Red-shanked douc

The red-shanked douc is native to Indochina; Vietnam, southern Laos, and possibly northeastern Cambodia, east of the Mekong river. In Laos, red-shanked doucs occur from the southern Nam Ghong Provincial Protected Area to the central-north part of the country. Laos is believed to have the largest population of red-shanked doucs, with Nakai-Nam Theun National Protected Area in central Laos having the most individuals of approximately 4,420 groups, followed by the Hin Namno National Protected Area. In Vietnam, the species lives between Nghệ An and Gia Lai provinces, from 18°29'N to 14°21'N. The Sơn Trà Nature Reserve on Sơn Trà Mountain in central Vietnam holds the greatest Vietnamese population with approximately 700–1300 individuals. The Phong Nha – Kẻ Bàng National Park is also an important Vietnamese site for the species. There was a report of a red-shanked douc specimen that was given to the Staatliches Museum by the Dresden Zoological Garden who had said that it originated in Hainan, China but the zoo records no longer exist so it remains uncertain. Red-shanked doucs are found in evergreen, semi-evergreen and occasionally limestone forests, up to in elevation. Their home range is approximately and they have a core area of , with a smaller range in the dry season of and a larger range in the wet season of . There are weak correlations between precipitation, temperature, and diet and home range but not enough to draw conclusions from them. ==Characteristics==

Like other Doucs, the red-shanked douc is a long, slender monkey. The male has a head and body length of with a tail that measures , and the female is between long with a tail that measures long. Males weigh , and females . Males of all ages have a white spot on both sides of the corners of the rump patch, and red and white genitals. Red-shanked douc langur (Pygathrix nemaeus) male Son Tra.jpg|Male Red-shanked douc langur (Pygathrix nemaeus) female Son Tra.jpg|Female Red-shanked douc langur (Pygathrix nemaeus) juvenile Son Tra.jpg|Juvenile ==Behavior==

This monkey communicates using facial expressions. It has a specific "play face" with the mouth open, teeth partially bared and chin thrust forward. Sometimes, it closes its eyes and paws blindly towards another douc without regard for the hazards of doing so when up a tree. A fixed stare is a threat display. A grimace with the mouth open and the teeth exposed is a submissive gesture given in response to a stare and is also used to initiate grooming or play. The red-shanked douc has a low-pitched growl that is given as a threat, and a short, harsh distress squeal. During adult play, they perform an eyelid display where they blink their eyes open and closed to show their light blue eyelids. They are a fairly peaceful species and agonistic behavior has been very rarely reported. In the San Diego Zoo, researchers observed that in the instances where there was agonistic behavior, it only lasted a few seconds and did not result in injury. Group composition Red-shanked doucs live in multilevel, fission-fusion societies in one-male/multi-female or multi-male/multi-female groups with a male-to-female ratio of 1.0:1.63 and an adult-to-young ratio of 1.1:1.0. The bands contain a mean of 18 individuals in a mean of 2.7 units per band and a mean of 6.5 individuals per unit. Both males and females have their own hierarchies and males are dominant to females. Both males and females will eventually leave the group they were born into. Red-shanked doucs fuse overnight and fission during mornings and early afternoons. When they are fused, they rest more and when they fission, they are more active. There does not seem to be any difference in daily fission-fusion from wet to dry season yet overall fission-fusion events increase during part of the wet season, from October to December. In a study at the Sơn Trà Nature Reserve, 55.32% of their observations were fusion events and 44.68% were fission events. This behavior is believed to help with regulating feeding competition. Red-shanked doucs are very inflexible with membership into their groups. ==Locomotion==

In captivity, red-shanked doucs use brachiation for almost half of their locomotion whereas, in the wild, arm-swinging accounts for an average of 18% of locomotion. Juveniles use arm-swinging the most (34.3%), followed by subadults (21.7%), adult females (17.6%), adult females carrying infants (15.5%), and then adult males (9.8%). This showed that with increased body weight there is a decreased amount of brachiation. When they travel by foot, their tail will usually hang down. Like all other Old World monkeys, its tail is not prehensile. It uses its tail solely for balance, and it uses its arms and legs to move through the forest along established routes. When on the move, the group is led by adult males, with juvenile males bringing up the rear and the females and infants staying safe in the middle. This douc is an aerial specialist, moving high up in the canopy. It is very agile and frequently makes breath-taking leaps of up to 6 meters (20 feet), leaping with its arms outstretched over its head, pushing off with its legs and landing on two feet. When the group is untroubled, the red-shanked douc will move noisily from branch to branch through the forest, crashing through foliage, swinging under branches and leaping with two feet together, displaying its remarkable sense of balance. But when a group is disturbed, by either a predator or other dangers, it can flee silently through the trees, away from danger. If it is startled, it may produce loud barks and rush around the trees slapping branches with its hands and feet. ==Mating and development==

