- Kingdom :Animalia
- Phylum :Chordata
- Class :Mammalia
- Order :Artiodactyla
- Family :Bovidae
- Subfamily :Bovinae
- Scientific Name :Boselaphus tragocamelus
Description:
The nilgai is the largest antelope in Asia.It stands 1–1.5 metres (3.3–4.9 ft) at the shoulder; the head-and-body length is typically between 1.7–2.1 metres (5.6–6.9 ft).[6] Males weigh 109–288 kilograms (240–635 lb); the maximum weight recorded is 308 kilograms (679 lb). Females are lighter, weighing 100–213 kilograms (220–470 lb).Sexual dimorphism is prominent; the males are larger than females and differ in colouration.A sturdy thin-legged antelope, the nilgai is characterised by a sloping back, a deep neck with a white patch on the throat, a short mane of hair behind and along the back ending behind the shoulder, and around two white spots each on its face, ears, cheeks, lips and chin.The ears, tipped with black, are 15–18 centimetres (5.9–7.1 in) long.[2] A column of coarse hair, known as the "pendant" and around 13 centimetres (5.1 in) long in males, can be observed along the dewlap ridge below the white throat patch.The tufted tail, up to 54 centimetres (21 in), has a few white spots and is tipped with black.[6] The forelegs are generally longer, and the legs are often marked with white "socks".
While females and juveniles are orange to tawny, males are much darker – their coat is 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 (Rajasthan, India) while individuals with white patches have been recorded at zoos.The hairs, typically 23–28 centimetres (9.1–11.0 in) long, are fragile and brittle.Males have thicker skin on their head and neck that protect them in fights.The coat is not well-insulated with fat during winter, and consequently severe cold might be fatal for the nilgai.
Only males possess horns, though a few females may be horned as well. The horns are 15–24 centimetres (5.9–9.4 in) long but generally shorter than 30 centimetres (12 in).Smooth and straight, these may point backward or forward.The horns of the nilgai and the four-horned antelope lack the ringed structure typical of those of other bovids.
The maximum recorded length of the skull is 376 millimetres (14.8 in). 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 sharp ears and eyes, though its sense of smell is not as acute.
Ecology and behavior:
The nilgai is diurnal (active mainly during the day). 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 ten or fewer individuals, though groups of 20 to 70 individuals can occur at times.In a 1980 study in the Bardiya National Park (Nepal), the average herd size was of three individuals;In a 1995 study in the Gir National Park (Gujarat, India), 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 300 metres (980 ft)-or even 700 metres (2,300 ft) on galloping-away from the danger.Though generally quiet, nilgai have been reported to make short guttural grunts when alarmed, and females to make clicking noises when nursing young.Alarmed individuals, mainly juveniles below five months, give out a coughing roar (whose pitch is highest in case of the juveniles) that lasts half a second, but can be heard by herds less than 500 metres (1,600 ft) 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, who stood erect.The nilgai mark their territories by forming dung piles as much as 50 centimetres (20 in) in radius. The defecation process is elaborate-the antelope stands with his legs about a metre apart, with the rump lowered and the tail held almost vertical; it stays in the same posture for at least ten 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 the Ranthambore National Park (Rajasthan, India) 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 Indian tiger and the lion may prey on the nilgai but they are not significant predators of this antelope.Leopards prey on the nilgai, though they prefer smaller prey.Dholes generally attack juveniles.Other predators include wolves and striped hyenas.
Diet:
Herbivores, the nilgai prefer grasses and herbs; woody plants are commonly eaten in the dry tropical forests of India. Studies suggest they may be browsers or mixed feeders in India, whereas they are primarily grazers in Texas.The nilgai can tolerate interference by livestock and degradation of vegetation in its habitat better than deer, possibly because they can reach high branches and do not depend on surface vegetation.The sambar deer and nilgai in Nepal have similar dietary preferences.Diets generally suffice in protein and fats.The protein content of the nilgai's should be at least seven percent.The nilgai can survive for long periods without water and do not drink regularly even in summer.However, a nilgai died in Dwarka (India) allegedly due to the heat wave and acute shortage of water.A 1994 study of the nilgai's diet in the Sariska Reserve revealed its preference for herbs and grasses; grasses became more important in the rainy season, while during winter and summer it fed additionally on flowers (Butea monosperma), foliage (Anogeissus pendula, Capparis sepiaria, Grewia flavescens and Zizyphus mauritiana), pods (Acacia nilotica, A. catechu and A. leucophloea) and fruits (Zizyphus mauritiana).Preferred grass species include Cenchrus species, Cynodon dactylon, Desmostachya bipinnata, Scirpus tuberosus and Vetiveria zizanoides. Woody plants eaten include Acacia nilotica, A. senegal, A. leucophloea, Clerodendrum phlomidis, Crotalaria burhia, Indigofera oblongifolia, Morus alba and Zizyphus nummularia; herbs favoured are Cocculus hirsutus, Euphorbia hirta and Sida rhombifolia.Seeds of Paspalum distichum occurred in the dung of nilgai most of the year; Acacia nilotica and Prosopis juliflora seeds were discovered in the dry season and those of Echinochloa crusgalli during the monsoon.
