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

Abstract

Manyspecies use social interactions to cope with challenges in their environment and a growing number of studies show that individuals which are wellconnected 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. Beingwell-connected can be conceptualized in four mainways: Individuals can be socially integrated by engaging in a high rate of social behaviour or havingmany 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 wellconnected 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.