The Number of White-Headed Langurs in the Nongguan Mountains

In Nonguan Mountain area, there are 220 hills scattered in the dense jungle. Due to the restriction of the landform, we tracked the white-headed langur troops on fixed spots, along with line transect surveys, to estimate their numbers. From April till December 2015, we surveyed white-headed langur distribution in the Nongguan Mountains and divided it into three districts. According to our survey, we estimated a total of 798 (216 + 425 + 157) individuals. Since 1996, the langur population has been growing rapidly. The sex ratio within phase 1 and 2 was 1:1, but the phase 3 sex ratio after maturity was strongly biased toward females, with a ♀:♂ ratio of 22:3 (overall mean 7.3:1). Old white-headed langurs accounted for 6.5% of the population, adults at reproductive ages accounted for 32.3%, and the pups, juveniles, and adolescents made up 61.3%. Age distribution as such indicates that the age structure of the FJC white-headed langur population is balanced. Meanwhile, the net rate of annual population increase of six families during the last 20 years ranged from 4.0% to 54.5%, with a mean value of 40%.