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Overview

Brief Summary

Biology

The Old World monkeys (family Cercopithecidae) are split into two subfamilies: the Cercopithecinae and the Colobinae, or colobine monkeys. As a colobine, the white-headed langur has large salivary glands and a complex sacculated stomach. This is an adaptation to the highly folivorous lifestyle of the leaf monkey or langur. Leaves are very difficult to process, requiring digestion by bacteria in the neutral upper chamber of the stomach before moving into the lower acid region. As well as consuming a large volume of leaves daily, the white-headed langur also eats fresh shoots, flowers, bark and some fruits. The very high concentration of fibre and tannic acids in this diet would be poisonous to many other species, including humans (3). The white-headed langur lives in groups of about five to nine individuals (2), usually with just one dominant male (3). The group sleeps together in limestone caves, spending one or two nights in each one before moving on to another. There may be up to 12 resting caves in the range of a group, although rock ledges and tall trees are also used as sleeping sites, particularly in good weather. The group leaves the sleeping sites between 5 and 6:30 am according to season, and will spend a short time socialising before moving out to forage. Resting periodically through the day, the group makes its way towards the new sleeping sites as it feeds, settling down at around 5 or 6pm (3). Females, who all mate with the only male of the group, give birth to a single, golden-orange infant. The majority of births appear to occur in April, but very little is known of the reproductive biology of this species. The young are thought to stay with their mother's group for up to two years, before leaving to find or start a group of their own (4).
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Description

This beautiful and extremely rare colobine monkey is part of the genus Trachypithecus, in which the dark chocolate brown coat of adults contrasts spectacularly with the golden orange fur of infants, which turns to whitish-grey in juveniles (2) (3). The head and neck of adults are golden to yellowish-white in T. p. poliocephalus, with the pointed crest of hair on the top of the head being the most brightly coloured (3), and creamy-white in T. p. leucocephalus. A grey V-shaped area runs from the thighs to the back (3), and the fur of the pubic region ranges from white to pale orange (4). Adults are also adorned with a cape-like area of longer fur across the shoulders (3). The hands and feet are very slim, and the thumbs are notably shorter than in other primates (4).
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Distribution

Range Description

This species is known only from northern Viet Nam and adjacent southern China.

T. p. poliocephalus
Confined to Cat Ba Island, in Ha Long Bay off the northeastern cost of Viet Nam. There it is further restricted to about a 100 km2 area of occupancy, mostly inside Cat Ba National Park (Stenke and Chu Xuan Canh 2004). It ranges from 70-100 m in elevation (Le and Campbell 1994) and possibly from 0 to 200 m.

T. p. leucocephalus
Occurs in south China (southwestern Guangxi province), in isolated areas from the Shiwan Dushan north to the Zuo River, specifically in the karst hills of Gang Nature Reserve, Fushui Nature Reserve, Chongzuo Nature Reserve, and Longrui Nature Reserve.
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Range

The Cat Ba langur (T. p. policephalus) is endemic to Cat Ba Island, the largest of more than 3,000 islands in Halong Bay off the northeastern coast of Vietnam (4). There is no evidence that this subspecies has ever lived on the mainland (3). The white-headed black langur (T. p. leucocephalus) is found in south China where it occupies seven karst regions in Guangxi Province. These regions are spread across three isolated, protected areas known as the Fusui Rare and Precious Animal Reserve, the Chongzuo Rare and Precious Animal Reserve, and the Longgang National Nature Reserve (5).
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
This species is associated with forests on limestone (karst) hills. The caves found in this habitat are thought to offer protection from predators and temperature extremes but, if accessible to people, this habitat is also where human hunters capture or kill sleeping langurs (Nadler et al. 2003). It is arboreal and terrestrial, and diurnal. Like other langurs, this species is mainly folivorous, with leaves making up between 60-80% of its diet; the rest is composed of shoots, fruit, flowers, and bark (Li et al. 2003).

Systems
  • Terrestrial
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In common with many members of the Trachypithecus genus, the white-headed langur is associated with the striking lush green hill forests on a limestone base that have become an icon of the southeast Asian landscape. They prefer altitudes of between 70 and 100 metres above sea level (4) and will regularly sleep within the complex cave systems of the karst landscape, particularly to shelter from poor weather (3).
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
CR
Critically Endangered

Red List Criteria
A2cd

Version
3.1

Year Assessed
2008

Assessor/s
Bleisch, B., Xuan Canh, L., Covert, B. & Yongcheng, L.

