Delacour's Langur
Encyclopedia
The Delacour's langur, or Delacour's lutung, (Trachypithecus delacouri) is a critically endangered
species of lutung
endemic to Vietnam
. It is considered to be one of the world's most endangered primate species
. It is named for French-American ornithologist Jean Théodore Delacour
.
and the Laotian langur
, but in other respects has a similar appearance. Adults measure from 57 to 62 cm (22.4 to 24.4 ) in head-body length, with a tail 82 to 88 mm (3.2 to 3.5 ) long. Males weigh between 7.5 and 10.5 kg (16.5 and 23.1 ), while the females are slightly smaller, weighing between 6.2 to 9.2 kg (13.7 to 20.3 ). Their fur is predominantly black, with white markings on the face and distinctive creamy-white fur over the rump and the outer thighs, while females also have a patch of pale fur in the pubic area. Like other closely related lutungs, Delacour's langur has a crest of long, upright, hair over the forehead and crown; this is, however, somewhat taller and narrower than in other species.
, where it is found only in an area of around 6000 square kilometres (2,316.6 sq mi) in the provinces of Ninh Binh
, Ha Nam, Hoa Binh
, Thanh Hoa
, and Ha Tay in the north of the country. The largest surviving population is believed to be in Van Long Nature Reserve in Ninh Binh, where the monkey inhabits open forest up to elevations of 328 metres (1,076.1 ft), in terrain dominated by limestone
karst
.
In previous decades, Delacour's langurs were reported to live in troops of up to thirty individuals, often including a mix of males and females, although single-male groups are more common, and some small all-male groups have also been reported. In more recent years, the typical group size seems to be much smaller, with only about four to sixteen members each. Males defend the troop's territory from outsiders, often standing watch on rocky outcrops. When potential rivals are spotted, the males in a troop initially try to intimidate them with loud hoots and visual displays, resorting to chasing and fighting if this fails. Within the group, social bonds are maintained by grooming and play.
Despite living in forested habitats, Delacour's langur is primarily terrestrial, only occasionally venturing into the trees. They swing by their hands when travelling through trees, and use their tail for balance when scrambling over steep rocky terrain, which may allow them to move more rapidly than other related lutungs.
period of 170 to 200 days. The young are born with orange fur, and precocial
, with open eyes and strong arms. The fur begins to turn black at around four months, and the young are probably weaned at 19 to 21 months, by which time the mother is likely ready to breed again. However, the full adult coat pattern is not achieved for around three years. Females reach sexual maturity at four years, and males at five years; the total life expectancy is around twenty years.
, and only that in the Van Long Nature Reserve may still be large enough to remain viable.
Classified as critically endangered
by the IUCN, the primary threat to the species is hunting for traditional medicine
, with loss of forest habitat and the local development of tourism also being a potential risk. As of 2008, less than 250 animals were believed to remain in the wild, with nineteen in captivity.
Critically endangered
Version 2010.3 of the IUCN Red List of Threatened Species identified 3744 Critically Endangered species, subspecies and varieties, stocks and subpopulations.Critically Endangered by kingdom:*1993 Animalia*2 Fungi*1745 Plantae*4 Protista-References:...
species of lutung
Lutung
The lutungs are a group of Old World monkeys and make up the entirety of the genus Trachypithecus. Their range is split into two parts; one part is much of southeast Asia , the other part is extreme southern India and Sri Lanka. The greater part of India has lutungs...
endemic to Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
. It is considered to be one of the world's most endangered primate species
The World's 25 Most Endangered Primates
The World's 25 Most Endangered Primates is a list of highly endangered primate species selected and published by the International Union for Conservation of Nature Species Survival Commission Primate Specialist Group , the International Primatological Society , and Conservation International...
. It is named for French-American ornithologist Jean Théodore Delacour
Jean Théodore Delacour
Jean Théodore Delacour was an American ornithologist of French origin. He was renowned for not only discovering but also rearing some of the rarest birds in the world...
.
Description
Delacour's langur is somewhat larger than its two closest relatives, Francois' langurFrancois' Langur
Francois' langur or Francois' leaf monkey is a species of lutung and the type species of its species group. Francois' langur belongs to the Colobinae subfamily, Cercopithecidae family, in the Primates order...
and the Laotian langur
Laotian Langur
The Laotian langur or white-browed black langur is a species of primate in the Cercopithecidae family. It is endemic to Laos. Its natural habitat is subtropical or tropical dry forests...
