Nilgai

The nilgai is the largest antelope of Asia, and is ubiquitous across the northern Indian subcontinent. It is the sole member of the genus Boselaphus, which was first scientifically described by Peter Simon Pallas in 1766. It is a sturdy, thin-legged antelope with a sloping back, a deep neck with a white patch on the throat, a short crest of hair along the neck terminating in a tuft, and white facial spots. A column of pendant, coarse hair hangs from the dewlap ridge below the white patch. It stands at the shoulder; males weigh, and the lighter females. A Sexual dimorphism is prominent; while females and juveniles are orange to tawny, adult males have a bluish-grey coat. Only males possess horns, long.
Major nilgai populations occur in the Indian and Nepal Terai. The diurnal nilgai prefers areas with short bushes and scattered trees in scrub forests and grassy plains. It commonly occurs on agricultural land and rarely in dense forests. Its diet encompasses grasses and herbs, though it also eats woody plants in the dry tropical forests of India. Females become sexually mature by two years, while males do not become sexually active until four or five years old. The time of the year when mating takes place varies geographically, but a peak breeding season lasting three to four months can be observed at most places. Gestation lasts eight to nine months, following which a single calf is born, sometimes also twins or even triplets. Nilgai calves stay hidden for the first few weeks of their lives. Three distinct kinds of groups have been observed: one or two females with young calves, three to six adult and yearling females with calves, and all-male groups with two to 18 members. The lifespan of the nilgai is around 10 years. Typically tame, the nilgai may appear timid and cautious if harassed or alarmed; it flees up to, or even, galloping away from the source of danger.
The nilgai is categorised as least concern on the IUCN Red List. It was introduced to Texas in 1924.

Taxonomy

The nilgai was described by Peter Simon Pallas, who in 1766 proposed the scientific name Antilope tragocamelus. Pallas based his description on an account of a male nilgai by James Parsons.

Etymology

The vernacular name "nilgai" comes from the fusion of the Hindi words nil and gai. The word was first recorded in use in 1882. Alternative origins could be from the Persian gaw. The nilgai has been referred to by a variety of names - neelghae, nilgau, nilgo, nylghau, and nylghai, constructions referring to other "blue" animals. During Mughal emperor Aurangzeb's reign of India, the nilgai was known by the name nilghor.
The generic name Boselaphus comes from the combination of the Latin bos and the Greek . The specific name tragocamelus is derived from the joining of the two Greek words tragos and kamelos. The binomial combination was first used by English zoologist Philip Sclater in 1883.

Evolution

A 1992 phylogenetic study of mitochondrial DNA sequences showed a strong possibility of a clade consisting of Boselaphini, Bovini, and Tragelaphini. Bovini consists of the genera Bubalus, Bos, Pseudoryx, Syncerus, Bison and the extinct Pelorovis. Tragelaphini consists of two genera: Taurotragus and Tragelaphus. A closer relationship between Boselaphini and Tragelaphini was predicted, and seconded by a similar study in 1999.
Though the tribe Boselaphini has no African representation today, fossil evidence supports its presence in the continent in the prehistoric times, as early as the late Miocene. The two living antelope species of this tribe have been found to have a closer relationship with the earliest bovids than do the other bovids. This tribe originated at least 8.9 million years ago, in much the same area where the four-horned antelope lives today, and may represent the most "primitive" of all living bovids, having changed the least since the origins of the family. The extant and extinct boselaphine forms show similar development of the horn cores. Though the extant nilgai females lack horns, historic relatives of the antelope had horned females. Fossil relatives were once placed in the subfamily Cephalophinae which now contains only the African duikers. Fossils of Protragoceros and Sivoreas dating back to the late Miocene have been discovered not only in Asia and southern Europe but also in the Ngorora Formation and are thought to belong to the Boselaphini. Other Miocene fossils of boselaphines discovered are of Eotragus, Miotragocerus and Tragoportax; fossils of Miotragoceros are not apparent in Africa, but have significant presence in the Shiwalik Hills in India and Pakistan, as do several Tragoportax species. A 2005 study showed the migration of Miotragoceros to eastern Asia around eight million years ago. Alan W. Gentry of the Natural History Museum reported the presence of another boselaphine, Mesembriportax, from Langebaanweg.
Remains of the nilgai dating back to the Pleistocene have been discovered from the Kurnool caves in southern India. Evidence suggests that they were hunted by humans during the Mesolithic period.

