Deconstructing sociality: the types of social connections that predict longevity in a group-living primate

Abstract

Many species use social interactions to cope with challenges in their environment and a growing number of studies show that individuals which are well-connected to their group have higher fitness than socially isolated individuals. However, there are many ways to be ‘well-connected’ and it is unclear which aspects of sociality drive fitness benefits. Being well-connected can be conceptualized in four main ways: individuals can be socially integrated by engaging in a high rate of social behaviour or having many partners; they can have strong and stable connections to favoured partners; they can indirectly connect to the broader group structure; or directly engage in a high rate of beneficial behaviours, such as grooming. In this study, we use survival models and long-term data in adult female rhesus macaques ( Macaca mulatta ) to compare the fitness outcomes of multiple measures of social connectedness. Females that maintained strong connections to favoured partners had the highest relative survival probability, as did females well-integrated owing to forming many weak connections. We found no survival benefits to being structurally well-connected or engaging in high rates of grooming. Being well-connected to favoured partners could provide fitness benefits by, for example, increasing the efficacy of coordinated or mutualistic behaviours.

Social bonds, social status and survival in wild baboons: a tale of two sexes

“…Our findings for adult female survival add to a growing body of evidence that links social bonds with female longevity in various populations of non-human primates [5][6][7]9,11]. They also recapitulate previous work in our study population, which used a different metric of social bonds called 'social connectedness', a measure of normalized grooming frequency with all partners of a given sex [6].…”

“…Sociologists have long known that social integration [1,2] and socio-economic status [3,4] are among the most powerful predictors of mortality risk in humans. In the last decade, similar strong relationships between lifespan and social environments have been revealed in primates [5][6][7][8][9][10][11][12][13], hyraxes [14], ungulates [15,16], whales [17,18], rodents [19], carnivores [20] and lagomorphs [21]. These findings have enhanced our understanding of the evolution of animal social relationships and uncovered links between sociality and ageing [22].…”

Rhesus macaques as a tractable physiological model of human ageing

“…Immune signatures of social status in macaques and ageing in humans have also been shown to overlap substantially in their transcriptional profiles [75], suggesting that chronic social adversity may accelerate physiological aging. Further supporting this idea, social integration-a condition that is believed to buffer against adverse effects of social stress-predicts survival in female macaques [42,76].…”

Hurricane-induced demographic changes in a nonhuman primate population

“…However, following hurricane María, a higher density in proximity networks and less isolation of individuals was reported in Cayo Santiago [56,57]. Strong social ties with other members of the population may act to lower cortisol levels or heighten immune responses following stressful events [58][59][60].…”