Walrus (Odobenus rosmarus) prey extensively on the bivalve Mya truncata, removing the siphons. We performed a simple experiment whereby the siphons from 27 M. truncata were removed, 33 controls were left intact, and the clams left on the sea bottom for a year. All the damaged Mya died; all but 2 controls lived. We conclude that M. truncata whose siphons have been grazed by walrus die, leaving over half the clam to predators or scavengers.