a major threat. The White Headed Langur The White Headed Langur The White-headed Langur (Trachypithecus poliocephalus) is a  critically endangered   langur  from  Cat Ba Island ,  Vietnam  (T. p. poliocephalus), and  Guangxi ,  China  (T. p. leucocephalus). Both  taxa  are overall blackish, but the crown, cheeks and neck are yellowish in T. p.