The killer whale or orca is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. Killer whales have a diverse diet, although individual populations often specialise in particular types of prey. Some feed exclusively on fish, while others hunt marine mammals such as seals and dolphins. They have been known to attack baleen whale calves, and even adult whales. Killer whales are apex predators, as there is no animal that preys on them. Killer whales are considered a cosmopolitan species, and can be found in each of the world’s oceans in a variety of marine environments, from Arctic and Antarctic regions to tropical seas—killer whales are only absent from the Baltic and Black seas, and some areas of the Arctic Ocean.