BREEDING HABITS OF AMPHIBIA 



37 



RANA PIPIENS, the leopard frog. This is the common leopard frog most frequently used 

 in our laboratories. It is found in almost all parts of the United States and parts of Can- 

 ada and Mexico. The adults rarely exceed 4 inches in body 

 length (96 mm. ) but females must be 72 mm. or longer be- 

 fore they can be considered sexually mature. The general 

 color is green with light dorsal plicae. The rounded dark 

 spots on the skin have light colored borders. The under- 

 side is white. The male is darker and smaller than the 

 female, with firm abdominal muscles, lateral cheek pouches 

 when croaking, and prominent thumb pad. These frogs are 

 omnivorous feeders and difficult to maintain as adults in the 

 laboratory except under conditions simulating hibernation 

 when they can go for long periods without food. The newly 

 metamorphosed frogs may be fed earthworms cut into 1 

 inch lengths. These segments of worm will continue to 

 move and thus attract the frogs. 



These frogs breed from March to May depending upon the 

 latitude in which they are found. They lay about 5, 000 eggs 

 (diameter about 1. 75 mm. ) which generally reach metamor- 

 phosis during the summer. The span from fertilization to 

 hatching is about 8 days and to metamorphosis (in the lab- 

 oratory at 23°C. ) is about 75 days. The eggs are normally 

 layed in water at about 1 5°C. and the upper limit of tem- 

 perature tolerance is about 31°C. Leopard frogs have been 

 known to live for 5 years. 



Male Rana pipjens, the 

 leopord frog, with vocal 

 sacs inflated, as seen 

 from above. 



(Courtesy C. H. Pope 

 1944: Chicago Mus. 

 Nat. Hist. ) 



nucleus N-JZ 



Hgmenlum ^ „,; dorsoNs, 



hypotholofnus { 



^pors ventrolis 



mH WARNING CROAK £ 



^ SFttWNWG MOVEUCMTS B 

 ^ RELEASE 



olfoclory bulb 

 cerebroJ hemisphefe 

 preoptic Oreo 



SWIMMING RESPONSE 



End of oviposition. The male, 

 about to release, is showing the 

 pre-release movements. Note 

 the female (beneath) shaping 

 the eggs into a clump. 



(From Aronson 1942: Bull. Am. 

 Mus. Nat. Hist. 80:127) 



Diagrammatic sagittal section through the brain of 

 Rana pipiens indicating the regions of the brain that 

 were found to be of primary importance for the 

 medication of each of four phases of sexual behavior. 



(From Aronson 1945: Bull. Am. Museum Nat. Hist. 

 86:89) 



RANA SYLVATICA , the wood frog. This frog is found only in the Northern States and 

 Canada. It rarely exceeds 2-3/4 inches in body length, and is light brown in color with 

 a dark streak on either side of the head and a dark line from the tip of the snout to the 

 eye. There is also a black patch over the tympanum. The dorsal plicae are prominent 

 but not of a different color. The head is pointed. Its feeding habits are like those of 

 Rana pipiens. 



