124 
Charles R. Blem 
Reproduction by individual females within many species of snakes 
apparently is not an annual phenomenon. Evidence indicates that many 
viperid species produce young at two-year or longer intervals (St. Girons 
1957, Tinkle 1962, Fitch 1970, Aldridge 1979). Burkett (1966) and Whar- 
ton (1966) reported a biennial cycle in A. piscivorus, but an annual cycle 
has been found in some populations of Louisiana cottonmouths (see 
Kofron 1979). It is generally believed that snakes at northern latitudes 
often are not able to accumulate sufficient energy to produce and mature 
a set of eggs annually (Rahn 1942, Klauber 1972, Tinkle 1957, St. Girons 
1957), but my data contradict this generalization. If reproduction is bien- 
nial or less frequent, 50% or less of the mature females collected should 
possess ripe eggs in the uterus (as did Florida cottonmouths; see Wharton 
1966). However, at Hopewell during 1977-1979, 83% of the females that 
could have possessed uterine eggs were, in fact, gravid. This ratio is 
significantly different from 50:50 and indicates that Hopewell cotton- 
mouths breed more regularly than expected. 
Frequency of reproduction of viviparous snakes is believed to be a 
function of fat storage (Tinkle 1962, Wharton 1969, Aldridge 1979). 
Assuming this is true, the Hopewell population during 1977-1979 seemed 
to be well prepared for reproduction. Lipid reserves were sufficient for 
most mature females to produce full litters. Hopewell cottonmouths also 
exceeded the lipid levels found in all reproductive classes (reproductive 
and non-reproductive females, males) in Wharton’s (1966) Florida study. 
A low population density at Hopewell may have reduced competition for 
food and provided for more productive foraging. At present there are no 
data with which to assess this hypothesis, but a subjective evaluation 
indicates that cottonmouths are more abundant in the main part of the 
range (e.g. extreme southeastern Virginia). The high rate of reproduction 
found in my study may also be related to winter extremes. Mild winters 
may cause decreases in fat reserves because of elevated metabolism 
(Wharton 1966), and conversely, very cold winters may encourage repro- 
duction through conservation of fat stores. As stated above, the winters 
during my study were among the coldest of the decade. 
Few data are available regarding size of female cottonmouths at first 
reproductive effort. Arny (in Wharton 1966) found that female A. p. 
leucostoma may mature at a total length of 594 mm. Wharton (1966) 
noted that 800 mm was the minimum total length of mature females in 
the Cedar Keys of Florida. At least three Hopewell cottonmouths less 
than 800 mm total length (732, 770, and 791 mm; =619, 654, and 684 mm 
snout-vent length) contained oviductal eggs, and two females (707 and 
756 mm total length) collected in September had ovarian eggs of 10-11 
mm. I conclude that early maturation at the Hopewell site is a viable 
hypothesis that requires further study. 
