Picture a dolphin diving toward the seafloor with something odd on its nose. It is not a shell or a fish. It is a sea sponge.

Also known as skunk dolphins or Commerson's dolphins, these mammals weigh up to 190 pounds and often approach boats.

Off the Pacific coast of Canada, scientists have captured something that challenges long‑held assumptions about life in the sea: killer whales and dolphins moving in sync as they pursue the same prey.