Eastern Cottonmouth Reproduction 
125 
Although sufficient data are not available for rigorous testing, time of 
ovulation apparently varies little from one site to the next. Wharton 
(1966) estimated that Florida cottonmouths ovulated in the period 20 
May-8 June, and Burkett’s (1966) data indicate similar timing, as do my 
data. I have no measurements of growth of young because smaller speci- 
mens were absent throughout this study. 
Weight of young at birth could be a fundamental indication of the 
fitness of offspring. Young cottonmouths at Hopewell are born in Sep- 
tember (usually around the middle of the month, the mean date = 18 
September, range = 5 September-23 September, N=13). They therefore 
have little opportunity to forage (and accumulate energy stores) before 
finding a hibernaculum for the winter. In addition, increased body mass 
may conserve heat and enhance survival at low ambient temperature in 
the hibernaculum. Cooling rates of large snakes should be slower, allow- 
ing them to survive short periods of extreme cold or to move to deeper 
parts of the hibernaculum before cooling to fatal temperatures. Snout- 
vent lengths and weights of young from other parts of the range largely 
reflect size of the parental race (see Wright and Wright 1957) and it 
appears that Hopewell cottonmouths do not produce particularly large 
young (Table 2). Weights and total lengths of young Florida cotton- 
mouths (324-343 mm; 28.0-33.7 g) are distinctly greater than those of the 
Hopewell population (Allen and Swindell 1948, Wharton 1966). Reduced 
size of young cottonmouths at Hopewell could be interpreted as an evolu- 
tionary compromise that maintains litter sizes while reducing the expen- 
diture of energy per litter. This would be advantageous where fitness of 
small young is high and availability of energy is low. Neither seemed to be 
the case at Hopewell in 1977-1979, and the significance of small offspring 
there remains to be shown. 
Size of mature females at the Hopewell site varies less than in popula- 
tions in southeastern Virginia or northeastern North Carolina, and mean 
snout-vent lengths of Hopewell snakes (excluding newborn young) aver- 
age significantly longer than those in the main part of the range to the 
southeast (Blem and Gutzke, in preparation). Moreover, within the total 
range of size, reproductive output is a linear function of weight of the 
female. Larger females are apparently able to mobilize greater amounts 
of energy in reproduction, and we have found that, in general, larger 
individuals have larger fat reserves. The so-called “biennial reproduc- 
tion”, with 40-60% of females breeding in any given year, may only be an 
artifact of the collective reproductive rates of a population of females of 
diverse sizes. Large females reproduce more frequently than small (Bur- 
kett 1966), and generally have larger lipid reserves; at Hopewell: g lipid = 
0.05 snout-vent length (mm) - 19.65, r=0.55. It is therefore likely that 
larger individuals are capable of collecting and mobilizing larger energy 
