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Charles R. Blem 
date; all known birth dates are earlier than this). Only 5 of the remaining 
29 were not gravid; the rest contained uterine eggs or produced young in 
the laboratory. This ratio (24:5=83% gravid) deviates significantly from 
the 50:50 ratio predicted from published studies (see below, X =11.18). 
(Note: during research of fat cycles and energetics of cottonmouths in 
1980, we collected 5 adult females; all were gravid.) 
Based on the number of yolked, oviductal eggs or actual number of 
young born, mean litter size for the 24 gravid females is 7.68 ± 1.77. The 
mean caloric value of yolked cottonmouth eggs is 6.136 ± 0.067 kcal/g 
dry weight (N=3); newborn young contain a mean of 5.5 10 ± 0.055 kcal/ g 
dry weight (N=3). After correcting for water content of young and eggs, I 
computed the total caloric content of the offspring of 1 1 female cotton- 
mouths that gave birth in the laboratory. Three of these females pro- 
duced single infertile eggs along with viable litters. The eggs are counted 
as part of the litter, and the caloric content computed separately and 
added to the calories invested in living young. The total represents total 
caloric output (but not expenditure) in reproduction. All the females in 
this part of the study were held for relatively short periods (45 days or 
less) and all births occurred without mortality. The caloric content of the 
litter is a significant function of the weight of the female shortly after 
giving birth (Fig. 2): kcal = 0.61 weight (g) - 41.20, r = 0.93 
Cottonmouth fat bodies are composed of 26.8% water and the remain- 
ing dry material is 94.5% lipid. Using the caloric content of lipids 
extracted from the fat bodies (x=9.227 ± 0.030 kcal/g, N=4), the mean 
caloric reserves of the fat bodies of female cottonmouths were computed. 
Assuming that the caloric content of the smallest litter (104.9 kcal) 
represents a threshold minimum, no cottonmouth possessing fat bodies 
weighing less than 16.5 g (=105.3 kcal) could be expected to reproduce, 
especially those collected in early spring or summer. A distinct cycle of 
lipid deposition is discernible in female cottonmouths at Hopewell, in 
which reserves are generally low in spring and increase in autumn (Blem, 
unpublished). In early spring, before the first gravid female was collected, 
3 of 6 nongravid females did not possess lipid in excess of this threshold. 
During the period 31 May - 30 September, 3 of 5 nongravid females had 
fat bodies below threshold levels, and after 30 September all females (3) 
had less fat than the amount apparently necessary for reproduction. 
Seven female cottonmouths collected during mid-September in extreme 
southeastern Virginia likewise possessed insufficient reserves (fat bodies 
weighed from 1.5 to 11.0 g) for reproduction. Overall, nonreproductive 
females possessed slightly more fat than those containing eggs or produc- 
ing young (“reproductive females”), although the difference is not statis- 
tically significant (Table 1). Male cottonmouths possessed significantly 
greater amounts of fat than females in either category, but the difference 
