Texas Parks & Wildlife Magazine   


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Nature Without Borders

Protecting and managing wildlife and habitat in the Big Bend.

By Melissa Gaskill

Driving from one side of Big Bend National Park to the other easily takes an hour. Exit to the west and you’ll need more time than that to reach Presidio. Rangers at Big Bend Ranch State Park recommend allowing a couple of hours for the 27 miles of unpaved road from RM 170 to the park’s Saucedo headquarters complex. Drive across the Rio Grande (or Rio Bravo, as it’s known in Mexico) into Ojinaga — one of the only places you can do so between Del Rio and El Paso, 300-plus miles by road — and you’ll need a day to navigate a patchwork of paved and unpaved road to Boquillas, Mexico, at the base of the Maderas del Carmen.

It’s a vast, wild landscape.


The desert blooms at Big Bend National Park

Within it, several designated areas protect more than 3 million acres. The land is diverse — desert, mountains, river and transition zones between them. Its inhabitants are even more so. Big Bend National Park alone contains 1,200 species of plants, 75 species of mammals, 450 species of birds, 11 species of amphibians, 56 species of reptiles and 40 species of fish. In Mexico’s Maderas del Carmen, scientists have documented 79 mammal species, 80 reptile and amphibian species and more than 250 bird species, as well as 400-plus plant species.

This abundant wildlife knows no borders, and for a diverse group of agencies, organizations and individuals, its conservation and management know no borders, either. The U.S. Fish and Wildlife Service, National Park Service, U.S. Geological Survey and Texas Parks and Wildlife Department formally created the Big Bend Conservation Cooperative in 2010. That group works with various agencies in Mexico, including the Secretariat of Environment and Natural Resources, National Commission on Natural Protected Areas, National Water Commission and National Institute on Ecology and Climate Change. Private landowners and universities from both countries, the World Wildlife Fund, the Nature Conservancy, Sierra Madre Association and corporations such as Coca-Cola and CEMEX (a worldwide building materials company based in Mexico) also participate.

The challenges they face are as large and diverse as the landscape itself, from a struggling river to wildlife threatened by habitat loss, climate change and exotic invaders.

Addressing these issues wouldn’t be easy under the best of circumstances; here, the job is Herculean.

Still, progress has been made. Bighorn sheep, black bears and beavers thrive. Rio Grande silvery minnows may make a comeback, and biologists are closing gaps in knowledge about bats. Some battles with invasive cane have been won, and a reopened (albeit roadless) border crossing at Boquillas makes everyone’s job a bit easier.


Desert bighorn sheep are making a comeback in the Big Bend region.

Bighorn Sheep

This area offers perfect habitat for bighorn sheep, which cope well in dry areas and prefer steep, sparsely vegetated slopes. Although the state outlawed hunting of bighorns in 1903, by 1958, the animals had disappeared in Texas. Sheep from Nevada, Arizona and Utah were released in Texas in the 1980s and ’90s, and the animals did well at TPWD’s Elephant Mountain Wildlife Management Area. Between 1995 and 2000, 58 sheep from there were transplanted to Black Gap WMA, and that population is thriving, in part thanks to artificial water catchments. Bighorns have expanded into surrounding private properties and Big Bend National Park.

In 2010 and 2011, 140 collared sheep were transferred to Big Bend Ranch State Park, a move that has increased the numbers and distribution of the Texas population. TPWD monitors the animals to help gauge the success of management activities.

Bighorn populations have now been established in several West Texas mountain ranges in cooperation with private landowners and the Texas Bighorn Society, a nonprofit organization dedicated to returning the bighorn sheep to its range in Texas.

In Mexico, CEMEX began purchasing land in and around Maderas del Carmen in 2000, creating the 400,000-acre El Carmen conservation project. In 2001 and 2002, managers removed domestic livestock and fences, developed water sources and released 48 bighorns from Sonora into a 12,300-acre brood facility encircled by a predator-proof fence. Project managers released animals into the wild in 2004 and 2005. In Mexico and the United States, bighorns face competition from exotic Barbary or aoudad sheep (native to North Africa) and threats from recurring drought. Mexico’s National Commission of Natural Protected Areas is developing a climate change strategy for the 174 protected areas it manages, including Maderas del Carmen.

The project’s bighorns are expected to mix with those in Texas and help expand the population. In anticipation of that, Big Bend National Park’s chief of science and resource management David Larson says the park may more aggressively manage its aoudad. Unlimited hunting of aoudad is allowed year-round on private land in Texas (hunting license required), and special hunting permits are granted periodically in certain state parks and WMAs.

Black bears

One of our continent’s largest mammals, black bears reach up to 6 feet in length and 300 pounds. They eat mostly leaves, fruits, berries, roots and other vegetable material, along with insects and small mammals when the opportunity arises.

Black bears once roamed throughout North America, with two subspecies in West Texas: the Mexican and the New Mexico black bear. Both disappeared here by the 1950s, but remnant populations remained in the northern Mexican state of Coahuila and the Carmens. Thanks to protection there, their numbers grew and, after occasional, temporary forays by individuals across the river, bears returned to Texas for good, on their own, in 1988. Big Bend National Park wildlife biologist Raymond Skiles first spotted one in the national park in 1989, an event he calls one of the most important in the park’s history.

An extensive study from the late 1990s through 2005 documented collared bears readily crossing the border; scientists in both countries share information on the population.

The population in the national park has ranged from a high of 30 to lows of fewer than a dozen.

