Snake Charmer - diamondback rattle snakes

National Wildlife, Feb-March, 1999

After two decades of studying eastern diamondback rattlers, the author finds that America's deadliest snake is surprisingly timid

Kneeling motionless on the ground, I watched as a husky eastern diamondback rattlesnake slid from my 5-gallon can into its winter home, a dark gopher tortoise burrow.

"See you soon," I whispered, expecting to recapture this and eight other rattlesnakes I had recently caught, marked and released in the open pine forests of northern Florida.

But I did not see any of the snakes again until the following winter, when they had returned to their underground refuges to hibernate. My planned study of the life history of this widely feared but little- understood creature ended in failure because I couldn't find any of my subjects in the piney woods.

When I began my research in 1976, I was amazed at the dearth of scientific information on eastern diamondbacks. In the two decades since, I have learned why my first attempted study failed and, more important, I have filled in many details of the life history of the species. I have discovered that this creature, long despised by people, is highly evolved, incredibly complex and surprisingly gentle.

The eastern diamondback is the largest of the world's 32 species of rattlesnakes. Adults usually stretch 4 to 5 feet long and weigh from 4 to 8 pounds, but rare monsters more than 7 feet long and 15 pounds have been recorded. The distinct yellow and brown diamond patterns on its back give the snake its name. These rattlers are found in open-canopied pine forests throughout the southeastern United States, although their range and numbers are declining.

Like other rattlesnakes, the eastern diamondback's tail is tipped by a series of horny segments that rattle when shaken. And like its relatives, the eastern diamondback kills prey with venom injected through two fangs. Because of its large size and the potency of its venom, the eastern diamondback is the deadliest snake in the United States.

This latter fact, together with long-standing myths about rattlesnakes (see box at left), probably accounted for much of the ignorance about eastern diamondbacks I encountered when I began my studies in the mid- 1970s. At the time, I had recently been hired as a research biologist at Tall Timbers Research Station, a nonprofit biological field station in northern Florida. To my dismay, the station managers allowed venomous snakes on the grounds to be killed, and I was determined to show them this policy was ill-advised. When my search of the scientific literature turned up little about the eastern diamondback, I realized I was situated perfectly to undertake the first long-term study of this species.

After my first attempt at recapturing the snakes failed, I decided to use radio transmitters. I made small cigar-shaped packages out of a transmitter and battery coated with beeswax, and gently pushed them down the throats of the snakes. (An adult eastern diamondback can hold a full-grown rabbit in its stomach, so the transmitters were not burdensome.) Radio tracking gave me the means to find my subject animals any time I wished--day or night.

With the help of the transmitters, I learned why I could not find the marked eastern diamondbacks in my first attempt. Their diamond-shaped color pattern blends well with dappled light and shadows, making it difficult to see against grass stems or dry leaves. But camouflage was only part of the answer. I also learned that the eastern diamondback, unlike its irascible cousin, the western diamondback, is a very placid animal that rarely moves or even rattles when approached by humans.

I have been bitten only once in the field (when I was attempting to catch a snake), despite hundreds of close encounters with eastern diamondbacks. Recently I performed a crude experiment to test how complacent the eastern diamondback is. I purposely stepped twice on a rattler coiled under a clump of muhley grass. When I tried to capture it, I was shocked to discover that under my other foot my weight had been bearing down on a second snake coiled under an adjacent muhley grass clump! During the episode, neither rattler moved nor rattled.

I believe there are two reasons why the eastern diamondback is reticent. First, the tendency to lie still and not rattle assists the rattlesnake in remaining camouflaged. Second, in the open pine forests of its native habitat, there are no places to escape from large predators. Rattling, which may have evolved to keep Pleistocene mammals from trampling rattlesnakes, became a distinct liability for eastern diamondbacks when people came on the scene. Native Americans would have been attracted to any rattling snake as an easy source of food, and eastern diamondback remains have been found in ancient Indian middens.

It is a good thing for humans that the eastern diamondback is so complacent. Because of its large size, it delivers a very large dose of venom. I know firsthand how potent the venom is. In 1976, I was bitten on the index finger by a small, three-foot-long snake. I felt no pain at first, but after four minutes my legs became paralyzed and I collapsed, unable to stand or walk. (Although most rattlesnakes have blood- attacking venom, the venom of the eastern diamondback is largely nerve- attacking, resulting in paralysis. Prey are quickly immobilized so they don't run far away and become difficult for the predator to locate.) I required 31 units of antivenin and a nine-day hospital stay to recover.