SHEEHY III, C. M.*; LILLYWHITE, H. B.; Univ. of Florida, Gainesville; Univ. of Florida, Gainesville: Foraging Behaviors of Insular Cottonmouth Snakes

Florida cottonmouth snakes (Agkistrodon piscivorus conanti) exhibit significant variation of foraging behavior on a single island at Cedar Keys, Florida. Snakes in this population characteristically remain beneath avian rookeries where colonial nesting birds drop or regurgitate fish that are consumed (by snakes) as carrion. Observations and studies using radio telemetry indicate these snakes move little, having home ranges of 0.18 to 1.72 ha in area. Snakes typically scavenge at night, restricting movements largely to substrate beneath rookeries, but daytime feeding is sometimes observed. Rarely, it appears, snakes at the periphery of the island scavenge at the intertidal zone of beaches where dead fish may be washed ashore by tidal waters. Occasionally, snakes ingest marine debris, including marine plants, presumably due to presence of fish odors. In the laboratory we show that snakes will ingest marine algae that have contacted dead fish. In contrast with snakes at rookeries, snakes on half of the island where bird nesting is absent move over greater distances (e.g., 10.29 ha), feed on rats (Rattus rattus), and have lower body condition than snakes at rookeries (mean of 5.2 g/cm vs. 10.4 g/cm), presumably owing to lesser concentration of resources. Laboratory studies show that newborn snakes accept a wide range of prey items and do not appear to have innate preferences, similarly to snakes born on the mainland. Thus, insular cottonmouths benefit from resource subsidy brought to the island by nesting birds, and they also employ other foraging strategies when these resources are scarce or absent. Success of these snakes is important to bird rookeries owing to mutualism wherein cottonmouths deter potential avian nest predators.