Sociality, Dominance Rank, and Hair Cortisol in Tufted Capuchin Monkeys

Abstract

When an animal perceives a threat to its well-being, glucocorticoid hormones such as cortisol are released to help the animal avoid that threat. This can be lifesaving in cases of predation or food scarcity, but chronically high glucocorticoid levels are associated with health risks such as cardiovascular disease, compromised immunity, and decreased neuroplasticity. Social relationships can reduce cortisol levels through positive social interactions, but can also cause chronically high cortisol when those interactions are unpredictable and aggressive in nature. Understanding the interplay between cortisol and social relationships is essential to understanding how an individual’s social situation relates to their physiological and psychological well-being. We studied this relationship in 16 socially-housed captive brown capuchin monkeys (Cebus apella) by comparing long term hair cortisol with behavioral measures of social integration and success in the group. Hierarchical multiple regression revealed a relationship between long term cortisol and dominance rank and centrality to the social contact network; centrality to the contact social network was the most important predictor of hair cortisol levels while explaining the variation predicted by dominance rank. These results suggest that contact is an important metric of close social bonds in capuchins, and that social network measures are useful for capturing the complexity of animals’ social lives and assessing how those relationships relate to their physiological and psychological well-being