Dolphins generally sleep at night, but only for a couple hours at a time; they are often active late at night, possibly matching this alert period to feed on fish or squid, which then rise from the depths.

Do dolphins not sleep?

Humans have a breathing reflex and when we sleep or become unconscious, we continue to breathe automatically. Dolphins cannot sleep in this way; they have to remain conscious, even when they are sleeping. This is because their breathing is not automatic, it is consciously controlled.

How Long Can dolphins hold their breath while sleeping?

Bottlenose dolphins, for example, can stay underwater for around 8 to 10 minutes. Even when sleeping, a dolphin's lighter bone structure allows them to sleep just below the surface. This allows them to pop up with their tail flukes every so often whilst asleep to take in the oxygen they need.