, but in other respects has a similar appearance. Adults measure from 57 to 62 cm (22.4 to 24.4 ) in head-body length, with a tail 82 to 88 mm (3.2 to 3.5 ) long. Males weigh between 7.5 and 10.5 kg (16.5 and 23.1 ), while the females are slightly smaller, weighing between 6.2 to 9.2 kg (13.7 to 20.3 ). Their fur is predominantly black, with white markings on the face and distinctive creamy-white fur over the rump and the outer thighs, while females also have a patch of pale fur in the pubic area. Like other closely related lutungs, Delacour's langur has a crest of long, upright, hair over the forehead and crown; this is, however, somewhat taller and narrower than in other species.
Distribution and habitat
Delacour's langur is endemic to VietnamVietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
, where it is found only in an area of around 6000 square kilometres (2,316.6 sq mi) in the provinces of Ninh Binh
Ninh Bình
Ninh Bình is a city in the Red River Delta of northern Vietnam. It is the capital of Ninh Binh province.-Geography:Ninh Binh city located in the southernmost plains north Vietnam...
, Ha Nam, Hoa Binh
Hoa Binh
Hòa Bình is a city in Vietnam. It is the capital of Hoa Binh province and is located 76 kilometres from Hanoi, a 5 kilometres from the Da River. The Battle of Hoa Binh was fought around the city in 1951-52 during the First Indochina War.-References:...
, Thanh Hoa
Thanh Hóa
Thanh Hóa is the capital city of Vietnam's Thanh Hoa province. The population is nearly 200,000 with an area of only 57.9 square kilometers....
, and Ha Tay in the north of the country. The largest surviving population is believed to be in Van Long Nature Reserve in Ninh Binh, where the monkey inhabits open forest up to elevations of 328 metres (1,076.1 ft), in terrain dominated by limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
karst
KARST
Kilometer-square Area Radio Synthesis Telescope is a Chinese telescope project to which FAST is a forerunner. KARST is a set of large spherical reflectors on karst landforms, which are bowlshaped limestone sinkholes named after the Kras region in Slovenia and Northern Italy. It will consist of...
.
Diet and behaviour
Delacour's langurs are diurnal, often spending the day sleeping in limestones caves, although they will sleep on bare rocky surfaces if no caves are available. They are folivorous, without about 78% of the diet reportedly consisting of foliage, although they will also eat fruit, seeds, and flowers. It has been reported that the monkeys will eat leaves from a wide range of different plant species, indicating that their apparent dependence on limestone habitats is not related to their diet.In previous decades, Delacour's langurs were reported to live in troops of up to thirty individuals, often including a mix of males and females, although single-male groups are more common, and some small all-male groups have also been reported. In more recent years, the typical group size seems to be much smaller, with only about four to sixteen members each. Males defend the troop's territory from outsiders, often standing watch on rocky outcrops. When potential rivals are spotted, the males in a troop initially try to intimidate them with loud hoots and visual displays, resorting to chasing and fighting if this fails. Within the group, social bonds are maintained by grooming and play.
Despite living in forested habitats, Delacour's langur is primarily terrestrial, only occasionally venturing into the trees. They swing by their hands when travelling through trees, and use their tail for balance when scrambling over steep rocky terrain, which may allow them to move more rapidly than other related lutungs.
Reproduction
Females give birth to a single young after a gestationGestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
period of 170 to 200 days. The young are born with orange fur, and precocial
Precocial
In biology, the term precocial refers to species in which the young are relatively mature and mobile from the moment of birth or hatching. The opposite developmental strategy is called "altricial," where the young are born or hatched helpless. Extremely precocial species may be called...
, with open eyes and strong arms. The fur begins to turn black at around four months, and the young are probably weaned at 19 to 21 months, by which time the mother is likely ready to breed again. However, the full adult coat pattern is not achieved for around three years. Females reach sexual maturity at four years, and males at five years; the total life expectancy is around twenty years.
Conservation
The population of Delacour's langurs has declined rapidly in recent years. As of 2006, only nineteen populations were known, following a dramatic decline in the total population of around 20% between 1999 and 2004. Since that time, two of the populations have been extirpatedLocal extinction
Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...
, and only that in the Van Long Nature Reserve may still be large enough to remain viable.
Classified as critically endangered
Critically endangered
Version 2010.3 of the IUCN Red List of Threatened Species identified 3744 Critically Endangered species, subspecies and varieties, stocks and subpopulations.Critically Endangered by kingdom:*1993 Animalia*2 Fungi*1745 Plantae*4 Protista-References:...
by the IUCN, the primary threat to the species is hunting for traditional medicine
Traditional medicine
Traditional medicine comprises unscientific knowledge systems that developed over generations within various societies before the era of modern medicine...
, with loss of forest habitat and the local development of tourism also being a potential risk. As of 2008, less than 250 animals were believed to remain in the wild, with nineteen in captivity.