Dolphins Sleep With One Eye Open U0026 Half The Brain Active

When it comes to how dolphins sleep, keep in mind that they must come to the surface to breathe, which does not seem to be compatible with sleeping. But the fact is that …
Dolphins sleep with one eye open & half the brain active

Dolphins spend all their time in water, but they must come to the surface to breathe. So how do they sleep? In this article we will talk about the sleeping habits of whales and other marine animals.

How do dolphins sleep?

Dolphins, like whales or killer whales,  must sleep with their eyes open… and half of their brains remain awake. Yes, you read that right! These mammals experience what is known as  “hemispheric long-wave sleep”. This means that when they rest, only one of the halves of the brain loses consciousness. The other half remains active.

The same goes for the eyes. because one closes – that which is opposite the closed half of the brain – while the other is kept open. The cerebral hemisphere that does not sleep in the animal is responsible for monitoring respiration so that the dolphin can go up to the surface and breathe when needed. During a 24 hour period, each hemisphere rests for 4 hours. Thus, a dolphin sleeps eight hours a day.

Sometimes dolphins can float lifeless near the surface while “sleeping”, and at other times they swim very slowly. They can also dive closer to the bottom of the ocean and then back to the surface to breathe as often as needed. Because they are not active, they do not need to breathe as often.

Dolphin at the surface

Usually this animal sleeps at night: two hours with the right hemisphere and another two hours with the left. Then they repeat this process until they have eight hours of sleep.

Why do dolphins sleep that way?

There is a popular expression that reads: “Nature is wise”. Nothing is random and each species is equipped with what it needs to survive. This of course includes dolphins, which can sleep without drowning.

Unlike terrestrial mammals , marine mammals do not deactivate the entire brain when they are at rest. Not their muscles either. They can not risk relaxing and sleeping deeply and they need to breathe at the surface. If they were in deep sleep, they would not be able to breathe in the oxygen they need.

Another important thing is that they do not deactivate any of their senses, not even sight and smell, as terrestrial animals do.

Another reason why dolphins sleep with one eye open and one hemisphere active is so that they can be aware of possible dangers around them,  such as fishing boats, sharks or killer whales, which are a major danger to dolphins.

Swimming dolphin

In addition  , they are capable of maintaining specific biological processes throughout the day as well as the muscular movements necessary to maintain body temperature while in the water. While they tend to live in tropical climates and are warm-blooded, their body temperature can still drop if they stay still. This can be harmful to their health.

And what about whales?

Something similar happens with large marine animals, such as whales and porpoises. They must also go up to the surface to breathe. This means that they can swim slowly and very close to the surface of the sea, thanks to the fact that half of their brain is awake.

Another interesting fact about whales’ sleep cycle is that when they are small, they rest, eat and sleep with their mother, who never stops swimming for a minute. The calf holds such a position that the movements performed by their mother allow it to be pushed forward by itself. That way , it can sleep most of the time without drowning or sinking.

It’s really fascinating to discover how dolphins and other marine animals sleep. With this technique of having a brain half awake, they ensure their survival and avoid danger.

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