Impact of Social Grooming on Age-Related Immune Health in Captive Baboons

Primate social behaviors are known to mitigate a number of negative psychological and physiological problems. Social connectedness in wild baboons can predict longevity and health, but the relationship between social grooming and physical health in captive baboons is less known. We studied rates of social grooming in captive olive and olive/yellow hybrid baboons (Papio anubis; P. anubis/cynocephalus), the factors that influence social connectedness, and its potential impacts on health as measured with neutrophil and lymphocyte levels. These white blood cell measures are available through routine bloodwork and the neutrophil-to-lymphocyte ratio (NLR) is known to be predictive of health outcomes. Subjects were 162 adult baboons housed in groups consisting of 1 male, 3 to 12 females, and associated offspring. Four 30-min all-occurrence observations per group were used to collect behavioral data. Blood data was collected opportunistically during veterinary check-ups for 45 of the females. Despite group compositions differing significantly from those in the wild, the captive baboons exhibited some similar patterns of social grooming and social connectedness to those of wild baboons. NLR was not significantly associated with any measure of social connectedness initially assessed, but a relationship between social network size and lymphocyte levels emerged. Baboons with few social grooming partners exhibited an expected decline in lymphocyte levels with age, but baboons with many social grooming partners did not show this expected trend. It appears, therefore, that older female baboons with many social partners may be buffered against age related immune health declines and that social connectedness is potentially acting to mediate some of the detrimental effects of aging.