How dolphin sleep underwater?

Dolphins have cheerful personalities. They love to play with their ball. They like to jump out of the water. They must have very tiring days. So, when time comes for them to rest, how do they sleep underwater without drowning? That is a very good question we'll answer in today's episode of Comamber. To understand how dolphins sleep, we must first analyze three key points. First of all, dolphins must breathe. And yes, dolphins, unlike sharks or salmons, do not breathe underwater, just because they don't have gills. They are mammals, like elephants or humans. So a dolphin has to come back to the surface to breathe. But unlike humans and other mammals, its breathing is not automatic. It is not a reflex. It must therefore consider it. So they have to come up to the surface. It will begin by expelling the air from its lungs through its blowhole, making the noise that everyone knows. Then the dolphin will fill its lungs with a big breath. It can now close its vent and dive again. It's a bit like when you pinch your nose when diving in the swimming pool. Dolphins can stay in apnea for 12 minutes, which may not seem much when you know that the apnea record held by a human is 11 minutes 54. But that is a static apnea record, whereas dolphins are moving a lot. So ultimately, the dolphin's breathing is a bit like when you swim the crawl in the pool. Even if the ancestor of the dolphin had legs, this ancestor lived on Earth over 50 million years ago. But that Pachycetis evolved. So today, the dolphin doesn't have the possibility to take its little legs to go nap on the beach. Therefore, it will have to stay in the water, which is colder than its body. This leads us to the second point that a dolphin must absolutely do, which is to move around to keep his body temperature between 95 and 96.8 degrees Fahrenheit. If not, it might just end up a frozen… I mean it will die. But that's not all. Since dolphins are not the big boss of the seas, they must continually escape from their predators, which include the killer whale and the shark. That's another reason why dolphins can't really stop moving. But then, how do they manage to sleep while breathing, moving to keep their temperature up, and escaping from predators who eat them as snacks? The answer is simple. It's called unihemispheric sleep. This is a very complicated word, but it's a very, very simple concept, and it works like this. The dolphin's brain has two hemispheres that take turns sleeping. When the right hemisphere is sleeping, the left hemisphere will take control of the navigation and the breathing. After a few minutes, they'll reverse. The left one will sleep and the right one will take over. And the funny thing is that all the members of the same dolphin gang, also called the pod, are sleeping simultaneously, so they'll all swim slowly as a group in order to stay close. The hardest part is for the dolphin moms and nannies, because they have to watch over their offspring all the time, as they are even more vulnerable to predators. To protect their young, they place themselves in a special formation, the echelon. That way, babies can follow their mothers and come up to the surface. They also swim faster with less effort. So this is not easy for dolphin moms, but as you're not a dolphin mom, you must surely have time to watch this next video, where I answer the most important question. Do fish drink water? But if you prefer to come back to Earth, you can check out this video, where I tell you how much wheat you would need to grow to get one kilo of flour.