Behavioral Contagion in Wild Ecuadorian White-Fronted Capuchins (Cebus aequatorialis).

Behavioral contagion is spread across animal species and is thought to promote social cohesion and group synchronization. While yawn contagion has been extensively studied, scratch contagion remains comparatively under-researched, particularly in wild populations. We investigated whether yawn and scratch contagion occurred in a wild group of Ecuadorian white-fronted capuchins (Cebus aequatorialis, N = 16) at La Hesperia Cloud Forest Reserve in Ecuador. We assessed whether scratching or yawning were more likely to occur after observing a conspecific (i.e., the trigger) scratching or yawning (i.e., triggering event) compared to a control condition. We further examined whether this effect was modulated by the (a) individual characteristics of the trigger and the partner (sex, age category, and social centrality), and (c) dyadic-level variables (sex and age similarity, social bond strength). Our results showed that the probability of scratching was significantly higher in individuals that observed the triggering event, as compared to individuals that did not observe it. However, scratch contagion was not modulated by any of the individual or dyadic predictors included in our models. No yawning events were recorded during the study period. Our findings contribute to understanding scratch contagion in wild primates and underscore the need for further exploration of social factors influencing behavioral contagion.