118 
Charles R. Blem 
North Carolina 
Fig. I. Localities from which the eastern cottonmouth has been taken in Virginia 
and northeastern North Carolina. Hollow circle represents the Hopewell site. 
Florida were of the subspecies A.p. conanti and those by Burkett (1966) 
and Kofron (1979) involved the western subspecies A. p. leucostoma. 
Also, there is practically nothing in the literature about the ecology of the 
cottonmouth in Virginia. In fact, Wood (1954), in a survey of the distri- 
bution of the snake in Virginia, did not mention the Hopewell site and 
maintained that cottonmouths did not occur west of the Appomattox 
River. 
In this paper I also examine briefly some hypotheses regarding animals 
at the northern edges of their ranges. For example, environmental condi- 
tions in such peripheral areas usually are severe relative to the tolerance 
of a species. Mortality of adults and/or young is expected to be high and 
occasionally catastrophic; reproduction rates should be adjusted corre- 
spondingly. A less variable population may be produced through stabiliz- 
ing or normalizing selection, or, in time, the species may be eliminated 
entirely. Additionally, the size of young might be adjusted through natural 
selection in ways that promote survivorship early in life. 
