Behaviour 2019
The Development of Grooming Behavior in Wild Baboons: Sex Differences in Mother-Offspring Social Relationships
Madison D. Griffin1, Elizabeth C. Lange1, Allison A. Galezo1, Jacob B. Gordon1, Emily J. Levy1, Matthew N. Zipple1, Susan C. Alberts1,2,3. 1Department of Biology, Duke University, Durham, NC, United States; 2Institute of Primate Research, National Museums of Kenya, Nairobi, Kenya; 3Department of Evolutionary Anthropology, Duke University, Durham, NC, United States

In primates, grooming is a key indicator of sociality, which is linked to fitness and health benefits in many species. However, the development of grooming behavior is unknown, especially with respect to whether and how grooming reciprocity develops between mothers and offspring. We used five decades of observational data from a wild baboon population to identify the age at which baboon infants first start grooming, who they groom first, and how mother-offspring reciprocity changes as offspring age. We used a model selection approach and found that age at first observed grooming was at a younger age for females, offspring of multiparous mothers, and those without siblings. Offspring groomed their mother first before beginning to groom others. Mother-daughter dyads became more reciprocal than mother-son dyads as offspring developed, achieving full reciprocity by four years of age. These results suggest that the strong mother-daughter bonds between adult baboons emerge early in juvenile development. They also suggest that sons–who disperse in early adulthood–invest less in bonds with their mothers, and that family structure is an integral predictor of how grooming behavior develops.