Limestone langur

Delacour’s langur is a critically endangered monkey, confined to small pockets of forest amid the jagged limestone karst mountains of northern Vietnam.

Named in honour of ornithologist Jean Théodore Delacour, the first western scientist to encounter the species, this elegant primate is characterised by its distinctive black-and-white fur coloration, a long, bushy tail and a conspicuous crest.

Its local name – voọc quần đùi trắng (loosely translated as ‘langur with white pants’) – derives from the sharply delineated markings, which give the visual impression of a predominantly black monkey wearing a pair of knee-length white shorts or an unnecessarily large nappy.

Groups of Delacour’s langur average around ten individuals and typically comprise a single adult male, several females and their offspring.

These monkeys are equipped with specially adapted pads on their hands, feet and rump that enable them to run, jump and sit on the razor-sharp limestone. They moves through their steep, treacherous and rugged habitat with supreme confidence, clinging to precipitous cliffs and making death-defying leaps.

Delacour’s langurs eat mainly leaves, with a small number of plant varieties making up the vast majority of their diet, along with fruit, flowers and bark.

At a glance
Trachypithecus delacouri
Critically Endangered Critically Endangered
Vietnam Vietnam





Est. in the wild:



  • Delacour’s langur was first identified in 1930.
  • The species is among the world’s 25 most endangered primates.
  • It is one of six langur species in Southeast Asia that favour limestone habitat.
  • Of all Asia’s langurs, it is the most reliant on leaves as a food source.

Delacour’s langur is found only in Vietnam.



Estimated number of Delacour’s langurs left in the wild.


The number of viable Delacour’s langur populations remaining in the world.


Delacour’s langur is in urgent need of conservation intervention. The entire world population – believed to comprise no more than 250 individuals – is clinging to survival amid shrinking islands of limestone habitat in its final Vietnamese stronghold.

Remorseless hunting and – more recently – widespread habitat destruction caused by deforestation, agricultural conversion and industrial quarrying have driven this critically endangered monkey to the brink of extinction.

The largest population – and one of only two with any realistic prospect of being viable in the long term – is found in Van Long Nature Reserve. It currently comprises around 150 Delacour’s langurs.

In 2016, scientists from FFI discovered a new population – the world’s second largest – of this gravely threatened primate, comprising an estimated 40 individuals, in Kim Bang district. A more recent follow-up survey, supported by FFI, confirmed the presence of a heart-warming 73 Delacour’s langurs in 13 separate groups. With several other groups reported, there could be up to 100 monkeys in total.


The Delacour’s langur population at Kim Bang is crucial to the survival of the entire species.

Following recommendations from FFI, and recognising the vital importance of Kim Bang’s remaining forests, the Vietnamese provincial government agreed in principle to establish a new protected area specifically to safeguard this charismatic monkey and its limestone habitat from the combined threats posed by hunting, illegal timber extraction and quarrying for cement. The precise boundary, which has yet to be finalised, is likely to encompass almost 2,500 hectares of forest.

FFI is working closely with government agencies and other local partners to halt the cement mining that poses an immediate threat to the irreplaceable and fragile karst limestone habitat on which the species depends for survival, and to claw back as much as possible of the remaining forest area that is currently earmarked for mining.

We have also set up community-led patrol teams that include former hunters to monitor and protect the Delacour’s langur and its home.