Snakes (2nd ed, 1984)

[Applause] [Music] snakes amazingly adapted reptiles reptiles who no longer need legs for moving about there are more than 2200 species of snakes and they're found in a variety of habitats most live on land as this garter snake does others like the brightly colored Scarlet king snake are burrowers living underground much of the time some live in or near water like the cotton mouth or water moccasin some species including the gray rat snake live mostly in trees and bushes snakes belong in a class of animals called reptiles a class which includes lizards Turtles and crocodilians crocodiles and alligators and their close relatives like other reptiles snakes have a dry scaly body covering they breathe air their body temperature depends on the temperature of their surroundings that's why snakes are normally seen only during warmer months except in the tropics where they're found throughout the year snakes that live in areas that have cold Winters must find some kind of shelter to survive the very cold weather like the Eastern hognose snake they may stay under rotting logs under large rocks or in holes in the ground until warm weather returns snakes share certain characteristics which separate them from other reptiles snakes have a very long body a short tail and usually just one long lung and unlike nearly all other reptiles snakes have no legs yet they move about with ease snakes usually move by bending into a series of s-shaped Curves like most snakes this bull snake forces itself forward by pushing the backside of each curve against the ground movement is aided by large overlapping scales called scutes skuts help the snake grip the ground and push against it a loose surface like sand offers less support to push against and makes rapid movement more difficult but sand is no problem for the desert snakes that use a special means of moving called side winding moving in Loops this Sidewinder rattlesnake keeps most of its body off the ground snakes have highly developed senses to help them find their food some have very good eyesight snakes which hunt in the daytime usually have eyes with round pupils narrow slit-like pupils identify a snake with good night vision snakes have no eyelids the eyes are covered by a single transparent scale which is part of the outer skin layer so a snake snake's eyes are always open even when it's at rest the snake's most important sense organ is its Fork tongue flicking in and out the tongue picks up tiny particles in the air and carries them to organs of smell in the roof of the mouth the tongue is not a stinger it's really quite harmless and notice a snake can flick out its tongue without open opening its mouth snakes have no outer ear openings but they can sense sound when vibrations in the air pass through their skin into their internal ears snakes can also feel sound as vibrations along the surface of the ground rattlesnakes and some other venomous species have another sense organ a heat sensitive pit between each eye and nostril these organs help the snake find warm blooded prey even in the dark snakes that have these pits are called pit vipers most snakes catch and eat live prey small mammals birds and insects the snake seizes its prey and holds it with sharp recurved teeth constrictors squeeze an animal to death before swallowing it the teeth are for grasping not chewing most non-venomous snakes except for constrictors swallow their prey alive and because the teeth curve backward the more an animal struggles to escape the firmer the teeth hold it venomous snakes kill their prey with Venom injected by Hollow or Groove teeth called fangs snakes Venom is a complex substance it's produced by special glands and flows to the fangs through canals in the upper jaw there are about 350 species of venomous snakes in the world snake Venoms May attack either the victim's blood or nervous system or both a snake can swallow an animal larger than its own head its jaws are hinged in such a way that they can spread both sideways and up and down like the snake's Jaws its body covering also stretches this stretching is made possible by areas of skin between the scales over the scales there is a thin outer skin which is shed every few months as the snake grows even the eye caps transparent scales over the eyes are shed they become clouded as shedding time near a new skin layer forms under the old skin by rubbing against some object the snake breaks the old skin around the edge of its mouth then the snake gradually crawls out of its old skin most snakes reproduce by laying eggs many like the black racer lay their eggs in rotting logs or some other warm damp Place snake eggs are flexible and leathery not hard and brittle like bird eggs eggs of most snakes hatch in 6 to 8 weeks the hatchlings are equipped with a special egg tooth to help them slit through their shells this tooth falls off in a few hours snakes give No Parental care to their babies the young are perfectly able to take care of themselves other snakes like rattlesnakes and garter snakes give birth to live babies the young are born covered by a thin membrane which they break out of in a short time while most snakes are harmless and easily studied the venomous species should be avoided there are 19 kinds of venomous snakes in North America 17 of which are pit vipers pit vipers are identified by their heat sensitive pits broad head heavy body rough scales and short thick tail the most widely found pit vipers are the rattlesnakes there are 15 species in the United States the rattlesnake's most significant feature is the chain of horny rattles at the end of its tail rattlesnakes May coil and sound their rattles before striking but if surprised they can strike without these preparations you can't tell a Rattler's age by the number of rattles it has that's because two or three rattles may be added each year one each each time the skin is shed also rattles are sometimes broken off two other kinds of pit vipers are found in the United States neither has a rattle one species the copper head usually has dark hourglass-shaped markings on the back the copper head is found throughout the eastern and southern states its venomous bite is dangerous but not usually fatal to humans the second kind of pit viper without a rattle is the water moccasin or cotton mouth this venomous pit viper lives in wet swampy areas of the southeastern United States a good swimmer it spends a lot of time in water catching fish and frogs the reason this snake is also called a cotton mouth is that the skin inside its mouth has a cottony appearance two other kinds of venomous snakes found in the United States are burrowing snakes related to the Cobra the Eastern coral snake lives in the South Eastern United States while the Western coral snake is found in Arizona coral snakes are shorter and thinner than Pit viers with venom more deadly like all animals snakes have their natural enemies many predators large birds like the roadrunner and skunks weasels and raccoons include snakes in their diet some snakes pre on snakes too the king snake for example will even kill and eat rattlesnakes the Rattler's Venom doesn't affect the king snake though many animals prey on snakes humans are snakes biggest enemy some people forget that snakes play an important role in the balance of nature many harmless snakes are valuable to humans because they feed on rats mice and and other rodents that damage crops and spread diseases yet many harmless snakes are needlessly killed most often because they are mistaken for some venomous species the harmless corn snake for example is often confused with the venomous copper head but the corn snake has bold markings on its head the copper head doesn't notice too the differ in head shape the corn snake's head on top is long and thin the copper head's head is thick and Broad typical of the pit vipers the hog noose is another harmless snake that's often mistaken for a venomous species and for good reason when threatened the hog noose pops up and flattens its head mimicking a thick-bodied pit viper sometimes it's called a puff adder it looks ferocious but it's really quite harmless if bluffing fails the snake uses another method of self-defense it plays dead and it's no use turning the snake over either it quickly returns to its deathlike position like the hog knows most snakes are harmless and can be safely handled and studied only a few are venomous the rattlesnake the copper head the cotton mouth or water moccasin and the coral snakes no other snakes native to the United States or Canada are dangerous to people snakes reptiles whose unique abilities and special adaptations have made them very successful in their ecological niche [Music]