Description

The nilgai is sturdy with a deep neck, a sloping back and thin legs; it has a short mane of hair behind and along the back ending behind the shoulder, a white patch on the throat, and around two white spots each on its face, ears, cheeks, lips, and chin. The ears, tipped with black, are long. Along the dewlap ridge below the white throat patch, it has a column of coarse hair, known as the "pendant" which is around long in males. The tufted tail has a few white spots and is tipped with black. It is up to long; the forelegs are generally longer than the hindlegs, and are often marked with white "socks". While females and juveniles are orange to tawny, males are much darker and typically bluish grey. The ventral parts, the insides of the thighs, and the tail are all white. A white stripe extends from the underbelly and broadens as it approaches the rump, forming a patch lined with dark hair. Almost white, though not albino, individuals have been observed in the Sariska National Park. while individuals with white patches have been recorded at zoos. The hairs, typically long, are fragile and brittle. Males have thicker skin on their head and neck that protect them in fights. The nilgai is not well-insulated with subcutaneous fat during winter, so severe cold might be fatal for the nilgai. Males are horned, and the occasional female. The horns are long but generally shorter than. Smooth and straight, these may point backward or forward. The horns of the nilgai lack the ringed structure typical of those of other bovids.
The nilgai is the largest antelope in Asia. It stands at the shoulder; the head-and-body length is typically. Males weigh ; the maximum weight recorded is. Females are lighter, weighing. Sexual dimorphism is prominent; the males are larger than females and differ in and colouration.
The maximum recorded length of the skull is. The dental formula is. The milk teeth are totally lost and the permanent dentition completed by three years of age. The permanent teeth get degraded with age, showing prominent signs of wear at six years of age. The nilgai has keen senses of vision and hearinng, though its sense of smell is not acute.

Distribution and habitat

The nilgai is endemic to the Indian subcontinent; major populations occur in India, Nepal, and border areas of Pakistan.
Significant numbers occur in the Terai lowlands in the foothills of the Himalayas; it is abundant across northern India. It prefers 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 in area.
The Indian population was estimated at one million in 2001.
The population in Bangladesh was thought to be extinct, but some individuals from India and Nepal have crossed the border into the northwest of the country.
The nilgai were first introduced to Texas in 1924, by Caesar Kleberg, onto a ranch near the Norias Division of the King Ranch, one of the largest ranches in the world. The feral population had a spurt toward the latter part of the 1940s, and gradually spread out to adjoining ranches.
Population densities show great geographical variation across India. Density can be as low as 0.23 to 0.34 individuals per km² in Indravati National Park. and 0.4 per km² in the Pench Tiger Reserve, or as high as 6.6 to 11.36 per km² in Ranthambhore National Park, and 7.0 individuals per km² in Keoladeo National Park. Seasonal variations were noted in Bardiya National Park in a 1980 study; the density 3.2 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 3–5 per km² in 1976.
Historic notes mention nilgai in southern India, but these may have been feral:

Behavior and ecology

The nilgai is diurnal. A 1991 study investigated the daily routine of the antelope and found feeding peaks at dawn, in the morning, in the afternoon, and during the evening. Females and juveniles do not interact appreciably with males, except during the mating season. Groups are generally small, with 10 or fewer individuals, though groups of 20 to 70 individuals can occur at times. In a 1980 study in Bardiya National Park, the average herd size was of three; In a 1995 study in the Gir National Park, herd membership varied with season. However, three distinct groupings are formed: one or two females with young calves, three to six adult and yearling females with calves, and male groups with two to 18 members.
Typically tame, the nilgai may appear timid and cautious if harassed or alarmed; instead of seeking cover like duikers it would flee up to -or even on galloping-away from the danger. Though generally quiet, nilgai have been reported to make short guttural grunts when alarmed, and females make clicking noises when nursing young. Alarmed individuals, mainly juveniles below five months, give out a coughing roar that lasts half a second, but can be heard by herds less than away and responded to similarly.
Fights take place in both sexes and involve pushing their necks against each other or ramming into one another using horns. Fights can be gory; despite the protective skin deep, lacerated wounds and even deaths might occur. Display behaviour focuses on the throat patch and the beard, and threatening opponents by pointing the horns toward them. A young male was observed making a submissive display in the Sariska Reserve by kneeling before an adult male that stood erect. Nilgai mark their territories by forming dung piles as much as in radius. The defecation process is elaborate; the antelope stands with its legs about 1 m apart, with the rump lowered and the tail held almost vertical; it stays in the same posture for at least 10 seconds after relieving itself. The process is not as elaborate in the females as it is in the males.
In India, the nilgai shares its habitat with the four-horned antelope, chinkara, chital, and blackbuck; its association with the gaur and the water buffalo is less common. In Ranthambore National Park, the nilgai and the chinkara collectively prefer the area rich in Acacia and Butea species, while the sambar deer and the chital preferred the forests of Anogeissus and Grewia species. In India, the Bengal tiger and Asiatic lion prey on the nilgai, but the latter is not a significant predator of this antelope. Leopards also prey on the nilgai, though they prefer smaller prey. Dholes generally attack juveniles. Other predators includes the Indian wolf and striped hyena.