The adrenaline surges, the heart races. The buzz of a rattlesnake is an unmistakable warning: Stay away! Most of us get the message and keep our distance.
But a dedicated few are undeterred. Dr. Vicente Mata-Silva is a herpetologist at the University of Texas at El Paso. He’s placed radio transmitters in rattlers to track their movements, and his work reveals the snakes’ hidden lives.
“When we do these implantations, the snakes go under anesthesia that lasts like 10 to 15 minutes,” Mata-Silva said. “So during that time, you implant the transmitter, and by the time they wake up, they don't know what happened.”
The Chihuahuan Desert is rich in rattlesnakes, with six species calling the region home. Western diamondbacks are the most common, followed by black-tailed rattlers. But in his PhD work, Mata-Silva focused on a lesser-known species: the rock rattlesnake.
Rock rattlers are small, rarely exceeding 2 ½ feet. Their coloration reflects their environment. Rock rattlers in limestone landscapes are typically light grey, while those found in the Davis Mountain are often pink.
At UTEP’s remote Indio Mountains Research Station, south of Van Horn, Mata-Silva captured 12 of the snakes. Safety, of course, was paramount. He returned to Indio weekly, to follow the rattlers’ movements via the transmitters he’d implanted in their bodies.
As their name implies, rock rattlers have long been associated with boulders, cliffs and other rocky terrain. The snakes do winter in such places, Mata-Silva found. But they spend the warm months elsewhere.
“When summertime arrives, they go down into the arroyos in the vegetation,” Mata-Silva said. “They spend most of the time there, which was kind of interesting, because at the beginning we always went up in the rocky slopes looking for them.”
In a brushy pocket within an arroyo, a rock rattler lies in ambush. Each snake has several sites, in adjacent arroyos, among which it rotates, and it returns to those sites year after year. It mostly hunts at night, with lizards as its prey. Two or three lizards will suffice for a summer.
And a winter – because Mata-Silva found that the snakes spend winters tucked away in rocky crevices, eating nothing.
“But they do drink water,” he said. “We saw a big rain, or one time we had sleet, and this individual came out. I guess it was very thirsty, so they will come out for water.”
Only one thing interrupts the solitude. In late summer, females emit pheromones broadcasting their readiness to mate, and male rattlers travel across hills and arroyos in pursuit.
When they meet, the males engage in ritual combat. Competing snakes don’t strike one another, but rise up, entwining and wrestling. The winner does the mating.
“Nobody gets hurt,” Mata-Silva said. “They're very smart, and they will just push each other until one gets tired and just moves away. It’s a very intelligent strategy to resolve an issue.”
The female stores the sperm through the winter. Fertilization happens in spring, and baby rattlers are born in July or August. After a week with mom, the young are on their own – hunting insects until they graduate to lizards.
Since his initial fieldwork, Mata-Silva and his collaborators have conducted similar research with other species at Indio. Black-tailed rattlers, they’ve found, also do their hunting in arroyos. But diamondbacks hunt almost everywhere – from hillsides to open desert – which likely explains their abundance.
Now, Mata-Silva’s students are studying rattlers at El Paso’s Franklin Mountains State Park – to understand how human activity impacts snake behavior.
Most of us are content to keep our distance from rattlesnakes. But thanks to Mata-Silva’s efforts, we know a little more about these quintessential desert creatures.
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