CLASS AMPHIBIA 



481 



a scarcity of food, most of them hibernate. Frogs crawl into the 

 mud in the bottom of ponds or other damp spots, dig into the ground 

 under logs, or crawl into cracks and crevices. Toads burrow into 

 the ground, the depth to which they go depending on the type of 

 soil. They may go as far as 18 inches underground in sandy 

 soil. Salamanders may bury themselves in the mud, under rocks 

 in running streams, in rotting tree stumps or in burrows in the 

 ground. 



Fig-. 265. — ^Axolotl larva of the tiger salamander, Ambystoma tigrinum. 



graph by Sanders.) 



(Photo- 



'■i'-S*. <«»',•' 



T 



"^m^: 



'*g! *.«».(*'• 



Fig. 266. — Ambystoma texanum, one of the most common salamanders in Texas. 



(Photograph by Sanders.) 



After establishing itself in hibernation quarters the amphibian 

 reduces all vital activities to a minimum. Respiration is carried on 

 entirely through the skin, and the body in its dormant state secures 

 the slight amount of nutriment needed from the food stored in its 

 tissues. In some hot countries during the dry, torrid season amphib- 

 ians aestivate in a protected moist place, reducing their activities 

 until the severest weather is over. 



