The distribution of organisms within a community can often be determined by the degree of plasticity or degree ofspecialization of resource acquisition. Resource acquisition is often based on the morphology of an organism, behavior, or a combinationof both. Performance tests of feeding can identify the possible interactions that allow one species to better exploit a preyitem. Scavenging behaviors in the presence or absence of a competitor were investigated by quantifying prey selection in a trophicgeneralist, spiny dogfish Squalus acanthias, and a trophic specialist, smooth-hounds Mustelus canis, in order to determine ifeach shark scavenged according to its jaw morphology. The diet of dogfish consists of small fishes, squid, ctenophores, and bivalves;they are expected to be nonselective predators. Smooth-hounds primarily feed on crustaceans; therefore, they are predictedto select crabs over other prey types. Prey selection was quantified by ranking each prey item according to the order it wasconsumed. Dietary shifts were analyzed by comparing the percentage of each prey item selected during solitary versus competitivescavenging. When scavenging alone, dogfish prefer herring and squid, which are easily handled by the cutting dentition ofdogfish. Dogfish shift their diet to include a greater number of prey types when scavenging with a competitor. Smooth-houndsscavenge on squid, herring, and shrimp when alone, but increase the number of crabs in the diet when scavenging competitively.Competition causes smooth-hounds to scavenge according to their jaw morphology and locomotor abilities, which enables themto feed on a specialized
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