Yawning and scratching contagion in wild spider monkeys (Ateles geoffroyi)

Behavioural contagion is a widespread phenomenon in animal species, which is thought to promote coordination and group cohesion. Among non-human primates, however, there is no evidence of behavioural contagion in Platyrrhines (i.e. primates from South and Central America) yet. Here, we investigated whether behavioural contagion is also present in this taxon, by assessing yawning and scratching contagion in a wild group (N = 49) of Geoffroy's spider monkeys (Ateles geoffroyi). We conducted focal samples to examine whether individuals observing the triggering event (i.e. a naturally occurring yawning or scratching event in the group) would be more likely to yawn or scratch in the following 3 min, as compared to individuals who did not observe the triggering event. We ran generalized linear mixed models using a Bayesian approach, and found that the probability of yawning and scratching was higher for individuals observing others yawning and scratching, respectively, as compared to individuals who did not observe such an event. Behavioural contagion did not vary depending on the observer's sex, kinship or relationship quality with the individual performing the triggering event. These findings provide the first evidence for yawning and scratching contagion in a wild group of spider monkeys, and importantly contribute to the debate about the evolutionary origins of behavioural contagion in primates.

Automated summary

A study found that yawning and scratching contagion exists in a wild group of Geoffroy's spider monkeys. Individuals who observed others yawning or scratching were more likely to exhibit the behavior themselves. This finding is important for understanding the origins of behavioral contagion in primates.