Snakes

SNAKES Justin Keith Mr. Curtwright Biology Keith 1 Have you ever wondered exactly what a snake is? Snakes are elongated, limbless reptiles that have often appeared in art and mythology. Scientists have currently discovered an estimated 2,500-3,000 living species of snakes living throughout the world except in the arctic regions. There is one exception to the old world viper, which has been found as far north as Scandinavia (60 North Latitude). The size variation of snakes ranges from slender blind snakes (family Leptotyphlopidae) which reaches a maximum length of 13cm (5 in.), to the largest snake on record, the Asiatic reticulated python, which attained a record length of 10m (33 ft).

Have you ever asked anyone what the phyical characteristics of a snake is? To answer your question: Snakes lack limbs, a sternum (breast bone), shoulder girdle, exterior ear openings, and urinary bladder, and most snakes (but not all) lack a pelvic girdle. There are two types of snakes: constrictors and poisonous. Constrictors will either stalk their prey or lay very still until Its prey come near it. It will then strike forward and wrap around the prey crushing it and cutting off all air supply. The initial strike takes less than one-half second. It will then swallow the prey animal head first because the hair of animals folds backwards and makes it easier to swallow.

Poisonous snakes inject a very potent venom into their prey Keith 2 through fangs. There are three different class of venomous snakes: Opisthoglyphus (rear fanged), Proteroglyph (front fanged, with holes pointing outward for “spraying”) and Solenoglyph (front fanged and carved). The most common of these three are Solenoglyphs, which have fangs that can be folded along the roof of the mouth. All snakes have powerful digestive enzymes to breakdown the hair, bones, and other parts of their preys’ body. As part of the digestive system the salivary glands also produce powerful enzymes. If saliva containing these enzymes enters the wounds of a prey animal, it not only starts the digestive process, but also may cause such serous tissue damage that the prey dies.

The destructive substances in a snakes venom include neurotoxins and hemotoxins. Neurotoxins paralyze the central nervous system and cause heart and respiratory failure; hemotoxins destroy blood vessels and blood cells and cause internal hemorragins. The different substances are not uniformly present in all snake venom, but vary with the species and the individual snakes within a species. Venom retains digestive powers; injected into a prey animal it may shorten the usual days-long digestive process of a snake by more than half. Less than one-third of the 2,500-3,000 living species of snakes are classified as venomous, and less than 300 species are fatal to humans.

In the United States, more than twice as many people are killed by bees, wasps, and scorpion stings as by snake bites. Keith 3 There are four basic kinds of snake movement: Lateral (horizontal) undulation, conceltina movement sidewinding and rectilinear. Lateral undulating, also called serpentine movement is the most common form and is used by all snakes. By alternately contracting and relaxing muscles down each side of the body, the snake forms itself into a number of rearward-moving horizontal waves. While doing so, the snake maneuvers its body so that the rear of each backward moving wave pushes against something resistant. In concertania movement, also called earthworm movement, the snake anchors the forepart of its body and pulls the rest of its body behind it in the form of hoizontal curves; it then extends out the forepart of its body, anchors it, and repeats the process. Sidewinding is employed on soft sand or other surfaces that offer no resistance or slip.

In sidewinding the snake loops its body into an S-shape, with only two points of its body coming in contact with the surface of the ground. It then progressively shifts the two contact points back along the body consequently propelling its body forward. Rectilinear, or caterpillar, movement involves a sliding of the skin back and forth over the body musculature and is therefor possible only in those kinds of snakes, such as rattlesnakes and boas, which do not have the skin tightly attached to the underlying musculature. The ribs remain essentially motionless, and the scales only provide body-to-ground friction. Keith 4 The vast majority of snakes lay eggs, but in some, the eggs are retained in the female until hatched, and the young are born live.

