SW 422

May 2001

W I L D L I F E P R O J E C T

Learning About Snakes INTRODUCTION Few native animals are more disliked or more misunderstood than snakes. In fact, most snakes are not poisonous and are beneficial predators of rodents and insects. The study of snakes can be a fascinating project. This activity will deal mainly with life history studies of snakes to provide the following information about their habitat, foods and feeding, breeding habits, growth and life span, skin shedding, defense and warning behavior, sense organs, and economic value. Also, some myths about snakes will be uncovered. Snakes are limbless reptiles that are thought to have evolved from lizard-like ancestors about 130 million years ago. During the snake’s evolution, its body was greatly lengthened and the number of its vertebrae and ribs was greatly increased. Long snakes have between 200 and 400 vertebrae and ribs, all nearly alike in size and structure.

Figure 2. A long snake (above) has between 200 and 400 vertebrae and ribs of similar size and shape.

Snakes, like all reptiles, are cold-blooded. They have no temperature control mechanism and are greatly affected by extremes of hot and cold. Their body temperature will vary with that of the environment. Their nervous and muscular activities are affected by outside temperatures. Increasing cold greatly slows down their movements, so that at around 32 F they stop moving completely. Snakes, like other reptiles, reproduce sexually by means of the union of a male sperm cell with a female egg cell, or ovum. Many snakes, including bull snakes and cobras, lay eggs that later hatch. Others, including rattlesnakes and garter snakes, retain the eggs within their body. The eggs hatch in the oviduct, and the young are born alive. Snakes crawl on large scales that cross the belly like the treads on a caterpillar tractor. The snake moves in two fashions. When moving fast, the snake pushes from side to side using the sides of those scales. When moving slowly, the snake can crawl or climb in a straight line by pushing with the middle of the scales.

Figure 1. Most snakes are not poisonous.

Why do snakes shed their skins? As a snake grows, its skin gets too small and tight, just as your shoes get too tight when your feet have grown. So the snake grows a new skin and gets rid of — or sheds — the old one. Some snakes may do this three or four times Figure 3. Snake shedding skin a year. Because young snakes grow faster than older snakes, the young ones shed their skins more often. Usually the skin is shed in one unbroken piece. SOME FACTS ABOUT POISONOUS SNAKES Of the 250 kinds (species and subspecies) of snakes found in the United States, only 36 are considered poisonous or otherwise dangerous. These include rattlesnakes, copperheads, coral snakes and cotton mouths, or water moccasins. None of the other species need be feared. All dangerous snakes in the United States belong to two groups — coral snakes and pit vipers. The pit vipers are rattlesnakes, copperheads and cottonmouths. All rattlesnakes can be identified by a rattle on the tail. Only rattlesnakes have rattles, but some species will shake their tail vigorously when alarmed. The rattles are hard rings made of a material similar to fingernails. When the rattlesnake is excited, it usually shakes its tail. The hard rings hit against each other, making a rattling noise. Figure 4. A rattle: Inside and out.

Copperheads can be identified by wide bands across the back (in the West) or hourglass patterns (in the Southeastern United States). All have vertical pupils (like cat’s eyes) and a deep pit on each side of the head between the eye and nostril. These pits have nerve endings at their base that are sensitive to heat. They are so sensitive that a pit viper can sense a mouse, by the heat that it radiates, from several feet away. It then strikes the animal and the venom, or poison, from the snake’s fangs kills it. If a snake does not have pits or vertical pupils, you can be sure it is not a rattlesnake, copperhead or cottonmouth.

Figure 5. Copperhead.

Figure 6. Timber rattlesnake.

A snake’s fangs are a special kind of modified teeth. All snakes have teeth, but only poisonous snakes have fangs. Fangs are actually hollow teeth with a tiny hole at the bottom. When a fanged snake bites an animal, the venom is forced through the fangs into the victim. A poisonous snake bites small animals in order to kill them for food. A snake bites people and other large animals only if it is scared and wants to protect itself.

BENEFICIAL SNAKES Nonpoisonous snakes usually take their food in one of two ways. Species such as garter snakes, water snakes, racers and some others grab prey with their mouths and immediately begin to swallow them whole. Other kinds like kingsnakes and rat snakes are constrictors. These snakes bite their prey to hold it and then wrap their bodies around it. Then they squeeze until the animal suffocates. Snakes are not scavengers. They must kill their prey themselves. How can a thin snake swallow a fat rat? All snakes swallow their prey whole, even though the animal may be many times as large as the snake’s head. They

Figure 7. Fangs in a pit viper’s mouth act like hypodermic needle to inject a small amount of venom.

