Influence of Day Length, Ambient Temperature, and Seasonality on Daily Travel Distance in the Yunnan Snub-Nosed Monkey at Jinsichang, Yunnan, China

This article examines the effect of ambient temperature, day length, weather conditions, and seasonality on daily path length (DPL) of a free-ranging group of Yunnan snub-nosed monkeys (Rhinopithecus bieti) using an auto-released GPS collar. Data were collected from December 17, 2003 to October 22, 2004 at Laojunshan in northwestern Yunnan province, China. The average DPL of the monkey group was 909 + 472 m (n = 291), with the shortest distance being 180 m and the longest distance 3,626 m. Ambient temperature and day length were found to affect DPL. Both factors were positively correlated with DPL,, which means that the monkey group traveled greater distances on longer and warmer days. At the study site, three distinct seasons were identified, and DPL did not vary significantly across these periods. The time of sunrise was not correlated with DPL. Nevertheless, we sometimes observed the group starting its daily trip later on cloudy days than on sunny days. Furthermore, weather conditions (e.g. rainy, cloudy, and sunny) did not influence the average DPL of the study group. Overall we found that the primary factors affecting DPL in R. bieti were day length and ambient temperature, especially daily highest temperature. Am. J. Primatol. 71:233-241, 2009. (c) 2008 Wiley-Liss, Inc.