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Snakes and Frogs and Their Relatives 



SIOEWINDINO FOR DESERT TRAVEL 



Most snakes move forward with the body flat against the ground. Not so this desert 

 rattler, which progresses in S-shaped loops a motion known as sidewinding. This 

 is an effective technique for crawling on sand and it is used not only by the 

 American rattler, but by snakes in the deserts of Africa and Asia as well. 



loops and seems to be flowing sidewise. Using these motions a snake 

 does not waste energy building pivots; yet it does not slip back- 

 ward. 



Snake Tracks: Snakes leave trails in sand or dust that are just as 

 revealing in their way as mammal footprints. Experts not only 

 identify the kind of snake by its trail they can tell the approxi- 

 mate rate of speed at which it was moving when the trail was made. 



How Snakes Breed 



It is often said that some snakes lay eggs while others bear 

 living young; yet actually all species reproduce by means of eggs. 

 The difference between egg-laying and "live-bearing" consists in 

 this: The live-bearing female retains the eggs in her oviduct 

 until the embryo is fully developed. When the offspring are 

 "born" they are covered by a thin membrane which soon bursts. 

 Only about one-fourth of the known species of snakes follow this 

 procedure. 



SNAKE EGGS 



When a female of the other species is ready to deposit her 

 eggs, she finds a sunny sandbank or rotting log in which to burrow 

 a hole. There she lays her eggs the number, size, and shape 



