How Do Dolphins and Whales Sleep?

Ever wonder how dolphins or whales sleep? They're mammals just like we are and need oxygen. Well, since when we humans are asleep, we are completely unconscious and do not have to brain capacity to support active thoughts and movement. Then the question is, if dolphins and whales are just like we are, wouldn't they drown if they were to fall asleep in the ocean?

The answer to that question is obviously no considering dolphins and whales are very much still alive. Let's first go over the different types of breathing. There is involuntary and voluntary breathing. We humans are involuntary, which means that if we do not breathe, our bodies will automatically try to induce air. Since dolphins and whales have a unique respiratory system which allows them to hold in air for a long period of time, they are voluntary breathers. Voluntary breathers are also known as conscious breathers, which simply means that they need to be conscious in order to breathe because they control when to and when not to breathe. Which brings us to the next question, if they are conscious breathers then how do they sleep since sleeping involves unconsciousness?

You may start to think that perhaps dolphins and whales just take cat-naps and never really are fully unconscious. Well, in order for a mammal to stay healthy, the brain needs to be in an unconscious state from time to time. So, how do they do it? Well, simply by being unconscious with only half of their brain at a time. Researchers have discovered this with electroencephalography, also known as EEGs. It showed that one side of the brain would literally shut down while the other side of the brain would be completely active. This allows dolphins and whales to come up above the water and get air every so often. Researchers have observed that they do this for eight hours a day, similar to us humans.

With being humans, we cannot understand exactly how this feels but we can make a reasonable guess. It's more or less similar to the state we're in right before we're about to fall asleep. We're really close to unconsciousness but still completely aware of our surroundings. That would be the best guess that we can take to understand the feeling of sleeping with only half of our brains.

We humans need beds or something similar to sleep in, so where do dolphins and whales sleep for comfort? Well, they can sleep anywhere since they are technically half conscious! As a matter of fact, it's not completely uncommon to see a dolphin or whale swim very slowly near the surface of the ocean at night. This is generally a sign of a dolphin or whale at rest.