White-headed langur

The white-headed langur (Trachypithecus leucocephalus) is a critically endangered species of langur endemic to Guangxi, China. It was formerly considered a subspecies of the Cat Ba langur, which is now thought to be endemic to Vietnam, and its taxonomy was long uncertain, since it has also been treated as a partly albinistic population of Francois' langur or as a subspecies of that species. The IUCN Red List assessors and the American Society of Mammalogists now recognise it as a distinct species on the basis of a 2007 study. The animal is blackish with a white crown, cheeks and neck, unlike the similar Cat Ba langur, which has a golden crown, cheeks and neck. It has a very small range in the southernmost Chinese province of Guangxi, endemic to karst hills, where it is known from a few scattered populations separated from Francois' langur by the Zuo River. The population is thought to be no more than 600 animals with roughly 250 mature individuals, and none of the subpopulations has more than 25. Poaching is the main threat, hybridization with released Francois' langurs is a risk, and genetic diversity is very low.