Any living creature needs rest to recuperate. So conceived by nature itself. Sleep is necessary for all - birds, mammals, any animals of the highest order, to which we are humans. We are used to associating sleep with a state of complete relaxation and stillness. This is how almost all representatives of a highly organized sauna sleep.
It is common for lions to sleep on their backs most of the day. Elephants in Africa tend to doze standing for two or three hours. Long-legged giraffes for recreation are curled up.
But how does a dolphin sleep? After all, no one ever saw him motionless. These amazing animals always move in the water space with extraordinary ease and grace. It seems that they are awake around the clock, and sleepiness is not peculiar to them in principle.
But this assumption is wrong, which is finally proven by modern scientific research.
How does dolphin breathing work?
We, people, hardly ever think about our breath - this process is natural for us. But dolphins are a little more complicated. Every 5 or 10 minutes, any of the dolphins needs to ascend to the surface to replenish their oxygen supply, which implies the coherence of the muscles and the brain.
Everyone has long known that a dolphin is not a fish, but a real mammal. And they are considered secondary aquatic mammals. That is, their ancestors originally existed in the water element, but over time they mastered the land and were able to breathe with the help of the lungs. The reasons for which such animals are returned to the water element are unknown to scientists.
Such mammals, unlike fish, do not have organs or devices that allow breathing underwater. That is, they do not have gills. To stock up air for breathing, the dolphin needs to surface to the surface.
Consequently, leading the life of a marine inhabitant, the dolphin continues to breathe light. He has a special valve that the dolphin opens, approaching the water surface. After exhaling and inhaling, the animal closes the valve and carries a fresh portion of oxygen under water. This process is quite complex for the body and is almost impossible in a sleepy state.
However, the received portion of air is enough, as mentioned above, for as long as five to ten minutes. For many years, biologists have taken the obvious question - how a dolphin sleeps in this mode, because the intervals through which this mammal must emerge to get a portion of atmospheric oxygen are fairly short.
There have been many versions. The most extreme of them argued that dolphins do not need sleep at all, that is, they never stay in this state. According to another theory, they are characterized by a short rest between surfacing to the surface.
Do dolphins sleep at all? For a long time, these animals were considered somnambulists, resting in a state of muscle tension and with open eyes. They also believed that they are characterized by periods of sleep in the short intervals between inhalation and exhalation, and they awaken from chemical changes in the composition of the stored portion of oxygen.
Some scientists attributed dolphins to automatism of actions, like lunatics. To determine the true state of affairs, studies were organized in which registration of the biocurrents of the dolphin brain was intended.
How a dolphin sleeps - the word science
This procedure is very difficult. Animals needed to be placed in a pool, electrodes were implanted into the brain. The signals were recorded using radio waves, which made it possible for dolphins to lead a normal life.
The work was carried out at the Black Sea biostation by researchers from the Academy of Sciences. Finally, in order to find out how dolphins sleep, Soviet scientists A. Ya. Supin and L. M. Mukhametov, representatives of IEMAE (Institute for Evolutionary Morphology and Ecology of Animals) organized a mammal observation, which was carried out both in aviaries and in the open pool.
To implant electrodes into the brain, we selected several copies of bottlenose dolphins and Azovka. Animals were given the opportunity to habitually frolic, during which the electroencephalogram of the brain was recorded using a radio signal. The resulting figure made it possible to trace the activity of each of its hemispheres.
The results of the research scientists were simply shocked. It turned out that dolphins are not completely drowned in sleep. That is, their brain remains active continuously. The discovery was that his hemispheres literally sleep in turns. Each of them receives a portion of full normal sleep for about 6 hours during the day. At intervals of an hour or one and a half, a replacement occurs when the opposite hemisphere plunges into sleep.
The most interesting thing is that during such a dream a dolphin can behave as if nothing had happened - swim, hunt and so on. So it is hardly possible for outside observers to determine with the naked eye whether an individual is sleeping at the moment or not.
How does a dolphin sleep - eyes open or not?
Almost everyone, both people and animals, close their eyes in a dream. And what about dolphins? In full accordance with the alternate wakefulness of each of the hemispheres! That is, one eye of a sleeping dolphin is always closed.
