BULLFROG AS TYPICAL VERTEBRATE ANIMAL 



65 



frog. It prefers bodies of quiet water where there are both shallows 

 and deeper water, such as lagoons, small lakes, and the cypress 

 ponds of swampy regions. Crayfish, insect larvae, water beetles, 

 snails, and other aquatic organisms make up the bullfrog's diet. 

 This diet is quite varied and may even include younger frogs. 



Bullfrogs are found in North America east of the Rockies from 

 Canada to Mexico. They have also been introduced into the western 

 portion of the United States and into various foreign countries. 



Fig. 17. — The bullfrog, Rana catesbeiana. (Courtesy of Southern Biological Supply 



Company. ) 



External Structure 



Bullfrogs obtained in the South and Southwest are usually of tAvo 

 species, Rana catesbeiana Shaw, the common bullfrog, or Rana grylio 

 Stejneger, the southern bullfrog. Individuals of the former species 

 attain larger sizes, and the giant "bullfrogs of the southern swamps 

 usually are Rana catesbeiana. The two species differ not only in size 

 but also in external appearance, particularly when alive. However, 

 they are essentially the same anatomically, and this chapter is based 

 on a study of Rana catesbeiana. 



The common bullfrog is ordinarily greenish or olive brown. Un- 

 derparts are mottled with dark spots on a white background, and 

 the upper surfaces may be plain or marked with large dark splotches. 



