SREL Reprint #2038

Temporal changes in reptile populations: Effects of a severe drought on aquatic snakes

Richard A. Seigel, J. Whitfield Gibbons, and Tracy K. Lynch

Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802, USA

Abstract: During the summers of 1985-1987, the southeastern United States suffered a drought equaled in severity only five times since AD 372. We monitored the abundance and population structure of five species of aquatic snakes before, during, and after this record event in South Carolina. There was significant variation among species in response to drought conditions. Based on capture records before the drought, Nerodia fasciata and Seminatrix pygaea left the study site in relatively high numbers whereas Nerodia floridana left in relatively low numbers. We found significant variation in the timing of movements among species; N. fasciata left the site mainly in 1986 and 1988 whereas Seminatrix pygaea left the site mainly in 1987. We suggest that N. fasciata left the site in direct response to low water levels whereas S. pygaea left in response to the absence of suitable prey. Snakes exited the site using discrete, non-random corridors. Long-term changes in abundance and species composition were marked; the prey base was altered radically, overall abundance of snakes was lowered, and Nerodia floridana was not seen at the site for five years after the drought. Our results support earlier suggestions that long-term data on populations are needed to determine whether population declines result from natural or anthropogenic factors.

Keywords: Snakes; Drought; Conservation; Movements; Feeding; Farancia; Nerodia; Seminatrix

SREL Reprint#2038

Seigel, R.A., J.W. Gibbons, and T.K. Lynch. 1995. Temporal changes in reptile populations: Effects of a severe drought on aquatic snakes. Herpetologica 51:424-434.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).