No abstract

Affiliative social relationships and high social status predict longer lifespans in many mammal species, including humans. Yet, the mechanisms by which these components of sociality influence survival are still largely unknown. Using 10 years of long-term data on the incidence of injuries in a free-ranging population of rhesus macaques (Macaca mulatta), we investigated two possible mechanisms that could underpin the relationship between sociality and survival: sociality (1) reduces injury risk; and/or (2) increases the probability of survival after an injury. Our results showed that injured animals had a near three-fold increase in the probability of dying, confirming that injuries can be fatal in this population. Crucially, we found that sociality may reduce an individual's injury risk, but had no effect on the probability of injured individuals dying. Individuals with more affiliative partners and higher social status experienced fewer injuries compared to less socially integrated or lower status animals, with the effect of social status varying with age. Females living in bigger groups were more likely to be injured than those in smaller groups, while in males, smaller groups were associated with higher chances of being injured. Our study contributes novel evidence that sociality does not provide fitness benefits via socially-mediated promotion of injury recovery, but instead can enhance fitness by reducing the risk of being fatally injured in the first place.