1Department of Evolutionary Anthropology, Duke University, 2Department of Anthropology, University of Waterloo
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Among mammals, primates have the longest juvenile periods relative to body size. Extended juvenility entails delayed reproduction and an increased chance of dying before reproductive age. To account for its evolution, the protracted juvenile period must provide a significant fitness benefit over the course of an individual’s lifespan. The sex-typing hypothesis proposes that extended juvenility allows for selective attention toward same-sex adults.
We test this hypothesis in a group of ring-tailed lemurs (Lemur catta) at the Duke Lemur Center consisting of three juveniles (two females, one male) and three adults (two females, one male). We predict that juveniles will spend more time grooming and as nearest neighbor to same-sex adults than opposite-sex juveniles will. From October 2010 through June 2011 we conducted scan sampling at 2-minute intervals, recording the activity and nearest neighbor of each juvenile and adult.
While the juvenile females did spend more time as nearest neighbor to adult females than the juvenile male did, this difference was not significant. Excluding the juveniles’ mothers, the juvenile females spent equal amounts of time in closest proximity to the other adult female and the adult male (their father). The juvenile male, however, spent significantly more time as nearest neighbor to the adult male than either of the juvenile females did. There were no sex-based differences in the percentage of time that juveniles groomed with adults. These results suggest that the juvenile period may be especially important in that it provides time for juvenile males to associate with adult males.