They are known to frequently eat large whelks (Buccinum), cockles (Polynices, Chrysodomus and Sipho), sea clams (Mactra), large hermit crabs, starfish, sea urchins and green crabs (Carcinus maenas).
Other shells found in Japanese mounds include those of sea snails, surf clams (Mactra veneriformes), and Japanese littleneck clams (Tapes japonica).