Reproduction of the Eastern Cottonmouth Agkistrodon 
piscivorus piscivorus (Serpentes: Viperidae) at the 
Northern Edge of its Range 
Chari.es R. Beem 
Department of Biology, 
Virginia Commonwealth University, Academic Divison, 
Richmond, Virginia 23284 
ABSTRACT. — Eastern cottonmouths, Agkistrodon piscivorus pisci- 
vorus, were studied at the apparent northeastern edge of the species’ 
range (Hopewell, Virginia). Although biennial reproduction is generally 
typical of viperid snakes, with approximately 50% of the females pro- 
ducing young in any given year, 83% of the females collected at the 
Hopewell site were gravid. Mean litter size (7.7) does not appear to 
differ from that of populations in other parts of the range. Young 
cottonmouths at the Hopewell site appear to be smaller than those from 
other areas and survival is much reduced in years having cold winters. 
Average snout-vent length of adult females at Hopewell currently is 
greater and less variable than at locations to the southeast and within 
the main range of the species. Production of offspring is a function of 
female size; larger females produce more calories of young and larger 
offspring. Reproduction in kcal may be accurately predicted from the 
weight of the female (g) using the equation: kcal = 0.61 weight - 41.20. 
INTRODUCTION 
The Eastern Cottonmouth, Agkistrodon piscivorus piscivorus, is one 
of the more widespread and abundant poisonous snakes in the Southeast. 
It is generally a lowland species (e.g. Kofron 1978), although in the deep 
South it may be found in a variety of habitats (Burkett 1966, Mount 
1975). In the northern part of its range the cottonmouth becomes more 
selective in its choice of habitat, and in Virginia it is known only from 
wetlands in the Coastal Plain. The northeastern extreme of the species’ 
range apparently is represented by an isolated population at the conflu- 
ence of the Appomattox and James rivers near Hopewell, Virginia (Fig. 
1). At this locality the species occurs in the lower reaches of Swift Creek, 
Chesterfield County, and along both west and east banks of the Appo- 
mattox River. No cottonmouths have been collected on the James River 
in this region. The vegetation of the area, a mosaic of tidal swamps, tidal 
marshes, and upland forests, will be described elsewhere (Blem and 
Gutzke, in preparation). This population is at least 60 km from the 
nearest known locality in the main part of the range, and repeated efforts 
to find the species in apparently excellent habitat at other sites near 
Hopewell have been fruitless. 
Little information is available regarding reproduction of snakes at the 
northern limits of their distributions and no studies of reproduction of A. 
p. piscivorus have been published. Studies by Wharton (1966, 1969) in 
Brimleyana No. 5:1 17-128. July 1981. 117 
