Abstract
Many octopus species consume their prey in a shelter, where discarded prey items accumulate to form a midden. The shelters of Octopus bimaculatus rarely have middens. Some discarded prey items are present at 20% of the shelters of O. bimaculatus, but these do not accumulate to form middens. A field experiment using artificial middens demonstrated that currents and/or surge moved some bivalve shells, and hermit crabs rapidly removed snail shells from the middens. Snails are very important in the diet of O. bimaculatus but not most other octopus species; middens do not form around O. bimaculatus shelters because hermit crabs remove the discarded snail shells.