The Foraging Strategy of Vermivorous Conid Gastropods

Abstract

A heuristic model, developed from simple assumptions, generates testable hypotheses that predict the foraging patterns of predators which invest a significantly greater amount of energy in search for, as compared to pursuit and handling of, prey. Given: (1) the environmental distribution of potential food size, (2) the environmental distribution of potential food diversity within food size, and (3) the manner in which the limits of consumable food size vary with predator size; food and microhabitat niche breadths as a function of predator size can be predicted. The assumptions and derived hypotheses of the model are tested with data from vermivorous prosobranch gastropods of the genus Conus, ubiquitous associates of tropical Pacific Ocean and Indian Ocean coral reefs. Predictions are: (1) small Conus (<10 mm shell length) are trophic specialists; (2) medium—sized Conus (10—25 mm shell length), trophic generalists; and (3) large Conus (> 25 mm shell length), trophic specialists. This pattern is supported by both within— and between—species comparisons of Conus populations of different mean sizes. Relationships of food niche breadth with predator size are interpreted in light of the marked behavioral and morphological stereotypy of Conus, probably evolved in response to evolutionary and proximate predictability of available prey.