Interesting facts about dolphins for children, 4th graders

Dolphins are mammals, they are found in the open sea, at the mouth of rivers. They are ideal swimmers as their bodies are adapted for movement in water. The body of a dolphin measures from 2 to 3.6 m, it weighs from 150 to 300 kg. They have sharp teeth, their number is a record – 272, in the form of sharp spikes. This is necessary to keep slippery prey.

Here are 10 interesting facts about dolphins for 4th graders that will help you learn more about these mammals. So far, the information we receive about them is surprising and amazing, because. Dolphins cannot be compared to any living animal on our planet.

10. The name can be interpreted as “newborn”


The word “dolphin” comes from the Greek δελφίς, and it comes from Indo-European, meaning “uterus”, “uterus“. Therefore, some experts translate it as new born“. Such a name could appear because the dolphin looks a bit like a child, or its cry sounds like a baby’s cry..

9. The dolphin’s brain weighs more than a human and has more convolutions


The brain weight of a dolphin is 1700 g, while the brain of an ordinary person does not exceed 1400 g. Researchers have found that it is striking not only in size, but also quite complex in structure. It contains more nerve cells and convolutions than in humans. They differ only in form. with them it looks like a sphere, while with us it is slightly flattened.

The association zone of the cerebral cortex is the same as in humans, which may indicate a developed intellect. The parietal lobe is the same size as in humans. But a very large visual part of the brain.

They know how to sympathize with others, can, if necessary, come to the rescue. So, in India, they have been officially recognized as individuals, so dolphinariums that violate their rights are banned in the country.

8. Have a sound signaling system


Dolphins have their own language. Psychoanalyst and neuroscientist John C. Lilly wrote about this in 1961. He said that these mammals have 60 basic signals. The researcher hoped that in 10 to 20 years, mankind would be able to master this language and communicate with them.

They have as many sound organizations as a person, i.e. they compose sounds into syllables, words, then sentences, paragraphs, etc. They have their own sign language as they strike various poses, wave their heads, tails, and swim in different ways.

outraged There is also a spoken language. It consists of sound pulses and ultrasound i.e. screams, chirps, squeaks, roars, etc. They have 32 types of whistles aloneeach means something.

So far, 180 communication panels have been found. Now they are trying to systematize in order to compile a dictionary. Scientists are sure that the dolphin makes at least 14,000 sound signals, but we don’t hear many of them, because. they are emitted at ultrasonic frequencies. Despite the fact that work is being done in this direction, it has not been possible to completely decipher their language.

Everyone has their own name, given to them at birth. This is a characteristic whistle, lasting 0.9 seconds. When the computer was able to determine these names and they were paraded with several captured dolphins, only one individual responded to them.

7. “Grey’s Paradox”


It is associated with dolphins. In the 1930s, James Gray discovered that dolphins move at enormous speeds, at least 37 km/h. This surprised him, because. according to the laws of hydrodynamics, they should have had 8 to 10 times more muscle power. Gray decided that these mammals control the rationalization of their bodies, their bodies have 8 to 10 times less hydrodynamic resistance..

In our country, research was conducted until 1973, the first experiments appeared that confirmed Gray’s statements. Most likely, Gray was wrong about the speed of movement of the dolphins, but they still know how to reduce the resistance to their movement, but not by 8 times, as the Englishman believed, but by 2 times.

6. Pregnancy lasts 10-18 months


Dolphins live for about 20 to 30 years, but their gestation period is longer than that of humans. They carry babies from 10 to 18 months. They can be born both small, up to 50-60 cm, and larger. When a dolphin is about to give birth, it begins to move, arching its tail and back. Other dolphins surround her in a tight ring, trying to help and protect her.

As soon as the baby is born, it is pushed up so that its lungs expand and it can take a sip of air. He recognizes his mother by her voice, as she starts whistling immediately after giving birth, 10 times more often than usual.

In the first months, an adult dolphin does not leave its child, if it is hungry, the baby starts crying, as in humans. All young mammals sleep a lot in the first months after birth. But not the dolphins.

At first, the little dolphin does not know what sleep is at all, he only begins to sleep 2 months after his birth. The first year of life, the baby lives next to his mother, she not only feeds him, but also educates him, punishes him if he does not obey. Then the mother begins to teach him how to feed and communicate. The dolphin grows in the herd of females, and the males live separately. A mother can have 7-8 cubs or only 2-3.

5. “Fighting” dolphins in the USA and the USSR


The use of dolphins was first proposed in the 19th century, but this idea was not realized until the 1950s. The US Navy conducted many tests in which different animals participated (over 19 species). Dolphins and sea lions have been selected. They were trained to find underwater mines, destroy submarines by kamikaze. But the US Navy denies ever doing anything like that. But, nevertheless, training bases exist, they have a special fleet of marine mammals.

The USSR established its own research center near the Black Sea in 1965, in Sevastopol. By the early 1990s, dolphins were no longer trained for military purposes. But in 2012, Ukraine continued to train, and in 2014 the Crimean Fighting Dolphins were put into service with the Russian Navy.

4. On ancient coins there are images of dolphins


From the 5th century BC e. dolphin images can be found on ancient Greek coins, as well as ceramics. In a cave in South Africa in 1969, a stone was found that is at least 2285 years old. A man and 4 sea inhabitants resembling dolphins were drawn there.

3. Dolphins have only one of the two hemispheres of their brain in non-REM sleep.


Animals and humans cannot stay awake for a long time, after a while they are forced to sleep. Corn dolphins are designed so that only half of their brain can sleep, while the other remains alert at this time. If they didn’t have this characteristic, they could drown or fall prey to predators.

2. Dolphin therapy is a method of psychotherapy


Swimming with dolphins is useful for those who have suffered severe psychological trauma. It helps to recover. Dolphin therapy is used to treat cerebral palsy, childhood autism, Down syndrome, mental retardation, speech and hearing disorders. It also helps to cope with depressive disorders, if they are not endogenous.

1. The dolphin family includes about 40 species


The dolphin family is a suborder of toothed whales, which includes about 40 species.. There are 11 in our country. These include bottlenose dolphins, killer whales, whale dolphins and many more.

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