Pawnee National Grasslands – Sometimes he dreams of flying serpents, which is understandable. Biology professor Stephen Mackessy studies rattlesnakes, and on a recent warm Friday afternoon, he fulfilled a familiar job requirement: He slipped a long-handled hook beneath a viper basking beside a prairie dog hole and flung it high.
In midair, in the middle of the Pawnee National Grasslands, all 3 feet of the startled snake thrashing. The rattle broadcast a crisp buzz, a white noise.
Mackessy spent 20 minutes corralling the livid whip of muscle before permitting it entry to a hole, the snake pouring down the dark entrance like oil in a funnel. It kept rattling, the sound flowing up from of the burrow.
Mackessy, a University of Northern Colorado scientist, has captured and studied rattlesnakes for more than 25 years, but new technologies and science reveal to him and other snake researchers much more about their fanged objects of study than ever before.
“There is a lot of new information coming to light that is telling us just how well-adapted these animals are to their environment,” he says, adding that for rattlesnakes living in places like the Pawnee National Grasslands, the environment is harsh: often frigid, frequently broiling and in terms of prey, slim pickings. “There is good parental care that goes on, there is very good recognition of den mates, there is likely all sorts of different aspects of social interaction that we have only scratched the surface on.”
Rattlesnakes are “precision predators” that use “chemistry to do a lot of their prey capture and digesting,” he says, scoffing at the “primitive” killing methods used by carnivores like mountain lions – all teeth and claws and strength.
Snake tongues slip from their mouths and flip up and down, essentially “reading” the outside environment through their palette of chemicals. Their heads register the slightest vibrations. Rattlesnakes have good eyesight and a solid sense of smell, and they also sport holes that look like nostrils but instead are thermal-imaging pits.
With the pits, “they can see a mouse in complete darkness,” Mackessy says.
In essence, a rattlesnake’s skull is something like a Department of Defense dream: an array of extremely complicated sensors all yoked to weaponry tailor-made for killing.
And then there’s the infamous tail, which may be the fastest-contracting muscle in the world. It can shake for hours, and with such speed that the flat, segmented rattle can sound more like a cicada’s drone than an infant’s toy. At other times, however, the snake will slow its tail and make castanet music, with individual clicks and clacks.
The whole beast thrills Mackessy, but much of his professional work centers on the biochemistry of venom, which places him – when he’s not looking for rattlesnakes in the wild – in a windowless laboratory full of machines, test tubes and refrigerators stuffed with vials of venom.
Studying venom can lead not only to better antidote serums and a richer understanding of snakes, but to new drugs. To examine venom, however, you must have the stuff.
So part of Mackessy’s job involves using a hook to hoist angry snakes from terrariums, pinning their heads to the ground with the tool, using his thumb and forefinger to seize them behind their jaws, thrusting their curved fangs into a plastic cup, and squeezing: Venom the color of light honey drips.
Many of his lab snakes come from Colorado. Of the estimated 33 species of rattlesnakes in the world, Colorado supports three – the prairie rattlesnake, which can be found anywhere from the Front Range east; the desert massasauga rattlesnake, in southeast Colorado; and the midget faded rattlesnake, on the Western Slope.
You think all rattlesnakes in Colorado have the same type of venom? Wrong. You think the venom always remains the same between youth and adulthood? Wrong again. What’s the worst snakebite in the state? It depends.
Go with a prairie rattlesnake, and you’ll get the kind of pain that makes you hoarse from screaming. Body parts will swell like water balloons. A hypodermic-needle fang to the toe, for example, could make a foot look like it has been cooked over a campfire. The victim could suffer permanent tissue damage.
A bite from the Western Slope’s midget faded rattlesnake probably wouldn’t cause massive tissue damage, and the pain might not verge on the otherworldly. But since the venom holds neurotoxins – famously fatal cobras have neurotoxic venom, although the toxins are different from those in the midget faded – it could lead to respiratory failure and death.
Were he faced with the proposition, “Steve, you’re going to be bitten by a Colorado rattlesnake. Which one do you choose?” Mackessy reluctantly would select the midget faded. Assuming you can get quick medical attention, the chances of long-term damage from the Western Slope’s snake are lower, he says.
Colorado’s other rattlesnakes, it appears, do not have neurotoxins in their terrible potions. Instead, their venoms include more proteins that act as meat tenderizers.
Neurotoxins and meat tenderizers are just small ingredients in the overall broths of venoms. In a prairie rattlesnake, for example, some proteins attack muscles, while others cause blood pressure to drop, which in prey leads to something like fainting.
Parsing the individual ingredients of each venom occupies much of Mackessy’s time. His work helps illustrate that prairie rattlesnake venom, for example, is almost cunning in its approach to prey such as ground squirrels.
By attacking muscles, the venom cripples the squirrel, and other components of the venom cause the rodent to faint. Neither kills the squirrel right away, though, because the snake needs the squirrel’s blood to carry the meat tenderizer through the body. The tenderizer, in effect, begins the digestive process before the snake decides to eat.
With some rattlesnake species, the chemical composition of venom changes with age, says Mackessy.
The venom of youthful midget faded rattlesnakes that Mackessy has studied targets the ectotherms – cold-blooded lizards and frogs – crawling and hopping their way across the Western Slope. The adult midget faded’s venom, however, is custom-made for the furry creatures – endotherms – it enjoys for meals.
Unfortunately for humans, both versions are highly toxic.
Colorado rattlesnakes shrink from humans, Mackessy says. They would much rather escape than strike, something evident after several viewings of Mackessy with live rattlesnakes. He routinely stands 18 inches from angry serpents, his big blond-and-gray beard nearly hanging over the snakes as they buzz and wrap themselves into taut springs and stare at him with inflamed eyes.
His research has never led to a bite. Playing around with a rattlesnake as a kid in California, however, did. He was 15, a big fan of snakes, and on April Fools’ Day, a friend brought over a newborn Southern Pacific rattlesnake in a terrarium.
One misplaced hand and wham! A bite between his index and middle finger. First the digits swelled, then his hand, then his entire arm. He remained in the hospital for nearly a week, his arm swollen to twice its size from fingers to shoulder.
What did it feel like? Walking across the Grasslands with his hook in hand, peering into prairie dog holes – many of them containing not snakes but black widow spiders – he responded: “Fire under the skin.”
Staff writer Douglas Brown can be reached at 303-820-1395 or djbrown@denverpost.com
