There are only a few three-meter long river dolphins that inhabit the largest rivers in the subtropical Amazon, La-Plata in South America, including Indus and Gandus in the South Asia: and the only specie, which is Chinese dolphin that lives in the Dongting Hu Lake, China, at a location within 1000 kilometers offshore the mouth of the Yangtze River. Like a dark shades they slide over the shallow waters either in pairs or in small groups searching for prey like small crustaceans, shellfish, and small fry ransacking the near-bottom waters or poking its long thin sharp-toothed “peak” on their agile heads. As long as they live in the muddy waters that carry tons of small clays, the river dolphins cannot guide themselves by the sight: their eyes are too small and semi-blind. This disadvantage is compensated by the ability of underwater echo sounding: they produce sharp clicks in the ultrasonic range and the echo sound they receive back they can understand what surrounds them.
Everyone who has ever been in the sea could probably see small dolphins playing all around in front of the ship’s head. These were likely to be white-bellied porpoises, which belong to the number of common dolphins, and you can even consider them as a model of the wide-ranged sea dolphins. You can find them in all warm and moderate ocean and sea waters, which follow the shoals of herrings, sardines and sauries in large pods of dolphins. The white-bellied porpoises prefer to be 10-15 meters below the water surface and don’t like to dive in deep waters. They are constantly making whistling sounds, creak, and crackle and even “shout”: these are the unusual powerful sounds that resemble a shot or a roll.
The bottle-nosed dolphin is somehow alike the white-bellied porpoise, though it’s bigger and is not so well-shaped. It has got a large brain, it’s even bigger than the human’s with lots of convolutions. The bottle-nosed dolphins are very friendly, and help each other when there is a trouble. When someone falls into a net or an enclosure, all the rest spin around, bear it up and try to free the captive.
You can easily observe the bottle-nosed dolphin from the sea-cliffs. During the still water you can see them traveling along the curved 2-3 meter deep coastline, taking sharp turns and dashes and also chasing the shoals of fish. Sometimes you can see the bright bellies instead of the back parts: the dolphins usually turn on the side at the raised curves. At the deep waters the bottle-nosed dolphins go down as much as possible for 5-7 minutes and when they break the water surface they splash out small fountains. These dolphins have got rich vocal characteristics. When they are full of energy they usually they make a shrill whistle; at lunchtime you can hear something like a mew or a bark sound that comes out; while arguing with other dolphins their jaws are chattering.
Agility, friendly character and spacious mind make the bottle-nosed dolphins a welcome guest in the aquarium circuses. They can easily stand enclosed places, easy-trained, quick trick-learners: in response to a signal it goes out from the water, finds and brings any objects, takes fish from the hands.