Bonobos and chimpanzees overlap in sexual behaviour patterns during social tension.

Abstract

Sexual behaviour during tense social situations is extensively documented in various animals. Bonobos, our closest living relatives alongside chimpanzees, habitually perform genital contacts during social tension, which is thought to enhance cooperation and conflict management. While chimpanzees also engage in genital contacts during these contexts, the two sister species have yet to be compared systematically, which may have led to inaccurate assumptions. To address this, we directly compared genital and non-genital affiliation among sanctuary-living bonobos and chimpanzees during two socially tense contexts-post-conflict and pre-feeding. Following conflicts, we observed triadic affiliation between bystander-victim pairs and reconciliation between aggressor-victim pairs. Additionally, we experimentally induced a pre-feeding context to examine affiliative contact between group members. During post-conflict contexts, bonobos used genital contacts more than chimpanzees. However, both species used genital contacts comparably during pre-feeding affiliation, although female bonobos and male chimpanzees were most likely to initiate them. In addition, we found group-level variation indicating an influence of demographic factors. Our results indicate that chimpanzees and bonobos overlap significantly in their use of genital contacts during periods of social tension. Given similar evidence in humans, our results support the notion that this was a trait probably also present in our last common ancestor.