Dolphins are active, opportunistic predators that feed on many different kinds of fishes, squids and crustaceans. Their diet varies according to what is geographically available. Fishes and squid are staples for offshore dolphins, and coastal dolphins rely mainly on fishes and bottom-dwelling invertebrates.
Adult bottlenose dolphins tend to eat 4 to 6 percent of their total body weight on a daily basis. A nursing mother may take in as much as 8 percent. Instead of chewing their prey, dolphins rub or shake large fish on the ocean floor in order to break off appropriately sized chunks. They have compartmentalized stomachs, which helps them to digest food very quickly.
Dolphins are very intelligent hunters. It is common for them to follow commercial fishing vessels, eating fish or shrimp that is discarded. They often hunt cooperatively, herding schools of fishes together and then taking turns feeding on the condensed mass. They also hunt fish individually when the opportunity arises.
Some species of dolphin knock fish out of the water with their flukes and then attack the stunned prey. Some species make their prey vulnerable by driving them onto a beach. Offshore dolphins have been found with deep-sea fishes in their stomachs, which is evidence that they may dive to over 1,600 feet.