Rattlesnakes: Deadly Adaptations

Although rattlesnakes evolved long before the world’s deserts took their present form, they were exquisitely preadapted to desert conditions. The fear of rattlesnakes is greatly exaggerated, since far more people die from bee stings or dog bites than rattlesnake venom. But something about the coiled warning, slitted eyes, and flicking tongue of the venomous rattlesnake, a type of pit viper, stirs a deep-seated fear in many people. In truth, rattlesnakes are a marvel of evolution. The toxic saliva they interject through their hollow, needle-sharp, wickedly curved, and pointed fangs contains a mixture of enzymes unique to pit vipers. These enzymes paralyze muscles, destroy blood vessels, and actually start the digestive process before the snake even swallows its prey. They are one of the few creatures with dual visual systems, since they can spot prey with either their eyes or with infrared detecting, heat-sensitive pits in their upper jaws, giving them the real-world equivalent of the color-coded vision of the monster in the movie Predator. They can detect the heat of a candle from 0 feet away and detect rodents like kangaroo rats that remain their favorite meal even in the pitch-dark desert night when they do most of their hunting. These heat-detecting pits can sense temperature differences of a fraction of a degree at the range of the snake’s coiled strike. Rattlesnakes strike, let their venom work, then slither up, unhinge their jaws, and swallow their prey whole. They cannot eat larger creatures, so when they strike a human being it is only after attempts to warn off the threat with their trademark rattles have failed. The rattles, which can vibrate up to 60 times a second, are composed of the same fibrous protein as a human’s fingernails, and the snake gets another rattle every time it sheds another layer of skin. Half the time, when they bite a creature as large as a human being they do not even bother to interject venom. Recent research has suggested that mother rattlesnakes may hang about their nests for a week or more to protect their newborns.

Most people bitten by rattlesnakes survive, even without treatment. Moreover, most people who get bitten provoke the bite. One Phoenix emergency room physician recalled one case involving a rattlesnake bite. A young man with a pet rattlesnake got drunk and started showing off to his friends. He bent down close to his pet rattlesnake and flicked his tongue out at the snake. So the snake bit him on the tongue. Still drunk and befuddled, the young man had heard an old wives’ tale that suggested an electrical current can break down rattlesnake venom. So he went out to the garage and had a friend wire his swollen tongue to the battery of his truck. Naturally enough, that only made things much worse. The drunk and foolish man ended up in the hospital, where antivenom saved his life.