V 



Observations on the Ecology and Natural History of Anura. 



XIV. Growth Rates and Age at Sexual Maturity 



of Bnfo Cognatiis under Natural Conditions 



in Central Oklahoma 



ARTHUR N. BRAGG AND A. O. WEESE 



THE varying sizes of the toads found in the spring suggested to Dick- 

 inson ( 1913) that several years probably elapse between metamor- 

 phosis and sexual maturity in Bujo cognatus Say. Bragg (1940) noted, 

 however, that the sizes of juveniles of essentially the same age, collected in 

 October, 1938, varied sufficiently to indicate marked differences in individual 

 growth rates during the first summer. This indicates that a juvenile toad's 

 age cannot be successfully deduced from its size alone. Both Dickinson and 

 Bragg commented on the probable age or size reached at sexual maturity 

 but neither had data to substantiate his deductions. Actually, practically noth- 

 ing is known concerning age or size at sexual maturity of B. cognatus and a 

 search of the literature revealed little data on other species. 



In central Oklahoma, particularly in the region about Norman, Cleve- 

 land County, the breeding habits, dates of breeding congresses, success in 

 production of metamorphosed young each year, and general movements and 

 reactions of these toads at all ages were under nearly continuous observation 

 for twelve successive seasons, 1935-1947, inclusive. The principal breeding 

 sites in this area are well-known and records have been kept of their use by 

 the toads, and soniething learned as to the degree of success in breeding each 

 year. Data on growth rates and observations on age and size at sexual maturity 

 as interpreted on this rather extensive background of general observation are 

 now available. A preliminary note has already been published (Bragg and 

 Weese, 1942). 



Since we wished to secure data on growth rates under natural condi- 

 tions we did not, except incidentally, study captive toads. However, one group 

 of fifty young toads of known age was confined in August, 1941, and meas- 

 ured at intervals thereafter for two years. Some of these were still alive in 

 September, 1947, having never since capture lived elsewhere than in the 

 artificial environment into which they were placed as very young toads. 

 Another small group of captive juveniles was under observation during the 

 summer of 1947. 



Our principal method of studying growth rates consisted of collecting 

 young toads in selected, restricted regions, measuring them, and releasing 



47 



