Diet specialization in Octopus vulgaris at San Salvador, Bahamas

Abstract

Populations of resource generalists are often made up of individuals specializing on a narrower range of resources; such individual specialization can have important ecological and evolutionary significance. We quantified individual diet variation in Octopus vulgaris, the common octopus, at 3 locations around San Salvador, Bahamas, using repeated collections of midden contents. We quantified the degree of individual specialization using the proportional similarity index and individual diet breadth using the Berger-Parker index of dominance and the number of prey types per den. As in other populations, the San Salvador O. vulgaris population has a broad diet, consuming at least 49 prey types; however, most individuals (59%) had significantly specialized diets. The amount of specialization varied significantly among locations. At one location, all octopuses were generalists and consumed relatively uniform proportions of prey types (lower dominance) compared to the other 2 locations, where about 70% of individuals were specialists with diets dominated by 1 or a few prey types. Individual specialization has been documented in numerous species but mostly vertebrates; this is only the second quantified example from the cephalopods.