Figure 3.

Monthly aggression given by male chimpanzees by rank (n=910 months, 17 adults). Across contexts, high-ranking males were more aggressive than low-ranking males. Males were more aggressive in months when they associated more with parous estrous females (top panel) and in months with more days of instability in the dominance hierarchy (bottom panel). Parous estrous females had a greater effect on the amount of aggression given by higher-ranked males. Counts were based on a mean monthly observation time of 122 hours. Although instability and presence of estrous females were continuous variables in the models, for visualization purposes they are shown here as categorical variables. The shaded areas indicate 95% confidence intervals. (Figure S2 plots the same data showing individual points.)