How Do Whales Sleep?
Whales don’t sleep at night as you do. They sleep by taking “half naps” at the water surface for a few minutes at a time when they are tired. Whales seem to be able to sleep with one eye open, and with half the brain still awake.
After approximately two hours, the animal will reverse this process, resting the active side of the brain and awaking the rested half. This pattern is often called cat-napping.
That way, they do not go to sleep completely and forget to breathe. Whales live in groups called “pods,” or “herds.” When whales are resting or sleeping, other whales in the pod watch them to make sure they are breathing and to watch out for danger.
Observations of whales show two basic methods of sleeping: they either rest quietly in the water, vertically or horizontally, or sleep while swimming slowly next to another animal.
Whales need only about as much sleep as dolphins and porpoises—about two or three hours a day. To avoid drowning during sleep, it is crucial that marine mammals retain control of their blowhole.
The blowhole is a flap of skin that is thought to open and close under the voluntary control of the animal.
Although still a matter of discussion, most researchers feel that in order to breathe, a dolphin or whale must be conscious and alert to recognize that its blowhole is at the surface.