Sex differences in copulation attempts in wild bonobos at Wamba

Area of Science:

• Primate Behavior
• Ethology
• Primatology

Background:

• Sexual behavior in non-human primates is crucial for understanding mating systems and social structures.
• Bonobos (Pan paniscus) exhibit unique social and sexual behaviors compared to their closest relatives, chimpanzees (Pan troglodytes).
• Previous research indicates a strong correlation between female perineal swelling and sexual activity in chimpanzees.

Purpose of the Study:

• To investigate sex differences in the initiation and acceptance of copulation attempts in wild bonobos.
• To compare bonobo sexual behavior patterns, particularly concerning female perineal swelling, with those of chimpanzees.
• To explore the potential evolutionary significance of female receptivity during non-swelling phases in bonobos.

Main Methods:

• Observational study of a wild bonobo group in Wamba, Congo.
• Analysis of behavioral sequences, focusing on approach, courtship, solicitation, and copulation attempts.
• Categorization of sexual interactions based on female perineal swelling status (swelling vs. non-swelling phase).

Main Results:

• Male bonobos predominantly initiated copulation attempts through approach and courtship behaviors.
• Females in the swelling phase were solicited more frequently and accepted copulation more readily than those in the non-swelling phase.
• A significant proportion of copulation attempts (one-third) involved females in the non-swelling phase, with half of these attempts being accepted, contrasting sharply with chimpanzee behavior.

Conclusions:

• Bonobo sexual behavior is distinct from chimpanzees, with females exhibiting receptivity outside the swelling phase.
• The perineal morphology of females in the non-swelling phase may offer some sexual attractiveness to males.
• Female receptivity during non-swelling phases might serve to mitigate male-male sexual competition and enhance female social status.