Dominance rank of adult females and mating competition in Sichuan snub-nosed monkeys (Rhinopithecus roxellana) in the Qinling Mountains, China

Dominance hierarchy reflects resource competition in male primates as well as females. In this study, we collected data on the social rank and mating competition of female Sichuan snub-nosed monkeys from September 2009 to June 2010 in the Qinling Mountains, Shaanxi, China. Displacement was used to determine social hierarchy of the studied wild females. A total of 1223 displacement bouts between adult females and 316 mating behaviors within one-male units (OMUs) were recorded. Competitive displacement among females was very low (0.22 displacements per observation hour). The dominant ranks of females in target OMUs were determined by displacement, from one OMU to another: JB unit: YL > DBC > YCM >XBC > BD; JZT unit: XHW > JG > DT; PK unit: QQ > TM > HF; LP unit: SK > TH > WM. Higher-ranking females performed significantly more sexual behavior than lower-ranking females in this rare monkey. High-ranking females were more likely to win mating contests within those OMUs. Based on these studies, we assessed the social relationships among adult females and clarified possible explanations for the strategies of female mating competition in the OMUs. Furthermore, the notion that reproductive success may also be related to female dominance hierarchies in this polygynous species should be considered in future research.