===========================================================
|Number in| Mean size |Size range
Time of sample | sample | in mm. | in mm.
--------------------+---------+----------------+-----------
August 27 to 31 | 27 | 15.55 +/- .079 | 15 to 17
--------------------+---------+----------------+-----------
September 11 | 114 | 17.2 +/- .033 | 14 to 20
--------------------+---------+----------------+-----------
September 15 to 22 | 12 | 18.7 +/- .090 | 16 to 20
--------------------+---------+----------------+-----------
September 27 to 30 | 37 | 19.3 +/- .055 | 17 to 21.5
--------------------+---------+----------------+-----------
October 1 to 7 | 62 | 20.8 +/- .072 | 17 to 24
--------------------+---------+----------------+-----------
October 12 to 17 | 49 | 22.3 +/- .092 | 18 to 24
===========================================================
By mid-October, six weeks after metamorphosis, these frogs had increased
in over-all length by approximately 50 percent. Having grown a little
more than 1 mm. per week on the average, they were approximately
intermediate in size between small adults and newly metamorphosed young.
The frogs hatched in June were present in relatively small numbers
compared with those hatched in August, and were not observed
metamorphosing. In late August a sample of 33 judged to belong to the
June brood averaged 26.2 (22-28) mm. long. A sample of 39 from the first
week of October averaged 28.1 (24.5-32) mm. Frogs of this group thus
were approaching small adult size late in their first growing season.
Such individuals possibly breed in the summer following their first
hibernation, when they are a year old or a little more. Because
recaptured frogs were not sacrificed to determine the state of their
gonads, the minimum time required to attain sexual maturity was not
definitely determined. The available evidence indicates that sexual
maturity is most often attained late in the second year of life, at an
age of approximately two years. The darkened and distensible throat
pouch of the adult male probably is the best available indicator of
sexual maturity.
[Illustration: FIG. 3. Growth shown by successive samples of young
ant-eating frogs of two size groups in late summer and early fall of
1954. For each sample the mean, standard deviation, and range are shown.
Lower series are those metamorphosed in late August, and upper series
are those metamorphosed in late June.]
[Illustration: FIG. 4. Rapid growth of a young female caught in June,
July, and August, 1949. Presumably this individual metamorphosed late in
the summer of 1948, and at the age of approximately one year it was near
small adult size.]
Frogs that metamorphose in late summer have little time to grow before
hibernating, and still are small when they emerge in spring. The
smallest one found was 19 mm. long (May 19, 1951), and in each year
except 1954 many such young were found that were less than 25 mm. in
length in May or early June. None of the frogs marked at or near
metamorphosing size has been recaptured, but the trend of early growth
is well shown by Table 2 and Fig. 3. However, many juveniles that were
captured and marked within a few weeks of metamorphosis were recaptured
as adults. The selected individuals in Table 3 are considered typical of
growth from "half-grown" to small adult size. Growth in many other
individuals is shown in Figs. 6 and 7.