Female chimpanzees adjust copulation calls according to reproductive status and level of female competition

Abstract

Female chimpanzees (Pan troglodytes) are usually depicted as sexually submissive and bound by male coercion, because males are able to monopolize oestrous females, limiting a female's options for mate choice. We present behavioural data from a group of wild chimpanzees during a rare period in which up to 10 females cycled simultaneously, which prevented males from monopolizing oestrous females, thus changing the dynamic of male-female sexual interactions. Overall, we found that nulliparous and parous females employed different copulation calling strategies, reflecting their relative reproductive attractiveness and social standing within the community. Male partner rank, copulation duration, and dominant male audience further influenced calling behaviour, and there was a non-significant trend for females to increase calling as the number of cycling females increased. We conclude that female chimpanzees are capable of adjusting their copulation calling flexibly, by taking into account their own sexual attractiveness in order to incite male competition.