Little has been recorded concerning the growth rate of _Gastrophryne_ or
the time required for it to attain sexual maturity. Wright (1932) found
that _G. carolinensis_ in the Okefinokee Swamp region has a mean
metamorphosing-size of 10.8 mm. Young thought to be those recently
emerged from their first hibernation were those in the size group 15.0
to 20.0 mm., while the frogs in the 20 to 27 mm. size class and those in
the 27 to 36 mm. class were interpreted as representing two successively
older annual age classes. Anderson (1954: 41) thought he could recognize
four successive annual age classes in the same species in southern
Louisiana. He found that sexual maturity is attained at a length of 21
to 24 mm. in frogs which he believed to be late in the second year of
life.
Allowing for size differences between the two species, Wright's and
Anderson's conclusions regarding growth in _G. carolinensis_, on the
basis of size groups, are largely substantiated by my own data on the
growth of marked individuals of _G. olivacea_ living under natural
conditions in Kansas.
In 1954, an opportunity to investigate the early growth was afforded by
unusually favorable circumstances. The population of frogs that emerged
from hibernation in the late spring of 1954 included few, if any, that
were below adult size; drought had prevented successful breeding in 1952
and 1953. Heavy rains in the first week of June, 1954, and again in the
first week of August, resulted in the production of two successive crops
of young so widely spaced that they were easily distinguishable. Some
young may have been hatched after other minor rains, but certainly these
were relatively few. Young from the eggs laid in the first week of
August were metamorphosing during the last week of August. Growth in the
frogs of this group can be shown by the average size and the size range
of the successive samples collected.