Reviewer/s
Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)

Contributor/s

Justification
Listed as Critically Endangered as there is reason to believe the species has declined by at least 80% over the past three generations (36 years, given a generation length of 12 years) due primarily to hunting and habitat loss.

History
  • 2000
    Critically Endangered
  • 1996
    Endangered
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Status

The white-headed langur is classified as Critically Endangered (CR) on the IUCN Red List. There are two subspecies. The Cat Ba langur, (T. p. poliocephalus) is classified as Critically Endangered (CR) and is less commonly referred to as the Cat Ba hooded black langur, golden-headed langur, golden-headed hooded langur or Tonkin hooded black langur. The white-headed black langur or white-headed hooded langur (T. p. leucocephalus) is also classified as Critically Endangered (CR) on the IUCN Red List (1).
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Population

Population
The current total population of T. p. poliocephalus as of August 2006 is 64 individuals (Stenke pers. comm.), down from an estimated 100 individuals in 2000 (Nadler and Long 2000), but apparently an increase from the all-time low (less than 60 individuals) in the interim period. These animals are fragmented into seven isolated subpopulations; average group size is low, at 3.7 individuals, and there are 3-4 all-female groups, which are consequently non-reproductive (Stenke and Chu Xuan Canh 2004).

As of 2003, T. p. leucocephalus totaled about 700-800 individuals remaining in the wild, 250 of which live in Nong Gang, a maximum of 350 individuals live in Nong Lin. Also as of 2003, the population had begun to grow after a period of human-induced decline (Wang and Tong 2004). A survey conducted in Fusui Rare and Precious Animal Nature Reserve between September 1996 and April 1997, found a 24% decline in the population density over the past 10 years, with a current population of less than 150 langurs (Li et al. 2003).

Population Trend
Decreasing
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Threats

Major Threats
Poaching, both for meat and traditional ?medicine,? has been recognized as the most severe threat to Cat Ba langurs, and the reason for the precipitous decline in their population over the past couple of decades. Reproductively valuable males were often the most common victims due to their behaviour (Stenke and Chu Xuan Canh 2004). Habitat disturbance and fragmentation resulting from the growing human population on Cat Ba Island (due in part to the country?s designation of the island as a new tourism centre for northern Viet Nam), and rampant fires due to honey collectors (Nadler and Long 2000) are also threats. Tourism in the inadequately managed Cat Ba National Park has direct effects on langur natural history, such as the disturbance to habitat and perhaps behaviour caused by things like nightly spotlighting trips in speed boats around the karst archipelago where these monkeys live. The small size and fragmented nature of the remaining Cat Ba langur population means that the subspecies is at risk of inbreeding effects (or intrinsic effects to avoid inbreeding by not breeding at all), extremely limited mate-choice due to the small number of males per group, and the chance of a natural or human disaster causing total or effective extinction.

In China, clearing of land with fire, burning of agricultural residue and burning charcoal often leads to uncontrolled fires that escape into adjacent karst landscapes. The white-headed Langur is surrounded in some areas by subsistence agriculture, such that much of the habitat is fragmented (Li and Rogers 2005). Tree cutting for firewood has caused further degradation to the remaining habitat (Li and Rogers 2005). Along with habitat destruction, poaching has been the primary cause of the most recent decline in the population (Wang and Tong 2004). There is some evidence that breeding is hindered in degraded habitats.
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Granted the dubious honour of being one of the International Primatological Society's 'World's Top 25 Most Endangered Primates', the white-headed langur is in the company of such conservation priorities as the Sumatran orangutan (Pongo abelii) and the eastern gorilla (Gorilla beringei) (6). The focus of conservation efforts must fall primarily on the Cat Ba Island subspecies, with possibly as few as 59 individuals remaining today. This shockingly low number is the result of a massive 98% decline over the course of 40 years, from between 2,500 and 2,800 individuals in the 1960s to just 53 in 2000. Such a dangerously small population of Cat Ba langurs gives the impression that the Chinese subspecies, Trachypithecus poliocephalus leucocephalus, is thriving, with between 600 and 800 individuals alive today. This is, of course, far from the truth, particularly as declines were recorded in the populations at Longgang National Nature Reserve and the Fusui Rare and Precious Animal Reserve in 1998 (5). In both range states of this monkey species, the major threat is hunting, which is exacerbated by habitat destruction and exploitation; for the creation of sugarcane plantations in China (5), and for timber, fuel-wood, honey, bamboo shoots, edible roots, and frogs and geckos in Vietnam (7). Cat Ba Island has seen considerable change in the past 20 – 30 years. Prior to 1979 very few people lived on the island, but it is now home to a large population, of whom 12,300 live in the buffer zone of Cat Ba National Park, and 850 in the park itself. Until 1989 commercial logging took place but this is no longer viable due to the scarcity of large trees (7). Hunting of this rare primate is not for food, as the meat is said to be smelly and fetid, but for the creation of 'monkey balm', a traditional 'medicinal' preparation. Currently the Cat Ba langurs are split into just a few isolated sub-populations, many of which are all-female groups. This fragmentation creates further challenges for the recovery of the population due to low reproductive rates and the dangers of inbreeding (3).
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Management

