How Many Nilgai Are in Texas? A Population Overview

Texas is home to an estimated 36,000 or more nilgai antelope, making it by far the largest free-ranging population of this species outside their native India and Nepal. Nearly all of them live in a handful of counties at the southern tip of the state, where the subtropical brush country provides year-round forage and mild winters. The number has grown steadily since a handful of nilgai were first released on private ranches in the 1930s, and their expansion raises questions about ecology, disease, and wildlife management that go well beyond a simple headcount.

How Nilgai Arrived in Texas

Nilgai are the largest antelope species native to the Indian subcontinent, where bulls can weigh over 600 pounds. They were brought to the South Texas region through the King Ranch in the 1930s as exotic game animals, part of a broader trend of introducing foreign wildlife onto large private ranches for sport hunting and aesthetic novelty.¹ Some animals escaped or were deliberately released, and with no natural predators large enough to threaten an adult nilgai and plenty of thorny brush to shelter in, the population grew. By the 1960s, free-ranging herds were established across several counties, and the population has increased dramatically since then.

Where They Are Concentrated

If you drew a circle around the southernmost tip of Texas, you would capture the vast majority of the state’s nilgai. Cameron, Willacy, and Kenedy Counties form the core of their range, with smaller numbers spreading into Hidalgo and Kleberg Counties. The habitat in this region, a mix of dense thorn scrub, open grassland, and coastal prairie, suits nilgai well. They browse on a wide variety of shrubs and grasses, and the mild winters allow them to maintain body condition year-round without the seasonal stress that limits many ungulates farther north.

This geographic concentration matters because it puts nilgai in close contact with cattle ranching operations and the international border with Mexico. The overlap creates management headaches that a more dispersed population would not, from crop damage on citrus and grain farms to the movement of disease vectors across property lines and even international boundaries.

Why the Exact Number Is Hard to Pin Down

Counting large free-ranging animals across thousands of square miles of dense brush is genuinely difficult. Texas Parks and Wildlife Department has periodically surveyed nilgai from helicopters, but the thorny vegetation that nilgai prefer makes aerial detection unreliable. An animal standing under a mesquite canopy is essentially invisible from the air.

Researchers have worked to improve survey accuracy using mark-recapture distance sampling, a statistical approach applied to aerial surveys of ungulates including nilgai, white-tailed deer, collared peccary, and feral hogs on rangelands in the region.² The basic idea involves flying systematic transects, recording which animals are detected and how far they are from the flight path, and then using the detection patterns to estimate how many were missed. This yields more reliable population estimates than simple direct counts, but it still comes with wide confidence intervals when applied to animals that are large, mobile, and fond of dense cover.

The commonly cited figure of roughly 36,000 represents the best available estimate from state wildlife agencies, but wildlife managers acknowledge it could be conservative. Private landowners control access to most of the nilgai range, and not every property is surveyed in every cycle. Some biologists suspect the true number has already climbed higher, especially in years with favorable rainfall and mild winters.

What Keeps the Population in Check

Without wolves, tigers, or other large predators in South Texas, nilgai face few natural threats as adults. Coyotes may take very young calves, but a healthy adult nilgai is far too large for any native Texas predator to bring down. That leaves weather, hunting, and disease as the main population regulators.

Extreme Cold Events

Nilgai evolved in tropical and subtropical South Asia and have limited tolerance for prolonged freezing temperatures. The February 2021 winter storm that paralyzed much of Texas hit nilgai populations hard in certain areas. Research documented significant mortality in parts of South Texas, particularly in northern Hidalgo and Kenedy Counties, where temperatures stayed below minus three degrees Celsius for more than eleven consecutive hours.³ By contrast, mortality was minimal in Cameron County and across the border in northeastern Tamaulipas, Mexico, where sub-freezing conditions lasted only five to six hours.³

The geographic pattern is telling. The farther north you go, the more severe and prolonged the cold, and the higher the nilgai die-off. Researchers have concluded that extreme cold weather events are likely to limit how far north nilgai can ultimately expand their range in Texas.³ In a warming climate, however, these events may become less frequent, which could remove one of the few natural brakes on northward spread.

Hunting Pressure

Texas classifies nilgai as an exotic species, which means they receive none of the seasonal protections that native game animals like white-tailed deer enjoy. On private land, nilgai can be hunted year-round with no bag limit and no closed season. Landowners or their paying clients can take as many as they want, whenever they want. Despite this liberal policy, hunting alone has not reversed the population trend. Nilgai are wary, fast, and tough to approach in thick brush. A successful nilgai hunt typically requires either a well-placed blind near a water source or a helicopter, making it more expensive and logistically demanding than most Texas deer hunts. Some outfitters charge several thousand dollars for a guided nilgai hunt, which limits the number of animals taken each year relative to the overall population.

The Cattle Fever Tick Problem

The issue that has drawn the most federal attention to nilgai numbers is not crop damage or competition with native wildlife. It is cattle fever ticks. These ticks carry the parasites that cause bovine babesiosis and anaplasmosis, diseases devastating enough that the United States mounted a decades-long eradication campaign that finally succeeded in 1943.⁴ Since then, the ticks have been repeatedly reintroduced from Mexico, and nilgai are one of the primary wildlife hosts carrying them back across the border.

Surveillance of over 500 nilgai in southeastern Texas between 2014 and 2017 found that the proportion of fever tick-infested animals varied in a north-to-south pattern. The northern survey area, dominated by upland thorn scrub with more vegetative canopy, was more conducive to tick survival and had higher infestation rates than the southern lowland floodplain habitat.⁵ This matters because it means tick risk is not uniform across the nilgai range; habitat type shapes the disease picture as much as animal density does.

