NATURE NOTES:
At Big Bend Park, A New Plan to Fight Exotic Wildlife

By Andrew Stuart

Science confirms what visitors intuit: Big Bend National Park is a singular place. At 1,200 square miles, it’s the largest protected Chihuahuan Desert landscape in the U.S. The diversity of desert life it contains is unparalleled. It’s not only a place of recreation – the park exists to preserve ecosystems. 

That work falls to the park service, and it’s not always simple. “Exotic” or non-native species are among the the starkest of challenges.

In 2018, the park adopted new plans for addressing “exotics.” They include ambitious efforts to eradicate or reduce two non-native mammals – aoudad, or Barbary sheep, and feral hogs.

Watching a herd of aoudad stream effortlessly up a steep, rocky slope, one might think these powerful creatures utterly “belong” in West Texas. In fact, they illustrate the perils of exotic wildlife. Introduced from North Africa in the 50s as a game animal, they’ve flourished here. But at significant cost.

Raymond Skiles, wildlife biologist, retired in 2018 after 30 years at Big Bend. He spearheaded the park’s exotic species plans.

“In areas where they’re in large numbers – as one of the local ranchers said, it just looks like a big mowing machine has come through,” Skiles said. “It’s an immense impact on the vegetation of the park, and the ecosystem that depends on the plants that are there.”

Effects may be especially acute for desert bighorn sheep. These natives had vanished from Texas by the 50s, but reintroduction efforts have had success. Barbary sheep can outcompete desert bighorn for food and water, and could transmit disease.

Aoudad have been present in the park for decades. But control efforts have been limited. Under the new plan, the park has partnered with Texas Parks & Wildlife. Shooters have operated from a Parks & Wildlife helicopter to take out aoudad in the park. About 80 were killed in August 2019.

Skiles said that while these killing operations are a grave matter, they are in fact required by the laws and policies that define national parks.

“It’s extremely important to know, what is a national park?” he said. “Sometimes in the public’s eye, and certainly in mine when I was young and visiting parks with the family, it was a place to go have outdoor recreation for humans. That’s a clear value of the national parks. But if you look at the official statements that established the national park system, those make it very clear that the purpose of the parks is the native, indigenous wildlife, and plants and other resources, and exotic invasives that may somehow degrade those native species are to be addressed when possible.”

The exotics plan was developed in accord with the National Environmental Protection Act. The process took years, and involved public meetings and public comment. Skiles identified some two dozen non-native species in the park. In most cases, eradicating those animals is impractical. But the means, and the need, to control aoudad were there, Skiles said.

And those conditions applied to a second non-native: the feral hog.

“Some people might even now be surprised, as I was, that feral hogs would even think of living in such an arid environment,” Skiles said, “but they were first identified in the mid- to late-90s in the northern part of the park.”

Descended from domesticated pigs, feral hogs can consume “vast numbers” of other species, Skiles said – from deer fawns to reptiles and birds. And their wallowing destroys wetlands, and facilitates the spread of non-native plants.

Park staff have for years trapped and shot feral pigs where they’ve entered the park’s northern end. But hog populations are expanding around the park – downstream on the Rio Grande, across the river in Mexico, and in adjacent Big Bend Ranch State Park. 

“It was quite clear that if we hoped to have a robust protective effort going on, we would need to prepare on a large-scale basis for not-yet-realized – thank goodness – but potential future problems with feral hogs,” Skiles said.

The plan calls for helicopter-based shooting of feral hogs if populations grow. 

The control of both hogs and aoudad will likely be an ongoing process – and funding for the work is not guaranteed.

For many visitors, Big Bend National Park is an escape from aspects of the modern world. It’s also a sanctuary for living things that far predate that world. Safeguarding that sanctuary involves difficult choices.