BULLETIN FLORIDA MUSEUM NATURAL HISTORY 38(1)


effects of drought and lack of recruitment. If the 1985 cohort had any effect on the
population's size-class or age structure, it was not apparent.

 Sex Ratio.-Skewed sex ratios have been observed in other Gastrophryne
populations. Anderson (1954) also reported a male bias of eastern narrow-
mouthed toads trapped in Louisiana, but he captured the sexes in a 1:1 ratio by
hand. Freiburg (1951) captured more females than males in three of the four
months that he sampled.
 Male frogs are generally more abundant at breeding sites than females
(Crump 1982; Woodward 1984 and references therein) and remain for longer
periods of time. However, a drift fence should capture all animals irrespective of
the length of time that they remain at the breeding site. Thus, in the absence of a
priori reasons to suspect that the sex ratio is different from 1:1 in the local
population of eastern narrow-mouthed toads, a skewed sex ratio over the course of
a breeding season was not expected. The preponderance of females caught after
August 1989 also is difficult to explain. I suggest several hypotheses that might
account for the observed skewed sex ratios.
 First, the actual sex ratios really may be skewed, and the capture data mirror
the population's sex ratio, although sex ratio theory suggests that this is not
typically the case for iteroparous species (Fisher 1930). Alternatively, males may
move more often and remain at the breeding site longer than females. However, if
males move more often than females, they should be exposed to greater risks of
predation and desiccation. If they continued to do so during the early stages of a
severe multi-year drought, male mortality might be greater than female mortality
and lead to skewed sex ratios as the drought progressed. Finally, there may be
different tendencies between the sexes in their propensity to move to breeding sites,
especially during an environmental stress. For example, males might be less likely
than gravid females to leave secure refugia and move to breeding sites during
drought conditions. Also, individuals may not breed every year (Bull and Shine
1979; Gill 1985). One of the cobalt tagged adult females followed by Franz et al.
(1989) for more than one year lived 20 m from Breezeway Pond but never went to
the pond or made any other long-distance movements. Unfortunately, available
data are not sufficient to select among these hypotheses.

 Individual Size.-Breezeway Pond G. carolinensis are within the SUL range
 reported elsewhere in the literature for this species (Hecht and Matalas 1946;
 Wright and Wright 1949; Anderson 1954; Duellman and Schwartz 1958).
 Anderson (1954) reported a maximum size of 32.2 mm for males and 34.3 mm for
 females in Louisiana. Weights have never previously been reported, except for five
 G. carolinensis used in experiments on evaporative water loss (Wygoda 1984).
 Sexual dimorphism is common in anurans, with males usually smaller than
 females (Shine 1979; Duellman and Trueb 1986).