Population Structure, Body Size, and Seasonal Activity of Black Swamp Snakes (Seminatrix pygaea)
CHRISTOPHER T. WINNEI1, MICHAEL E. DORCAS2, AND
SEAN M. POPPY1
Abstract -We examined the ecology of a Black Swamp Snake
(Seminatrix pygaea) population inhabiting an isolated wetland
in the upper Coastal Plain of South Carolina. The observed population
structure was skewed towards mature individuals, with neonates and juveniles
underrepresented, perhaps due to trapping bias. The sex ratio was biased
during May and June, with females outnumbering males, but no sex ratio
bias was evident at other times of the year. Seminatrix pygaea
showed sexual dimorphism in body size, with females being longer and heavier
than males and males having relatively longer tails than females, but
there was no difference in monthly growth rates. Approximately 76.3% of
the mature females captured in May and June 1998 were pregnant. Therefore,
most mature females in this population probably exhibit annual reproduction,
while some undergo biennial reproduction. The majority of fe- males gave
birth in July or August, with a few births occurring in September and
October, and perhaps even as early as Mayor June. Our mark-recapture estimates
suggest a population density greater than 60 adult snakes per hectare,
which indicates this small aquatic snake, endemic to the Southeast, may
play a large role as both predator and prey within isolated wetland ecosystems,
SREL Reprint #2828
Winne, C. T., M. D. Dorcas and S. M. Poppy. 2005. Population structure, body size, and seasonal activity of black swamp snakes (Seminatrix pygaea). Southeastern Naturalist 4:1-14.
