THE AMPHIBIA OF OKLAHOMA 



viduals and the probability that the two males of September 15 may have 

 belonged to another age class. The resulting formula, the curve for which 

 is shown in Fig. 2 is: 



60.24 



""" 1 I gi:.0:!-0.041.5t 



where L is length in millimeters and / is time in days from May 24. 



No theoretical significance is here assigned to the apparently close agree- 

 ment between the computed curve and the observed data. 



Summary and Conclusions 



1. Juveniles of Bnjo cognatiis in central Oklahoma vary considerably in 



growth rates during their first summer. This is true even of those emerg- 

 ing from pools at the same time. Those metamorphosing late in the 

 summer may not be more than 30 mm. in length at the beginning of 

 hibernation while those emerging early in the season may be as large as 

 the smaller adults of broods of the preceding year. 



2. Variation is also, in part, caused by difiEerences in success in securing food. 



Some young toads are more aggressive than others. Toads which are 

 injured are less adept at catching insects than their fellows. Some, also, 

 may be more fortunate in finding areas in which suitable insects occur. 



3. The rate of growth of young toads during their first season after emer- 



gence in early summer may be expressed at least roughly by a curve of 

 sigmoid type. 



4. Secondary sex characters of males tend to begin development toward the 



end of the first season. Males emerging from pools in mid-May begin 

 to "protest" when handled in late August or early September at which 

 time the dark-colored gular pouch may or may not have begun its devel- 

 opment. By mid-October most males have developed the protesting note 

 and have a dark smudge on the throat indicating the beginning of the 

 pouch. 



5. These secondary sex characters usually appear at this age irrespective of 



the size attained by the individuals. 



6. On emerging from hibernation in the spring of the second year ( approxi- 



mately ten to eleven months after metamorphosis) all males "protest" 

 when handled and all show some development of the gular pouch. The 

 latter, however, is not fully developed. There is evidence that few, if 

 any, males of this age frequent breeding pools or attempt to call females. 



7. Late in the second summer some individuals (males) show practically 

 complete development of the gular pouch and on emergence the follow- 

 ing spring (second from the time of metamorphosis) practically all do 

 so. In breeding pools, the sizes of the smallest males at this time compare 

 favorably with the sizes of those taken in adjacent roadways, which indi- 

 cates that the young males have now reached sexual maturity. A further 

 indication of this is that in practically all young males the protesting note 

 has now changed in pitch trom the juvenile "peep" to the adult "quack." 



56 



