Dolphins are water mammals. Most dolphins are small in size but belong to whale family. They have white bellies, black backs and their tails look like half moons. They live in large herds and like to follow ships. They feed on squids, crabs, cuttlefish and various types of fish. Dolphins communicate with one another in a unique way to avoid danger. They have friendly nature. There are around 40 species of dolphins across the world. Different types of dolphins include bottlenose dolphin, white-beaked dolphin, killer whale, humpbacked dolphin, etc.