Nilgai (Boselaphus tragocamelus) are a very hardy antelope, a fact made evident by their ability to survive and flourish in a part of the world that has seen most of its megafauna disappear. Big mammals are having a bad time in South Asia of late. Ever since the population of human beings exploded in this part of the world, they have been under great pressure. Due to poaching, pollution and habitat destruction. Examples that bear out this narrative include the likes of the Tiger (Panthera tigris), the Asiatic Elephant (Elephas maximus) and the One Horned Rhinoceros (Rhinoceros unicornis). However, this very hardiness has earned the Nilgai a bad reputation in a land halfway across the globe, in the southern United States.

Like the Small Asian Mongoose (Herpestes auropunctatus) that has spread to island groups across the globe, the Asian antelope has colonized Texas. But they are two very different creatures. The former is a lightweight – just 67 cm long and 660 g in weight, living in an arc stretching across the southern half of Asia, from Iraq in the west to Myanmar in the east.  A diurnal species with a preference for dry forests, scrub and grasslands, the Small Asian Mongoose feeds on insects, arachnids, crustaceans, amphibians, lizards, snakes, ground dwelling birds, rodents and fruits. The Nilgai is a giant in comparison (with males reaching an impressive 1.5 m at the shoulder and weighing up to 300 kg), ranging over the grasslands and scrub forests of Pakistan, India, Nepal and Bangladesh.

Back in the 19th century, when rodents were threatening to destroy the very basis of many island economies – the sugarcane plantations of the Caribbean and the South Pacific, the tiny carnivore was introduced to these far away lands. The intentions were good – controlling rats and snakes that had gone on a rampage. But the results were mixed at best. While the mongoose’s ability to control its intended targets began to be questioned, its impact on native wildlife was deemed to be negative. Today, the Small Asian Mongoose is counted among the 100 Worst Invasive Species of the World (according to a IUCN report issued in 2014). The story of the Nilgai’s appearance in the American Deep South has a similar flavor. Here is the Texas State Historical Association’s observation:

Nilgai antelope (Boselaphus tragocamelus Pallas) were apparently brought to the United States from India as zoo animals before the mid-1920s and were released in South Texas about 1930. Their skin is thick, particularly on the chest and neck of the bulls, where it forms a dermal shield. The eyesight and hearing of nilgai are considered equal to or better than that of white-tailed deer, but their sense of smell less acute. They have speed and endurance and, over rough terrain, may outrun a horse with rider. Nilgai make several low-volume vocalizations, including a short, guttural “bwooah” when alerted. They live on a variety of land types from hillsides to level ground with scattered grass steppes, trees, and cultivated areas, but not in thick forests. Their habitats are characterized by paths, waterholes, defecation sites, and resting cover.

Nilgai were common in India and parts of Pakistan during the 1880s and were hunted for sport by the British. Besides man, the tiger is their principal Asian predator. The King Ranch pioneered the release of nilgai in Texas. Between about 1930 and 1941 the ranch made several acquisitions of nilgai zoo stock and released them in Kenedy County. With limited hunting and predation, protection, and favorable habitat, nilgai adapted well. Their primary range now includes the area from Baffin Bay south to near Harlingen. They have been distributed to numerous counties by landowners releasing brood stock. Approximately 15,000 nilgai are now on Texas rangelands. They will probably not become widespread. They suffer in extreme cold, and even in temperate South Texas they may die during unusually cold winters when food is scarce.

Nilgai segregate into male and female groups except during the breeding season. Some breeding takes place year-round, but the principal breeding period in Texas is November through March. At that time breeding groups of one dominant bull and one to several cows are found. The peak calving period is September through November. Female nilgai breed at age two to three years, whereas males may not breed until their fourth year. The gestation period is approximately 245 days. Twinning is common, and triplets occur occasionally. The cow-to-calf ratio of Texas nilgai is approximately seventy-five to 100, and the sex ratio at birth is approximately even. In Asia nilgai eat mainly woody plants supplemented by agricultural crops. Grass forms the bulk of their diet in Texas. They upgrade their diet nutritionally by eating forbs, browse, and plant parts (flowers, seeds, fruit, leaves, stem tips). In the absence of preferred food they readily alter their diet.

Nilgai in Texas harbor low numbers of parasites. Gastrointestinal nematodes and ticks, including fever ticks, have been taken from them.The species has not been intensively studied. Baseline studies of distribution, social organization, behavior, food habits, and population ecology have been published by Texas A&M University, but more ecological, economic, and management information is needed. The limited hunting of nilgai in Texas and their high rate of increase make the control of their numbers a major management concern. Developing economic uses may be the best means of controlling the nilgai and assuring their compatibility on Texas ranges. Currently, sport hunting and meat supply are the best potential uses for these antelope.

The excerpt above shows just how successful the Asian antelope has been in its new home. Apart from being a prolific breeder, the Nilgai has earned notoriety as a reservoir for harmful parasites and pathogens. Cattle ranchers and the U.S. Fish and Wildlife Service officials have been organizing culling operations for the species using helicopters. The presence of fever ticks (such as Rhipicephalus microplus and Rhipicephalus annulatus) on the Nilgai is seen as a particularly dangerous development.  Fever ticks have devastated Texas’ cattle herds in the past. The American government had to work very hard to bring them under control, restricting their presence to a zone stretching along the US-Mexico border. The proliferation of Nilgai in areas like the Lower Rio Grande Valley and Laguna Atascosa National Wildlife Refuges that lie along this frontier could negate those measures. It will be interesting to see how the tenacious quadruped deals with this new predicament.

Image Attribution: The image above, sourced from Wikimedia Commons, shows an illustration of the Nilgai from the book ‘The Wild Beasts of the World’ (authored by Frank Finn). This particular painting was done by the English artist Winifred Maria Louise Austin (1876-1964). She was famed for her portraits of wild creatures and was appointed a fellow of the Royal Zoological Society.