52 
C. Kenneth Dodd, Jr. 
samples (4.3 females/ male) as opposed to the other months (range 1.4 
to 2.4 females/ male). Males were never caught in greater numbers than 
females. 
Several studies have reported sex ratios of 1:1 (Tinkle 1961, 
Mahmoud 1969, Mitchell 1982, Ernst 1986) or favoring females (Risley 
1933, Cagle 1942). Bancroft et al. (1983), with the largest sample size of 
all studies to date, found that males outnumbered females (1.16:1) in a 
Florida lake population. They attributed the skewed ratio to the tendency 
of males to move greater distances than females, an explanation also 
used by Dodd et al. (1988) to explain a similarly skewed ratio for S. 
depressus in Sipsey Fork, Alabama. The tendency of males to move 
more often and over greater distances than females may not explain sex 
ratios in favor of females in Brushy Creek Lake, however. 
It is possible that different sex ratios would result from more 
extensive collections made at different times of the reproductive season 
or from a sampling regime that placed traps over a larger portion of the 
lake. In Alabama, K. R. Marion (pers. comm.) found that males were 
caught more often in early spring and fall samples and that females 
tended to be more common in late spring and early summer samples. 
His overall results, however, still indicated a female-biased sex ratio. In 
Virginia, J. C. Mitchell (pers. comm.) also found sex ratios in a stinkpot 
population in an urban area that varied depending on season, although 
in his study the overall sex ratio remained at 1:1. 
Moreover, if there are differences in habitat selection between the 
sexes, and if a sampling effort does not equally sample all potential 
habitat, the resulting sex ratio may be biased and not indicative of the 
overall sex ratio within the population. This may explain the female- 
biased sex ratio of stinkpots in the present study. In any case, the 
interpretation of studies reporting female-biased sex ratios in S. odoratus 
is often difficult because of small sample sizes and differences in 
trapping techniques between studies. Sex ratios based on relatively 
small sample sizes should be interpreted with caution (Gibbons 1970b, 
Bury 1979). 
Mass. The average body mass for all stinkpots was 71.3 g (N = 
108). Males averaged 78.9 g (range 46.0-130.0 g, SD = 22.6) and females 
averaged 76.8 g (range 47.0-132.0 g, SD = 14.4). There was no significant 
difference in body mass between adult males and females {t - -0.4819, P 
- 0.63). Log(body mass) was significantly correlated with both log(cara- 
pace length) and log(plastron length) (Fig. 4) regardless of sex. Power 
function exponents ranged from 2.5 to approximately 2.9 (Table 1). 
Only four studies have reported biomass data for S. odoratus in 
lentic habitats. The estimates ranged from 1.2 to 41.7 kg/ ha, but mean 
body mass varied considerably between studies (Wade and Gifford 
1965; Iverson 1982; Congdon et al. 1986; J. C. Mitchell, pers. comm.). 
