Orcas , also known as killer whales, are toothed whales of the dolphin family found in a wide range of areas, in oceans all over the world. Three distinct subspecies can be distinguished: the resident orcas eat fish and live in large matriarchal groups, the transient orcas eat marine mammals and cetaceans, and travel in smaller less table groups, and little is known about the last type, the offshore orcas. Due to differences in behavior, diet, vocalizations ("dialects") and genetics, scientists have started suspecting these could in fact be three different species entirely. Orcas are highly social animals, with social structures comparable only to that of elephants and higher primates. They can be seen traveling in groups called "pods" formed of one to four matrilineal lines, comprising on average 5.5 animals per line.