DEAR EDITOR,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.