Tomeo, O. B., Sosnowski, M. J., Benitez, M. E. et al. 2018. The relationship between self-directed anxiety behaviors and cortisol in socially housed capuchin monkeys (Cebus [Sapajus] apella). American Journal of Primatology 80(S1), 32 (40th Meeting of the American Society of Primatologists Scientific Program, Abstract #64).
Non‐human primates are excellent models for the study of human social anxiety. Both humans and non‐human primates form complex relationships with others, and exhibit signs of distress when those relationships become unstable. Self‐directed behaviors, such as self‐scratching, have traditionally been used to non‐invasively measure stress and social anxiety levels in primates. Surprisingly few studies have correlated anxiety behaviors, such as scratching, with levels of glucocorticoids such as cortisol, which is a well‐established biological marker of stress. This study aimed to determine whether stress‐related behaviors are correlated with cortisol hormone levels in socially housed capuchin monkeys (Cebus [Sapajus] apella). To assess the relationship between stress and scratching behavior, we conducted 32.8 hr of observation and collected 103 fecal samples from 21 capuchin monkeys. Initial results suggest that individuals with higher average cortisol levels scratched more often than those with lower circulating cortisol (Spearman's Rho = 0.46, p = 0.04). We found that status significantly influenced both cortisol levels (Mann‐Whitney U = 23, z = −2.2, p = 0.028) and scratching behavior (Mann‐Whitney U = 19, z = −2.03, p = 0.041). Lower‐ranking monkeys had higher baseline cortisol and scratched more often than higher‐ranking individuals. These results suggest that scratching behavior in capuchins is a viable marker of baseline stress.