Why do dolphins sleep with one eye open? Even before the study, many people paid attention to the fact that one eye in dolphins is often closed, but no one had previously guessed to associate it with a dream. Thus, as a result of the research, a real scientific sensation was born.
It turns out that the nature of the dolphins was presented with a truly magical possibility of simultaneous rest and wakefulness. That is, full and deep sleep, like in other mammals - with the disabling of both hemispheres of the brain - in dolphins never occurs.
What it looks like
Now we all understand how a dolphin sleeps. Each of the hemispheres alternately keeps its watch. Then they switch places. The active hemisphere is immersed in sleep, the opposite begins to stay awake. When the dolphin’s sleep stage passes, both hemispheres are included in the work.
This evolutionary mechanism is provided by nature in order to survive the species. Constantly awake one of the hemispheres solves the problem of delivery of oxygen to the brain and warns of the danger of choking.
Interesting information about dolphins
Dolphins - warm-blooded mammals from the order of cetaceans - rightfully gained fame among some of the most mysterious creatures on Earth. The characteristic nickname of dolphins - "People of the Sea" - emphasizes the fact that their intellectual potential is so great that they are considered smarter and smarter than all the other animals of the planet.
Dolphins live in flocks. Mutual aid to each other, sometimes reaching to self-sacrifice, is developed among these creatures. Dolphins are able to talk, emitting about ten variations of different sounds on both normal and ultrasonic frequencies. In addition, they have a unique ear, which operates on the principle of the sonar and allows you to determine not only the distance to the object or object, but even its size and shape.
Dolphin is considered one of the fastest marine animals - in the water, it is capable of speeds up to forty kilometers per hour! These animals are predators, they feed mainly on fish. The life span of a dolphin is about thirty years.
In the wild, many dolphins are willing to contact people. A dolphin that saves from the danger of its kinsman will likewise float to the aid of man. He will pull the drowning man ashore, drive the shark away from him, show the way to the sailors. This fact has long been proven, but the essence of this phenomenon has not yet been able to explain.
Do dolphins sleep?
Sleep to the dolphins is vital - just like all other mammals. However, it is special in these animals. Observations, as well as studies of the bioelectrical activity of the brain, have revealed a very definite picture of how dolphins actually sleep.
In order not to drown during sleep or to become a victim of a predator attack, these marine mammals sleep "half". One hemisphere of the brain of the animal during sleep gets a good rest, while the second continues to stay awake, controlling what is happening around and responsible for the respiratory function. That is why dolphins sleep with one open eye: if the right brain rests, the left eye is closed, and vice versa. Such a dream takes about six or seven hours a day. And when the dolphin wakes up, both hemispheres begin to work.
How the dolphins sleep
At first glance, the unusual feature of the “half-hearted” dolphin’s sleep does not prevent him from going through all the phases, from fast to deep, and at the same time providing the animal with proper rest. Scientists have closely watched how the dolphins are sleeping and identified common patterns. It always happens at a shallow depth, near the surface of the water. Due to the high content of adipose tissue in the body, dolphins very slowly go down. Now and then an animal, while in a dream, strikes the water with its tail and floats to the surface in order to inhale the air. After that, it again slowly descends into depth.
Dolphin breathing in a dream
Sensing a change of environment when diving to the surface, the dolphin opens a breath (nostril). He breathes very quickly: due to the nature of the airways, he is able to inhale and exhale simultaneously. While under water the breather remains tightly closed tight valve.
Newborn dolphins do not sleep for a month!
Studies have proven: the assumption that dolphins never sleep is a myth. However, another interesting fact was discovered. Scientists at the University of California at Los Angeles found out that newborn baby dolphins and whales do not fall asleep at all during the first month of their lives! In addition, the kids are also forcing their mothers to stay active all the time ...
Tiny dolphins are constantly in motion, floating to the surface for air every three to thirty seconds. And only a month later, in their daily routine, short periods of sleep begin to appear, which are gradually approaching the rate characteristic of an adult animal.
American biologists have suggested that this behavior reduces the risk for children of dolphins and whales to be eaten by predators, and also enables them to maintain a stable body temperature. In this regard, they raised an interesting question about the presence of a certain reserve in the body of mammals, allowing them to go without sleep for a long time without experiencing any harm to their health.