SPECIAL ISSUE: BEHAVIOR, ECOLOGY, AND CONSERVATION OF COLOBINE MONKEYS Population Structure and Ranging Patterns of Rhinopithecus roxellana in Zhouzhi National Nature Reserve, Shaanxi, China Chia LR Tan & Songtao Guo & Baoguo Li Received: 13 January 2005 / Revised: 5 April 2006 / Accepted: 16 May 2006 / Published online: 23 June 2007 # Springer Science + Business Media, LLC 2007 Abstract We describe the population structure and ranging patterns of a troop of Sichuan snub-nosed monkeys (Rhinopithecus roxellana) based on a study conducted between November 2002 and November 2003 in Zhouzhi National Nature Reserve, Shaanxi Province, China. The troop comprised several 1-male units and an all-male unit. Opportunistic censuses revealed that there were ≥112 individuals in the troop. The adult sex ratio (male vs. female) was 1:3.7. The ratios of adults to immatures and infants to adult females were 1:0.7 and 1:2, respectively. Via a grid system, we estimated the home range of the troop to be 18.3 km 2 , of which 7.4 km 2 was the core area. The subjects exhibited distinct seasonal ranging patterns. Their movement across the home range was extensive in spring and restricted in autumn. In addition, reuse of quadrats was highest in winter and lowest in spring in comparison with other seasons. The daily path length (DPL) varied from .75 to 5 km, with a mean of 2.1 km. Seasonal analysis showed that DPL is significantly shorter in winter than in spring or summer; however, there is no significant difference between the DPLs of spring and summer or those of spring and autumn. The monkeys occupied elevations 1500–2600 m above sea level; the annual mean of altitudinal range is 2137 m. Contrary to early studies that reported Rhinopithecus roxellana migrates to lower elevations in winter, we found no evidence supporting a seasonal altitudinal shift. Using the highest troop count and home range estimate, and considering the extent of range overlap between neighboring troops, we calculated the population density and biomass of Rhinopithecus roxellana to be 7.2 individuals/km 2 and 68.3 kg/km 2 , respectively. The temporal and spatial distribution of food resources may be the most important determinant of ranging behavior in Rhinopithecus roxellana, though Int J Primatol (2007) 28:577–591 DOI 10.1007/s10764-007-9147-3 C. L. Tan (*) Conservation and Research for Endangered Species (CRES), Zoological Society of San Diego, 15600 San Pasqual Valley Road, Escondido, CA 92027, USA e-mail: ctan@sandiegozoo.org S. Guo : B. Li College of Life Sciences, Northwest University, Xi’an 710069, China