Social bias affects vigilance contagion in Japanese macaques

Abstract

In group-living animals, behavioural contagion is associated with essential functions such as information acquisition and group cohesion. Studies have shown that several social factors (e.g. familiarity, dominance, the mother–offspring relationship) affect behavioural contagion. However, as previous research has focused mostly on play signals and yawning, it is unclear whether such social biases apply to all types of contagious behaviour. Using data from a group of Japanese macaques, Macaca fuscata , we investigated the social biases associated with the contagion of vigilance. Our findings revealed that vigilance exhibited by a given individual was more contagious to lower-ranked than to higher-ranked individuals. In addition, vigilance was more contagious to mothers from their offspring than vice versa. Thus, the susceptibility to vigilance exhibited by others varies according to the social status of each individual and the relationship between each pair of individuals. By contrast, we did not find any effects of kinship on vigilance contagion. This implies that familiarity bias, which is often reported to be associated with the contagion of yawning and play signals, does not influence vigilance contagion. Overall, our findings indicate that behavioural contagion does not occur with equal likelihood but is affected by the interplay between the type of behaviour and social structures. • We examined how social biases affect vigilance contagion in Japanese macaques. • Vigilance was more contagious to lower-ranked than to higher-ranked individuals. • Vigilance was unidirectionally contagious from offspring to their mothers. • Kinship did not influence vigilance contagion. • Social bias may vary between vigilance and other contagious behaviours like yawning.