How Do Dolphins Sleep in the Ocean?
Dolphins don’t sleep soundly at night like we do. When it’s time to rest, a dolphin undergoes an unusual form of sleep called “unihemispheric slow-wave sleep.” Also known as deep sleep, slow-wave sleep is a type of sleep thought to help the brain consolidate new memories and recover from its daily activities.
They have to stay awake to breathe, so they take half naps at the water surface when they are tired. Some scientists believe that dolphins sleep with one eye open, and with half the brain still awake. During this time, the other half of the brain monitors what’s going in the environment and controls breathing functions.
This way, they do not go to sleep completely and forget to breathe. Dolphins rest in large groups with other dolphins. When they are sleeping or resting, there are always dolphins in the group watching out for danger. Dolphins need only about as much sleep as whales —about two or three hours a day.