126 
Charles R. Blem 
reserves and have a greater statistical probability of reproducing in any 
single year. It appears from this that descriptions of reproductive fre- 
quency at specific sites are of little value without a description of the 
sizes of the females involved. The percentage of gravid females in popula- 
tions composed predominantly of large individuals generally should 
exceed that of populations containing significant numbers of smaller (but 
mature) females. 
The size of young cottonmouths is at least partly determined by the size 
of the female parent, and as shown, the correlation between female size 
and that of offspring is fairly large. While selection for large body size in 
female cottonmouths at Hopewell may be only a phenomenon related to 
periodic mortality of small snakes, the present situation probably reduces 
the amplitude of population oscillations at least partly as a result of the 
relationship between female size and reproductive output. Increase in 
reproductive output appears to be related to number of mature ova pro- 
duced and size of offspring (Burkett 1966, and the present study). Elimi- 
nation of small individuals in extreme years should decrease competition 
for food among females and might further insure their successful contact 
with males. Production of young with a relatively high degree of fitness 
could occur, with most females producing young in breeding seasons 
following severe winters. Mild winters should enhance subsequent survi- 
val of young, and decreased lipid reserves and increased competition 
would result in decreases in the number of females producing offspring. 
The bias toward large size is even more striking in males (Table 1). No 
males less than 640 mm total length were captured in 1977-1979 and 18 
males were collected that exceeded 1000 mm and 1000 g (the largest was 
1345 mm and 2008.5 g). Since Wharton (1966) considered males above 
650 mm to be sexually mature, it is likely that the male segments of the 
1977-1979 populations were almost entirely mature. It appears that males 
generally exceed females in size; Wharton (1966) obtained a similar result 
in his Florida studies. 
The cottonmouth at Hopewell is much more habitat-specific than in 
some other parts of its range. For example. Mount (1975) described the 
cottonmouth in Alabama as “occurring in almost every type of perma- 
nently aquatic habitat”. At Hopewell it is found very locally and only at 
sites where tidal marshes and nearby upland provide feeding and hiber- 
nating sites, respectively. The apparent failure of the species to colonize a 
number of nearby sites that seem superficially suitable is evidence that 
relatively inconspicuous factors may be influential in determining habitat 
suitability for the cottonmouth at the northern edge of its range. Precise 
habitat selection may be an important factor in enabling female cotton- 
mouths to obtain sufficient energy for reproduciton. 
It is obvious that with the present survival rate of young the future of 
