Extremely endangered Cat Ba langur, one of the 25 most imperiled primates in the world.
The ones with color down to their shoulders and on their tails are sub-adults or juveniles.
NOTE: this is NOT a White-Headed Langur, those are found in Guanxi in southern China, not Vietnam where this primate is found.
I see these often, so the date is irrelevant here.
The lutungs are a group of Old World monkeys and make up the entirety of the genus Trachypithecus. Their range is split into two parts; one part is much of southeast Asia (northeast India, southern China, Borneo, Thailand, Java and Bali), the other part is extreme southern India and Sri Lanka. The greater part of India has lutungs. Most of the species in this genus can be referred to as lutungs, as langurs, or as leaf...