Indochina Grey Langur individuals above named as Trachypithecus crepusculus science. They are discovered at Xuan Lien  Nature Reserve under mountainous district of Thuong Xuan in recent times.

To preserve this langur species, Xuan Lien Management Board promoted the prevention and control of hunting and wildlife trade; implementation of protection and restoration of forest habitats with living primates and etc.

Reportedly, at present in our country, Indochina gray langur is only recognized in a number of areas in the provinces of Dien Bien, Yen Bai, Son La, Thanh Hoa, Nghe An, with small size and small population. The investigation, detection and identification of Indochina gray langur populations at Xuan Lien Nature Reserve has the largest number of langur individuals so far.