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Pronghorns: A Story of Survival

Pronghorns: A Story of Survival

Article by: Lorie A. Woodward

Photos by: Larry Ditto, Rita Frey, Russell Graves, Cullom Simpson  

 

Pronghorns, iconic symbols of wide, open spaces, are survivors.

“There’s a lot of history in this one unique, highly specialized animal that thrives on the big open grasslands of Texas and the American West,” said Shawn Gray, Mule Deer and Pronghorn Program Leader at the Texas Parks and Wildlife Department. “As the last survivor of its family, it has seen a lot of other animals come and go.”

Pronghorns are the only surviving member of the Antilocapridae family, which appeared in North America during the late Miocene era (23 million to 5.3 million years ago). During this epoch, grassland ecosystems emerged. The pronghorn adapted to the wide, open terrain.

The pronghorn’s scientific name, Antilocapra americana, means “American goat-antelope,” although it is neither. Evolution equipped the unique American species with very large, wide set eyes that provide a sweeping field of view and can spot threats at distances accessible to humans only with the assistance of 8x binoculars. They also have acute senses of hearing and smell. Active both day and night, pronghorns are vigilant and flighty by nature.

While their heightened senses are the first line of defense, pronghorns rely on speed to escape. Pronghorns evolved alongside fleet-footed predators such as the now-extinct North American cheetah. In short bursts, pronghorns can run up to 60 mph and bound up to 20 feet. Today, only the African cheetah is faster, but pronghorns, the fastest herbivore on the globe, can sustain speeds of up to 40 mph for much longer distances than the feline predator.

When the pronghorns were originally catalogued by explorers Meriwether Lewis and William Clark on their epic 1804 journey through the West, the herds numbered in the tens of millions. Despite the pronghorns’ speed, they couldn’t outrun the commercial market hunting of the 19th century. By the early 20th century, the population plummeted to about 13,000.

Under the leadership of the Boone and Crockett Club, which rallied political, conservation and philanthropic support, the pronghorn was brought back from the brink of extinction. Because of effective strategies that included hunting regulations, protected habitat and state-level management, pronghorn populations have risen to about 700,000 animals scattered through northern Mexico, the Great Plains including Texas, the American West and southern Canada.

At one point, the range of pronghorn in Texas stretched from present-day I-35 west. As land practices changed, pronghorns disappeared from the mid-Texas prairies westward. Now the species is found on about 14 million acres scattered through the upper reaches of the Panhandle, throughout the Trans-Pecos and most highly concentrated on the Marfa Plateau, the Hudspeth and Marathon Grasslands, and in pockets west of Lubbock and near San Angelo.

“In Texas, we’re on the southern edge of pronghorns’ traditional North American range,” said Dr. Louis Harveson, the Dan Allen Hughes Jr. Endowed Director of the Borderlands Research Institute at Sul Ross University. “Because we’re on the periphery of habitat, our populations like those in New Mexico and Arizona are subject to more violent fluctuations than the more stable populations in Wyoming and Montana.”

About 35 years ago, pronghorn populations in the Trans-Pecos, historically the state’s densest, were estimated to be about 17,000. The number slowly declined over time, with losses picking up speed in 2008 and accelerating through the devastating drought of 2011. In 2012, after record-low fawn production three years prior, the population in far West Texas dropped below 2,500.

“We drew a line in the sand [and were determined] not to see this species diminish on our watch,” said Harveson in an article published on the National Geographic website on August 19, 2016.

In implementation, the sandy line of determination functioned as a buttress against future losses. Built on practical research, purposeful translocations and unmatched cooperation between universities, state agencies and private landowners, the multi-faceted effort that began in 2008 is making a difference for Texas pronghorns.

“We are working to ensure that pronghorn will always have a home on the Texas range,” Harveson said.

Lone Star Legacy

Initial efforts focused on pure research.

“We wanted to use the animals themselves to find answers,” Gray said. “Early on, we just found more questions.”

By 2011, the pieces were in place to begin a series of relocations and restorations.

“In the past nine years, we’ve learned a lot about successfully translocating pronghorns—and about the animals themselves,” Gray said.

The Source

The largest populations of Texas pronghorns historically existed in the Trans-Pecos. Over the past two decades, thanks in large part to the historic drought of 2008-2012 and the related die-off, the population center shifted to the Panhandle.

“Texas currently has about 20,000 pronghorns,” said Gray. “About 13,000 of those are located in the Panhandle, another 6,500 or so are in the Trans-Pecos and the rest are in Irion County.”

