The Frog: A Representative Vertebrate 49 



toward nearby water. Once in the water, it swims and dives readily. 

 Here, also, the hindlegs provide the necessary propulsion. As the 

 frog moves rapidly through the water, the hindlegs move in the well- 

 known "frog-style kick." Between the toes are webs which are a great 

 aid in swimming. 



The frog spends much of the time squatting in moist, shady places, 

 or floating partly submerged in the water. When it is partly sub- 

 merged, only the eyes and part of the head protrude from the surface. 

 This protects the frog from being seen too easily by some water bird 

 while at the same time it can easily see any approaching danger. 



Certainly the frog needs all its protective devices, for it is a favorite 

 article of diet for a great many animals including fish, snakes, turtles, 

 water birds, and mammals such as the raccoon. Perhaps R. pipiens' 

 chief enemy is man who collects enormous quantities for zoology and 

 physiology laboratories, for food, and for bait. 



Fig. 6. — Life history of Rana pipiens. 



The adult frog lives entirely on insects and their larvae. Some 

 are captured in the water, but most are caught on the marshy banks. 

 Here R. pipiens sits quietly waiting for an insect to fly past. When 

 one does, the highly protrusible tongue is flipped out rapidly and the 

 insect sticks to this mucus-coated organ. 



Life History.— In late April and early May, the croaks of this 

 frog increase in volume, signaling the fact that this is their matmg 

 season. Only the males are able to make this deep guttural sound, and 

 it appears that the croaks are useful chiefly to attract mates. 



When 



