Deadly snake hunt – Life Science: Snakes Venom Anatomy – Cover Story – venomous snakes
Kim Masibay
“Cobra! Cobra!” A woman’s screams pierce the hot night in a tiny village in Myanmar, formerly Burma. An American snake expert–the first scientist ever to survey all reptiles in this isolated region–happens to be in the village in his quest for new cobra species. He races toward the cries, tailed by a throng of curious villagers. Inside a hut, the woman’s family stands rooted in fear. Coiled near the back wall, a 3-foot-long cobra arches with a hiss, poised to strike.
Stealthily, the American approaches the hissing creature. With a few awkward thrusts of a “grab stick”–an aluminum pole with two 6-inch fingers or tongs–he grasps at the lightning-fast, poisonous animal, and snags it. Elated villagers crowd around to shake the hand of herpetologist (snake and reptile scientist) Joe Slowinski.
Now the cobra hunter has good reason to be excited. The snake he’s nabbed turns out to be an unidentified species–a spitting cobra that only inhabits the arid terrain of central Myanmar. Named the “Burmese spitting cobra” (Naja mandalayensis), it’s the first new cobra species to be discovered since 1922. Surprisingly, cobras are usually shy and nonaggressive–deadly only when threatened or hunting prey. “Ever since I was a kid, I’ve loved snakes,” Slowinski says. “I got bit by a rattlesnake when I was 15, and that didn’t stop me.”
What is it about snakes that mesmerize us? For thousands of years, these slithery creatures have inspired religious myths, fanatical fear, and endless curiosity. Streamlined to the bare essentials–mouth, belly, brain, spine–snakes manage to slink over desert sands and rocky slopes as well as swim in rivers and glide through the rainforest canopy.
In more than 100 million years on Earth, they’ve evolved to elegant perfection. “The way a snake moves, through sleek body curves, light shining off its scales, is one of the most impressive sights nature has to offer,” says cobra expert Wolfgang Wuster at the University of Wales, who collaborated with Slowinski in naming the new cobra.
PERFECT BODY
Apes climb with powerful anus and hands; frogs swim with webbed feet; falcons seize prey with sharp talons. Snakes–merely with a backbone–do all these things. Sheathed in smooth or rough scales, a snake’s limbless body contains a long string of 100 to 600 vertebrae (backbones), which provide spectacular flexibility without sacrificing strength. Each vertebra features a pair of ribs that curve and attach to the inner surface of a broad scale on a snake’s under-belly. Essential for snaky locomotion, these belly-side scales run crosswise like bulldozer tread; a snake’s skeleton and belly scales are linked by muscles in complex overlapping layers, letting snakes crawl, climb, zigzag, caterpillar creep, coil, and crush.
Cruising roads at nightfall is one way Slowinski sleuths cobras, since the species he’s after tend to be nocturnal, or active at night. Cobras are nocturnal because the rodents they love to eat scurry around at night; also, cobras can overheat and die in intense tropical sunlight. Since snakes are cold-blooded, or ectothermic, external sources–sunlight, air, water, or warm blacktop roads–heat their bodies. When snakes need to conserve heat, they coil into a compact mass. Some scientists think snakes bask on warm blacktops after they’ve eaten to heat their bodies and speed up the digestive process.
DEADLY VENOM
One night in rural Myanmar, Slowinski came upon a spitting cobra lying on a road. As he moved to bag the snake, the cobra reared, hissed, and spit at him. Wearing protective glasses, Slowinski didn’t back off. With his grab stick he snatched the snake behind its head and wrangled it into his cloth sack, trying to avoid a vicious bite. But he miscalculated: “Suddenly it bit me right through the bag!”
The fang sank into his finger, and Slowinski sat down and waited for the pain–which never came. “I got lucky. The bite was dry.” In other words, the snake released no venom, a poisonous saliva used to kill prey. If the cobra had injected venom, Slowinski’s finger would have swelled within minutes. His muscles would have weakened and his eyelids drooped; he would have drooled and slurred his speech. Breathing would have become laborious–then impossible. In 12 to 24 hours, he could have died. “But the last thing cobras want to do is waste venom on animals they can’t swallow whole, like people,” Slowinski says.
Snake venom is produced by special cells in two large venom glands on each side of the head. Out of 3,000 known species of snakes, more than 500 are venomous. The 10 most lethal snakes in the world belong to the elapids–often called the cobra family. Cobra venom kills via neurotoxins, proteins that paralyze an animal’s nervous system and diaphragm, abdominal muscles used to breathe. The snake metes out the exact amount of venom needed to suffocate the prey, then swallows its catch. Headfirst.
