Scientists have put forward the theory that the ancestors of whales were mammals that previously lived on land. The structure of the skeleton of these animals now living in the sea confirms this hypothesis. They do not look like fish because they do not spawn, they do not breathe with gills, their cubs are born fully formed and are fed with mother's milk. What are whales? The size of some representatives of this detachment is impressive. Consider them.
The biggest whale
The dimensions of the largest giant, according to some sources, were: body length of about 34 meters and a weight of 180 tons. The blue, or, as it is also called, the blue whale, according to the classification, belongs to the mammalian vertebrate animals. On average, representatives of this species grow up to 30 meters. They weigh about 150 tons.
The size of whales (photo) of other species is more modest. For example, a toothed sperm whale has a body length of about twenty meters, and a killer whale - no more than ten. Dolphins also belong to cetaceans. The size of these mammals is even smaller. The largest dolphin rarely grows more than three meters long.
Many people consider whalesbig fish. In fact, this is an erroneous opinion. Similar in them is only the general structure of the body and habitat. There are significant differences in nervous activity, blood circulation, skeletal structure, and skin. The reproduction of offspring and its rearing is the same as that of land mammals.
Whales: sizes and varieties
Scientists divide representatives of these mammals into two suborders. They differ significantly in lifestyle and nutrition. One group is baleen whales, the other is toothed. The names already contain the characteristics of their way of life.
Baleen whales are peaceful animals. They feed on plankton and mollusks, filtering them out of the water column through whalebone plates. Most of them in adulthood have a body length of more than ten meters. Species features of representatives of this suborder and lifestyle differ little.
Toothed whales are predators. Their food is fish and other mammals. This suborder is more diverse. Most representatives have body sizes up to ten meters. The following families are distinguished: oceanic and river dolphins, sperm whales, beaked dolphins. They, in turn, are divided into subfamilies and genera, depending on the characteristics of the lifestyle and habitat.
Belukha
In the suborder of toothed whales, there are representatives that differ in a special skin color. She is white. Hence the name - white whale. Animals belong to the narwhal family. The size of the white whale is up to six meters. The mass of adult males reaches two tons. Forcomparison: a newborn baby of a blue baleen whale has approximately the same dimensions.
Belukha lives up to forty years. Hunts for schooling fish, crustaceans and mollusks. Lives in northern latitudes. Features of the species: a thick layer of epidermis and fat that protects against hypothermia, a "lobed" head and short oval pectoral fins.
Belugas have a specific color not from birth. Cubs are born dark blue. At the age of one year, they brighten and become a grayish tint. And only after three years (more often by five years) they acquire a characteristic white color.
Despite the fact that this is a large animal, another representative of cetaceans, the killer whale, can hunt the beluga whale. Polar bears can also pose a threat to them. This happens when beluga whales find themselves trapped in polynyas by dense ice. They cannot stay underwater for long, as they come up every two minutes to get some air.
Blue whale
This is the largest animal on the planet. Scientists distinguish three types. Two of them: northern and southern - live in different latitudes. The third representative is the pygmy blue whale. Its dimensions are much more modest. An adult reaches only the weight of a cub of its usual counterpart. Pygmy blue whales are quite rare and are found only in the southern seas.
Big animals have everything big. The size of a whale's heart is comparable to a small car, it can weigh up to 700 kg. This is not surprising, because this body constantly pumps up to10 tons of blood. The diameter of the giant's artery is 40 cm, and a child can freely crawl into it. The tongue weighs up to three tons. With it, the whale pushes through the mustache large volumes of water from its mouth, the area of \u200b\u200bwhich is more than twenty square meters.
Features
The color of blue whales is actually grey. But when you look at them through the water column, it seems that they have a bluish tint. The sense of smell, taste and vision of these giants are poorly developed. But they hear well. Communication is carried out by transmitting ultrasonic signals, and orientation in space is carried out using echolocation.
Is the blue whale dangerous to humans? The size of these animals is enormous by our standards. However, they cannot eat a person. They have different food preferences. The diameter of the pharynx is only 10 cm. This is enough to pass plankton, small fish, crustaceans and molluscs. The only harm that a blue whale can cause is to accidentally turn over a vessel that will be in its immediate vicinity when it rises.
Cetaceans breathe atmospheric air. They must from time to time rise to the surface for the next portion of oxygen. In the normal state, the blue whale dives for 10-15 minutes. When ascending during exhalation, a characteristic fountain of water appears.
Habitat and lifestyle
Do blue whales have enemies? Dimensions, as it turns out, do not save even the largest animals on the planet from killer whale attacks. These hungry relatives, straying into flocks, can attack even a thirty-meter giant. They tear off pieces of meat from the whale's body. seriouswounds can lead to death. There were facts when the carcasses of blue whales with characteristic damage from killer whale teeth were found washed ashore. These giants, despite their size and weight, quite often jump out of the water. It is believed that this is how animals try to get rid of molluscs and crustaceans parasitizing on their bodies.
The habitat of whales is extensive. Scientists do not have sufficient capacity to track all their movements. It has been established that, depending on the season, blue whales migrate in search of food and optimal conditions. According to other observations, some of the animals are constantly in the equatorial Pacific Ocean.
It is believed that the lifespan of blue whales can reach hundreds of years. They are loners. Only sometimes they gather in small groups during seasonal migrations. The mother nurses the cubs for at least six months. During the day, a growing "baby", weighing up to ten tons, can drink 600 liters of mother's milk.
Population and commercial catch
Scientists suggest that before the start of active whaling in the waters of the oceans, there were at least 250 thousand individuals of the largest animals on the planet. To date, according to the most optimistic forecasts, there are no more than 10 thousand left.
What value do whales have for humans? The body size of these animals is large by commercial standards. From one carcass, whalers received not only meat, but also fat and whalebone. Meat is still popular in Japan, and it is not surprising that the fishery there is the mostactive.
The population of blue whales has decreased significantly. Over the past decades, a large number of adults have been destroyed. Female whales reach sexual maturity at ten years old. Once every two years, they can give offspring. But the situation is such that most of the young animals become a victim of fishing, never reaching their maturity.
Today, blue whales are protected. They are listed in the Red Book. But man and the consequences of his activities associated with environmental pollution still pose a serious threat to the entire population.