“The Chisos is a very small habitat,” Skiles says. “There is more habitat in the mountain ranges in Mexico. The Maderas del Carmen probably has well over 100 animals and del Burro several times that. Our population is truly dependent for long-term sustainability on being part of that larger international population.”

The Borderlands Research Institute monitors and studies the bears, but there is no active management in the park.

“We preserve their habitat and analyze any activity such as new structures or trail work to determine its potential impact on bears and other species,” Skiles says.


A black bear looks for a beehive in a tree in Big Bend's Chisos Mountains.


These large rodents are known for their ability to alter the landscape, creating ponds and wetlands that provide vital habitat for other wildlife and improve water quality by removing sediments and pollutants.

In Mexico, beavers remain only on tributaries of the Rio Bravo del Norte, as the river is known there. The NPS sponsored a study in the 1970s that provided a baseline for the population, and a second survey two years ago documented the extent of invasion by exotic nutria, which compete with beavers.

Still, beavers seem to be thriving in the Rio Grande, says Skiles.

“It’s kind of ironic, as the river is only a shadow of its historic self,” he says. “The floods that scoured vegetation from the shores no longer occur due to dams upstream, and beavers seem to be one of the few species benefiting from that.”

Beavers also benefit from removal of invasive cane, which leads to recolonizing by native willows.


For decades, no one knew much about the movement patterns of roosting locations of the endangered Mexican long-nosed bat, says David Elkowitz, chief of interpretation at Big Bend National Park. NPS, Bat Conservation International, Texas A&M University and university students from Mexico are working together to fill in the knowledge gaps.

Mothers have their pups in central Mexico from April to early June, and then move into northern Mexico. Some of the bats cross to roosting sites in the national park and New Mexico. After August, the Big Bend colony returns to Mexico, moving south with the agave blooms.

The bats feed on agave nectar at night, pollinating the plants, and the researchers are documenting where the bats feed and roost. The rugged nature of the land south of the border and difficulty accessing private land make the work very challenging, as does starting from a blank slate.

While the roost in Big Bend National Park is protected, in Mexico, human disturbance and destruction of roost sites is common, as many people believe all types of bats spread diseases. Education is, therefore, an important component of the research project.

“We don’t just say we’re scientists looking for bats,” Skiles says. “We talk to community groups or schools about the importance of bats and how people can live compatibly with them.”

Silvery Minnow

This 3½-inch fish once lurked in backwaters and pools of the Rio Grande from Española, N.M., to the Gulf of Mexico, but by 1994, the minnow occupied about 7 percent of that range, none of it in Texas. Its decline is attributed to habitat destruction and river modification, invasive species introduction and water quality degradation.

Every year from 2008 through 2012, thousands of fish were reintroduced into the river.

“It’s an experiment,” Skiles says. “We’re not certain the fish will survive, but river conditions are better than they were back in the 1960s, particularly from a contaminant perspective.”

The Fish and Wildlife Service, TPWD, New Mexico Department of Fish and Game and Mexican managers are evaluating and monitoring the fish.


The South Rim of the Chisos Mountains lights up at sunrise in Big Bend National Park.

River Cane

Giant river cane, thought to be native to Asia, was introduced into the U.S. in the early 1800s for erosion control. It does that well but, unfortunately, also crowds out native plants, reduces wildlife habitat, contributes to higher fire frequency and intensity and modifies river hydrology by trapping sediments. National park staff and their colleagues in Mexico have fought the cane for three decades.

Removal is 90 percent complete in Boquillas Canyon and upriver to Rio Grande Village, according to Big Bend botanist Joe Sirotnak. The effort will expand through a partnership with the World Wildlife Fund and Coca-Cola. Sediment studies guide cane control efforts, and once removal is complete in Boquillas Canyon, scientists on both sides will be watching to see how that affects river flow.

“Right now the river is channelized by walls of trapped sediment,” Sirotnak explains. “The hypothesis is that, without the cane, floods can reshape the channel into a more natural habitat and that will benefit most if not all the aquatic species.”

Removal, a combination of herbicide and prescribed burns, is definitely labor intensive, Sirotnak says, and could not happen without active participation from both sides of the border. In fact, none of these efforts likely would bear fruit without cross-border cooperation.

International Cooperation

In April 2014, the Commission for Environmental Cooperation convened 60 stakeholders and experts and identified 29 conservation priorities for this region. The report emphasized a binational, collaborative approach.

“The future of these natural resources depends upon shared management and the understanding that these populations and habitats are dependent on one another,” says Skiles.

Collaboration requires bridging two languages, two cultures and different conservation philosophies, support and funding. Managers point out that the U.S. conservation community is used to the national park model, in which human use is limited to recreation and the land is managed for wildlife. In Mexico, only 20 percent of protected lands — classified as flora- and fauna-protected areas — are owned by the government, the rest operating more like conservation easements. Villages and ranches dot the land across the river.

“Mexico has a history and dynamic that needs to be respected, and vice versa,” says Skiles. “I have been extremely impressed with their dedication, motivation and ability to be creative. I’m humbled quite often by our dependence on systems and programs. We rarely have to be as creative and collaborative as they do.”

The border crossing at Boquillas, which opened in April 2013, is just one crossing along the several-hundred-mile contact zone of these protected areas. Still, it exponentially increased the ability for scientists and managers to collaborate.

“We’re getting the word out that the crossing is open and we want to collaborate again,” Larson says. “Otherwise, we are only looking at half the river.”

For wildlife along the border, half is not enough.

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