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Theoretical Work

Extension of the Socioecological Model

Male intrasexual competition and relationships have never been investigated in the same systematic manner as female social relationships. It has been recognized early that males either contest or scramble for access to fertile females. But relevant comparative tests are lacking and it has been ignored that male intrasexual competition may occur both within and between groups. As with females competitive regimes in males are best defined according to patterns of reproductive skew in relation to group size. Preliminary investigations have shown that applying the same principles used to explain the evolution of female social relationships has the potential to integrate much of the current knowledge (e.g. variation in number of males per group, patterns of sexual dimorphism, reproductive skew models, variation in coalition type, reconciliatory tendencies, sexual conflict) into one theoretical framework. Moreover, our framework includes the following ecological factors on male social relationships (1) influence of folivory vs. frugivory on flexibility in male time budgets and hence monopolization abilities, (2) large scale patchiness of habitat putting extra-group males to energetic disadvantage, (3) seasonal effects on energetic costs of mate guarding, (4) group density influence on extra-group paternity, and (5) pure mating scrambles leaving potential for food competition to determine male relationships. We use comparative data to test this extension of the model.

 
     
   
     
  This recent mathematical model by Shuster and Wade (2003) shows how the potential for sexual selection changes with changing female group size (m*) and reproductive synchrony (t*). It explains how changes in two continuous predictors can yield distinct classes in a dependent variable that allow for the definition of just a few competitive regimens.