Social Factors Variably Predict Salivary Cortisol Levels in Tufted Capuchins

Abstract

Glucocorticoids (GCs) have become a prime focus in studies involving the relationship between psychosocial factors and physiology. For social animals, determining the social variables that relate to both GC release and buffering can help tease apart the complex interplay between the psychological and physiological dynamics of individuals and their communities. A 2019 study found relationships between social factors and hair cortisol in a group of socially housed tufted capuchin monkeys in which social support correlated negatively with cortisol levels while received aggression correlated positively. The present study examined the relationships between similar social measures and salivary cortisol in the same group of capuchin monkeys to test whether these relationships remain constant over time and in different biological matrices. Salivary samples were collected from the group in 2022 and 2023 and median and standard deviation (SD) of GC release were calculated and compared to four social measures of interest (dominance rank, aggression received, social network centrality, and grooming received) which were derived from long-term behavioral observations of the group. SD in 2022 was predicted by two social measures, social network centrality and aggression received, consistent with the results of the previous study, but neither SD in 2023 nor medians of either year were predicted by any social measures. Though methodological differences between this and the previous study may explain the lack of consistency in findings, I highlight the importance of considering changing social dynamics as a significant factor affecting socio-physiological relationships. Additionally, the potential association between long term cortisol exposure and short term cortisol variability is discussed