The social correlates of self-directed behaviour and faecal glucocorticoid levels among adult male olive baboons (Papio hamadryas anubis) in Gashaka-Gumti National Park, Nigeria

Abstract

Sociality confers many benefits to gregarious animals, but group-living does not come without associated costs. Social living can cause anxiety, which if prolonged can lead to stress. We investigate correlates of anxiety and stress among wild adult male olive baboons (Papio hamadryas anubis) in Gashaka-Gumti National Park, Nigeria, and present the first examination of these correlates for male baboons living in forested environments. We used rates of self-directed behaviours (SDB) to  quantify anxiety, and faecal glucocorticoid (FGC) concentrations to quantify  physiological stress. We first examined the relationship between SDB rates and FGC concentrations, and then examined each measure in relation to a range of variables previously linked to anxiety or stress. We found that SDB rates and FGC  concentrations were not correlated with each other, nor were they related to any measure of  grooming or receiving aggression. SDB rates were negatively correlated with time spent with an adult female as nearest neighbour, but were unrelated to time with another adult male as closest conspecific. FGC concentrations were unrelated to time with adult nearest neighbours of either sex. Our results add to the growing body of literature examining the psychological and physiological costs of social living among wild primates.

Key words: self-directed behaviour, glucocorticoids, aggression, grooming,  proximity.