RESEARCH ARTICLE Juvenile Social Relationships Reflect Adult Patterns of Behavior in Wild Geladas CAITLIN L. BARALE 1 *, DANIEL I. RUBENSTEIN 1 , AND JACINTA C. BEEHNER 2,3 1 Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey 2 Department of Psychology, University of Michigan, Ann Arbor, Michigan 3 Department of Anthropology, University of Michigan, Ann Arbor, Michigan Unlike many mammals, primates spend much of their lives as reproductively-immature juveniles. During the juvenile period, they develop social relationships and physical skills that both facilitate survival to adulthood and impact adult fitness. In this study, we use 2 years of observational data to examine the development of these skills across the juvenile period in a wild cercopithecine primate, the gelada (Theropithecus gelada). As adults, male and female geladas require different skills to be successful; we therefore expected sex differences in social behavior and partner choice during the juvenile period to already reflect these sex-specific trajectories. For example, males, who disperse at puberty and ultimately must challenge other adult males for access to mates, should invest in high- energy play-fighting with other males to develop fighting and rival assessment skills. In contrast, philopatric females, who remain with their close kin throughout their lives, should invest more in forming less-physical and more-social bonds with other females within their group. As predicted, sex differences that foreshadowed sex-specific adult roles were apparent in play rates, the average number of play partners per individual, grooming partner types and social partner preferences. Males played more and had more play partners than same-age females. Males also groomed more often with individuals from outside their natal group than females, although no sex difference was observed in either grooming rates or number of grooming partners per individual. Females stopped playing earlier than males, and instead invested in grooming relationships with close relatives. Additionally, we found that individual play and grooming rates were temporally consistent for both males and females (i.e., from one year to the next year), suggesting that individuals exhibit stable behavioral phenotypes. We conclude by discussing how early life in geladas may shape adult behavior and reproductive strategies. Am. J. Primatol. 77:1086–1096, 2015. © 2015 Wiley Periodicals, Inc. Key words: juvenile social behavior; partner preference; play; sex-specific behavior; male dispersal INTRODUCTION A lengthy juvenile period distinguishes primates from other mammals. Young primates spend the time between weaning and sexual maturation developing species-specific and sex-specific behav- iors, building relationships, and skills for adult life, and learning to negotiate their complex social and physical environments [Bekoff, 1984; Byers, 1998; Martin and Caro, 1985; Thompson, 1998]. Despite the demonstrated importance of this developmental period, primate research typically focuses on the adults of a species. Juveniles are notoriously challenging to study in the wild: their small body size makes them difficult to spot and individu- ally identify, they move unpredictably, and they are constantly growing and changing. Yet, research on a diverse set of non-primate taxa has linked juvenile behavior and sociality to fitness-related skills such as territory establishment, successful reproduction, Contract grant sponsor: Wildlife Conservation Society; contract grant sponsor: National Science Foundation; contract grant numbers: BCS-0715179, BCS-1154314, IOS- 1255974; contract grant sponsor: Leakey Foundation; contract grant sponsor: American Society of Primatologists; contract grant sponsor: International Society of Primatologists; contract grant sponsor: National Geographic Society; contract grant numbers: Gr.# 8100-06, 8989-11; contract grant sponsor: Princeton University; contract grant sponsor: University of Michigan  Correspondence to: Caitlin L. Barale, 106A Guyot Hall, Princeton University, Princeton NJ. E-mail: cbarale@prince- ton.edu Received 2 March 2015; revision accepted 9 June 2015 DOI: 10.1002/ajp.22443 Published online 26 June 2015 in Wiley Online Library (wileyonlinelibrary.com). American Journal of Primatology 77:1086–1096 (2015) © 2015 Wiley Periodicals, Inc.