Texas is home to some of the creepiest, crawliest, and otherwise oddest animals on the planet. We introduce you to them in What in Tarnation?!, an occasional series.

The indigo snake appeared without a sound. It was the summer of 2020, and the trails around the visitor center of the Laguna Atascosa National Wildlife Refuge, seventeen miles northeast of the Lower Rio Grande Valley city of Los Frenos, were cloaked in the eerie hush of early dawn. The dark blue serpent emerged from the thornscrub, tongue flicking, a six-foot streak of darkness in the morning gloom. Green jays and chachalacas scattered as it slithered across the leaf litter toward a bird fountain. The snake paid them—and me—no mind, moving with the absolute confidence of an apex predator. It ducked its head in the water and drank in long, silent gulps. A moment later it was gone, vanishing back into the forest to hunt. 

It was a characteristic encounter with a Texas indigo, the state’s largest native serpent. Known to science under the evocative genus name Drymarchon—“lord of the forest”—it’s one of the few Texas snakes to enjoy an unambiguously positive reputation, at least among those in the know. Texans, after all, can appreciate an animal of superlative size; the species’ natural charisma and taste for rattlesnakes doesn’t hurt, either. “Indigos are actively appreciated,” said Paul Crump, state herpetologist for Texas Parks and Wildlife. “A lot of ranchers and farmers will leave them alone.” 

Indigo snakes get their name from their prevailing color: a deep, magisterial blue-black that shimmers with iridescence under the right light. Unlike its southeastern cousin, the federally endangered eastern indigo snake, the Texas indigo is also graced with a rust-red hue around its face and throat. Adults commonly hit five to six feet in length, and have been known to grow considerably longer. “Eight or nine feet is the record,” Crump said. “They probably take a really long time to get to that upper end of the record—who knows if we have the habitat and the food for a snake to get that old these days.” No one has studied the species’ lifespan, though one captive individual lived for almost 26 years.

In fact, Texas indigos represent the northernmost population of a wide-ranging species, Drymarchon melanurus, whose home range stretches down through Central America and into northern South America. Also called the blacktail cribo, it includes five subspecies; ours is the erebennus variety. Inside the state, Crump said, they can be found from the Rio Grande Valley to the Balcones Escarpment (the fault line that runs from Del Rio to Waco), with very occasional appearances north of Interstate 10. Generally speaking, the species prefers the thornscrub of South Texas, but is fairly adaptable: semitropical valleys, forests, pastures, and semiarid landscapes all fall under the indigo’s dominion.

These forest lords earn their name. They’re extremely active, powerful predators, spending much of their time prowling for anything small enough to devour: rodents, birds, lizards, baby turtles. They aren’t venomous, and don’t squeeze their prey to death. Indigos instead simply chase down and overpower smaller animals, looping a powerful coil over their prey to pin it in place. They also exercise their monarchical prerogative by catching and eating other snakes, including rattlesnakes and other venomous neighbors. The field guide Herping Texas includes some truly alarming photos of an indigo decapitating a western diamondback by sheer force. 

As impressive as this mighty apex predator is, it tends to deal badly with human encroachment. The eastern indigo snake, found in southeastern states such as Florida, Alabama, and Georgia, is federally endangered due to the usual brutal pressures of habitat loss and the murderous open road. For a long time, Crump said, indigos were listed as threatened in Texas as well, in part due to a perception that they were also rare. But with the rise of iNaturalist and other citizen science reporting websites, Crump said, researchers realized within the past few years that Texas indigos are actually doing reasonably well. 

“There’s eight hundred observations of the species on iNaturalist, which is really high,” Crump said. “Our understanding of where they were was kind of biased, because people didn’t like to collect them.” Now, he said, Texas Parks and Wildlife is pretty sure that the species’ range in Texas isn’t shrinking. The snake was removed from the state’s threatened list in 2020.

