NATURE NOTES:
Adventures in Herpetology in the Big Bend Borderlands

By Andrew Stuart

photograph courtesy Sean Graham. Harmless to humans, the Trans-Pecos black-hooded snake has a venom that’s effective on its favored prey: centipedes. The snake was only known from a few West Texas counties, until Graham’s team made the first record in Mexico.

The Chihuahuan Desert is the largest desert in North America, and, in terms of the richness of species, it may be the most biologically diverse desert in the world. That diversity encompasses the range of fauna and flora. There are mammals – and a surprising number of fish – found nowhere else on Earth. Almost a quarter of the world’s cactus species are found here. 

Yet it’s no surprise that this sun-blasted place is a particular haven for so-called “cold-blooded” creatures. When it comes to herpetology – the study of reptiles and amphibians – this region is renowned. 

Now, a professor at Sul Ross State University, along with U.S. and Mexican colleagues, and a few intrepid Sul Ross students, is expanding our knowledge – with expeditions across the Rio Grande in Big Bend.

Dr. Sean Graham, of Sul Ross, is a “herp” specialist.

“This part of Texas is kind of hallowed ground for herpetologists,” he said. “At some point or another in their careers, they always make it out here to see some of the rare and fantastic snakes, and other reptiles and amphibians, of the Chihuahuan Desert.”

There are 18 reptile species found only in the Chihuahuan Desert. In the U.S., Texas is generally the only place to see them. 

The gray-banded kingsnake is uncontested for top billing. Ringed in lustrous orange or red, no two are identical in coloration. If you see someone lighting a roadcut here on a summer night, they’re likely looking for this snake.

There’s the Trans-Pecos rat snake, the Texas lyre snake, and the Trans-Pecos black-hooded snake, which specializes in centipedes. A venomous desert centipede can be 8 inches long, but for this snake, it’s good eating.

“It’s meaty, and elongated,” Graham said, “so you just have to swallow it down. Other than the fact that they’re hideous and have big fangs – if you can get around that, centipedes wouldn’t be a terrible thing to eat.” 

In most cases, these snakes had only been documented in a few West Texas counties. Presumably they were present in Mexico. For Graham, the mountains of Chihuahua and Coahuila beckoned.

Every Big Bend lover has felt their pull. Whether it’s the shining cliffs and darkly wooded heights of the Sierra del Carmen, or distant ranges seen from the South Rim, Mexican landscapes are central to the Big Bend experience. 

They’re no “tierra incognita” – these are areas of historic communities and ranches, of rich traditions. But, scientifically, they’re little-studied.

The key for Graham was friend and colleague Tomas Hernandez, of Midland College. Hernandez’ family owns land in Chihuahua. With Hernandez’ help, Graham has made eight trips into Mexico.

They’ve been fruitful journeys. Graham’s team documented the first Trans-Pecos black-hooded snake in Mexico, and the first Texas lyre snake in Coahuila, among other new records. 

On their trips, Graham’s team cruises the area’s few paved roads, where snakes stand out.

They photograph what they find. For specimens, they collect roadkill. In the past, U.S. biologists often took specimens back with them – making them unavailable to Mexican scientists. But Graham sends specimens to a university in Monterrey, Mexico.

“We’re kind of doing the opposite of that,” Graham said. “We’re collecting specimens for them, and they now have these new state records, and good specimens, most of which we collected dead on the road, so it’s kind of guilt-free collecting. So we’re not taking anything from that fabulous country – we’re leaving it all behind.”

In these journeys, Graham and his colleagues have experienced the federally protected areas opposite Big Bend National Park – the Santa Elena, Ocampo and Carmen Mountains preserves. When Big Bend park was created, these areas were envisioned as part of an “international peace park.” That vision remains unfulfilled, but there are campsites and public access here – particularly in the Santa Elena preserve.

Graham said a highlight of his research is the relationships he’s formed – including with landowners in the preserves, who’ve welcomed his team. He said more Americans should experience these stunning places.

“I call it ‘otro Big Bend,’” Graham said. “It’s another Big Bend, and it’s wide open and it’s free. And I wish the word would get out. What worries me is that if people never see it, they won’t care about it, on both sides of the border.”

Two-thirds of the Chihuahuan Desert is in Mexico. For scientists, and all desert lovers, it’s a world to explore.