Bangladeshi Dolphin a toothed whale that is related to the porpoise. The dolphin has a long, streamlined body and some species have a prominent beaklike snout. The dolphin travels in schools and can swim at a speed of up to 25 mph (40 km/h). After a gestation period of one year, the female gives birth to one young. The young suckles for up to two years in bay of bangle waters and rivers in Bangladesh. Dolphins are cetacean mammals closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from 1.2 m (4 ft) and 40 kg (90 lb) (Maui's dolphin), up to 9.5 m (30 ft) and 10 tonnes (9.8 long tons; 11 short tons) (the orca or killer whale). They are found worldwide, mostly in the shallower seas of the continental shelves and are carnivores, eating mostly fish and squid. The family Delphinidae, the largest in the order Cetacea, evolved relatively recently, about ten million years ago during the Miocene.
Bottlenose dolphins are well known as the intelligent and charismatic stars of many aquarium shows. Their curved mouths give the appearance of a friendly, permanent smile, and they can be trained to perform complex tricks. In the wild, these sleek swimmers can reach speeds of over 18 miles (30 kilometers) an hour. They surface often to breathe, doing so two or three times a minute. Bottlenose dolphins travel in social groups and communicate with each other by a complex system of squeaks and whistles. Schools have been known to come to the aid of an injured dolphin and help it to the surface. Bottlenose dolphins track their prey through the expert use of echolocation. They can make up to 1,000 clicking noises per second. These sounds travel underwater until they encounter objects, then bounce back to their dolphin senders, revealing the location, size, and shape of their target.
When dolphins are feeding, that target is often a bottom-dwelling fish, though they also eat shrimp and squid. These clever animals are also sometimes spotted following fishing boats in hopes of dining on leftovers. Bottlenose dolphins are found in tropical oceans and other warm waters around the globe. They were once widely hunted for meat and oil (used for lamps and cooking), but today only limited dolphin fishing occurs. However, dolphins are threatened by commercial fishing for other species, like tuna, and can become mortally entangled in nets and other fishing equipment.
Swimming upside down may also help the dolphins see. Even though their eyes are small, these dolphins do have good eyesight. But their puffy cheeks may be a problem. It’s hard to look down over those cheeks! The dolphins may be able to see prey better while swimming on their backs. A sleeping dolphin usually rests at or near the surface of the water. That way, the dolphin is not too far from the air it needs to breathe.
A sleeping dolphin usually has one eye closed. The dolphin’s breathing rate slows down. Still, it seems to be aware of the fact that it is breathing. When you sleep, you are not aware of your breathing. You don’t need to be conscious in order to breathe. But many scientists think that dolphins do need to be conscious. River dolphins usually live in fresh water or in water that is only slightly salty. Sundarban river dolphins may be bright pink, bluish-gray, or off-white in color. They have humps instead of dorsal fins. And they have long, narrow beaks that they use for feeding.