Biology
The Influence of Social Rank on Stress Physiology and Health in Rhesus Macaques
Quick fact
In rhesus macaques, lower social rank is associated with higher baseline cortisol levels and dysregulated HPA-axis function, which can lead to altered immune function, increased inflammation, and changes in gene expression related to stress and immune responses.
Why this is interesting
In any group of rhesus macaques, one individual always outranks another. Your place in the pecking order might not just affect your social life—it could literally change your hormones and your health.
Read the full explanation
Understanding The Influence of Social Rank on Stress Physiology and Health in Rhesus Macaques
Rhesus macaques live in groups structured by dominance hierarchies. Rank is determined by aggression and submission, and it dictates access to food, mates, and social support. When an individual is low-ranked, they experience more frequent harassment and social defeat. This chronic psychosocial stress activates the hypothalamic-pituitary-adrenal (HPA) axis, leading to increased secretion of glucocorticoids like cortisol. Over time, elevated cortisol can disrupt normal physiological regulation, leading to suppression of the immune system, increased susceptibility to infection, and behavioral changes. In contrast, high-ranking individuals often have lower baseline cortisol and more stable physiology. However, the relationship is not always linear: when the hierarchy is unstable, high-ranking individuals may experience more stress than expected.
A deeper explanation
The mechanism linking social rank to health involves the HPA axis and the immune system. Chronic activation of the HPA axis leads to elevated glucocorticoid levels, which bind to receptors in the brain and peripheral tissues. Prolonged elevation can cause glucocorticoid receptor downregulation, impairing feedback inhibition and leading to prolonged stress responses. This dysregulation affects immune cells, shifting toward a pro-inflammatory state and reducing natural killer cell activity. In rhesus macaques, low-ranking individuals show higher sympathetic activity and altered cytokine profiles, which may contribute to wound healing impairments and increased risk of cardiovascular disease. These effects are also mediated by social opportunity: high-rank individuals often have better access to grooming partners and social support, which can buffer stress responses. Importantly, rank itself can be both a cause and an effect of physiological traits, though in macaques, dominance rank is largely determined by maternal lineage and social alliances, making it a causal factor in shaping stress physiology.