Habitat, diet, and composition of assemblages of garter snakes (Thamnophis) at eight sites on Vancouver Island

Abstract

This study examines diet, habitat, and diversity relationships of three species of garter snakes (Thamnophis) at eight sites on Vancouver Island. Species diversity varied considerably among sites from a single species only to roughly equal representation of all three species; most sites were dominated by one or two species and were temporally stable in species composition. Relative abundance of each species at a site was generally associated with specific habitat features, but no direct relationship between habitat characteristics and diet was seen. Diet diversity of all species combined was positively correlated with species diversity over all sites. The three species had different diets, and differences within species among sites were attributable mainly to shifts in the proportions of different prey taken. Overall, diets of the three species were more distinct the more nearly equally represented the three were, suggesting a diffuse pattern of interspecific interactions.