free download PNG images :Dolphin

Dolphins are widely distributed and various aquatic mammals. They are an informal group of cetaceans, excluding whales and dolphins, so for zoologists, the group is symbiotic. These dolphins include the existing Delphinidae, the Indian puffer fish (Platanistidae), the new world puffer fish (iniidae) and the salty porpoise (salty porpoise), as well as the extinct Lipotidae (Baiji or Chinese puffer fish). There are 40 living dolphins. Dolphins, like other cetaceans, belong to the Cetartiodactyla evolutionary branch of ungulates with even toes. Their closest relative is hippopotamus, about 40 million years ago.

Dolphins range in size from 1.7 m (5.6 ft) long, 50 kg (110 lb) Maui dolphins to 9.5 m (31 ft) and 10 t (11 short tons) orcas. Several species show sexual dimorphism, in which males are larger than females. They simplified their bodies, transforming two limbs into flippers. Although not as flexible as seals, some dolphins can still travel at 55.5 km / h (34.5 mph). Dolphins use their conical teeth to catch fast-moving prey. Their hearing is well developed, suitable for air and water, and very developed, even if some people are blind can survive. Some species are great for diving. They have a layer of fat or fat under their skin that keeps them warm in cold water.

Although dolphins are widely distributed, most species prefer warm waters in the tropics, but some species, such as whales and dolphins, prefer a cold climate. Dolphins mainly feed on fish and squid, but like orcas, dolphins feed on seals. Male dolphins usually mate with multiple females each year, but females only mate once every two to three years. Calves are usually born in spring and summer, and the females take full responsibility for raising them. Mothers of some species fast and nurse young children for a relatively long time. Dolphins make all kinds of sounds, usually clicks and whistles.

Sometimes they hunt dolphins in places like Japan. This kind of activity is called "Dolphin hunting". In addition to driving and hunting, they are also facing the threat of simultaneous capture, habitat loss and marine pollution. Dolphins are depicted in various cultures around the world. In the movie and movie free Willie, dolphins occasionally appear in literature and movies. Dolphins are sometimes kept in captivity and trained in techniques, but the success rate of reproduction is very low, and animals often die within a few months after capture. The most common dolphins raised are killer whales and bottlenose dolphins.

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