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. During the Eocene, the Gulf of Mexico covered most of Florida and parts of Georgia, Alabama, Mississippi, Louisiana, and Texas. It even extended north into Arkansas.