Courtship communication in the wild chimpanzees of Budongo, Uganda

Abstract

This thesis examines wild chimpanzee mating behaviour, and considers in particular the role of communication during mating. Previous studies have focused on compiling behavioural ethograms, or on a small subset of courtship signals. More generally, research on chimpanzee sexual behaviour has rarely looked at intentional communication, but instead focused on a handful of courtship tactics, such as male long-term aggression or female proceptive behaviour, despite every indication across great ape species that intentional communication is important in courtship. On these grounds, I undertook an examination of both male and female communication in the Sonso chimpanzee community in the Budongo forest, Uganda.

The chapters comprising this thesis examine female copulation calling, male gestural displays during opportunistic mating, male gestural displays during consortship, and the role of female preferences on male courtship displays. Parous and nulliparous females have different calling strategies based on high-ranking male audience, copulation duration, and level of female competition. Males use a small subset of their gestural repertoire to solicit for copulation, concentrating the majority of gesturing in 5 gesture types. Gestures were successful for both high- and low-ranking males, although high-ranking males employed more agonistic gestures than low-ranking males. All males showed high rates of persistence following failure, especially during consortship. Overall, the likelihood of copulation was not influenced by traditional courtship factors such as vigour, but rather was dependent on effective use of gestures.

My research shows that both male and female chimpanzees use communication tactically during courtship: for females, this is evidenced by differing copulation call strategies in parous and nulliparous females. For males, social status plays less of a role than persistence for achieving copulation, although high-ranking males do use coercive gestures more frequently. Overall, I show that communication is an effective tool for answering questions about mating strategies in chimpanzees.