Crayfish Predation by Water Snakes 
97 
specimen of N. cyclopion and the crayfish have been deposited in 
the Clemson University Vertebrate Museum (CUSC#931). 
Examination of 60 N. cyclopion from this locality revealed 
that one other snake contained crayfish in its gut. Additionally, 3 
of 29 N. fasciata and 1 of 24 N. rhombifer examined from the 
same locality contained crayfish remains (Fontenot 1990). 
DISCUSSION 
Conant and Collins (1991) listed frogs, salamanders, fish, and 
crayfish as food items for members of the genus Nerodia. How- 
ever, chemical preference studies of newborn water snakes have 
shown that crayfish are not a preferred food item (Burghardt 1968, 
Mushinsky and Lotz 1980). Crayfish have been reported as prey 
items for adult N. cyclopion (Kofron 1978), N. erythrogaster (Clark 
1949), N. fasciata (Mushinsky and Hebrard 1977), N. rhombifer 
(Minton 1944, Sisk and McCoy 1964, Bowers 1966, Kofron 1978), 
and N. sipedon (Zelnick 1966, Fraker 1970, Camp et al. 1980), 
which suggests crayfish consumption might be restricted to larger 
individuals. In all cases except for N. erythrogaster (Clark 1949), 
crayfish were infrequent prey items. Brown (1958) concluded that 
the importance of crayfish in the diet of water snakes has been 
unintentionally exaggerated. He found no crayfish in 207 stomachs 
of N. sipedon he examined even though crayfish were abundant at 
his study site. Crabs, another crustacean, have been reported to be 
ingested by N. clarki (Mount 1975). 
Although some crayfish remains could be attributed to 
secondary ingestion, in many instances it is likely that crayfish are 
consumed as a primary prey item. Because molting crayfish lack a 
digestive-resistant chitinous exoskeleton, they are probably consumed 
more frequently than food habits studies indicate. We suggest that 
in future studies the size and degree of digestion (intact crayfish or 
fragments) be noted to help determine if crayfish are primarily or 
secondarily ingested. 
Based on our limited observations and a review of the litera- 
ture, we believe that crayfish do not comprise a large portion of 
the diets of most species of water snakes; however, crayfish might 
be consumed directly by water snakes. Differential digestion rates 
of vertebrate and crayfish prey might introduce bias in analysis of 
reptile food habits (Jackson et al. 1974, Garnett 1985). Patterns of 
use of this food resource by water snakes may be subject to onto- 
genetic shifts and seasonal or regional differences in foraging 
ecology. 
