In a study of wild baboons living in the Amboseli ecosystem in southern Kenya researchers recorded how often female baboons were observed grooming or being groomed by male or female social partners. Using data spanning 27 years the researchers found that the female baboons who were more often observed grooming or being groomed had longer life spans than those who were recorded grooming less often.
Using grooming data the team scored each of the female baboons they observed on how socially connected they were with both males and other females. They found that these close social relationships, at times referred to as friendships, with both sexes were a powerful predictor of survival.
Analysing ‘friendships’ with other females the team found that the better connected the baboons were, the better their survival. The top 25% most socially connected females were 34% less likely to die in a given year than the females in the bottom 25%. The results also revealed a strong connection with lifespan. Female baboons that were consistently in the top 25% lived on average 2 years longer than the more socially isolated baboons in the bottom 25%.
The female baboons’ social relationships with males had a separate, and even stronger, effect on survival. High levels of connectedness with males reduced the risk of death of female baboons by 45% or more and the lifespan of female baboons who were well-connected to males was, on average, 3.3 years longer.
The researchers say that a unique aspect to their study is that it included female baboons’ social relationships with males as well as with other females. Though heterosexual relationships are relatively common in social species, so far investigation into the importance of these relationships has focused on reproductive fitness benefits. The results from this study suggest an additional, powerful fitness benefit of male-female relationships outside of reproductive benefits - namely increased survival.
‘In humans, it’s well known that the strength and quality of a person’s social relationships can affect their health and lifespan, but similar findings in animals are rare,’ say the team behind this study. By observing baboons over decades in the wild they conclude that survival may be a powerful advantage of social relationships in baboons and other social mammals.