Date on Master's Thesis/Doctoral Dissertation


Document Type

Doctoral Dissertation

Degree Name

Ph. D.



Degree Program

Biology, PhD

Committee Chair

Eason, Perri

Committee Co-Chair (if applicable)

Alexander, James

Committee Member

Alexander, James

Committee Member

Emery, Sarah

Committee Member

Mansfield-Jones, Jennifer

Committee Member

Kingsbury, Bruce

Author's Keywords

watersnake diet; niche overlap; sympatry; species coexistence


The coexistence of similar species may be related to a variety of resource utilization differences. Dietary resource utilization variation may be the most important difference allowing for the coexistence of sympatric snake species. Many watersnakes (Nerodia spp.) live in sympatry and use similar aquatic habitats feeding on similar prey. While these sympatric watersnakes may have different general foraging patterns, snake diet may be affected by a variety of factors. Therefore, I initiated an investigation to understand the coexistence of sympatric plain-bellied (N. erythrogaster), diamondback (N. rhombifer) and northern (N. sipedon) watersnakes by addressing their dietary resource utilization patterns. Results indicated that northern watersnakes ate fish families according to their availability except for the avoidance of Aphredoderidae. I also determined that northern watersnakes had smaller head sizes and a diet closer to the piscivorous diamondback watersnake. There were sex differences in snake head size and all three species had different head shapes relating to diet. In addition, gut contents were determined with plain-bellieds feeding mainly on anurans, diamondbacks on fishes, and northern watersnakes feeding mostly on fishes but with a higher anuran component than diamondback watersnakes. Stable isotope analyses provided long-term dietary information with diamondback watersnakes feeding at higher trophic levels while plain-bellied watersnakes fed more from terrestrial prey sources. The application of stable isotope techniques helped to demonstrate shifts in dietary resource utilization. This research has allowed me to reveal a complex foraging system affected by a variety of factors allowing for the coexistence of sympatric watersnakes.