Thomas says his team's work, which included surveying fish populations using sonar, has helped highlight the important role that herring play as a food source for sea lions.

Dolphins use sound to detect the size, shape, and speed of objects hundreds of yards away. The dolphin's natural sonar, called echolocation, is incredibly precise

In the 1950s, researchers weren't sure why dolphins produced their remarkable range of clicks, trills, moans, and squeaks.