The kouprey, kouproh, forest bull or grey ox is a wild, forest-dwelling ox, which may exist in protected areas in eastern and northern Cambodia (Lomphat Wildlife Sanctuary, Phnom Prich Wildlife Sanctuary, Mondulkiri Protection Forest and/or Siema Biodiversity Conservation Area) (17). It ha also lived in southern Laos, western Vietnam and southeast and eastern Thailand (16). Fossil evidence indicates that it was once present in central China (12). It lives in low, partially forested hills and prefers open deciduous dipterocarp forests, especially those areas with extensive grasslands, often near thick monsoon forests (17,18). It seems to use patches of mixed deciduous and semi-evergreen forest. Most of its range lies in a highly seasonal area receiving less than 2,000 mm of precipitation per annum. The presence of pools and mineral licks is important in areas of high rainfall (16). Some suitable kouprey has been created by natural forest disturbance and slash-and-burn agriculture. The kouprey measures 2.1-2.3 m along the head and body plus a 1 m tail. It stands 1.7-1.9 m high at the shoulder and weighs 680-910 kg  with unverified reports up to 1,700 kg from Vietnam are considered dubious, since they far exceed other recorded weights for the species. The kouprey has a tall, narrow body, long legs, notched nostrils, humped back and a long tail with a bushy tip. Adult males are dark brown to black, but females are more grey in colour and young are reddish with lighter coloured legs, becoming greyish-brown by 5-6 months. The lower legs are white or greyish. Males have a dewlap, a skin fold hanging from the neck (12). Their long, far-reaching horns arch forward and upward; they can reach up to 80 cm and begin to split and fray at the tips at about 3 years old (14). The horns of the female are lyre-shaped with antelope-like upward spirals and reach 40 cm.
The kouprey is diurnal, eating in the open at night and under the forest cover by day. It is said to have become nocturnal to avoid contact with humans. It is active and digs into the ground. Males butt tree stumps, causing fraying of their horns. The kouprey lives in herds of up to 20, primarily of females and calves and usually led by a single female. h banteng. Mature males form bachelor herds, but join the herds of cows and calves in the dry season. Many herds break up and rejoin as they travel  and may live with herds of banteng or wild buffalo . Kouprey probably to use some visual signals and body postures in communication. Scent is likely to play some role, especially in identifying mates and offspring. Bovids typically vocalize to one another. Tactile communication is probably important in competition and between a mother and her young. The kouprey usually travels up to 15 km in a night to graze on grasses, visit saltlicks and drink from waterholes. The kouprey feeds mainly on grasses, including bamboo, ploong, and koom; it also eats leaves, roots, tubers, sedges, and some browse. It spends a lot of time around salt licks and water holes. The only known predator of the kouprey is humans; kouprey have become nocturnal to avoid human predation.
Kouprey mate in the spring; their sexual dimorphism suggests some level of polygyny. Males may compete for females and successful males are polygynous. Females show low fertility and produce one calf in winter (typically December or January) after a gestation of 8-9 months. Females leave the herd to give birth, protecting the new-born calf amongst dense vegetation until it is about a month old when they return to the herd (12). The female provides the bulk of parental care, producing milk for the young, grooming it, and protecting it from danger. Male parental care has not been noted. Kouprey have a lifespan of about 20 years. Lifespan is limited by hunting, inbreeding, and disease.
The kouprey is believed to be a close relative to the aurochs and gaur. Some scientists compared mitochondrial sequences and suggedted the kouprey might be a hybrid between a zebu and a banteng , but later rescinded their conclusion  when a fossilized skull was found dating from the late Pleistocene or early Holocene. More recent genetic analysis has supported this position .
There are fewer than 250 mature kouprey left in the world, perhaps below 50 with some speculation that they are extinct. The population is estimated to have fallen over 80% in the last 30 years. When the Khmer Rouge fell in Cambodia, markets for bushmeat and trophies surged, resulting in intense pressure on large mammals.The low numbers are attributed to uncontrolled hunting by locals and soldiers for meat, horns, gall bladders and skulls for use in traditional Chinese medicine (6,16), along with diseases introduced from cattle and other livestock and loss of habitat due to agriculture and logging activity. Kouprey may compete with banteng and water buffalo for food. Prince Sihanouk designated the kouprey as the national animal of Cambodia in the 1960s, partly due to its mystique (5). No kouprey have been sighted since 1988 , but tracks have been seen some horns have been found in markets (6,14). The 2008 IUCN report lists the kouprey as critically endangered (possibly extinct) [7,16]. It is listed on Appendix I of CITES (19), on Appendix I of the Convention on Migratory Species (CMS or Bonn Convention) (20) and is legally protected in all range states. If the species is still extant it is most likely to be in eastern Cambodia in one of four protected areas There are no kouprey in captivity. There are suggestions that domesticated kouprey may survive in Cambodia (2), but this seems very unlikely, although domestic oxen in Cambodia may carry kouprey genes (2). Kouprey are thought to be very genetically diverse and immune to certain pests that plague domestic cattle in this region. Cross-breeding between kouprey and domestic cattle could potentially reduce disease. There is no captive population. The only individual in a western zoo was sent to the Vincennes Zoo, Paris in 1937; it was designated as the holotype by Urbain and died early in World War II [3,6,8]. The kouprey had been discovered in 1929, when an American man and his son shot and killed an unidentified ungulate to use as tiger bait. The bones were sent to the University of Kansas Museum of Natural History, but were not examined until 1982 (4). Pfeffer took the only reasonable photograph of a wild kouprey (9,13,15). The only significant scientific observation of the kouprey was made in 1957 when zoologist Charles Wharton studied and filmed the animal in the wild (1). By 1970 it was thought to be extinct following continued hunting for meat, horns and skulls(6,16); land mines along the borders of Cambodia may be responsible for kouprey deaths and hinder conservation efforts (16).