Pythons have laid over 100 eggs in a single clutch, and some live bearing snakes are remarkably prolific. The number of eggs or young is dependant on the species and how large or small the mother is. No true parental care of young is known, but a few snakes brood their eggs until they hatch. Gestation and incubation periods vary according to the species and temperature. Young snakes escape the eggs by splitting the shell with a special structure, the egg tooth, which falls off soon after. The life span of a snake is dependant on the species.

APPENDIX 1 COMMON BELIEFS ABOUT SNAKES 1.Snakes are not slimy. They feel more like shoe leather. 2.Snakes are not mean. Most snakes are shy, timid animals. 3.Snakes do not chase people 4.Snakes do not stalk humans. 5.Snakes are not fast.

The fastest snake, the Coachwhip, can go about as fast as the average person can run (7 m.p.h.) APPENDIX 2 Modern Myths Size. Snakes are almost always described as larger than they really are. Stories about New England water snakes eight and ten feet long are simply not true. Northern water snakes rarely exceed three and a half feet in length, with the largest stretching only four and a half feet. While the black rat snake, U.S.A’s largest native snake, can reach lengths of just over eight feet, most New England snakes are less than three feet long. Poisonous Snakes.

The regularity with which people kill a snake first and ask questions later might lead you to believe that the world is overrun with poisonous snakes. In fact, venomous snakes only make up about one-third of the 2,500-3,000 snake species worldwide, and in Massachusetts only two of the state’s fourteen species of snakes are poisonous (timber rattlesnake and northern copperhead). Both are rare, reclusive and generally confined to isolated areas. Folk Tales. Folk tales about snakes are handed down from generation to generation and include such things as snakes that charm prey, swallow their young for protection, poison people with their breath, roll like hoops, and suck milk from cows. These folk tales could be just interesting and amusing stories except that many people still believe them.

As we learn more about the true nature of snakes, we can begin to base our perceptions of them on fact rather than fiction. Hoop Snakes APPENDIX 2 CONT. Myth: When frightened, hoop snakes will bite their tails and roll downhill like a wagon wheel. Reality: Anatomically, snakes are not well equipped for rolling and there are no reliable accounts of this ever occurring. The hoop snake myth may have been associated originally with mud snakes found in the southern United States.

Mud snakes will occasionally lie in a loose coil shaped like a hoop, but they slither away from danger like other snakes. Swallowing Young Myth: When confronted with danger, mother snakes swallow their young, spitting them out later once danger has passed. Reality: Parental care is not very well developed in snakes and there is no evidence that mother snakes protect their young in this way. The myth may result from the fact that some snakes eat young snakes of their own species or of other species, though usually not their own brood. Charming Snakes Myth: Snakes have the ability to charm prey, especially birds, so they cannot flee.

Reality: There is no evidence that snakes charm their prey. Small animals may become “frozen with fear” when confronted by snakes but they are not charmed. Birds may flutter about in front of a snake in an attempt to lure it away from their nests; occasionally a bird may actually be captured by the snake, giving the impression that it was charmed. The fact that APPENDIX 2 CONT. snakes never blink may also have played a role in this myth’s origin. Sucking Milk Myth: Milk snakes are so named because of their ability to suck milk directly from the udders of cows.

Reality: Although milk snakes are common around barns that house cows, they completely lack the anatomy necessary to suck milk (or anything else for that matter). Barns are attractive to milk snakes because they provide abundant food in the form of small rats and mice. Poisonous Breath Myth: Puff adders (hognose snakes) mix poison with their breath and can kill a person at a distance of twenty-five feet. Reality: Although the bite of a hognose snake can produce swelling and a burning sensation, these snakes rarely bite people and are not considered poisonous. When confronted, they do puff themselves up and hiss, but their breath is harmless.

Cottonmouths in New England Myth: Swimmers in New England are advised to watch out for poisonous cottonmouths, also known as water moccasins. Reality: Simply put, there are no water moccasins in New England. The cottonmouth, or water moccasin, is a poisonous snake of the southeastern United States that occurs no farther north than the Great Dismal Swamp of Virginia. Many people mistake nonpoisonous water snakes for water moccasins.