The mating roar of a male harbor seal is supposed to attract a partner, not a predator. Unfortunately for the seals, scientists have found evidence that marine-mammal-eating killer whales eavesdrop on their prey. Previous research had shown mammal-eating killer whales are nearly silent before making a kill, neither vocalizing nor using their echolocation. The likely reason, researchers say, is the excellent hearing of the seals, porpoises, and other animals the whales stalk.