Mating (Macaca mulatta) In captivity, female red-shanked doucs reach sexual maturity at four years old and males at four years and eight months. Births occur year-round but peak between August and October and again between February and April. The gestation period lasts between 165 and 210 days, resulting in the birth of a single offspring or very rarely, twins. In captivity, it was observed that the pregnant female will find a high place in the enclosure to give birth. The head of the infant emerges after 90 minutes of labour which is followed by the placenta that weighs 90–120g. The oldest recorded birth was from a 26-year-old female. Development The young are born with their eyes open and they latch on to their mothers instinctively. The baby's body coloration is lighter than an adult's. Its face is more of a blue color and the body is a lighter beige. As it grows older, its body darkens while its face lightens, achieving adult colors at 10 months. In captivity, other group members may look after an infant, and other females may even suckle it. In one study, an orphaned infant was fed by two females in the group and also cared for by a male. The first six months of a red-shanked douc's life is the most challenging. In captivity, they can live for up to 25 years. ==Diet==

Red-shanked doucs are highly folivorous. In the Sơn Trà Nature Reserve found they consume 54.8% buds and young leaves, 22.6% mature leaves, 3.7% leaf petioles and 18.9% other plant parts. Per month, they found that the red-shanked doucs consumed a mean of 18 species per month and a total of 226 species consumed altogether. Out of the 226 species, there are five species that were eaten 47–82% of the time: Acacia pruinescens, Ficus racemosa, Millettia nigrescens, Zanthoxylum avicennae and Castanopsis ceratacantha. Red-shanked doucs are selective feeders and flexible eaters because of their ability to eat a wide variety of food in all seasons. Fruit is consumed mainly in the morning, which is common amongst leaf-eating monkeys as this is where they derive their energy for the day. They have different eating patterns during the wet season and the dry season both in what they eat and in the parts of the plants that they eat, although it is not a drastic change. Figs however, are consumed all year long and make up 16–36% of their diet. It is the second most commonly consumed plant by the monkeys and they eat the fruit, leaves and flowers. Like all other doucs, they do not have cheek pouches. ==Conservation==

In 2000, the IUCN Red List of Threatened Species classified the red-shanked douc langur as endangered. In 2020, the IUCN updated their classification of the species to critically endangered, due to the population's continual decline. It was also listed in the Vietnam Red Book in 2007. In 2019, the Vietnamese prime minister classified them as a high-risk species that needs protection, in Decree 06. The species is listed in CITES I, which prohibits commercial international trade. More than half of the species has been lost in the past 30–40 years. The main threat to the red-shanked douc is from hunting. Their meat is used for food, traditional medicine, and for international sale or trade. Local people often hunt the species for consumption, pets, or making glue. Although hunting of the species is technically illegal, it is not strictly enforced and has little effect. In the Dong Ampham National Protected Area in Laos, on the border with Vietnam, local hunters have estimated that approximately fifty red-shanked doucs are killed each year. From 2015 to 2018, the Bach Ma National Park Forestry Protection department in Vietnam confiscated 13 kg of red-shanked douc meat. Their behavioral characteristics are believed to make the species particularly easy to hunt. Vietnam has the highest hunting levels of the species. Their other main threats are pet trade, habitat fragmentation, creation of agricultural land, and military installations. With Laos having the biggest population of red-shanked doucs, the country has been marked as being the most important for the species' conservation. A study conducted by Camille N. Z. Coudrat et al. stated that the best approach to conserving the monkeys is to focus on the largest populations, specifically in Laos. At present, there is no conservation effort in that country. There have been efforts to breed red-shanked doucs in captivity since the late 1960s, but they are difficult to keep in zoos due to factors such as their diet, so currently, there are only 33 individuals in captivity worldwide. Habitat loss in Sơn Trà due to development plans poses a high risk to the monkeys. Historically, Sơn Trà had a military installation, so many animals in the region were shot as practice targets. Currently, the red-shanked doucs in Sơn Trà Nature Reserve are protected by the army, police and forest protection departments of Da Nang and Sơn Trà. ==References==