Wild chimpanzees have reduced stress hormone levels when social partners are present, finds a study published in Nature Communications this week. The benefits of social bonds are not limited to times of acute stress, as stress hormone levels are seen to be lowered in both stressful and non-stressful contexts.

Physical and psychological stress can perturb the hypothalamic-pituitary-adrenocortical axis, a major component of the neuroendocrine system that regulates many vital functions of the body. In humans, social interactions can buffer the effects of stress, but less is known about how stress is mediated in other animals.

Roman Wittig and colleagues compared levels of glucocorticoids (a class of stress-related hormones) in the urine of 17 wild chimpanzees following rest, grooming, or a stressful experience. Stressful experiences included both natural encounters with a rival chimpanzee band and mimicking of rivals’ tree-drumming signals by experimenters, which produced similar behavioural responses. The presence of a chimpanzee’s social bond partners during a stressful event prevented glucorticoid increases; meanwhile, grooming by a social partner reduced glucorticoid levels below those observed during resting. These findings suggest that social interactions play an important role in reducing stress levels and potentially in maintaining health.