Edition: U.S. / Global

Venomous and Sublime: The Viper Tells Its Tale

Published: December 10, 2002

Not long ago in Zion National Park in southern Utah, a couple of hikers -- O.K., one of them was this writer -- came upon a big and handsome Western rattlesnake off to the side of the trail. The snake was coiled on a rocky outcropping just below eye level, sunning itself, as ectotherms love to do. A dappled velvet cable at home on the checkerboard stage of the desert.

Soon, a throng of other hikers had gathered round to gawk, leaning in to take pictures and then squealing excitedly as the snake snapped its head toward a camera flash with a withering glower. When a park ranger arrived to see what the fuss was about and said yes, it was a real rattlesnake with genuine venom in its fangs, a teenage girl in the throng breathed out a sentiment surely shared by the group: ''That is so cool! I've never seen one of these things outside a zoo before.''

Is there anything cooler than a snake or more evocative of such a rich sinusoidal range of sensations? Snakes are beckoning. Snakes are terrifying. Snakes are elegant, their skins like poured geometry.

Snakes are preposterous. Just watch one galumph its jaws around a stunned hare or a chicken egg or even another snake.

Around the world, people dream of snakes more than of any other animal. As scientists learn more about the biology, evolution and behavior of these earthiest and most Freudianized of creatures, snakes just keep getting cooler, a fitting fate for a coldblooded reptile.

Lately, biologists have been particularly mesmerized by the large, ancient and wildly diverse group of snakes called the vipers, a family that includes rattlesnakes, coral snakes and black mambas and more than 200 other species dispersed across every continent, save Australia.

Some, like the rattlesnake, are pit vipers, with specialized concave pits between the snout and mouth that pick up heat signals from prey and foe alike. Others are pit-free.

Many New World vipers have elaborate rattles, a posterior shingling of fingernail-like plates that can shake a warning at 50 beats a second.

All vipers, however, are equipped with their signature erectile fangs, a cleverly designed set of daggerlike venom delivery devices that lie flat against the snake's upper palate when the mouth is closed, but that pop out to unexpectedly nightmarish dimensions when the snake is poised to strike.

Whereas most snakes lay eggs, a great majority of vipers give birth to live young, a fact reflected in the family name, taken from the Latin words vivo, meaning live, and partus, birth.

The vigor of the viper calling is shown in ''Biology of the Vipers,'' a generously illustrated volume being published by Eagle Mountain Publishing. In it, several dozen herpetologists offer an array of surprising, amusing and cautionary findings about their snakes.

They describe hawkish vipers and stalker vipers, males that devote the bulk of their mating energy to fighting other males and males that opt instead to pester a female, tailing behind her, interfering with her hunting and otherwise preventing her from choosing another forked tongue in the road.

They talk, as well, of the sweeter side of serpenthood, of vipers that seem to recognize their kin and seek out their siblings preferentially when it is time to den down and curl up for the winter; and of mothers that are anything but coldhearted.

Dr. Harry W. Greene of Cornell and his co-workers describe cases of parental behavior among black-tailed and pygmy rattlesnakes that defied all their presumptions.

''We'd expected that after giving birth the mothers would crawl one way and the babies another,'' Dr. Greene said.''But instead, we'd find a mother basking with her young day after day or guarding the entrance to a burrow while the babies were inside.'' Once, he said, he saw a little viper start to emerge from its hole, apparently against its mother's better judgment. ''She put her head on him and nudged him back inside.''

The researchers propose that parental behavior has evolved among some vipers, together with delayed skin shedding. While most baby snakes shed their skins as soon as they are born, viper newborns, which are comparatively larger, do not discard their birthday suits until they are about 10 days old. While they are shedding that skin, their eyes are beclouded, they are susceptible to water loss, and they are extremely vulnerable. Hence the need for a mother's watchful care.

Though snakes have long been viewed as little more than preprogrammed pinheads -- ''pretty low on the totem pole in intelligence,'' as one herpetologist put it -- Dr. Randall S. Reiserer of Vanderbilt University in Nashville tenders evidence that vipers can in fact learn from experience and fine tune their hunting strategies to suit new circumstances.

He took 10 young massasauga vipers into his laboratory, some from swampy regions of the Eastern United States and others from the Arizona deserts. As a rule, Eastern massasaugas lure fast-moving frogs by giving undulatory wiggles of their tail, which resembles a worm. But when they see a slower-moving lizard, they do not risk a tail nip and instead pursue on their bellies.

Western massasaugas, by contrast, are faced with fast-darting desert lizards. So they use their tails as lures, while they ignore the few frogs in the area as too toxic.