SPECIAL FEATURE: ORIGINAL ARTICLE Understanding the Variability of Gorilla Social Structure Sexual coercion and courtship by male western gorillas

Abstract Sexual coercion and courtship are possible explanations for why male primates may direct agonistic behavior towards females. If so, then in species where females exhibit mate choice by transferring between males: (a) females who are not lactating (potential migrants) should receive more agonistic behavior than other females, (b) males should exhibit more agonistic behavior towards females during intergroup encounters than when no rival males are nearby, and (c) males should show more herding behavior when their group contains potential migrant females. We tested those hypotheses in a population of approximately 150 western gorillas at Mbeli Bai, northern Congo. We also tested whether difference in male pheno-typic traits influenced their rates of agonistic behavior towards females. Of the 332 observed cases of male ago