Characterizing body size and the way it varies according to natal group and rank

Primates live in a striking variety of societies: mostly solitary orangutans, herds of hundreds of geladas, and nations with over a billion humans. Group living may provide both benefits — such as increased effectiveness in resource competition — and costs, including within-group competition for food and mates. While theory has long viewed grouping patterns as the net result of various costs and benefits of social life, obtaining reliable measures of these costs and benefits remains challenging. Body size correlates with many aspects of life history and can ultimately have lifetime effects on an individual’s reproductive success. Adult body size is likely influenced by food resource access as well as predator load. The degree to which body size is influenced by mother’s rank during the developmental period versus body size being a result of balancing predation avoidance and resource competition, requires further study.