Diet composition of Nerodia sipedon (Serpentes : Colubridae) and its dietary overlap with, and chemical recognition of Agkistrodon piscivorus (Serpentes : Viperidae)

JG Himes

Abstract

To address the potential role of the western cottonmouth (Agkistrodon piscivorus leucostoma) as a competitor for food and/or predator of the midland watersnake (Nerodia sipedon pleuralis) in drainages of the Gulf of Mexico, U.S.A., I examined the dietary compositions of these species from a series of museum collections. Small individuals of A. piscivorus consumed primarily lizards, fishes, and frogs, whereas large individuals consumed primarily fishes and frogs. No prey items of A. piscivorus were identified to be N. sipedon. Small individuals of N. sipedon consumed primarily fishes, frogs, and salamanders, whereas large individuals consumed primarily fishes. In a Y-maze experiment, a significantly higher number of individuals of N. sipedon selected the odorless arm of the maze over the arm containing the odor of A. piscivorus. However, N. sipedon did not exhibit a preference when presented with the odorless arm versus the arm containing the odor of a conspecific.