Female Bonds and Kinship in Forest Guenons

A general pattern in animal behavior is that group-living species tend to bias their sociopositive behavior toward genetic relatives. In nonhuman primates, kin-biased social bonds have been reported in large multimale, multifemale macaque and baboon groups, but little is known for other species. We addressed this with a comparative study on the genetic and social organization of two sympatric forest guenons, Diana (Cercopithecus diana) and Campbell’s monkeys (Cercopithecus campbelli). We conducted long-term observations of social interactions in two groups of each species in their natural West African forest habitat and collected fecal samples for subsequent microsatellite genetic analyses. We found that both formed female-bonded, egalitarian social organizations. We then compared patterns of genetic relatedness, spatial proximity, and key social behaviors and found that females consistently targeted individuals other than their closest relatives to form social bonds. The fact that females did not preferentially favor genetic relatives contributes to a growing literature showing that social bonds, or “friendships,” among unrelated individuals plays a key role in primate social organizations.