Date of Graduation

Summer 2012

Degree

Master of Science in Biology

Department

Biology

Committee Chair

Brian Greene

Abstract

Temperature governs physiological processes in ectotherms, imposing proximate effects on movement functions that may ultimately have important fitness consequences. Studies on the thermal sensitivity of performance in reptiles are useful in understanding how the thermal environment affects ecological function. I examined the effects of temperature on foraging success and locomotion in two sympatric semi-aquatic snakes, the Northern water snake (Nerodia sipedon) and Cottonmouth (Agkistrodon piscivorus). Dietary data for both species from a cold Ozarks stream habitat revealed that A. piscivorus does not consume aquatic prey at this site while N. sipedon is primarily piscivorous. I examined foraging success at water temperatures of 15, 20, 25 and 30°; C and tested the hypothesis that the dietary difference between species was caused by species-specific thermal constraints on foraging performance. However, both snake species captured prey in laboratory trials at all water temperatures suggesting that dietary differences observed for these species are caused by factors other than temperature constraints imposed by the aquatic habitat. I also examined locomotor performance at 10, 20 and 30°;C, and found that sprint speed and endurance increase with temperature in both species. All snakes swam faster than they crawled in sprint trials and thermal effects on endurance were more apparent in aquatic than terrestrial conditions. Water snakes were faster and exhibited higher endurance than cottonmouths across all temperatures and substrates which is consistent with predictions of differences in performance based on foraging mode.

Keywords

Agkistrodon piscivorus, Nerodia sipedon, foraging, performance, sprint speed, endurance

Subject Categories

Biology

Copyright

© Wendy Lee Evans

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