Giant Snakes and Tiny Seabirds on a Small Japanese Island

Abstract

Abstract The Izu Island Archipelago, a chain of volcanic islands off the coast of Japan, near Tokyo, provides opportunities to examine body size evolution in snakes related to their diets. Elaphe quadrivirgata, the most widespread and abundant snake of the Izu Islands, preys mainly on the lizard Plestiodon latiscutatus. However, on Tadanae Island, E. quadrivirgata is gigantic—not because of rapid juvenile growth, but rather because of pronged, continuous, and enhanced growth throughout adulthood through feeding on the eggs and chicks of sea birds. Large body size in addition to evolutionary modifications of the trophic apparatus and allometry of gape size enables the consumption of large bird eggs. The terrestrial, insular food web is ultimately tied to rich marine food webs via enhanced prey availability of seabirds, wherein complex species interactions among small pelagic fishes, seabirds, and large carnivorous fishes have occurred in relation to long-term dynamics of physical and biological oceanographic processes.