Dolphins are very intelligent animals, but how do scientists test that idea? In a 2001 study, two bottlenose dolphins used a mirror to examine marks on their bodies. At that time, only humans and great apes had shown convincing mirror self-recognition. Whistles give researchers another window. Each bottlenose dolphin develops its own signature whistle, and scientists think a signature whistle works like a name. In 2006 researchers played synthetic whistles to Sarasota Bay dolphins, and in 9 of 14 cases a dolphin turned toward the speaker more often when the whistle resembled a close relative's.

A calf starts to develop its signature whistle in its first months of life. Signature whistles make up about half of a bottlenose dolphin's whistles, and wild bottlenose dolphins often copy each other's signature whistles. Dolphins also find things by making sounds that bounce off objects and return as echoes. A waxy, lens-shaped part in the forehead, called the melon, focuses the clicks into a beam, and the echoes are picked up through the lower jaw. Some dolphins also find fish by listening for the sounds the fish make.

Bottlenose dolphins sleep with one half of the brain at a time, which is called unihemispheric slow wave sleep. Near shore, a bottlenose dolphin comes up to breathe about two times a minute. A dolphin's brain has no sense of smell, but a dolphin can see well both underwater and above the water. Its belly can turn pink when it is active, which helps it release extra body heat. For a short burst, a bottlenose dolphin can swim about 18 miles an hour.

At Laguna in southern Brazil, wild bottlenose dolphins chase mullet toward fishers standing in shallow water. In Laguna, 86 percent of the mullet that fishers caught came from catches synchronized with dolphins. Dolphins elsewhere also work together to herd fish into a group before they feed, and some bottlenose dolphins hit fish with their tails, which is called fish-whacking. The U.S. Navy trains bottlenose dolphins to find and mark mines on the sea floor.

Calves learn how to hunt mostly by watching their mothers. In Shark Bay, Australia, some dolphins wear sea sponges on their snouts while they search the sea floor for food, and calves can learn to use sponge tools from their mothers. Some bottlenose dolphins strand-feed, rushing onto mud banks or the shore to catch fish stranded there. Bottlenose dolphins also form nursery groups of mothers and calves, groups of young dolphins, and bonded pairs of adult males, and females can help look after one another's calves.

Since October 1970, the Sarasota Dolphin Research Program has studied the dolphins of Sarasota Bay, Florida. As of November 2026, it is the longest-running study of a wild dolphin population. As of November 2026, in Sarasota Bay a boat passes by a dolphin every 6 minutes, and 1 in 20 dolphins there has a scar from a boat collision. Getting tangled in fishing gear is one of the main threats to bottlenose dolphins, as of November 2026, and in the United States they are protected by the Marine Mammal Protection Act of 1972. Feeding wild dolphins is harmful because it teaches them to come close to boats and people. As of November 2026, people should stay at least 50 yards (46 meters) away from wild dolphins.

Words to know

• unihemispheric: one half-brain
• synchronized: timed together
• signature: one's own
• synthetic: made, not natural
• melon: forehead lump