Embracing in a female bonded monkey species (Theropithecus gelada)

In several primate species, including humans, embracing predicts the level of affiliation between subjects. To explore the functional meaning of embracing, we selected Theropithecus gelada as a model species. The basic level of the gelada society is the 1-male unit, and the integrity of the group is maintained by the strong bonds between females. In our study group, we observed 3 different kinds of embracing: the frontal and side embraces involving a face-to-face and chest-to-chest interaction and the posterior embrace that consists in putting the arms around conspecifics' back and posing a cheek on it. We verified that the quality of relationships between subjects predicts the type of embracing. Frontal and side embraces were more frequent between females sharing strong bonds. Posterior embracing was randomly distributed. We found a high level of female embracing among the mothers during the first months of lactation. This may improve female cohesiveness against males, thus reducing the risk of infanticide, which is particularly high in geladas. Embracing seems also to act as an ice-breaker favoring grooming. Female embracing could be an affiliative strategy that has evolved to maintain group integrity and high social cohesion among females, especially mothers.