Social animals have to establish and maintain social relationships with other group members throughout their lives. To do so, they rely on social grooming, a behavior which refers to the inspection and manipulation of the hair, skin, or oral structures with the hands or mouth of another individual (Boccia 1998). This behavior is often used as an index to evaluate the strength and quality of social relationships among pairs of individuals (Silk 2007) and it is broadly observed across animal taxa; from honey bees to bonobos (bats, Wilkinson 1986; primates, Goosen 1987; bonobos, Kano 1992; social insects, Schmid-Hempel 1998; ungulates, Mooring et al. 2004).

Conclusion

This chapter illustrates the importance of considering grooming patterns, such as body site preference, body orientations, and the occurrence of mutual and polyadic grooming, as opposed to only examining the amount of grooming received or given, when studying social relationships and grooming in nonhuman primates. These patterns can reflect dyad-specific characteristics (such as the levels of affiliation and dominance status), species-specific social characteristics (such as social tolerance and social attention), but also environment-specific characteristics (such as limited space and overcrowding in captive conditions, different levels of gregariousness, number of ectoparasites, etc.). This chapter also highlights that variations exist within species and between species, as well as between captive and wild groups, and researchers should therefore be careful when generalizing conclusions at group, population, and species levels. Moreover, comparisons between captive and wild groups as well as between captive groups are important since social and environmental factors such as food provisioning and group composition can be controlled. Future studies should focus on the specific patterns of social grooming presented in this chapter (body site and orientation preferences as well as mutual and polyadic grooming) in both wild and captive bonobo groups to help fill the gaps in knowledge and better understand the social functions of grooming.