Dolphins are mammals, they can be found in open seas, in estuaries. They are ideal swimmers, as their body is adapted to movements in water. The body of a dolphin is from 2 to 3.6 m, they weigh from 150 to 300 kg. They have spiky teeth, their record number is 272, they resemble spiky spikes in shape. This is necessary to keep slippery prey.
Here are 10 more interesting dolphin facts for Grade 4 students to help you learn more about these mammals. Until now, the information that we receive about them is surprising and amazing, because no animal living on our planet can be compared with dolphins.
10. The name may be construed as “newborn baby”
The word "dolphin" comes from the Greek δελφίς, and it is from the Indo-European, meaning "bosom "," womb". Therefore, some experts translate it as «newborn baby". This name could appear because the dolphin is somehow similar to a child or its cry resembles that of a baby.
9. The brain of a dolphin weighs more than a human and has more convolutions in it
Dolphin brain weight - 1700 g, while the brain of an ordinary person - no more than 1400 g. Researchers have found that it is not only striking in its size, but also quite complex in structure. There are more nerve cells and convolutions in it than in humans. They differ only in form. in them it resembles a sphere, but in our country it will be slightly flattened.
The associative region of the cerebral cortex is the same as in humans, which can speak of developed intelligence. The parietal lobe is the same size as humans. But a very large visual part of the brain.
They know how to sympathize with others, can come to the rescue if necessary. So, in India they were officially recognized as personalities, therefore dolphinariums that violate their rights are banned in the country.
8. Have an audio 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 10-20 years, humanity will 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, and then phrases, paragraphs, etc. They have their own sign language when they take various poses, give signs with their heads, tails, and swim differently.
Besides there is also an audio language. It consists of sound pulses and ultrasound, i.e. squeal, twitter, squeak, roar, etc. They have only 32 whistles, each of them means something.
To date, 180 characters have been found for communications. Now they are trying to systematize them in order to compile a dictionary. Scientists are sure that the dolphin emits at least 14 thousand sound signals, but many of them we do not hear, because they are emitted at ultrasonic frequencies. Despite the fact that work is being carried out in this direction, it was not possible to completely decipher their language.
Everyone has a name that is given to him at birth. This is a characteristic whistle lasting 0.9 seconds. When the computer was able to calculate these names and they were scrolled next to several dolphins caught, a separate individual responded to them.
7. "The Paradox of Gray"
It is associated with dolphins. In the 1930s, James Gray found that dolphins travel at tremendous speed, at least 37 km / h. This surprised him, because according to the laws of hydrodynamics, then they should have had a muscle power of 8-10 times more. Gray decided that these mammals control the streamlining of their body, their body has 8-10 times less hydrodynamic resistance.
In our country, studies were conducted until 1973, the first experiments appeared, confirming the statements of Gray. Most likely, Gray was mistaken about the speed of dolphins, but they still know how to reduce 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 about 20-30 years, but they have a longer gestation period than humans. They have babies 10-18 months old. They can be born both small, up to 50-60 cm, and larger. When the dolphin is about to give birth, he begins to move, arching his tail and back. Other dolphins surround her with a dense ring, trying to help and protect.
As soon as the baby is born, he is pushed upwards so that his lungs are straightened and he can swallow air. He recognizes his mother by voice, because immediately after birth she starts to whistle, 10 times more often than usual.
In the first few months, an adult dolphin does not move away from his child, if he is hungry, the baby begins to cry, like in humans. All young mammals in the first months after birth sleep a lot. But not dolphins.
At first, the little dolphin does not know what sleep is at all; he starts to sleep only 2 months after birth. The first year of life, the baby lives next to his mother, she not only feeds him, but also educates, punishes, if he does not obey. Then his mother begins to teach him how to get food and communicate. Dolphin grows in a female herd, while males live separately. One mother may have 7-8 cubs, or only 2-3.
5. "Fighting" dolphins in the USA and the USSR
Dolphins were first used in the 19th century, but they could only realize this idea in the 1950s. The US Navy conducted many trials in which various animals participated (more than 19 species). Dolphins and sea lions were selected. They were trained to find submarines, destroy submarines using the kamikaze method. But the U.S. Navy denies having ever done anything like that. But, nevertheless, training facilities exist, they have a special Fleet of Marine Mammals.
In the USSR, a scientific research center was established near the Black Sea in 1965, in Sevastopol. In the early 1990s, dolphins were stopped training for military purposes. But in 2012, Ukraine continued training, and in 2014, the Crimean fighting dolphins were hired by the Russian Navy.
4. On ancient coins there are images of dolphins
From the 5th century BC e. images of dolphins can be found on coins of Ancient Greece, as well as on ceramics. In a cave in South Africa in 1969, a stone was found that is at least 2285 years old. There was painted a man and 4 marine inhabitants resembling dolphins.
3. In a state of slow sleep in dolphins is only 1 of the 2 hemispheres of the brain
Animals and humans cannot stay awake for a long time, after some time they are forced to sleep. But dolphins are designed so that they can sleep only one half of the brain, and the other at this time remains on guard. If they did not have this feature, they could drown or become prey of predators.
2. Dolphin therapy - 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 impairment. It also helps to cope with depressive disorders if they are non-endogenous in nature.
1. The dolphin family includes about 40 species
The dolphin family is a suborder of toothy whales, which includes about 40 species. In our country there are 11 of them. These include bottlenose dolphins, killer whales, cetacean dolphins and many others.