The question is why, especially considering its eastern cousin’s struggles. One possibility is that, despite considerable suburban sprawl and development, rural South Texas is still a good place to be an indigo snake. The region has vast tracts of ranchland, where livestock and hunting operations don’t conflict much with the indigo’s needs. (In fact, they might help, given ranchers’ tendencies to dig permanent stock tanks, which snakes enjoy drinking from.) There are some development threats—thousand-acre tracts lost to solar farms or forests cleared for agriculture. “But it seems to me that the continued land uses are still compatible,” Crump said. That, as well as the numerous continuing observations from McAllen to Brownsville, suggests the snakes might be able to hack it on the rural fringes of cities as well.   

As matters stand, however, not much is known about the life history or population dynamics of the Texas indigo, especially compared to its Florida cousins. Much about it remains enigmatic. How large is its home range, precisely? Where do young snakes go, and what do they eat? Just how many of them are there? “The challenge for us is that we have so many species that are much closer to extinction that are a higher priority for our limited funding,” Crump said. But, he says, TPWD would love to embark on such a research project if someone wanted to privately fund it.

At the end of September, my partner and I decided to drive down to Brownsville to try our luck at seeing one. Our guide was Clint Guadiana, curator of reptiles and amphibians at the Gladys Porter Zoo in Brownsville. Guadiana is an old hand at finding indigo snakes: he once ducked out of a wedding held at the Sabal Palm Sanctuary to walk the trail in his tux, and caught an indigo snake near where the ceremony was held. The trick, he said, is to look near water sources, such as seasonal resacas, irrigation ditches, and the Rio Grande itself. Even then, the creatures are elusive. “Really all the parks you can observe them, but it’s kind of random,” Guadiana said. “They’ll pop up, basking or hunting, and then they’ll glide off into the thick brush and you won’t see them again.”  

On a warm evening, Guadiana took us driving out onto the backroads of Willacy County, where we kept our eyes peeled for the telltale black line of a snake crossing the white dirt roads. “We won’t have long if we happen to see one,” Guadiana said as the truck bumped along the track. “You’ll have to leap out of the car and go right for it before it gets into the grass.” 

Grappling with such a snake might sound unappealing. But despite their status as powerful reptilian predators, indigos that find themselves faced by humans tend to be shy and rather docile. If you’re lucky enough to lay hands on one (no easy feat, as they’re quite fast), it’ll generally default to an annoyed tail rasp or the release of pungent musk. Guadiana has caught his fair share and only once been bitten. Nor do they tend to thrash in panic: more often, the indigo simply turns to study the person holding it, body tense with a sort of active, wary regard. It’s a species with what can only be called personal magnetism—the sort of quiet confidence you might get from a very large, very serious dog. 

It’s the kind of stare you don’t forget in a hurry. Unfortunately, we weren’t to find ourselves subject to it that evening: the persistent, brutal drought had dried out much of the forest and roadside ditches. We scored a few baby rattlesnakes and a handsome, nervy Mexican racer; of forest lords, there was no sign. Nor did we spot any on a subsequent visit to Sabal Palm Sanctuary, where the piles of palm fronds and bougainvillea thickets remained conspicuously empty of black snakes. We walked back and forth along the shady trails in the muggy morning, Guadiana’s optimism fading as the hour passed. The indigos, he sighed, were like everyone else: waiting for a good, solid rain. 

But the funny thing about indigos is that—as both Crump and Guadiana remarked—you don’t find them. Often, they find you. Before leaving the valley, my partner and I stopped at Resaca de la Palma State Park, an expanse of thornscrub and dry oxbow meadows northwest of Brownsville. We biked along the hot trails, keeping our eyes peeled. Nothing. Only after we’d returned our bikes and were standing at the pollinator garden did I catch a glimpse of striking black scales. There it was: a four-foot indigo snake sprawled out in the wood chips, basking in the sun, its red-throated head raised slightly as it watched us. For a moment we traded stares with the lord of the forest. The snake’s tongue flicked. And then—moving easily, without any particular rush—it glided into the shadow of a tree and disappeared, as if it had never been there at all.