Are measures of sociality linked to Oxytocin and Glucocorticoid profiles and health in wild chimpanzees (Pan troglodytes verus)?

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Chronically elevated stress hormone levels occur from repeated exposure to stressors and can result in immuno-suppression, poor health and longevity in humans and other social mammals. In a number of primate species, deleterious effects of exposure to stressors can be mitigated through social coping strategies although little is known about the proximate mechanisms underlying such strategies. In chimpanzees, recent research shows that maintaining close social relationships can help regulate glucocorticoid levels. We will assess how and to what extent two social coping strategies impact on hormone profiles and health parameters in three communities of wild chimpanzees, in Taï National Park, Ivory Coast. The Social integration hypothesis states that maintaining either physically or socially central positions within a social group, such as through dominance, will minimize exposure to environmental and social stressors (seasonal effects, food or sexual competition). The social bonds hypothesis states that having close social bond partners should buffer the deleterious effects of stressors, even when exposure to stressors is high. We predict that individuals utilising, rather than not utilising, either coping strategy will experience lower average glucocorticoid levels and fewer pathogen infections, measured by virus load and urinary neopterin levels. In addition, whilst we expect benefits from social integration to be characterised by lower rates of received aggression, we expect benefits from maintaining close social bonds to be characterised by high rates of repeated, daily bond partner affiliations, such as grooming, which are associated with oxytocin release. Thus, bond partner grooming rates should correlate with higher average urinary oxytocin levels and lower average urinary glucocorticoid levels. This study will allow us to investigate the relationship between different parameters of sociality and health in wild chimpanzees including understanding aspects of the underlying mechanisms.