How do whales, penguins, dolphins and pinnipeds sleep? (8 photos)
Sleep is a necessary process for the life of living beings, since without restoration of strength it is impossible to exist. Here are some interesting facts about how some animals sleep. 
Sea animals and birds occupy places at the very top of ocean food chains for a reason. They all breathe atmospheric air, the oxygen content of which is at least 10 times higher than in water! And oxygen is the main reagent for converting fat into energy. Therefore, dolphins and penguins are faster, more active and smarter than fish. But there is one nuance: how to sleep? 
Kalan is the invited guest of this article. The sea otter can sleep on the surface of the water, but its sleep does not exceed 1 hour at a time. The animal is afraid that it will be carried too far by the current. To prevent this from happening, the animals wrap themselves in seaweed or take another sea otter by the paw.
Secondary aquatic and semi-aquatic animals will not lie down on the bottom among stones or bury themselves in the sand. They simply don’t have enough air for a peaceful nap. And hanging right in the water column is extremely dangerous: you will be eaten, and you won’t even notice. Only the largest of marine mammals - killer whales and sperm whales - can afford this type of recreation. 
Blue whales, for example, sleep right at the surface of the water so as not to waste time and energy on rising.
Sperm whales sleep in a particularly interesting way: they hang vertically right in the middle of the ocean and pass out for an hour. Although an adult toothed whale can hold its breath for 2.5 hours, it does not take the situation to the extreme. A couple of such hibernations during the day - and the animal got some sleep! 
“It won’t be enough!”, some of you will say. And the dolphins will not agree with him. In order not to accidentally suffocate, so as not to get caught in the teeth of sharks or the killer whales mentioned above, dolphins never sleep 100%. These animals have learned to rest in different hemispheres. While one half of the brain is asleep, the other follows the course predetermined by the body and raises the body to the surface for breathing. On average, dolphins spend about 6 hours a day in a strange half-sleep. 
You can tell which hemisphere a dolphin sleeps in by looking at its closed eye. If the right eye is closed, the left hemisphere of the brain sleeps; if the left one, the right hemisphere sleeps.
And they were lucky! During multi-day feeding migrations, elephant seals sleep at most 2 hours a day. To take a breather from the endless hunt, pinnipeds take in more air and slowly drift downward in a spiral for 10-30 minutes, diving to a depth of 200-300 meters. Then they wake up, rise to the surface and repeat the operation. 
But on land and off the coasts, the elephant seal sleeps sweetly and fully!
Chinstrap penguins next to them are just sleepyheads who can sleep up to 14 hours a day. Only their one-time swim into the kingdom of Morpheus lasts only 3-6 seconds. All they have to do is close their eyes briefly to fall asleep! During such a period, no one will be able to sneak up unnoticed, so underwater birds fall asleep right on the surface of the ocean. 
And the worst place for them to sleep, oddly enough, is on land, and not in the ocean full of dangers. A penguin resting on the shore sleeps less and more often: in a day he can fall asleep 11,000 times! And at least 2 out of 3 seconds of sleep involve multi-hemispheric sleep, just like dolphins. The reason for this is aggressive neighbors in the colony and the need to monitor the offspring. 
But most other species of penguins can afford a restful sleep.
What can this story teach us? And the fact that people are rare lucky ones. We have occupied the niche of the coolest predators on the planet, and we can bask in a warm bed for as many as 8-9 hours at a time. I do not advise you to neglect such a generous gift of fate!
