Aj Bb Bf Kk Lb Lm Ms Sl St Sy Tu Yb

Male

Fig. 3.2 Median dyadic rates of aggression for each of 13 male chimpanzees (Pan troglodytes) with 15 parous females. For each male, the median copulation rates were calculated with females who received above (white) or below (black) the median amount of aggression for that male. The difference was significant (Wilcoxon signed-rank test, p = 0.002). Data from Muller et al. (2007)

Prediction 3: Coercion is not simply an indirect cost of female choice. One of the noteworthy aspects of this study is its test of the alternative hypothesis that male aggression reflects female choice. Muller and colleagues marshal several lines of evidence to reject the possibility that intersexual aggression is a by-product of female mating preferences for aggressive males. First, male rank was uncorrelated with aggression directed at females. Second, the relationship between male coercion and mating success with targeted females also held for low-ranking males as well, who are arguably less preferred sexual partners. Finally, a matrix partial correlation analysis revealed a significant association between male aggression directed at individual females and the copulation rate with those females, controlling for time spent together.

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