The most successful marine mammals on Earth are cetaceans. Their bodies and limb bones have evolved like fish, and it is no wonder that they are commonly known as "whales". Of course, they are not fish, they are warm-blooded, fetal mammals and higher vertebrates with high intelligence.
Whales are warm-blooded animals, and their body temperature is always maintained at about 37 ° C, which is similar to the body temperature of a human. However, the sea is cool, especially in the Arctic, where the water temperature is often below freezing. Moreover, water absorbs heat much faster than air, so cetaceans have a thick, spongy cortex and a thick layer of fat below the cortex as an insulating layer to ensure that the heat in the body is lost as little as possible. In addition, since the resistance of water is much greater than that of air, whales need more energy and physical strength to move. Of course, there must be advantages and disadvantages, because the sea food is abundant and there are few competitors, so it is easier to eat a full belly. And, perhaps more importantly, although the sea water has a lot of resistance, but the buoyancy is also large, like the whale such a behemoth, up to tens of meters long, weighing more than 100 tons, on land is no matter how to survive, needless to say foraging, even if it is extremely difficult to move, it is difficult to walk. Therefore, the ancestors of cetaceans returned to the water, which was a smart choice.
Cetaceans
Whales gain forward momentum mainly by the swing of their tails and tail lobes when swimming, while their front fins are mainly used to control the direction of progress and grasp the depth of diving. The greatest thing about whales is not only that they are the largest animals on earth, but also that they are a global animal that wanders everywhere. In this kind of global migration, the polar regions are inevitable, because the food is abundant, the krill is abundant, you can eat for a while, reserve enough energy, and then you can return to the temperate ocean for a few months of vacation. Of course, there are also some whales that do not like to travel long distances and only recuperate in local areas, such as beluga whales, horned whales and Greenland whales, which live in the Arctic all year round.
In terms of feeding patterns, whales are divided into baleen whales and toothed whales. Baleen whales have a neat row of baleen on their jaws, like a grate, which acts as a filter, and when they take a big mouth, the water rolls the fish and shrimp into the mouth, and then when it is closed, the water is discharged, but the fish and shrimp are swallowed, and the tongue of the whale weighing several tons is rolled into the stomach. Toothed whales have sharp teeth that are used to bite and swallow.
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