Conservation Actions

Conservation Actions
This species is currently listed in CITES Appendix II.

Since November 2000, the subspecies T. p. poliocephalus and its habitat on Cat Ba have been the subject of the Cat Ba Langur Conservation Project (implemented by the Zoological Society for the Conservation of Species and Populations, ZSCSP), which has been focused on the improvement of protection status for the subspecies and its habitat, and has initiated two important programs. The first is a langur sanctuary located inside Cat Ba National Park and a ?buffer zone? of the World Heritage Site ?Halong Bay.? Thirty-five percent of the remaining population lives in the sanctuary. The second is a langur-guarding program that is meant to protect 35% of the population that exists outside of the national park. This program puts the subpopulations and their ranges under the control of local people that patrol the ranges and offer community conservation education. The most important steps in the recovery of this subspecies now are continued protection from poaching and encroachment, a reduction in the habitat fragmentation and subpopulation isolation, and an increase in reproductive output and genetic health of the entire population, suggesting the need for translocation (Stenke and Chu Xuan Canh 2004).

The largest populations of T. p. leucocephalus are expected to recover under proper conservation of their Nong Guan and Nong Lin limestone habitats (Wang and Tong 2004). Nong Guan and Nong Lin are now being included in a larger proposed national-level nature reserve called Chongzuo Eco-Park, a special nature reserve for the white-headed langur (381 km2) with a population of about 250 individuals (Nadler 2003). However, considering the precarious status of the populations of this subspecies, reliable information is desperately needed about the precise effects of habitat degradation on its activity and survival (Li and Rogers 2005).

There are currently no specimens of T. p. leucocephalus in captivity; a small number of T. p. poliocephalus are reported in the collection of the Endangered Primate Rescue Center, Cuc Phuong National Park, Viet Nam (Nadler 1999).
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Conservation

With just 53 Cat Ba langurs in the wild and two in captivity at the Endangered Primate Rescue Centre of Cuc Phuong National Park, the Cat Ba Langur Conservation Project was started in 2000 by Munster Zoo and the Zoological Society for the Conservation of Species and Populations (ZGAP). Given the cause of the langur's decline, the main aim of the project was to halt poaching, with the additional intention of promoting conservation awareness amongst the inhabitants of Cat Ba Island. The project has been extremely successful in dramatically reducing deaths as a result of poaching, bringing the number from 30 deaths in the eight months prior to its start, to three deaths in the first four years of the project. In this time nine langurs were born and have survived. The langurs are closely monitored and protection measures are in place, particularly in the newly created langur sanctuary within the National Park. This highly protected area is home to 20 individuals from a large, reproducing group, which are protected by a rotation of 20 rangers – an incredible ratio of one ranger to one langur. The sanctuary is visibly marked around its circumference and is inaccessible to tourists. The Cat Ba Langur Conservation Project has constructed two new ranger stations, provided boats to ease patrols and has even seen the voluntary relocation of several local, floating households to support the rangers (3). The Cat Ba langur also has the support of Flora and Fauna International's Flagship Species Fund (5) and the Cat Hai District Women's Union, who implemented a project entitled 'Contributing to Biodiversity Conservation in Cat Ba National Park through Community Activity' (7). Following the finding of a decline in the white-headed black langur in China, efforts were made to conserve this subspecies. With funding from the Asian Development Bank, a survey in January 2003 showed evidence of some recovery in the Fusui populations (5), and numbers in Chongzuo have seen a rise from less than 100 to more than 200 individuals since Professor Pan Wenshi of Peking University began a research program in 1996 that concentrated on the subspecies (5). Tourism has become central to economy of both Vietnam and China, and now must be controlled to prevent the disturbance of recovering habitats and species in the Conservation International's Indo-Burmese Biodiversity Hotspot (7).
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Wikipedia

