Department of Anthropology, University of Michigan
April 14, 2016 , Atrium Ballroom A/B
Dominance relationships play an important role in the lives of many social animals. Such relationships occur between adult male chimpanzees, who form linear dominance hierarchies. Status confers benefits, as high-ranking adult males reproduce more than do low-ranking individuals. Despite the significance of rank, it is unclear when dominance relationships develop between male chimpanzees. During adolescence, when males are reproductively but not physically mature, male chimpanzees begin to integrate into the social world of adults. Adolescents are subordinate to adult males, but it is ambiguous whether adolescent males have decided dominance relationships with each other. We studied 21 adolescent and 33 adult males for one year at Ngogo, Kibale National Park, Uganda. We conducted continuous focal animal sampling on adolescent and young adult males, and recorded pant grunts, a formal signal of submission, between members of all age- and sex-classes ad libitum. We recorded 859 pant grunts between adolescent and adult males. Although adolescent males frequently pant grunted to adults (n = 489), they rarely pant grunted to other adolescents (n = 18). Of these 18 interactions, 14 were given by young adolescent males (mean age = 9.67 years, range: 8.89 – 10.58) to older adolescents (mean age = 15.14 years, range: 14.22 – 15.52). The four pant grunts that did occur between adolescent peers all involved late adolescents. These observations suggest that male chimpanzees begin to form a decided dominance hierarchy with their peers at the end of adolescence, or alternatively, during the start of adulthood.
Funding for this project was provided by the Leakey Foundation, the National Geographic Society, the National Science Foundation and the University of Michigan