Dolphins are intelligent marine mammals that inhabit every ocean of the world and are very closely related to whales and porpoises. There are 33 known species of marine dolphins and another four species of dolphins that live in both the ocean and in rivers. The most commonly known dolphin is the bottlenose dolphin, while species such as the killer whale and pilot whale are not really whales at all, but dolphins.
Dolphin species are often characterized by where they are found. For example the Atlantic white-sided dolphin, Atlantic hump-backed dolphin and Atlantic spotted dolphin are all found in various parts of the Atlantic ocean.
Some dolphin species are named after the individuals who either first described them for the scientific community or discovered them. Such dolphins include the Commerson's, Heaviside's, Hector's, Risso's and Fraser's dolphin.
Killer whales are the largest members of the dolphin family. Some can grow to a length of 32 feet and weigh as much as nine tons.
Bottlenose dolphins are found across the globe in tropical and temperate waters, staying clear of colder temperatures around the polar regions. Featured in the television series "Flipper" in the 1960s, these mammals are the most frequently seen dolphins along the coast of the U.S.
Dolphins are social creatures, living in groups of several members known as pods. Dolphins communicate with each other with sounds such as whistles and clicks.