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Abstract

Predatory gastropod mollusks in the family Naticidae feed on bivalve mollusks and leave distinctive markings in the form of countersunk circular boreholes on the shells. These boreholes possess both an inner borehole diameter (IBD) and an outer borehole diameter (OBD) which are proportional to the size of the predator. It has been proposed that the ratio of IBD to OBD can be used to identify predator species. Variation in the ratio of the IBD to OBD was examined in two prey species (Dwarf surf clam, Incongruous ark clam) collected from Otter Island beach in South Carolina to determine if clams were eaten by a single species or multiple species of predator. Measurements of borehole diameter (inner and outer) were recorded in random samples of Anadara brasiliana (Incongruous ark, n = 100) and Mulinia lateralis (Dwarf surf clam, n = 100) shells. Comparison of the frequency distributions of the ratios revealed a unimodal, normal distribution in the combined sample indicating the potential for a single species effect. A similar pattern was revealed in the M. lateralis sample. In contrast, a unimodal skewed distribution was identified in the A. brasiliana sample indicating the potential for a multi-species effect.