Not only the attractiveness of a potential grooming partner matters to wild chimpanzees and sooty mangabeys, their choice also depends on who is observing them

When humans cooperate with others they take their previous experiences with specific individuals into account, as well as their usefulness for carrying out a specific task. Moreover, they consider whether a better candidate is available, and whether the potential cooperation partner is actually reliable. Researcher of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, show that wild chimpanzees and sooty mangabeys, two primate species who live in complex social groups, choose their grooming partners based on a variety of criteria, including their social relationship with them and their potential partner’s dominance rank. In particular, individuals of both species avoided grooming group mates whose friends were among the bystanders, as grooming might be interrupted.