What makes nilgai especially problematic as tick hosts, compared to white-tailed deer, is their mobility. Nilgai have large home ranges and can cover considerable distances, giving a tick-infested animal the ability to seed new outbreaks far from where it picked up the parasites. Currently, no approved method exists to treat nilgai for cattle fever ticks the way livestock can be dipped or treated with acaricides.⁴ Researchers have tested odor lures to attract nilgai to central treatment points, but developing a practical, scalable solution remains an ongoing challenge.

How Far Nilgai Roam

GPS tracking studies reveal just how mobile nilgai are, and why containing tick spread through these animals is so difficult. A study that followed 40 GPS-collared nilgai in Cameron County found that resident animals had an average maximum axial distance of about 7.8 kilometers, meaning some individuals regularly traveled that far from their core area and back.⁶ Two young females made separate dispersal movements of roughly 40 kilometers within a single year, suggesting that long-distance colonization events are not rare.

Home ranges were large and highly variable. The median annual home range for females was about 563 hectares, with individual ranges spanning from 105 to over 1,500 hectares. Males ranged even wider, with a median of 937 hectares.⁶ To put that in perspective, a typical South Texas ranch covers anywhere from 250 to 6,000 hectares, so a single nilgai’s home range routinely overlaps multiple properties. Peak movement occurred during dawn and dusk, with females averaging about 57 meters per hour and males about 66 meters per hour during active periods.

Research on movement patterns has also found that females may pose a greater risk than males for spreading cattle fever ticks through the landscape, though the spread can be partly mitigated by cattle fences running parallel to paved highways, which act as partial barriers to nilgai movement.⁷ This finding has practical implications for how ranchers and federal agencies think about quarantine zone design along the Texas-Mexico border.

Ecological Footprint Beyond Ticks

The disease vector issue dominates federal funding discussions, but nilgai affect South Texas ecosystems in other ways. Their browsing habits can reshape plant communities, particularly in coastal areas. Research at the University of Texas Rio Grande Valley has documented the effects of nilgai browsing on black mangrove stands, examining how the animals alter microenvironmental conditions, plant structure, and reproductive success of these coastal trees.¹ Mangroves serve as nursery habitat for fish and crustaceans and protect shorelines from erosion, so heavy browsing pressure in these areas has consequences that ripple through the coastal food web.

Nilgai also compete with native white-tailed deer for browse and cover, though quantifying the degree of competition is complicated by the fact that both species are generalist herbivores with overlapping but not identical diets. On agricultural land, nilgai damage citrus orchards and grain crops, and their size means they can push through or jump most standard livestock fences. A bull nilgai can clear a five-foot fence from a near standstill, which makes exclusion fencing impractical for most operations without specialized, expensive modifications.

Management and the Road Ahead

Texas has taken a largely hands-off regulatory approach to nilgai. Because they are classified as exotic, the state does not set harvest limits or seasons on private land. The practical management burden falls on individual landowners, the USDA’s Animal and Plant Health Inspection Service (which operates the cattle fever tick quarantine program), and occasionally the Texas Parks and Wildlife Department when public safety or conservation conflicts arise. Some landowners view nilgai as a valuable hunting resource and actively manage their properties to sustain herds. Others consider them an uncontrollable nuisance that damages fences, eats crops, and carries ticks.

The USDA has invested significantly in understanding nilgai movement and tick ecology in the border region, funding the GPS collaring studies, tick surveillance efforts, and lure-development research cited throughout this article. The quarantine zone along the Rio Grande, originally designed to keep cattle fever ticks from moving northward, increasingly has to account for wildlife hosts that ignore fences, property lines, and international borders.

Whether the nilgai population in Texas will continue to grow depends on a handful of interacting factors: the frequency and severity of winter freezes, the amount of hunting pressure landowners choose to apply, changes in land use that convert brush to agriculture or development, and whether scalable tick-treatment methods for wildlife are eventually developed. For now, the population appears to be either stable or still slowly expanding, with periodic sharp dips tied to extreme weather events followed by rebounds in milder years. In a region where cattle ranching, citrus farming, wildlife management, and international disease policy all intersect, the question of how many nilgai are in Texas turns out to be a question about much more than counting animals from a helicopter.

1
ScholarWorks @ UTRGV. Effects of Invasive Nilgai Antelope (Boselaphus tragocamelus) Browsing on Black Mangrove (Avicennia germinans) in South Texas
2
Wildlife Society Bulletin. Mark‐Recapture Distance Sampling for Aerial Surveys of Ungulates on Rangelands
3
Subtropical Agriculture and Environments. Nilgai (Boselaphus tragocamelus) mortality levels in South Texas after historic freeze event
4
PubMed Central. Comparison of natural and artificial odor lures for nilgai (Boselaphus tragocamelus) and white-tailed deer (Odocoileus virginianus) in South Texas
5
PubMed. TICK VECTOR AND DISEASE PATHOGEN SURVEILLANCE OF NILGAI ANTELOPE (BOSELAPHUS TRAGOCAMELUS) IN SOUTHEASTERN TEXAS, USA
6
Ecosphere. Movement ecology of exotic nilgai antelope: A threat to the re‐emergence of cattle fever ticks in the southern USA
7
Preventive Veterinary Medicine. Movement patterns of nilgai antelope in South Texas: Implications for cattle fever tick management