Most Old World monkeys show male-biased dispersal. We present the first systematic data on male dispersal in a provisioned multilevel group of Rhinopithecus roxellana, based on 4.5 years of field observations in Shennongjia National Nature Reserve, China. We evaluated both ultimate (inbreeding avoidance and male mating competition) and proximate (food availability and predation risk) factors influencing male dispersal. The focal group contained 34-53 individuals, in 3-4 one-male units (OMUs) and 1 all-male unit (AMU). We observed 37 dispersal events involving 10 of 11 adults, 7 of 8 subadults, and 7 of 15 juveniles. Most interunit transfers within the focal group occurred around the months of mating season. Adult males competed for the leader positions of OMUs mainly through aggressive takeovers, and young males transferred from the OMUs to the AMU at the median age of 41 months, forced out by leader males. No young males older than 4 years remained in natal or non-natal OMUs. The male mating competition hypothesis was supported. The young males emigrated voluntarily from the focal group at the average age of 58.6 months, and no young emigrating male was observed to return, suggesting inbreeding avoidance also played a role in the dispersal of young males. Most emigration/immigration events were parallel dispersal and occurred during intergroup encounters, suggesting increased predation risk during the dispersal period. Males were more likely to emigrate/immigrate during the months when preferred foods were most available. We compared the dispersal patterns in R. roxellana with those in gelada baboons and hamadryas baboons, both living in multilevel societies. Similar to R. roxellana, young male geladas disperse at puberty, but they may return and breed in their natal groups. Males in hamadryas also disperse, but much less commonly than in R. roxellana. Provisioning may have influenced results, and confirming studies on unprovisioned groups would be valuable.

The diet of Rhinopithecus roxellana is characterized by lichens, which are available year-round and an uncommon food source for nonhuman primates, supplemented by seasonal plant foods. We present the first study of foods eaten by R. roxellana in relation to nutritional chemistry in Shennongjia National Nature Reserve, Hubei Province, China. We analyzed the nutrients (crude protein, crude fat, and water soluble carbohydrate [WSC]) and feeding deterrents (crude fiber, condensed tannin [CT], and total phenolic [TP]) of 111 parts from 53 plant species and of 6 lichen species. Results showed that lichens were a good choice for R. roxellana living in habitats with limited and seasonally available plant foods. They contained higher concentrations of WSC than foliage, fat concentrations equivalent to those in plant parts (except fruits/seeds), and lower concentrations of fiber than mature leaves, flowers, and fruits. Although lichens were lower in protein than plant parts (except fruits), the monkeys could likely meet their protein requirement by eating seasonal plant foods rich in protein, including foliage, flowers, buds, and seeds. The monkeys were not observed to select foliage higher in protein, but appeared to select mature leaves higher in WSC and lower in fiber. Fruits were a good source of WSC and fat, and seeds were a good source of fat. Neither CT nor TP content showed negative effects on the selection of mature leaves or lichens.

Natural disasters can negatively affect primate population demography and social group structure. A clear understanding of these effects has important implications for wildlife conservation. The worst snow storms in nearly five decades hit portions of southern and central China between January 10 and February 6, 2008, presenting a unique opportunity to observe their immediate effects on a previously studied group of Hubei Golden Snub-nosed Monkeys (Rhinopithecus roxellana hubeiensis) in temperate forests in Shennongjia Nature Reserve, Hubei Province, China. We recorded social and demographic characteristics of the group before and after the snow storms. The average group size decreased from 270 individuals before the storms to 197 individuals after the storms, a reduction of 27.2%. Adult females (30.1%), juveniles (38.1%) and infants (55.4%) suffered higher mortality than did adult males (15.7%). Despite age and sex-based differences in mortality, the ratios of adult males to adult females, adults to immatures and adult females to immatures remained similar before and after the storms. However, higher mortality among females, juveniles and infants may reduce the group's long-term potential for growth.