The private lives of pit vipers

National Wildlife, August-Sept, 1995 by Michael Lipske

New research on rattlesnakes may help in the protection of the world's dwindling serpents

On this warm October afternoon in the craggy Chiricahua Mountains, Kevin Costner is sunning his body on a rock. Honest, right here in lovely southeastern Arizona!

On second thought, with the sun high and hot over the desert, the handsome devil may have crawled into the cool shade of an overhang. But he is up there in the thorny hell of Silver Creek Canyon, among the cholla cactus and cat's claw acacia, and biologist Harry W. Greene will find him. Cornering Costner - a blacktail rattlesnake - should be a cinch, half-an-hour's work, because the snake has a radio transmitter sewn into his abdomen, and Greene has a radio receiver that picks up the transmitter signal.

To Greene, a biology professor at the University of California-Berkeley and a highly regarded authority on venomous serpents, all blacktail rattlesnakes are "very, very beautiful animals," their greenish-yellow bodies crossed by dark, irregular bands, their tails the color of charcoal. But one male blacktail is special. Identified for research purposes simply as Number 9, this serpent is, in Green's eyes, such a standout that the biologist nicknamed him after a movie star.

For the past six years, the 49-year-old herpetologist has tracked a total of 19 blacktails up and down the arid flanks of the Chiricahuas, from the limestone rimrock where rattlesnakes hibernate in crevices through the cold months, to the canyon bottom where they hunt for rodents and engage in sex lives both robust and strange.

Greene's goal is to build a detailed chronicle of the life of the blacktail rattlesnake, a species found from central Texas to western Arizona. Herpetologists can then compare that information to what is being learned about other venomous snakes of the fascinating and fearsome reptile clan known as pit vipers. Greene and other scientists estimate that of the world's roughly 145 pit viper species - including 17 in the United States - at least 80 are threatened with extinction. Greene believes pit vipers are more victimized than vicious and that the more he can learn and then teach people about these snakes, the more likely the rest of us will be to cut them some slack.

A group that includes the New World's rattlesnakes, pit vipers range from Asia's green tree vipers to North America's copperhead and Latin America's bushmaster, which is the world's largest, sometimes exceeding 10 feet in length. All share a characteristic as technologically sophisticated as Harry Greene's radio gear. This is the heat-detecting, concave organ on each side of a pit viper's head (between its eye and nostril) with which hunting serpents home in on warm-blooded prey. Greene hypothesizes that the infrared-sensitive facial cavities developed not as aids to feeding but as defensive organs originally used to sense the size of, and thus the potential threat posed by, various creatures the snakes encounter.

Group members also share a more notorious characteristic. Folded against the roof of a pit viper's mouth are two long, curved, hollow teeth. When a pit viper strikes, the two fangs flip forward and, like dual hypodermic needles, inject the modified saliva that is viper venom. Pity the viper's prey, which for blacktails is most commonly wood rats, rabbits and rock squirrels. Propelled rapidly into shock as its dying heartbeats pump poison through its system, the small animal at the same time is internally tenderized by digestive enzymes in the venom that go to work even before the snake gets down to eating. Digestion before ingestion, snake people say.

Aside from an inquiring mind, sturdy shoes and steady nerves, the main tool that Greene brings to his searches is radio telemetry - the transmitters implanted in snakes and the antenna and receiver wielded by himself and his partner in blacktail tracking, David L. Hardy, Sr. A Tucson anesthesiologist who never lost his teenage passion for herpetology, Hardy, now 60, is also an expert on the effects and treatment of snakebite, comforting knowledge for the novice rattlesnake tracker accompanying the pair in the field.

Almost reverently, Greene calls the radio gear and what it accomplishes for him "the trick," the technologically enhanced ability to say "how do you do" to the same rattlesnake time and again - sometimes hundreds of times again - over the course of many years. Part science, part orienteering, the technique has revolutionized his and other studies of these elusive animals.

In this first detailed study of a blacktail population, Greene and Hardy have followed male snakes that crawled three yards a minute - as much as a quarter mile a day - in single-minded pursuit of breeding females. They have come across blacktails courting in trees (behavior hitherto unknown in rattlesnakes), and they have identified the snakes' favorite rocks and refuges for hibernating and for hanging out.

The search for Kevin Costner has gone on for 30 minutes now, the trackers climbing through what David Hardy calls "prickly terrain," the desert's heavy helping of cactus, shin-daggers and other evil-tempered plants. Greene calls this his favorite part of the United States. In Cochise County, in the neighborhood of the study area, he and Hardy can find seven other species of rattlesnakes - plenty of grist for students of snakes and snakebites.