|Range||Southeast Asia, specifically the countries Cambodia, China, Laos and Vietnam.|
The Red-shanked douc (Pygathrix nemaeus), is a species of Old World monkey, among the most colourful of all primates. This monkey is sometimes called the "costumed ape" for its extravagant appearance. From its knees to its ankles it sports maroon-red "stockings", and it appears to wear white forearm length gloves. Its attire is finished with black hands and feet. The golden face is framed by a white ruff, which is considerably fluffier in males. The eyelids are a soft powder blue. The tail is white with a triangle of white hair at the base. Males of all ages have a white spot on both sides of the corners of the rump patch, and red and white genitals.
Like other doucs, the red-shanked douc is a long, slender monkey. The male has an average head and body length of 61 cm (24 in), and the female averages 54.5 cm (21.5 in) long, with a tail that measures 55.8–76.2 cm (22.0–30.0 in) long. Males weigh on average 11 kg (24 lb), and females 8.44 kilograms (18.6 lb). There is a slight difference in rump markings between genders: the male has round white spots above the triangle of white on its rump, while the female does not.
Doucs are, like all monkeys, social animals. They live in groups with an average size of 4 to 15, but groups of up to 50 have been recorded. A group usually consists of one or more males and approximately two females per male. 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.
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 soundlessly through the trees, away from danger. If it is startled, it may give loud barks and rush around the trees slapping branches with its hands and feet. In contrast to their noisy travel, doucs spend most of their time quietly eating, digesting their bulky food, dozing and grooming each other's fur.
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 with remarkable disregard for the hazards of doing this 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. It 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.
This douc has been rarely observed in the wild and very little is known about its wild mating and breeding habits. Before mating, both genders give a sexual signal with the jaw forward, eyebrows raised and then lowered, and a head-shake. The female makes the first move, lying face-down on a branch, eyeing her chosen mate by looking over her shoulder. The male returns with a stare and may turn to look at another spot he considers more suitable for mating. Single-mount and multiple-mount matings have been reported.
Mating takes place from August to December. The pregnancy lasts between 165 and 190 days, resulting in the birth of a single offspring just before fruiting season of some favorite foods. Twins are very rare. The young are born with their eyes wide open and they cling to their mothers instinctively. The baby's body colouration is lighter than an adult's. Its short, downy grey hair has a dark stripe down the back and it has a black face and two pale stripes beneath the eyes. As it grows older, its body darkens while its face lightens, achieving adult colours 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. Females reach sexual maturity at about 4 years, while the males reach it at 4–5 years. They have a lifespan of about 25 years.
The main predator of the red-shanked douc is humans. It is threatened throughout its limited range by habitat destruction and hunting. Native people hunt it for food and body parts, which are used in traditional medicine. There is also a very lucrative and illegal wildlife trade for the red-shanked douc. During the Vietnam War, the douc habitat was heavily bombed and sprayed with defoliants like Agent Orange.
The red-shanked douc is diurnal and eats and sleeps in the trees of the forest. Its diet consists mostly of leaves high in fibers. Belonging to the subfamily Colobinae, or leaf-eating monkeys, it has a large stomach which is divided into sacs containing bacteria that break down the cellulose in the leaves through fermentation, giving the douc its pot-bellied look. This also makes it burp frequently from the resulting gas. It prefers to eat small, young and tender leaves, but will also eat fruit like figs, buds, petioles, flowers, bamboo shoots and seeds. It gets all the liquid and protein it needs from the food it eats and doesn't need to descend to the ground to drink. This monkey eats 50 different plant species but no animal prey. It is a messy and chaotic feeder, dropping much of its food onto the forest floor: old leaves, under-ripe or over-ripe fruits. It eats peacefully together, not quarreling over food, and has been known to share it with others. Often, it will share the same clump of foliage and may even break pieces off and hand them to each other, a type of active generosity that is rare among Old World monkeys. It does not have cheek pouches. This diet provides them with adequate protein and fluids.