can be described as a producer-scrounger, frequency-dependent game. In the game, scroungers (parasitic
individuals) do better than producers (food finders) when scroungers are rare in the group, but they do worse when scroungers
are common. When the individuals' payoffs do not depend on their phenotype (i.e. a symmetric game), this strong negative frequency
dependence leads to a mixed stable solution where both alternatives obtain equal payoffs. Here, we address the question of
how differences in social status in a dominance hierarchy influence the individuals' decision to play producer or scrounger
in small foraging groups. We model explicitly the food intake rate of each individual in a dominance-structured foraging group,
then calculate the Nash equilibrium for them. Our model predicts that only strong differences in competitive ability will
influence the use of producing or scrounging tactics in small foraging groups; dominants will mainly play scrounger and subordinates
will mostly use producer. Since the differences in competitive ability of different-ranking individuals likely depend on the
economic defendability of food, our model provides a step towards the integration of social foraging and resource defence
theories.
Received: 30 July 1997 / Accepted after revision: 15 November 1997 |
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Keywords: | Dominance hierarchy Game theory Group foraging Phenotype limitation Producer-scrounger |
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