The Panhandle populations, supplemented multiple times from the 1940s to the 1990s by pronghorns primarily translocated from the Trans-Pecos and the Rocker B Ranch in Irion County, stabilized and slowly increased over time.

“The pronghorns in the Panhandle benefit from row crop production,” Gray said. “While crops don’t replace forbs as their preferred diet, crops supplement them, especially during stressful times like drought.”

Using population survey data collected each year, TPWD personnel identify sites throughout the Panhandle with excess animals. Each year, the team sets out to translocate 100-125 animals.

“Over the past nine years, we’ve moved about 875 animals,” Harveson said. “Translocation is a tool that we’ll likely need to rely on for the immediate future because of significant habitat loss and fragmentation across historic pronghorn habitat.”

In recent years, most pronghorns have come from the areas around Dalhart and Pampa. TPWD staff work directly with local landowners, who voluntarily agree to contribute excess animals to the cause.

To get the most bang for the proverbial buck, wildlife professionals concentrate their efforts on trapping and translocating mature does; does can start reproducing as yearlings. The translocation process takes place in January and February when most does are pregnant; breeding season in Texas begins the last week of August and extends to the first week of October.

“Up to 95 percent of does have twins, so by translocating pregnant does we’re getting a ‘three-for,’” said Harveson, noting bucks breed multiple does they have claimed as part of their harem. “In the wild, pronghorns can live up to 15 years, so does can contribute to population growth in the long-term.”

As one example of the local impact, Harveson cited a 2013 translocation where more than 100 pregnant does were released onto a ranch on the Marathon Basin that had approximately 28 adult animals. Today, that herd has grown to about 300 adults.

In addition, translocating does doesn’t interfere with hunting opportunities or the vital income streams hunting bucks generates, making it easier for landowners to participate, Harveson said.

“None of this would be possible without the generosity and committed stewardship of private landowners,” Gray said.

Lessons Learned

The first relocation year, 2011, also happened to be the driest year on record for Texas.

“In hindsight, it was the worst possible year to start,” Gray said.

The team translocated 200 animals. Each was outfitted with a collar that transmitted a GPS point every hour for 300 days post-release, but today better technology provides the team with 15-minute GPS locations for 510 days.

“The collars not only track survival, but help us determine the cause of death,” Harveson said. “They track movement and habitat preferences. Because of the collars, the animals can tell us what is working and what is not.”

He continued, “Since that first release, we’ve collected 1.5 million data points. The more information we collect the more we know. The data sets provide a road map for improvement.”

The survival rate for the first release was an abysmal 20 percent. Data collected from the GPS collars pointed to a confluence of factors.

“The condition of the habitat dictates whether or not a translocation should take place,” said Dr. Carlos “Lalo” Gonzalez, the Nau Endowed Professor of Habitat Research and Management at Borderlands Research Institute. “We learned that lesson early on—the hard way.”

Obviously, drought affects plant availability, which in turn affects maternal nutrition and fawn survival.

“The drought was so bad that does abandoned fawns and many were stillborn,” Harveson said. “Those that were born alive were skin and bones. Instead of weighing 4 pounds like normal, they weighed 2 pounds or less.”

To make fawns even more vulnerable, drought destroys fawning cover, leaving fawns exposed to predators.

“Now, we just say ‘no’ if the weather and range conditions aren’t right,” Gonzalez said. “And we spend a lot of time getting the habitat into the best shape possible before animals are released.”

As part of the release preparation, TPWD now implements an aggressive coyote management program in January and February on and near release sites. Personnel also continue predator management efforts in all restoration areas during March to May, closer to fawning.

“Our goal isn’t to eradicate coyotes, but to temporarily reduce the number of adults in a given area to give translocated animals and newborn fawns a leg up,” Gray said.

The translocation of 2011 also clearly showcased the pronghorns’ inherent need to move freely.

“In Texas, pronghorns aren’t migratory like some of the northern herds that have to contend with winter snows, but they are nomadic,” Harveson said. “They follow the rain clouds to find fresh forage. As it becomes drier, they need more range to obtain proper nutrition.”

During the wet season, a pronghorn needs about 9,000 acres, while during the dry season, the range increases to 22,000 acres, Harveson said. During a drought, the range could encompass up to 40,000 acres.

Today to be considered as a site for translocation, TPWD requires at least 20,000 acres of contiguous, healthy open grassland, Gray said. However, the smallest Trans-Pecos restoration area is more than 70,000 acres, emphasizing that for pronghorns “more habitat is better.”

Pronghorns also prefer to crawl under fences instead of jump them, which impeded their survival.

