Dolphins are a kind of whale, most of them are small toothed whales. Dolphins also have many species, their distribution areas are different, generally speaking, the distribution range is relatively wide, in the world's oceans, inland seas, rivers and other salt and fresh water are distributed. Dolphins are also a very ancient mammal, which has existed for more than 20 million years. After the change of environment, the body structure of dolphins has also undergone great changes.
Dolphins are also very fast mammals, even faster than sharks, and are one of the fastest creatures in the water. Their hearing is also very good, both when they are in the water and when they are in the air or on land.
As mentioned above, a dolphin is a mammal. Although they live in the water, they live in the same environment as most fish, but they can not be mistaken for fish. As an aquatic mammal, dolphins share some characteristics with terrestrial mammals.
One of the most important features is the way they reproduce, which is viviparous. Moreover, the dolphin's pregnancy is relatively long, about 11 months; After giving birth, dolphins also have a lactation period, similar to that of humans and other mammals. In addition to the way of reproduction, another important feature is their way of breathing, they use lungs to breathe, which is the same as other mammals. Therefore, dolphins can not be considered as fish.
