With their long, spring baleen, the largest whales strain plankton out of the sea. Seals that live in Antarctica have very complex teeth which fit closely together. They use their teeth to strain small animals from seawater. Like bats, modern toothed whales can echolocate . The echoes tell them how close other objects are.
People can hear sounds echoing off mountains.
But it takes special ears to hear sound echoing off other animals. Fossil evidence indicates that archaeocetes had such advanced ears. It also appears that their jaws guided sound to their ears, similar to modern whales. But even if they couldn t, they probably had exceptional hearing. Ziggy lived some 55 million years ago, during the Eocene Epoch.