Individual variation and indirect social effects in Producer-Scrounger behavior in the House Sparrow, Passer domesticus
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- Institutt for biologi 
Game theory is a scenario where, at its simplest, two alternative tactics may yield different costs and benefits. Many organisms are tied to a dynamic environment where the actions, social behaviors, or even presence of each organism may affect one another such as with the producing and scrounging model. Producing involves searching for unexploited resources, and scrounging involves competing for already discovered resources. The unique approach of this study is its ability to measure individual variation in a game theory context for producing and scrounging behavior. Passer domesticus was chosen as the model species to test the following predictions on producing/scrounging: 1) Individuals differ consistently in their average behavior across the pair-wise trials, 2) Individuals have different propensities in switching between producer/scrounger strategies (plasticity), and 3) A particular opponent will influence the behavior of all the other individuals in that group (indirect social effect), to varying degrees. The following was demonstrated with 30 individuals (21 male, 15 female) over 278 trials: 1) Individual, repeatable variation in an individual s producing and scrounging, 2) Individuals exhibited repeatable plasticity that varied from one another for producing and scrounging, and 3) A opponent s identity significantly affected all other individuals scrounging, and to varying degrees, but had no effect on others producing. Therefore, this study provides evidence for significant opponent effects and indirect effects, as well as the presence of repeatable strategies, variation, and plasticity for individuals.