Proximate causes of dispersal for female Yunnan snub-nosed monkeys

Individual dispersal trends, unquestionably important for species ecology and evolution, are affected by multiple factors. Understanding the factors that influence female dispersal strategies offers important insight into primate dispersal mechanisms and female choice. To investigate the proximate causes of dispersal in female Yunnan snub-nosed monkeys (Rhinopithecus bieti), we observed and analyzed nine years of detailed dispersal and demographic data from a population of R. bieti in Xiangguqing, Baimaxueshan Nature Reserve, Yunnan Province, China. Results showed that females who lived long-term in a one-male unit (OMU), without giving birth and with few or no relatives, were more likely to leave that OMU. In addition, an OMU led by an outgroup male and containing more female relatives was significantly more likely to be chosen for immigration. Conversely, greater male age, longer male tenure, and more potentially fertile females discouraged immigration into an OMU. These results suggest that reproduction, male quality, and kin cooperation play the largest roles in female Yunnan snub-nosed monkey dispersal.