Population and Conservation Status of Indochinese Gray Langurs (Trachypithecus crepusculus) in the Wuliang Mountains, Jingdong, Yunnan, China

Abstract

Peripheral populations are valuable for conservation because of their potential genetic distinctiveness and ecological differentiation, but they tend to be smaller and more easily isolated than central populations. The Indochinese gray langurs living in the Wuliang Mountains of southwestern China, which form the northernmost peripheral population of the species, have ecological and behavioral features distinct from those of other such populations. We conducted semistructured interviews and field surveys on the population census and distribution of Indochinese gray langurs in Jingdong County from July 2013 to November 2013. These interviews provided the first large-scale data about the distribution and habitat use of these langurs; however, the group sizes estimated from interview reports were smaller than those obtained from direct counts. We estimate that 43 groups comprising ca. 1960 individual Indochinese gray langurs reside in evergreen broadleaf forests at an altitudinal distribution of 1700–2900 m in Jingdong. Of the 43 langur groups, 21 groups were observed outside the nature reserve or had estimated home ranges that straddle the boundary of the reserve. Because of the intensive conservation efforts to protect sympatric Nomascus concolor, hunting pressure on Indochinese gray langurs is minimal. However, the langur home ranges outside the nature reserve are not protected and remain threatened by deforestation for plantations (walnut, tea, etc.) and forest degradation caused by livestock grazing. More conservation attention than currently applied is needed to conserve langur groups living outside the reserve.