White-headed langur

The white-headed langur (Trachypithecus poliocephalus) is a critically endangered langur from Cát Bà Island, Vietnam (T. p. poliocephalus), and Guangxi, China (T. p. leucocephalus). Both taxa are overall blackish, but the crown, cheeks and neck are yellowish in T. p. poliocephalus, while they, as suggested by its scientific name, are white in T. p. leucocephalus.[3] As all members of the Trachypithecus francoisi species group, this social, diurnal lutung is found in limestone forests.[4]

The nominate subspecies, often known as the golden-headed or Cat Ba langur, is among the rarest primates in the world, and possibly the rarest primate in Asia.[5] The taxonomic position of the Chinese population, while also highly endangered,[6] is more confusing. It has been considered a partially albinistic population of the François' langur (T. francoisi), a subspecies of Francois' langur,[7] a valid species (T. leucocephalus), or a subspecies, T. poliocephalus leucocephalus.[1] Comparably, poliocephalus was considered a subspecies of Francois' langur until 1995.[7]

The golden-headed langur is considered to be one of "The World's 25 Most Endangered Primates,"[8] And is assumed to have declined by 80% over the last three generations. There are about less than 70 langur left in the world.

According to the Cat Ba Langur Conservation Project, the The Cat Ba langur's skin is black and the pelage color is dark brown; head and shoulder are bright golden to yellowish-white. The tail is very long (ca. 85 cm) compared to the body size (ca. 50 cm). Babies are colored golden-orange; the pelage starts to change its color from about the fourth month on. Males and females look alike. The Cat Ba langurs live in groups, usually one male with several females and their offspring. They are diurnal animals, adapted to living in limestone habitat. Each group has its own territory, defended by the adult male who also initiates the location of the group. The females usually give birth to a single baby every 2–3 years, which becomes mature at 4–6 years old. Langurs have an average life expectancy of 25 years. Food mainly consists of leaves, but also fresh shoots, flowers, bark, and some fruits.

References[edit]

  1. ^ a b Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M, eds. Mammal Species of the World (3rd ed.). Baltimore: Johns Hopkins University Press. p. 177. OCLC 62265494. ISBN 0-801-88221-4. 
  2. ^ Bleisch, B., Xuan Canh, L., Covert, B. & Yongcheng, L. (2008). Trachypithecus poliocephalus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 4 January 2009.
  3. ^ White-headed langur (Trachypithecus poliocephalus). ARKive. Accessed 2008-07-15
  4. ^ Rowe, N. (1996). The Pictorial Guide to the Living Primates. Pogonia Press, Charlestown, Rhode Island. ISBN 0-9648825-0-7. 
  5. ^ Stenke, R., Phan Duy Thuc and Nadler, T. 2007. Golden-headed Langur or Cat Ba Langur. In: Primates in Peril: The World’s 25 Most Endangered Primates 2006–2008, R. A. Mittermeier et al. (compilers), pp.14-15. Unpublished report, IUCN/SSC Primate Specialist Group (PSG), International Primatological Society (IPS), and Conservation International (CI), Arlington, VA.
  6. ^ Eudey, A. & Members of the Primate Specialist Group. 2000. Trachypithecus poliocephalus ssp. leucocephalus. 2007 IUCN Red List of Threatened Species. IUCN 2007.
  7. ^ a b Bradon-Jones, D. 1995. A revision of the Asian pied leaf monkeys (Mammalia: Cercopithecidae: Superspecies Semnopithecus auratus), with the description of a new subspecies. Raffles Bull. Zool. 43: 3-43
  8. ^ Mittermeier, R.A.; Wallis, J.; Rylands, A.B.; Ganzhorn, J.U.; Oates, J.F.; Williamson, E.A.; Palacios, E.; Heymann, E.W.; Kierulff, M.C.M.; Long Yongcheng; Supriatna, J.; Roos, C.; Walker, S.; Cortés-Ortiz, L.; Schwitzer, C., eds. (2009). Primates in Peril: The World's 25 Most Endangered Primates 2008–2010 (PDF). Illustrated by S.D. Nash. Arlington, VA.: IUCN/SSC Primate Specialist Group (PSG), International Primatological Society (IPS), and Conservation International (CI). pp. 1–92. ISBN 978-1-934151-34-1. 
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