Abstract

In this study we analyzed the natural diet and the dietary preferences of the octopus Robsonella fontaniana (d'Orbigny, 1834). Twenty-seven individuals were collected at San Vicente Bay, Chile, to study their stomach contents, and other 12 individuals were used in laboratory experiments for dietary selection tests. In the stomach contents 11 prey types were found, from which brachyuran crabs were the most frequent item. For preference tests, the animals were acclimated to constant temperature, air and water. Two experiments were performed: i) selection test on two gastropod species and three crustacean species, resulting in consume of crustaceans only (66.7% crustaceans and 0% gastropods), and ii) selection test on five crustaceans species, showing high preference for those highly motile (i.e. E. analoga was consumed 75% of the times offered). The scaling relationship between octopuses and preys showed a positive relationship between the size of octopuses and the fed preys. From field and experimental evidence we suggest that R. fontaniana has a selective hunting behavior and specialized diet with a narrow trophic niche breadth.