Use and Function of Bared-teeth Display After Aggression During Feeding in Japanese Macaques (Macaca fuscata)

Abstract Social communication, based on signals such as facial expressions, is a fundamental aspect of group living in animals, shaping cooperation, competition, and the regulation of conflicts. The bared-teeth display (BTD) has traditionally been considered a signal used by subordinate individuals to convey submissions to dominant individuals in macaque species that exhibit strict dominance hierarchies. Although previous studies have regarded BTD primarily as a signal of dominance–submission relationships, its other potential determinants and functions remain poorly understood. To address this gap, we investigated the factors influencing the occurrence of BTD and their effects in a provisioned group of 129 Japanese macaques ( Macaca fuscata ) in Katsuyama, Okayama Prefecture, Japan. We observed aggressive interactions during feeding and subsequent behaviors of victims for 1 minute following each event to analyze how BTD influenced post-conflict dynamics. We recorded counter-aggression only twice during the 100 days of the study, and BTD was consistently performed unidirectionally by the victim. Victims were more likely to show BTD when they were kin (mother-daughter, sister, or grandmother–granddaughter) to the aggressor, when the aggression involved physical contact, when the rank distance between the two individuals was smaller, and when the victim was closer to the aggressor at the end of the event. Furthermore, performing BTD reduced the likelihood of re-aggression and increased the likelihood of proximity to the aggressor 1 minute after the event. These findings suggest that BTD in despotic macaques may function not only to convey submission, but also to serve as an appeasement signal in feeding contexts.