|Species group:||T. francoisi|
|White-headed Langur range|
The white-headed langur (Trachypithecus poliocephalus) is a critically endangered langur. Two subspecies are recognized: T. p. poliocephalus in Cát Bà Island, Vietnam, and T. p. leucocephalus in Guangxi, China. The former (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, with population size estimated at less than 70 individuals.
Both subspecies are overall blackish, but the crown, cheeks and neck are yellowish in T. p. poliocephalus, while they are white in T. p. leucocephalus, as suggested by its scientific name. 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 with 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 Langur, which lives on Cat Ba Island in Vietnam, is one of the 25 most endangered species. Conservation efforts are helping to prevent this, however, and have greatly increased their population since 2003, when there were only 40. Until recently, the Cat Ba Langur was not considered a species but rather a subspecies of other Langurs that live in the Vietnam jungles. Cat Ba Langurs are diurnal creatures and travel in groups of about four to five animals. They prefer the steep limestone cliffs that make up most of Cat Ba Island. Most of the places that they are found are not accessible to humans by foot. Cat Ba Langurs spend around 66% of their time resting and the rest moving, foraging, and socializing, with the distribution changing between summer and winter. They eat less and rest more in the winter and the opposite in the summer.
The taxonomic position of the Chinese population is uncertain. It has been considered a partially albinistic population of the François' langur (T. francoisi), a subspecies of Francois' langur, a valid species (T. leucocephalus), or a subspecies, T. poliocephalus leucocephalus. Comparably, poliocephalus was considered a subspecies of Francois' langur until 1995.
Cat Ba island is the biggest of all the group island, with 366 small forms surrounding it. As all members of the Trachypithecus francoisi species group, this social, diurnal lutung is found in limestone forests. Critically endangered, the white-headed Langur resides near Ha Long Bay, specifically in Cat Ba Island, hence its common name “Cat Ba Langur”. This landscape is known as a karst formation that has been invaded by the ocean. The topography is of limestone that has been worn away through erosion, which later formed ridges, towers, fissures, sinkholes and other types of landforms. The Cat Ba Langur are diurnal animals, adapted to living in limestone habitat.The diurnal caves found within were thought to be used as protection from predators and extreme weather as well as provide shelter. Additionally, it was used as a hunting ground for humans to capture or kill langurs as they slept.
The Langur lives in a moist tropical rain forest on limestone hills, where they share with 6-7 other genus of the T. francoisi group. During the summer the weather is warm, and rainy with temperatures averaging 25 °C. In the winter, it is usually cold with little rain and high temperatures averaging less than 20 °C. Because there are no rivers and streams developed on the Cat Ba island, the Thuong Stream is the animal's source for water.Temporary streams form during rainy season, however disappear right after. The water is absorbed into caves. The soil is produced through a mixture of limestone, bedrock, karst land form, and the humid climate. The Cat Ba langurs live in groups, usually one male with several females and their offspring. 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. This type of habitat provided an arborous and terrestrial environment for langurs as well as one that provided sustenance that accommodated the langurs folivorous diet. Food mainly consists of leaves, but also fresh shoots, flowers, bark, and some fruits. The leaves make up over 70% of the langurs diet.
The golden-headed langur is considered to be one of "The World's 25 Most Endangered Primates  and is assumed to have declined by 80% over the last three generations. It is estimated that there are less than 70 langur left in the world.
In October 2002, Münster Zoo and ZSCSP, the Zoological Society for the Conservation of Species and Populations, started the Cat Ba Langur Conservation Project. The Cat Ba Langur's distribution range was declared a National Park in 1986, however that did not stop the poaching and decline of the population. About 30% of the population is located outside of the National Park and are highly endangered by human activities.
There is a strictly protected sanctuary, a peninsula on the eastern coast of Cat Ba Island, in the National Park and supports about 40% of the population. Fixed boundaries were set with blocking buoys and prohibition signs. Another step taken was to increase the amount of rangers in the area. Local citizens, especially fishermen, were informed and rangers were given permission to remove people and take away any poaching equipment they found. Any existing and potential caves and hunter trails are registered, regulated, and controlled.
At the end of 2001, there was no more hunting of the Cat Ba Langur. Since the beginning of the conservation efforts, nine langurs have been born and only three have died of natural causes.
The greatest populations of the Cat Ba Langur are expected to recover with the appropriate conservation of the limestone habitats.There are currently no langurs held in captivity.
Threats to Survival
Hunters of the white headed langur are common. There are several reasons for this, but the most relevant is that there is a belief among some Asian men that a balm made from these langurs will help with erectile dysfunction. Since the langurs are so few, hunting takes two to four weeks. A hunter can earn up to $50 from a single langur, which is a lot when the average annual per capita income is less than $350. Since it is so hard to find the langurs, the poachers do not go out with the intent on capturing one, but often capture them by chance when hunting other animals in the area. Between 1970 and 1986, an estimated 500 to 800 langurs were killed.
The hunters of the langurs have been known to attack people who get in their way. As part of a conservation effort, "body guards" for the langurs have been put into place. These guards are unarmed, and on several occasions have been severely hurt by the hunters. Teeth have been knocked out and several have been stabbed. Because of the fear of being attacked, the guards do not want to do their job anymore.
Cat Ba Island is in the process of creating a booming tourist industry. They are in the process of building luxury hotels around the island, with one hotel being 17 feet tall. To accommodate all the new tourists, the town of Cat Ba is building a new road that will connect the town to a small village on the northern edge of the island where a ferry will be to take tourists to another popular destination: Ha Long Bay. The road runs just along a border of the park which may attract more hunters to the area. There is a fear that the tourists may want to hunt and eat the meat of the langur even though their meat smells terrible. It may start to be considered a status symbol. Although these efforts for tourism would benefit Cat Ba, it's effects on the white headed langur may be detrimental.
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