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Managing Nilgai on Whitetail Land

Managing Nilgai on Whitetail Land

Article by Nicholas Kolbe

 

Photos by Katy Baldock, Blake Barnett, Justin Field, Chase Phillips, Wyman Meinzer

 

Exotic species were first introduced into Texas around 1930 for hunting; they substituted for extirpated native big game, provided viewing pleasure and/or sustained populations of endangered big game.

The first exotic game species to be introduced into Texas was the nilgai antelope (Boselaphus tragocamelus) brought here from India.

In 1929, 12 nilgai antelope were released on King Ranch. According to a study conducted in 2005, the population of nilgai had increased to an estimated 38,000 found in free roaming populations and high-fenced game enclosures across 25 Texas counties and in five Mexican states. Semi-free ranging populations occur on large ranches within Kleberg, Kenedy, Willacy and Cameron counties. King Ranch alone maintains a population of approximately 12,000 nilgai.

The deep South Texas Gulf Coastal Prairies and Plains are the perfect nilgai habitat with ample forage, temperate climate and large contiguous land tracts. Though not likely to significantly spread outside of their current free range, some nilgai have been captured, translocated and released as breeder stock to private high-fenced ranches scattered across Texas.

They are the largest antelope species roaming India’s vast and diverse landscapes. Male nilgai can weigh more than 600 pounds. Only male nilgai have horns. Immature nilgai males are light brown, turning blue to a dark blue once mature. Similarly, female nilgai are light brown however they retain the light brown coloration throughout their lifespan. Females can weigh upwards of 450 pounds.

Like white-tailed deer, nilgai breed between the months of November and February in Texas. The large bovid will generally give birth to twins roughly 245-250 days following conception.

Exotic species compete with our native species for resources such as food, water and territory. Furthermore, some exotic species actually “outcompete” our native game more times than not, because they are able to adapt quite well to our diverse Texas ecoregions and lack natural predators.

Nilgai are intermediate feeders with an expansive range of digestible food choices. Nilgai, like white-tailed deer, will browse on highly nutritional shrubs and forbs when available.

In a study conducted by Stacy Hines Adams on East Foundation lands in South Texas, it was determined that 90 percent of a nilgai antelope’s diet consisted of browse…same as that of a white-tailed deer during that season when other forage classes like forbs, succulents and mast were absent. And, nilgai can switch their diet to consume a higher quantity of lesser palatable and lower nutrient rich grass species when variety and quality of herbaceous choice diminishes like during droughts or high animal density settings.

When managing for both nilgai and whitetails, where the whitetail operation is the primary focus of the land manager, the nilgai population will need to be kept at an appropriate level to allow for adequate forage availability on the range. Conversely, if nilgai antelope are the target species of interest, the white-tailed deer and grazer species should be monitored and/or decreased to increase forage availability in respect to browse and grass species. To optimize the population of both means reducing numbers of both in order to avoid exploiting your respected rangeland’s food, water and space.

Besides habitat management challenges faced by landowners with nilgai, a potential problem concerns the spread of the cattle fever tick. The tick, hosted by white-tailed deer and nilgai, causes a deadly disease in cattle.

The eradication of the cattle fever tick as well as cattle fever was acknowledged as complete across all 14 states in 1943. However, the direct threat across the southern border and into deep South Texas was still a concern as the disease and tick still lingered from cattle and wildlife moving freely across the Rio Grande.

Because of the impossibility of completely stopping all livestock and wildlife crossings, a permanent quarantine zone was established to provide constant monitoring efforts in order to inspect and treat livestock and wildlife in the area. The buffer included eight counties: Val Verde, Kinney, Maverick, Webb, Zapata, Starr, Hidalgo and Cameron.

Through collaborative efforts between the U.S. Department of Agriculture and the Texas Animal Health Commission, this quarantine zone is still present and active today. Modern day cowboys known as “Tick Riders” patrol these eight counties along Texas’s Rio Grande border inspecting legally transported, permanent resident and stray hoofstock across the 500 miles and nearly 225,000-acre quarantine area.

Free roaming nilgai and white-tailed deer each pose their own unique set of challenges when working to contain and ultimately eradicate the vector fever ticks. The inability to contain white-tailed deer and nilgai in the vast and isolated landscapes of South Texas increases the struggle. Ranching operations near or within the quarantine zone realize the revenue recreational hunting and stocking of white-tailed deer and nilgai bring, and manage for stable populations granting continued income from hunting and translocation.

Both deer and nilgai are difficult to keep in designated areas given their large home ranges and their ability to jump or go under most standard five-strand barbed wire cross fencing. Nilgai can barrel through or under net wire fencing with ease making the 8-foot game fencing useless at times as well. Nilgai are being captured and moved across Texas to stock game ranches for hunter harvest opportunities.

Although there hasn’t been a case of cattle fever in Texas since the 1970s, in 2017 a total of 162 new tick infestations were recorded in Texas with 17 and 12 of those cases attributed to ticks found on white-tailed deer and nilgai antelope, respectively. These were the highest numbers of in Texas since 1967 and the highest number tick cases ever found on white-tailed deer and nilgai.

Five of the 12 nilgai cases were located in Willacy County, north of the permanent quarantine area. More recent 2019 numbers have declined to 78 cases with 10 associated with white-tailed deer and four from nilgai antelope.

One method of treating white-tailed deer is by feeding whole kernel corn medicated with Ivermectin, an anti-parasitic. Locations that do utilize this method must remove the medicated bait 60 days prior to white-tailed deer hunting season. Another method is by utilizing two or four permethrin-treated rubbing posts at feeding stations. The deer visiting feeding sites are subject to rubbing these permethrin-treated posts and self-medicating as the insecticide is applied topically while rubbing the post.

When it comes to treating nilgai, the options are more liberal. The same treatment options for white-tailed deer can and are applied to nilgai as they too visit feeding sites and utilize the medicated feed and rubbing posts.

Since there are no harvest restrictions on nilgai, many ranches take advantage of the open season to decrease potential spread of the tick. For example, East Foundation with part of its land holdings at risk within the quarantined and infested counties systematically harvest approximately 200-300 nilgai per year to reduce the threat. Personnel have also gone a step further by erecting their own fencing barrier to deter nilgai and white-tailed deer movement.

The Laguna Atascosa National Wildlife Refuge has similarly employed tick eradication measures by decreasing white-tailed deer and nilgai densities and increasing prescribed burning efforts.

The presence of exotic species like nilgai antelope is a double-edged sword. There is no doubt that exotics in Texas have fared well as economic drivers for ranches across the state. As a result, ranch owners have increased management efforts to improve habitat and holistically manage their native and exotic wildlife species.

Without sound management practices, exotics like nilgai can be problematic, outcompeting and dislocating native game and acting as hosts for deadly disease vectors. Mitigation efforts through population and habitat management techniques are necessary to strike a balance between exotic game and our native white-tailed deer.



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