There are about 37 species of dolphins in the ocean. A group of dolphins is called school of dolphins or pod of dolphins. A school may consist of 12 – 1000 dolphins. They can swim up to a speed of 40 km/hr. Though the dolphins live in the oceans, they are not classified as fish. They are indeed mammals. Unlike fish, they breathe air through their lungs. That is why they frequently make trips to the surface of water to catch a breath. They also have a blowhole on the top of a dolphin’s head that acts as its nose. They give birth to live young one rather than laying eggs.
Dolphins are better known for their intelligence and playfulness. They are trained by humans in the zoos or aquariums and also used in research activities. Adults and children would not afford to miss a dolphin show where the mammals happily play with a ball. They are highly social creatures and talk to each other by emitting various sounds. They feed mainly on fish, squids and crabs. Dolphins can recover from critical injuries such as shark bites very quickly.
Dolphins sleep somewhere close to the water surface so that they get some air to breathe. Sometimes only their blowholes and surrounding areas are brought to surface while the other parts remain hidden. They need to be conscious about breathing even while sleeping. They sleep with one eye open, one side of the brain active while the other side rests. The active side of the brain is what controls breathing and its movements.