Delacour's Langur, Trachypithecus delacouri - Top 25 Most Endangered Primates

Photo © 2005 by Tilo Nadler. Delacour's Langur
Trachypithecus delacouri (Osgood, 1932)
Vietnam
(2000, 2002, 2004, 2006)

Delacour’s langur is endemic to Vietnam and occurs in a very restricted area of northern Vietnam which comprises about 5000 km² between 20°–21°N and 105°–106°E. The distribution is closely linked to the limestone mountain ranges in the provinces of Ninh Binh, Thanh Hoa, Hoa Binh and Ha Nam. Currently there are 19 locations where Delacour’s langur is or was known to occur. They are isolated populations and when combined total at most only 400 to 450 km².
The extirpation of Delacour’s langurs has been reported by local people in three localities that we know of. There is a smaller limestone mountain ridge to the west extending to a large limestone region north of Son La, but there is no evidence of Delacour’s langurs in this area. The northwestern border of the distribution is Mai Chau between the Da River in the north and the Ma River in the south. The Da River appears to form the northern border of the species’ range. The exact southern boundary is unclear. There are some smaller isolated limestone areas south of the Ma River. The only area south of the Ma River where Delacour’s langurs have been confirmed is the limestone complex between Lang Chan and Ngoc Lan, but this population is now most probably extirpated. It seems that this species never occurred south of the Chu River.
During the decades following the discovery of Delacour’s langur in 1930 there was only scanty information on its existence and distribution. The first sightings of live animals were reported in 1987 from Cuc Phuong National Park. The most important, and for some subpopulations the only factor for the decline in numbers is poaching, which is not primarily for meat, but for bones, organs and tissues that are used in the preparation of traditional medicines. The 19 isolated wild populations of Delacour’s langur have been confirmed over 10 years of surveys and monitoring by the Frankfurt Zoological Society. The total population counted in 1999/2000 was about 280 to 320 individuals. The recorded numbers of animals hunted over the 10 years totaled 320, an annual loss of more than 30 individuals, but the real number is undoubtedly higher.
Sixty percent of all existing Delacour’s langurs occur in isolated populations with less than twenty animals. The loss of these subpopulations, and consequently sixty percent of the entire population, is foreseeable without management, strict regulations and law enforcement. Surveys in 2004 in two protected areas with important subpopulations, Cuc Phuong National Park and Pu Luong Nature Reserve, showed a decline in numbers of 20% in the last 5 years. It is to be expected that the population in unprotected areas which have yet to be surveyed will show a similar tendency. A reasonable estimate of the current population indicates numbers no higher than 200 to 250 individuals.
Four areas where Delacour’s langurs occur are protected: Cuc Phuong National Park, Pu Luong Nature Reserve, Hoa Lu Cultural and Historical Site, and the Van Long Nature Reserve (established in 2001). Van Long Nature Reserve is believed to harbor the largest remaining population of about 60 to 80 animals. They are well protected there due to patrols and close cooperation between the provincial forest protection authorities and Frankfurt Zoological Society. Currently two doctoral students are working in the area, studying the biology and population dynamics of the subpopulation.
Efforts to save this species are being led by Tilo Nadler, manager of the Vietnam Primate Conservation Program of Frankfurt Zoological Society and director of the Endangered Primate Rescue Center at Cuc Phuong National Park, established in 1993 primarily to safeguard the future of this and other endangered Vietnamese primates. The Endangered Primate Rescue Center is the only facility which keeps this species. The center started a breeding program with five confiscated animals, and 12 individuals have been born since 1996. The aim is to reintroduce the langurs into well-protected areas to establish additional free ranging populations.

Tilo Nadler & William R. Konstant

References
Nadler, T. 1996. Report on the distribution and status of Delacour’s langur (Trachypithecus delacouri). Asian Primates 6: 1–4.
Nadler, T. 2004. Distribution and status of the Delacour’s langur (Trachypithecus delacouri) and recommendations for its long-term conservation. In: Conservation of Primates in Vietnam, T. Nadler, U. Streicher and Ha Thang Long (eds.), pp.63–71.Frankfurt Zoological Society, Hanoi.
Nadler, T., F. Momberg, Nguyen Xuan Dang and N. Lormee. 2003. Vietnam Primate Conservation Status Review 2002. Part 2: Leaf Monkeys. Fauna and Flora International and Frankfurt Zoological Society, Hanoi. pp. 145–164.
Ratajszczak, R., R. Cox and Ha Dinh Duc. 1990. A Preliminary Survey of Primates in North Vietnam. Report to World Wide Fund for Nature – WWF, Project 3869, Gland.

Suggested citation:
Nadler, T. and Konstant, W. R. 2007. Delacour's Langur, Trachypithecus delacouri (Osgood, 1932). In: Primates in Peril: The World’s 25 Most Endangered Primates 2006–2008, R. A. Mittermeier et al. (compilers), p.14. Unpublished report, IUCN/SSC Primate Specialist Group (PSG), International Primatological Society (IPS), and Conservation International (CI), Arlington, VA.