THE AMPHIBIA OF OKLAHOMA 



tasteful (Trowbridge and Trowbridge, 1937; Bragg, 1941). Also, there is 

 some indication that adults of all species limited to a prairie distribution do 

 more feeding in the spring and early summer than later in the season. 



Breeding Habits 



For the study of the evolutionary development of habits during phy- 

 logeny the period of reproduction is of special interest, because success or 

 failure at this point in the life of the organism actually determines whether 

 there shall be a phylogeny, and if so, what kind it shall be. A species with 

 unvarying breeding habits is at a distinct disadvantage if the environment 

 changes or if it attempts to disperse to a different ecological community than 

 that to which it is already adapted. On the other hand, habits not too rigidly 

 fixed may gradually become modified (with or without change in the ani- 

 mals structure) in adjustment to changing environments. Accordingly, the 

 breeding pattern of a frog or a toad has considerable influence upon its dis- 

 tribution and upon the possibility of its dispersal to territory adjacent to its 

 present range. 



In Oklahoma, three patterns of breeding behavior among frogs and 

 toads are recognized and clearly correlated with the ecological distribution 

 of the organisms. They are not so clearly correlated with the taxonomic di- 

 visions, for they often cut across taxonomic lines in fundamental ways. In a 

 former paper (Bragg, 1945: 52-53) two of these patterns were defined and 

 named as follows: 



"There are two principal patterns, one characteristic of those species 

 especially adapted to drier habitats and manifested especially by those limited 

 to the grasslands or other more xeric environment; the other shown by those 

 organisms which inhabit moister environments (woodlands, savannahs, etc.) 

 whether restricted to these habitats or not. . . . For convenience, I propose to 

 call the breeding pattern characterized by a breeding season little influenced 

 by rain the mesic pattern; that characterized by no breeding season with all 

 breeding initiated by rainfall, the xeric pattern." 



The third breeding pattern mentioned above may be called intermediate 

 because it has some of the characteristics of both of the others. 



It should further be noted that in saying that a species has a xeric breed- 

 ing pattern I do not imply that it could never breed in a mesic environment, 

 or, conversely, that one having the mesic pattern will not do so in a xeric 

 environment. As a matter of fact, mesic and xeric are relative terms, each 

 more or less dependent upon the other for meaning. The real point is that 

 forms like Scaphiopus bombijrons, limited to prairies and deserts, have de- 

 veloped habits of breeding which adjust them to successful reproduction in 

 these regions. A definite breeding season, for example, would be a distinct 

 disadvantage to any amphibian attempting to live in a desert or grassland 

 country because water would not always be available at the right time. In 

 contrast, in the eastern woodlands, such a breeding season might be an ad- 

 vantage — at least, it would not be a definite disadvantage. 



No part of Oklahoma may properly be called ilescrt but several lorms 



66 