Learn how to identify coral snakes by their color patterns of red and yellow, black and red, and so on. The coral snake has the strongest venom. Fortunately, they are small and scarcely ever bite anyone. Poisonous snakes should not inhabit areas around human dwellings, no matter how beneficial their predator habits. Nonvenomous snakes, however, should be given as much consideration as any other animal that helps man combat pests that may devour his crops. All snakes are predators. When snakes are present in large numbers, there is usually an abundance of prey in the vicinity to attract them. (Some snakes, however, gather in large numbers to den together in winter. )

Figure 9. Snakes help to control the rodent population on farms and in the field.

Figure 8. Heat-sensitive pits on each side of the snake’s head serve as “detectors.”

can do this because the snake’s jawbones are attached very loosely and can spread so wide apart and down from the skull. The lower jaw is then on the same vertical plane as the upper jaw. The tiny needle-sharp teeth are all curved toward the back of the snake’s mouth. By moving one jaw forward and then the other, the snake pulls its prey into its throat. Once in

the throat, the neck muscles constrict behind the prey and push it to the snake’s stomach where it is digested. The rest of the body can stretch, too, so its meal can fit inside.

based antivenin. Have the doctor test you to see if you are allergic to horse serum before the antivenin is administered. If it would take you several hours to get to a doctor, use a snake bite kit according to directions.

Many snakes are valuable around farms because they feed almost entirely on rats and mice. They are much better predators than cats because a snake, with its legless, slender body, can go anywhere a mouse can, something a cat cannot do. Also, snakes cannot spread livestock diseases from one farm to another as cats can.

Very few people die from snake bites, but prevention is the best cure. Take these precautions in poisonous snake country:

DEALING WITH POISONOUS SNAKES Poisonous snakes should be respected and left alone. Most are not aggressive and do not attack people unless provoked. However, anyone trying to harm a poisonous snake, trying to catch it or accidentally stepping on it may be bitten. Many people are bitten each year trying to kill a snake because they are too close to it. Learn to recognize the poisonous snakes of your area and leave them alone. If you are bitten by a poisonous snake, the bite will burn and begin to swell immediately. (A nonpoisonous snake bite will leave only several rows of small scratches or puncture wounds and will not swell.) Go to a doctor or hospital immediately. The most dangerous result of a bite is panic and shock. If you are within 45 minutes of a doctor, do not try to cut around the bite. Stay calm and relaxed, and get to the doctor as soon as possible. If you go to a hospital, the doctor there may wish to administer horse serum-

1. Be careful when climbing rock piles, steep banks, or brush piles. Snakes often hide in rock crevices and under stones or brush. 2. Most snakes cannot stand the direct heat of the summer day, so they are more active at night. Use a flashlight or lantern when hiking in late evenings or at night. 3. Wear high boots or leggings. Seventy-five percent of all snake bites are on the lower legs. Remember, however, that wearing protective clothing does not give complete protection. MYTHS ABOUT SNAKES l. A rattlesnake always rattles before it strikes. Wrong ! Oftentimes, they strike several times before rattling. They may have recently shed or knocked off their rattles. 2. A snake cannot bite under water. Wrong! The pit viper’s fangs are made just like a hypodermic needle, and how can they catch fish if they can’t bite under water? 3. If you pull a pit viper’s fangs, it is harmless. Wrong! The fangs are shed and replaced quite often. It is not uncommon to observe a pit viper with two sets of fangs. One set will soon be shed. 4. A stinging snake is dangerous. Wrong! There is no such snake. The mud snake, which has a stiff spiny tail adapted to assist it in feeding, is harmless. Likewise, although many people think a snake’s tongue is a stinger, it is perfectly harmless. Snakes stick out their tongues in order to pick up smells and to feel things.

Figure 10. The best way to deal with a poisonous snake is to leave it alone.

