Play as an indicator of animal welfare in a captive colony of Cebus apella

Play behaviour is a potential indicator of animal welfare. The self-rewarding nature of play and its tendency to spread within the group make this behaviour an excellent mean to estimate the current (and potentially future) wellbeing of a single individual, as well as of its entire social group. Visual communication has a fundamental role in triggering and regulating a playful session by modulating the patterns through inhibitory and reinforcement mechanisms. This research evaluates the individual and collective welfare of a captive colony of 20 Cebus apella through the description of playful patterns and facial expressions. Facial expressions were then subdivided into two categories: playful facial expressions (i.e. those occurring exclusively during play) and all the others (i.e. those occurring also in other contexts). As occurs in numerous mammalian species, immature subjects showed a higher frequency of play behaviour than adults. Among adults, males played more than females. Although playful facial expressions were displayed at similar frequencies in all age/sex classes, the other facial expressions were exhibited more frequently by females and especially when the playmate could visually perceive the signal. Within the studied colony, only three subjects were never observed playing. These animals were socially isolated and characterized by anomalous behaviours. Taken together, all these findings strongly suggest that play behaviour should be considered as a highly reliable and accurate indicator of captive animal welfare.