Behaviour 2019
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Infant social development in savannah baboons: Age, sex, and demographic effects
Chelsea A. Southworth1, Matthew N. Zipple2, Elizabeth A. Archie1, Jeanne Altmann3, Susan C. Alberts2. 1University of Notre Dame, South Bend, Indiana, United States; 2Duke University, Durham, North Carolina, United States; 3Princeton University, Princeton, New Jersey, United States

An infant primate’s social environment can have profound effects on their later life, including their adult social relationships, reproductive success, and lifespan. However, most studies on the development of infant social behavior to date have been performed in captive settings, where social and ecological pressures may differ from those present in the natural environment. In this study, we conducted detailed focal follows during the first 9 months of life in 26 infant baboons (Papio cynocephalus) living in six different social groups in the Amboseli ecosystem. We report age-related changes in measures of infants’ social interactions that are consistent for each individual. Specifically, we report individual variation in the distribution of 6 types of social interactions between infants and non-maternal social partners of different age-sex classes, including grooming, carrying, vocalizing, tugging, play, and non-weight-bearing contact. We also investigate differences in social development between female and male infants, testing the sex modelling hypothesis, which posits that immatures learn adult sex roles by interacting with adults of their own sex at relatively higher rates.