SNAKE SNACKS
Small animals–frogs, birds, rodents, and snakes (even other cobras!)–whet a hungry cobra’s appetite. Cobras track prey using senses of smell, sight, and hearing. As the snake hunts, its forked tongue flicks in and out through a notch in the upper lip; odor particles from the air and ground stick to the extended tongue. Inside the mouth, the tongue transfers scent particles to the Jacobson’s organ, two pits on the mouth roof; the organ sends complex signals to the brain, which analyzes the scent chemicals.
Because its tongue is forked, a snake detects the direction of an odor–left or right; the snake also sniffs through its nostrils. With this double-barreled sense of smell, a cobra can easily pursue the trail of a rat, for example. If the rat wanders close by, the snake might see the rat. And the cobra’s body, stretched along the earth, feels vibrations of the rat’s paws on the ground; the vibrations also resonate in the snake’s inner ear.
In a flash the cobra lunges, sinking its fangs into the prey and quickly releasing it. If the prey is large, the snake bites down several times to inject a lethal dose of venom. A snake’s eight teeth-bearing jaw bones are connected by a stretchy ligament (a band of tissue that connects bones). This ligament lets snakes swallow food whole. “That’s what snakes are best at–swallowing enormous objects,” Slowinski says. “A three-foot cobra can easily swallow a rabbit that outweighs it.”
Even wilder–these jaws continue to work even when the snake is dead! A freshly decapitated rattlesnake will try to attack objects–like human hands waved in front of it–for up to an hour after death. Why? Certain snakes (rattlesnakes, for instance) “see” with heat-sensing pit organs, located between the eyes and nose or around the mouth. Pit organs can detect heat even after a snake dies. Although cobras don’t have pit organs, Slowinski says he’s not taking any chances: “Dead or alive, we take a lot of caution with cobras.”
Charmed?
The mystical shimmy between snake charmer and cobra isn’t a dance at all. Snake charmers in countries like Myanmar, India, and Pakistan catch a healthy cobra (usually in rat holes) and keep it cool under a lid in a basket or clay pot. The “dance” begins when the charmer lifts the lid, letting bright light stream into the container.
Startled, the shy cobra rises through the opening to defend itself. The charmer teases the snake, waving the flute in front of it. The snake follows the motion, but not the music. Snakes can’t hear airborne sounds well, since they lack external ears. Is it dancing? Not really, but it sure is smooth. Watch out, J. Lo!
TRY THIS: Feel how a snake hears. Strike a tuning fork on a hard surface and press the fork’s stern to your chin. What happens? Snakes lack external ears, but sound waves travel through a snake’s jaw and vibrate bones in its inner ear.
[ILLUSTRATION OMITTED]
Cross-Curricular Connection
Geography: Research and report on Myanmar’s geological features. History: Research the snake myths and legends of several cultures.
Did You Know?
* Worldwide, venomous snakes kill an estimated 10,000 to 50,000 people a year. Of those deaths, fewer than five occur in the U.S.
* Snakes breathe with one lung: they have an elongated right lung, but the left one is a useless nub.
* The small-sealed taipan, an Australian elapid, has the most toxic venom of any snake. The most aggressive snake is Russell’s viper, which is prevalent in Myanmar.
National Science Education Standards
Grades 5-8: form and function * structure and function in living systems * diversity and adaptations of organisms
Grades 9-12: form and function * biological evolution * interdependence of organisms * behavior of organisms
Resources
Snakes by David Badger, Voyager Press, 1999
The Singapore Zoological Gardens Web site www.szgdocent.org/cc/c-main.htm
“Snake Struck,” by Joe Slowinski, San Francisco Examiner Magazine, June 11, 2000
CHECK FOR UNDERSTANDING
Deadly Snake Hunt
Directions: Write answers to these questions. Use complete sentences.
1. What is venom? How do cobras use it?
2. Why don’t cobras respond to music? How does a snake charmer make one “dance”?
ANSWERS
Answers should include these points:
1. Venom is poisonous saliva that cobras use to kill prey. Neurotoxins in cobra venom cause paralysis and suffocation.
2. Snakes lack external ears and can’t hear airborne sounds. To make a cobra “dance,” a snake charmer startles one with light, and then teases it to follow the motion of a waving flute.
COPYRIGHT 2001 Scholastic, Inc.
COPYRIGHT 2002 Gale Group
