180 H. X. Tang et al.
FIG. 1 The distribution of the white-headed langur Trachypithecus leucocephalus in the Chongzuo White-Headed Langur National Nature Reserve, southern Guangxi Province, China, as recorded in the second survey, in 2020/2021.
size was 7.7 ± SD 4.3 (range 2–31). Althoughwe found white- headed langur groups in five forest fragments, 89%of groups were observed in only two fragments (60 groups in Qiuchongshan and 33 in Nongguan, and nine in Buzun, two in Nongban and one in Qufeng; Fig. 1). We calculated the index of langur population density in 2010/2011 to be 10 individuals/km2 and the total area occupied by all ob- served groups was 81.6 km2. In 2020/2021, we recorded 1,183 individuals in 128 groups
and one solitary adult male in the Reserve, and 56 indi- viduals in six groups outside the Reserve (Fig. 1). Mean group size was 9.2 ± SD 5.1 (range 2–39). The total area occupied by all observed groups was 99.3 km2. Over the 10-year period, the number of langur groups observed increased from 60 to 69 in Qiuchongshan (+15%), from 33 to 45 in Nongguan (+36%), from nine to 14 in Buzun (+56%) and from two to four in Nongban (+100%; Fig. 2). In both surveys, we recorded only a single langur group in Qufeng and no langur groups were observed in the Dawushan fragment of the Reserve. We recorded one group in the Nongbu fragment in 2020/2021 but not in 2010/2011 (Fig. 1). The index of langur population density in 2020/2021 was 15 individuals/km2. Thus, over this 10-year period the white-headed langur group size increased by 18%, the numbers of groups and individuals observed
increased by 22 and 45%, respectively, and the index of population density increased by 50%. Illegal poaching for food and traditional medicine has
been recognized as the main threat to the white-headed langur (Huang et al., 2002). Soon after the Chinese govern- ment created Chongzuo and Nonggang national Nature Reserves and white-headed langurs were listed as a Class I protected wild animal species in China, poaching was actively punished by the government (Huang et al., 2002). Thus, a marked reduction in poaching appears to offer the strongest explanation for the dramatic increase in the size of this white-headed langur population in the Reserve over the past 2 decades. At present, habitat loss and degradation are the main
threats to the long-term survival of white-headed langurs (Huang et al., 2002). Although the size of this population has increased over the past 2 decades, the distribution area has decreased, from 200 km2 in 1999 to 99.3 km2 in 2021. Prior to the founding of the Reserve, almost all of the relatively flat or arable land within the Reserve had been deforested for the cultivation of crops such as peanuts, green beans and sugarcane. These cultivated lands extend to the slopes of the limestone hills, which contain important feeding sites and are the last remaining habitat for the langurs. These dramatic habitat changes can affect langur
Oryx, 2024, 58(2), 179–182 © The Author(s), 2023. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605323000029
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