The nilgai, sometimes called nilgau, is an antelope, and is one of the most commonly seen wild animals of central and northern India and eastern Pakistan; it is also present in parts of southern Nepal. The species has become extinct in Bangladesh. The mature males appear ox-like and are also known as blue bulls. The nilgai is the biggest Asian antelope.
The nilgai has thin legs and a robust body that slopes down from the shoulder. They show marked sexual dimorphism, with only the males having horns. Adult males have a grey to bluish-grey coat, with white spots on the cheeks and white colouring on the edges of the lips. They also have a white throat bib and a narrow white stripe along the underside of the body that widens at the rear. The tips of the long, tufted tail and of the ears are black. They also possess a tubular-shaped "pennant" of long, coarse hair on the midsection of the throat.
In contrast, females and young are tawny brown in colour, although otherwise with similar markings to the male; they have no horns and only a very small "pennant".
Nilgai are habitat generalists, living in grasslands and woodlands where they eat grasses, leaves, buds, and fruit. They avoid dense forest and prefer the plains and low hills with shrubs, but may also be found in cultivated areas. Nilgai are diurnal, and tend to form single-sex herds outside of the breeding season. Herds are not of fixed composition, with individuals joining and rejoining through the year. Female herds typically contain three to six adults, together with their calves, whereas bulls form herds of two to 18 individuals.
Predators of nilgai include tigers and leopards, although the latter are only capable of capturing calves, and not fully grown adults. Like many Indian animals, nilgai are often victim to vehicular accidents, and their carcasses are often seen on major highways in northern India. The main threat to this species is the loss of habitat due to human population growth.