Strong social relationships are associated with decreased longevity in a facultatively social mammal

Humans in strong social relationships are more likely to live longer because social relationships may buffer stressors and thus have protective effects. However, a shortcoming of human studies is that they often rely on self-reporting of these relationships. By contrast, observational studies of nonhuman animals permit detailed analyses of the specific nature of social relationships. Thus, discoveries that some social animals live longer and healthier lives if they are involved in social grooming, forage together, or have more affiliative associates emphasizes the potential importance of social relationships on health and longevity. Previous studies have focused on the impact of social metrics on longevity in obligately social species. However, if sociality indeed has a key role in longevity, we might expect that affiliative relationships should also influence longevity in less social species. We focused on socially flexible yellow-bellied marmots (Marmota flaviventer) and asked whether female longevity covaries with the specific nature of social relationships. We quantified social relationships with social network statistics that were based on affiliative interactions, and then estimated the correlation between longevity and sociality using bivariate models. We found a significant negative phenotypic correlation between affiliative social relationship strength and longevity; marmots with greater degree, closeness, and those with a greater negative average shortest path length died at younger ages. We conclude that sociality plays an important role in longevity, but how it does so may depend on whether a species is obligately or facultatively social.