Abstract

In primates, copulation calls are thought to increase male-male competition, leading to a decrease in infanticide risk through concentrating or confusing paternity in polygynandrous species. Accordingly, their function in species where females mate monandrously within sexual cycles and paternity is concentrated, such as hamadryas baboons (Papio hamadryas), is not well understood. We propose that copulation calls in hamadryas baboons could serve to promote male takeovers in females belonging to small one-male, multifemale units (OMUs) and in females in large OMUs, but weakly bonded with the male, because these females could get benefits from transferring to other units. We studied copulation calls in a colony of hamadryas baboons consisting of 8 to 11 OMUs. We recorded 311 copulations involving adult females through behavioral sampling and documented the female’s reproductive state, the copulation outcome, the OMU size (to proxy male competitive ability), female-male grooming (to proxy the strength of female-male bond), the presence of female relatives of the copulating female in the unit, and whether she was transferred via male takeover in the next 2 years and 3 months. We found that copulation calls were more likely to be produced by females classified as strongly bonded to their males in small OMUs and by females classified as weakly bonded to their males in large OMUs. Moreover, females who produced copulation calls were more likely to be transferred to another unit during a male takeover. We argue that by calling, females instigate male-male competition, increasing the chance of male takeovers and thus expressing mate preferences even in a scenario of intense intersexual conflict. Larger, longitudinal studies are needed to test this hypothesis further. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.