5. A joint snake can break itself apart and rejoin these parts. Wrong! There is no such snake. The glass lizard, like most lizards, has a long

segmented tail which if grabbed will often be broken off. However, it does not later become reattached to the lizard. Instead, the lizard will ultimately grow another tail. 6. Once the snake has its head severed from the body, or is otherwise killed, it is harmless. Wrong! The mangled head of a snake such as the pit viper is still dangerous and should be handled carefully, making sure that the fangs are avoided. 7. Snakes are slimy. Wrong! In fact their skins are quite dry, and they feel something like leather. A snake appears to be slimy when it is lying in the sun, because its skin looks shiny and almost wet. 8. Snakes can be charmed. Wrong! In India, men called snake charmers play music for cobra snakes, and the snakes seem to dance to it. But they are not really dancing. The snakes cannot even hear the music — they are completely deaf! The snakes can feel vibrations in the ground. A snake charmer taps his foot as he plays and sways in time to the music. A cobra feels the tapping, gets excited, and rears up ready to strike him. When a cobra is ready to strike, it watches its victim carefully and follows the victim’s movements. And that’s just what a cobra does with a snake charmer. The snake charmer is taking a big chance when he excites a cobra. THINGS TO DO 1. Write a report on one pit viper, a coral snake and at least one nonpoisonous snake. Include information such as scientific name, description and identifying characteristics, habitat requirements, food and feeding habits, breeding habits, range (where it is found in North America), natural enemies, importance to man, and man’s effect on its environment. Present this report to your 4-H group or school class. 2. Design a poster which will help to teach others something about snakes. The poster should be colorful and neat and should reflect your knowledge of snakes. Exhibit this poster at a 4-H meeting or other function. 3. Visit a museum or zoo which displays live snakes. This will give you the opportunity to observe poi-

sonous snakes as well as others. Find out how these animals are studied and kept alive in captivity. You may be able to talk to a trained herpetologist if you make arrangements with him or her ahead of time. Report to your 4-H group or school class on what you have learned. This may be done as a group project. 4. Collect one or more snakes that have been killed along the road. Be cautious with poisonous snakes. The mangled body of such a snake does not make them harmless. On hot nights, asphalt roads maintain heat and attract snakes which lie out on them. These snakes are often killed by passing cars. Freshly killed snakes make good preserved specimens. Preserve these road kills in formaldehyde or alcohol. Identify the snake and label it with its common name, scientific name and the place and date that you found it. Learn something of the snake’s habits or life history. Exhibit the snake at a 4-H meeting and report on its habits. 5. Tan and display a snakeskin as described in the 4-H activity “Tanning Skins.” 6. Invite someone to your 4-H meeting who can discuss the recommended first aid for both poisonous and nonpoisonous snake bites. Learn how to identify the bite of a poisonous snake. 7. Contact your county Extension agent and find out from him the best way to rid an inhabited area of poisonous snakes. Give an oral report of what you have learned at a 4-H meeting. WORDS TO KNOW Antivenin: A substance found in blood serum which counteracts a specific poison Constrictors: Snakes that squeeze and suffocate their prey Habitat: The type of place where a particular plant or animal is found; its home Nonvenomous: Not poisonous Predator: An animal which kills and eats another animal Prey: An animal which is killed and eaten by another animal Venomous: Poisonous

ACKNOWLEDGEMENTS This material was prepared by the Southern Regional 4-H Wildlife Literature Committee through a grant from Atlantic Richfield Foundation. Committee: Alvin C. Blake, Tennessee; Dan T. Gardner, Alabama; Dennis Goodman, Kentucky; James E. Miller, Arkansas; Lewis R. Shelton, 111, Mississippi; Andrew Weber, North Carolina (Vice Chairman); and James L. Byford, Tennessee (Chairman). Special Assistants: Rita Schrader, Ben Nottingham, Dale Powell. Some material in this guide was adapted from existing 4-H literature, including Snakes and Snakeskin Tanning, Cooperative Extension Service, South Dakota State University, and Reptiles and Amphibians, Cooperative Extension Service, Kansas State University.

The Clemson University Cooperative Extension Service offers its programs to people of all ages, regardless of race, color, sex, religion, national origin, disability, political beliefs, sexual orientation, marital or family status and is an equal opportunity employer. Clemson University Cooperating with U.S. Department of Agriculture, South Carolina Counties, Extension Service, Clemson, South Carolina. Issued in Furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of May 8 and June 30, 1914 Public Service Activities