The Killer Whale or Orca (Orcinus orca), less commonly, Blackfish or Seawolf, is the largest species of the dolphin family. It is found in all the world's oceans, from the frigid Arctic and Antarctic regions to warm, tropical seas. Killer Whales are versatile and opportunistic predators. Some populations feed mostly on fish, and other populations hunt marine mammals, including sea lions, seals, walruses and even large whales. They are considered the apex predator of the marine world. There are up to five distinct Killer Whale types, some of which may be separate races, subspecies or even species. Killer Whales are highly social; some populations are composed of matrilineal family groups, which are the most stable of any animal species. The sophisticated social behavior, hunting techniques, and vocal behavior of Killer Whales have been described as manifestations of culture.