The role of grunts in reconciling opponents and facilitating interactions among adult female baboons

Female baboons, Papio cynocephalus ursinus, often grunt when approaching lower-ranking females. These grunts appear to have a mollifying effect on subordinates. Observations of 19 adult females conducted over an 11-month period in the Okavango Delta, Botswana, revealed that high-ranking females were less likely to supplant more subordinate females, and more likely to engage in friendly interactions with them, when they grunted to their lower-ranking partners than when they remained silent. Grunts also functioned to reconcile opponents following fights. In a series of playback experiments, subjects were played the potentially threatening scream of a higher-ranking female that had recently attacked them. Subjects responded less strongly to these screams when the dominant opponent had apparently reconciled after the fight by grunting to them than when the opponent had not interacted with them again. Subjects’ responses after a vocal ‘reconciliation’ were similar to their responses following a control period when the two females had not interacted at all. Even in the absence of more overt friendly behaviour, therefore, baboon grunts act to restore the relationship of opponents to baseline tolerance levels.