Habitat and distribution
Nilgai prefer areas with low bushes.
Nilgai prefer areas with short bushes and scattered trees in scrub forests and grassy plains. They are common in agricultural lands, but hardly occur in dense woods. In southern Texas, it roams in the prairies, scrub forests and oak forests. It is a generalist animal-it can adapt to a variety of habitats. Though sedentary and less dependent on water, nilgai may desert their territories if all water sources in and around it dry up. Territories in Texas are 0.6 to 8.1 square kilometres (0.23 to 3.13 sq mi) large.
This antelope is endemic to the Indian subcontinent: major populations occur in India, Nepal and Pakistan, whereas it is extinct in Bangladesh. Significant numbers occur in the Terai lowlands in the foothills of the Himalayas; the antelope is abundant across northern India. The Indian population was estimated at one million in 2001. The nilgai were first introduced to Texas in the 1920s and the 1930s in a 6,000 acres (2,400 ha) large ranch near the Norias Division of the King Ranch, one of the largest ranches in the world. The feral population saw a spurt toward the latter part of the 1940s, and gradually spread out to adjoining ranches.
Nilgai search for new areas if they run out of water.
Population densities show great geographical variation across India. Density can be as low as 0.23 to 0.34 individuals per km2 in the Indravati National Park (Chhattisgarh) and 0.4 individuals per km2 in the Pench Tiger Reserve (Madhya Pradesh) or as high as 6.60 to 11.36 individuals per km2 and Ranthambhore National
Park and 7 individuals per km2 in Keoladeo National Park (both in Rajasthan). Seasonal variations were noted in the Bardiya National Park (Nepal) in a 1980 study; the density 3.2 individuals per km2 during the dry season and 5 per km2 in April (the start of the dry season). In southern Texas, densities were found to be nearly 3–5 individuals per km2 in 1976.
Historic notes mention nilgai in southern India, but these may have been feral:
I believe that the Coimbatore and Salem collectorates are almost the only places in Southern India, in which nil-gai are to be found. It is difficult to account for the animals being thus so widely divided from their usual haunts unless as has been generally supposed, these Southern specimens are the progeny of a semi-domesticated herd, which, at some by-gone period, had escaped from the preserve of a native potentate.
— Andrew Cooke McMaster (Notes on Jerdon's Mammals of India, 1871)