Since 1991 Frankfurt Zoological Society has been working in Vietnam on primate conservation. The conservation of primates in Vietnam is considered to be an immediate priority since the country is home to some of the world's most critically endangered primate species. Seven species are listed as "Critically Endangered" and five are amongst the "25 World's Most Endangered Primates" by the IUCN/Primate Specialist Group.
One of the target species is the Delacour's langur (Trachypithecus delacouri), a "Critically Endangered" primate species, endemic to a restricted area in northern Vietnam. Field surveys and monitoring of the Delacour's langur for more than ten years show a dramatic population decline. Currently the whole population is estimated at about 200 individuals which occur in 9 completely isolated subpopulations. Sixty percent of the whole population exists in subpopulations with less than 20 individuals. The Delacour's langur is protected by Vietnamese law but the law enforcement is weak and the species is under high pressure through poaching for the use in "Traditional Chinese Medicine". Most of the subpopulations occur in unprotected areas without any protection activities.
The largest population of the Delacour's langur exists in Van Long Nature Reserve. In 2001 the area was granted the status of a nature reserve. Since the beginning of the establishment of the nature reserve Frankfurt Zoological Society supported the Management Board of the reserve, recruited and trained 28 local guards, paid their salaries, uniforms and equipment to support the protection of the nature reserve. Meetings and education events were organized in the surrounding communes to spread the message about protection and conservation. As a result of the joint activities from the provincial Forest Protection Department, the Management Board of the nature reserve and Frankfurt Zoological Society hunting of primates in the area has completely stopped.
The nature reserve was chosen as reintroduction area for captive bred individuals from the Endangered Primate Rescue Center to stabilize the only viable population of the species and to increase the genetic diversity. With a planned extension of the nature reserve and habitat restoration an adequate habitat should provided which can harbor a self sustaining population.