Responses to social and environmental stress are attenuated by strong male bonds in wild macaques

Male macaques form social bonds similar to human friendships that buffer them against day-to-day stressors. If male primates live in multimale groups they usually fight fiercely over access to females, but males can develop friendly relationships with a few group mates. The strength of these “friendships” has now been shown to buffer against the negative effects of social and environmental stressors, a phenomenon that was previously only described for females and pair-living animals. Long-term glucocorticoid (stress hormone) elevation can increase susceptibility to disease and mortality. This study shows that variation in everyday stressors such as the amount of aggression received or cold stress can cause such long-term elevated glucocorticoid levels but that keeping a few close male associates will avoid that.