Eastern Cottonmouth Reproduction 
119 
METHODS 
Cottonmouths were observed and collected by hand in more than 500 
hrs of field work during April through October 1977-1979. Newly cap- 
tured snakes were sacrificed, weighed to the nearest 0.1 g, and body 
measurements (total, snout-vent, and tail lengths; head width and length) 
were determined to the nearest mm. Each snake was dissected and the 
ova of the females were counted and their lengths measured to the nearest 
mm. Fat bodies were carefully removed to exclude obvious connective 
tissue, weighed to 0. 1 g, and freeze-dried to constant weight. Lipids were 
extracted from the fat bodies in Soxhlet refluxers in 5:1 petroleum 
ether:chloroform solution. Loss of weight of the dried sample after 
extraction represents the amount of extractable lipid. Some obviously 
gravid female cottonmouths captured in late July and August of each 
year were kept in captivity until the young were born. Shortly after birth, 
measurements of young were made as described above. Caloric equiva- 
lents of lipid, young snakes, and unfertilized eggs were determined by 
means of a Parr nonadiabatic bomb calorimeter. 
Scales were counted according to criteria of Burkett (1966), which 
essentially include Dowling’s (1951) technique for counting ventrals. For 
comparative purposes ventral melanism was quantified by counting all 
ventrals from the anal scale anteriad to (but not including) the first three 
consecutive scales with less than half of their total area covered by black 
pigment. 
RESULTS 
A total of 68 male and 38 female cottonmouths was collected from the 
study area. Chi-square tests (with Yates continuity correction) indicate 
that the maleifemale ratio differs significantly from 50:50 (X^=7.93). The 
difference may be due to intersexual variation in activity, but since most 
snakes were collected at rest near the entrance of “summer dens” I believe 
the sexual bias is real. Mainly two types of females were found: those 
possessing large, yolked follicles (45-50 mm), and those with small, yolk- 
less ova (8-1 1 mm diameter). This is similar to Rahn’s (1942) findings in a 
study of Crotalus viridis and those of Tinkle (1962) in an investigation of 
Crotalus atrox. Apparently, ovarian eggs ripen rapidly and yolk deposi- 
tion of the set may require only a few weeks at most. Two females 
captured 13 April 1977 and 13 April 1978 possessed ovarian eggs 16-20 
mm long; earliest gravid females were found 31 May 1977. 
In order to determine the relative occurrence of reproductive activity in 
mature females within the breeding season, I eliminated from the analysis 
all those smaller than 700 mm total length (the smallest gravid female was 
732 mm), all captured earlier than the first gravid one (3 1 May), and all 
captured after September 30 (no gravid animals were captured after this 
