Stability of partner choice among female baboons.

In a wide range of taxa, including baboons, close social bonds seem to help animals cope with stress and enhance long-term reproductive success and longevity. Current evidence suggests that female baboons may benefit from establishing and maintaining highly individuated relationships with a relatively small number of partners. Here, we extend previous work on the stability of female baboons' social relationships in three different ways. First, we assess the stability of females' social relationships in two distinct and geographically distant sites using the same method. Second, we conduct simulations to determine whether females' social relationships were more stable than expected by chance. Third, we examine demographic sources of variance in the stability of close social bonds. At both sites, females' relationships with their most preferred partners were significantly more stable than expected by chance. In contrast, their relationships with less preferred partners were more ephemeral, often changing from year to year. While nearly all females experienced some change in their top partners across time, many maintained relationships with top partners for several years. Females that lived in smaller groups and had more close kin available had more stable social relationships than those that lived in larger groups and had fewer close kin available.