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Delacour's Delicate Balance of Survival

Vietnam is home to a remarkable variety of primate species, belonging to several different groups. Due to lack of prior research many of these species are poorly understood and are now critically endangered, with many being endemic to Vietnam. One of the most varied groups in Vietnam are the langurs with 12 different species. Vietnamese langurs are some of the most endangered primates on Earth, living on the brink of existence. Langurs are being taken form the wild for food, traditional medicine or for house pets, leading to populations becoming dangerously low.

Vietnam has an especially high diversity of primates, some of which live in very small secluded locations. There are several theories for this diversity. Firstly the division between the more seasonal northern half of the country and the more tropical southern half leads to a large variation in available habitats. Species have spread as far as their ecological circumstances will allow, or until they are out competed by better adapted species. As well as the differing climates, the historical movements of the Mekong River have also played a role in the diversity. Since the Pleistocene period the Mekong has moved across the northern part of Vietnam. These changing conditions could have helped in the large speciation event.

Furthermore, there is also a very unique habitat which is centred on northern Vietnam which has allowed for species to specialise in different areas: the limestone hills. They are responsible for a wholly endemic species-group of primates, the limestone langurs. Although it has recently been argued that limestone hills are not necessarily the preferred habitat for the langurs, rather they are a refuge from human disturbance. Despite this the limestone hills are now home to a variety of highly localised different species.

Recently I was lucky enough to visit one of these limestone habitats at Van Long nature reserve, home to the Delacour Langur (Trachypithecus delacouri). Endemic to Vietnam the species is found only in North-central part of the country. It occurs in fragmented populations across the provinces of Ninh Binh, Nam Ha, Hoa Binh and Thanh Hoa. The species occurs in a very restricted area of about 5000 square km, but the distribution areas of all isolated subpopulations cover together only about 400 square km.

The black and white coloration and the long bushy tail of the Delacours Langur is very unique. The upper body is black, with a sharp demarcation to white from the hips to above the knees, making it look like a white nappy. Langurs have an incredible design allowing them to jump up to 12 m from high to low, making them perfectly adapted to their harsh limestone environments.

Following on, Langurs are a type of leaf-eating monkey whose multi-chambered stomach allows them to digest stodgy plant food in between feeding times. The complicated digesting system is the reason for their big belly. Meaning in captivity these monkeys need a huge amount of leaves to eat.

The total population of the Delacour’s is estimated to 200- 250 individuals, surviving in 19 isolated subpopulations. The biggest sub-population occurs at Van Long with around 120 individuals. The species is listed as critically endangered in Vietnam's red data book. The Delacour Langur is dangerously close to extinction.

So why is the species in such a dire situation? Hunting is the primary threat facing the species, for traditional medicine, food or for a cute pet to have at home. Their bones, organs and tissues are used in traditional medicines. Another major threat is the quarrying of the limestone cliffs that they live on in order to make cement. This industry is increasingly fragmenting the sub populations decreasing the chances of gene flow. This leads to increased inbreeding events decreasing the health and sustainability of the populations.

Eco-tourism incentives have been used at Van long and other sites, giving money to local villagers to take tourists to see the monkeys. However, the destructive practices and competition by local goat populations is making it increasingly difficult for the species to cling on to survival.

There is however hope for this species in the form of Cuc Phuong’s Endangered Primate Rescue Centre (EPRC). They run a successful captive breeding program for the species. The goal is the reintroduction of captive bred animals into the wild populations, connecting the fragmented populations. The EPRC has successfully created a population of 14 captive bred animals and have successfully released some with a pilot project. The aim is to slowly increase the wild population to increase its viability.

Beside population management by reintroduction, the establishment of migration corridors between the sub-divided populations would certainly improve the situation. As well as this locals most be shown the importance of the species, not only for eco-tourism but for the survival of an endemic species. They must be encouraged to stop mining the habitat of their rare monkey species.

The story of the Delacour Langur is a desperate one, but sadly it is not a unique one. 11 of Vietnam’s primate species are critically endangered and are facing similar situations. Pressure on primate populations is enormous and we are facing the loss of many beautiful endemic species. The EPRC is doing its best to help stop the illegal trade and also conserve the natural habitats and populations of these species. We are currently facing history’s biggest mass extinction event, and we need to do something about it before we lose natures beauty.

Footnote: If you would like to learn more about the work EPRC are doing or even donate money to help them continue their great work then you can follow this link:

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