“Looking at the GPS points, you’d see a single, straight line of dots stacking up against a fence and you’d know it wasn’t right, because pronghorns don’t have home ranges with straight lines and 90-degree angles,” Gray said.

The fences also made the pronghorns easy pickings for predators. Coyotes would herd the pronghorns into a fence corner, where the pronghorns couldn’t escape, Gonzales said.

The combination of these two findings prompted the team to embark on a widespread fence modification effort. Throughout the restoration areas, wildlife professionals worked with landowners to make fences pronghorn-friendly by raising the bottom wire creating openings that are at least 18 inches high at regular intervals in both cross and perimeter fences.

“Knowing that pronghorns cover a lot of ground, we want to connect habitat and give them more room to roam,” Gonzalez said. “We have completed about 2,000 modifications allowing thousands of acres to be connected.”

In addition, landowners have replaced many miles of restrictive fences with pronghorn-friendly fences, either on their own or using the Natural Resources Conservation Service (NRCS) cost-share programs.

As part of the connectivity effort, the team also wanted to create more suitable habitat through brush management. To these plains-dwelling animals, thick brush is a barrier as surely as fences. Mesquite and creosote/tarbursh encroachment on the Marfa Plateau is a particular concern.

“We’re focusing our efforts on brushy areas adjacent to prime habitat to protect the open grasslands,” Gray said. “As we improve habitat, we also strive for brush diversity because browse is a back-up food source for pronghorns.”

According to Gray, ideal pronghorn habitat has a brush cover of 5–15 percent. When the brush canopy, increases to 25–30 percent, it becomes marginal for pronghorns and more desirable for mule deer. BRI researchers are currently conducting research that could help verify these field observations.

The BRI research team is also exploring the impact that different grazing systems have on the vegetative mix and trying to determine the carrying capacity for pronghorns on the Marfa and Marathon grasslands.

“What is good for the [cattle] herd is good for the [grassland] bird—and the pronghorn,” Gonzalez said.

In 2008 NRCS implemented an EQIP cost-share program for landowners interested in restoring grassland habitat for pronghorns in the Marfa Grasslands by managing brush. The National Fish and Wildlife Foundation, with underwriting from major Permian Basin oil and gas producers, also created the Pecos Watershed Conservation Initiative to fund research and cost-share habitat practices such as brush management and fence replacement in the region.

“These programs not only allow us to conduct necessary research, but give landowners the tools to help improve the landscape,” Harveson said. “They get us all pulling in the same direction.”

Just as landowners, through responsible management, strive to leave the land better than they find it, wildlife biologists strive to improve their own professional techniques.

“We’ve gotten better at capturing pronghorns,” Gray said, noting the team has refined the way it captures, handles and transports the animals. “Pronghorns are high-strung, flighty animals, and they don’t respond to capture like a deer or a bighorn.”

The pronghorns are netted from helicopters. In 2011, the team used big nets, catching three or four animals at a time, Gray said. Today, they use smaller nets and capture one or two at a time, which helps keep the pronghorns from getting “banged up.”

To help reduce the stress, veterinarians administer a small dose of Haldol, a sedative. They also monitor the animals’ temperatures. If an animal’s temperature reaches 104 degrees, which can cause long-term problems, it gets a shot of flunixin meglumine, an anti-inflammatory and fever reducer sold under the trade name Banamine®, to drop its temperature quickly. The animals also receive vitamins, micronutrients, de-wormer and an antibiotic to put them on a high-health plane and offset any capture myopathy, which generally takes places within 10 days post-capture.

“It takes an animal a period of time to acclimate to a new place and get over the stress of capture,” Gray said. “In the short-term the first 10 days are crucial. In the long-term, pronghorns that survive the first six months generally contribute to the herd for years.”

Even the trailers, which were originally livestock trailers with plywood additions, have been customized.

“The pronghorns seemed to be claustrophobic in the old trailers and tended to overheat,” Gray said. “In 2016, we designed four aluminum trailers with more room, floor mats, air vents and large openings covered with aluminum expanded metal to specifically accommodate pronghorns and other big game.”

Aluminum does not conduct heat like steel, he said.

These small changes have made a big difference.

“Between 2011 and now, we’ve reversed our mortality and survivability numbers,” Gray said. “About 75 percent of our translocated animals survive after six months of a translocation, giving us one of the best track records in the nation.”

While the ongoing project requires herculean effort from many, it is worth it.

“Without the translocations, some of these smaller populations would’ve just blinked out,” Harveson said. “This is much more than an academic exercise, because we’re having a direct, true impact on populations and re-establishing pronghorns in the wide, open spaces they’ve called home through time.”



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