Habitat and Distribution:
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.[59] 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).[40] In southern Texas, densities were found to be nearly 3–5 individuals per km2 in 1976.
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.
Reproduction:
Observations of females in southern Texas revealed that ovaries are developed by two years of age and the first birth takes place typically a year later, though in a few cases females as young as one-and-a-half years may mate successfully.Females can breed again around a year after parturition.Males in the same location were found to have active testes by the age of three years, that matured considerably by the next year.Males become sexually active at four or five years. Mating may occur throughout the year, with peaks of three to four months. The time of the year when these peaks occur varies geographically. In Texas, a peak is apparent from December to March.In Bharatpur National Park (Rajasthan, India) the breeding season is from October to February, peaking in November and December. The Sariska reserve witnesses a similar peak in December and January.
In the mating season, rutting males move about in search of females in oestrus.Males become aggressive and fight among themselves for dominance. These fights are characterised by displays of the enlarged chest, the throat patch and the beard while holding the head upright; and threatening the opponent by running with the horns pointed toward him and circling him.The victorious bull would protect the vicinity of the targeted female from other males. The courtship typically lasts for 45 minutes. The male, stiff and composed, approaches the receptive female, who keeps her head low to the ground and may slowly walk forward. The male licks her genitalia, upon which the female holds her tail to a side and the male gives out a flehmen response. Finally, the male pushes his chest against her rump, and mounts her.
Gestation lasts eight to nine months, following which a single calf or twins (even triplets at times) are born. In a 2004 study in the Sariska reserve, twins accounted for as high as 80 percent of the total calf population.[42] Births peak from June to October in the Bharatpur National Park, and from April to August in southern Texas. Calves are precocial; they are able to stand within 40 minutes of birth, and forage by the fourth week.Pregnant females isolate themselves before giving birth. As typical of several bovid species, nilgai calves are kept in hiding for the first few weeks of their lives. This period of concealment can last as long as a month in Texas.Calves, mainly males, bicker playfully by neck-fighting.Young males would leave their mothers at ten months to join bachelor groups.The lifespan of the nilgai is typically ten years in Texas.
In the mating season, rutting males move about in search of females in oestrus.Males become aggressive and fight among themselves for dominance. These fights are characterised by displays of the enlarged chest, the throat patch and the beard while holding the head upright; and threatening the opponent by running with the horns pointed toward him and circling him.The victorious bull would protect the vicinity of the targeted female from other males. The courtship typically lasts for 45 minutes. The male, stiff and composed, approaches the receptive female, who keeps her head low to the ground and may slowly walk forward. The male licks her genitalia, upon which the female holds her tail to a side and the male gives out a flehmen response. Finally, the male pushes his chest against her rump, and mounts her.
Gestation lasts eight to nine months, following which a single calf or twins (even triplets at times) are born. In a 2004 study in the Sariska reserve, twins accounted for as high as 80 percent of the total calf population.[42] Births peak from June to October in the Bharatpur National Park, and from April to August in southern Texas. Calves are precocial; they are able to stand within 40 minutes of birth, and forage by the fourth week.Pregnant females isolate themselves before giving birth. As typical of several bovid species, nilgai calves are kept in hiding for the first few weeks of their lives. This period of concealment can last as long as a month in Texas.Calves, mainly males, bicker playfully by neck-fighting.Young males would leave their mothers at ten months to join bachelor groups.The lifespan of the nilgai is typically ten years in Texas.
