The killer whale (Orcinus orca), also referred to as the orca whale or orca, and less commonly as the blackfish or grampus, is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. Killer whales are found in all oceans, from Arctic and Antarctic regions to tropical seas. Killer whales have a diverse diet, although individual populations often specialize in particular types of prey. Some feed exclusively on fish, while others hunt marine mammals like pinnipeds, and even large whales. They have been known to attack baleen whale calves. Killer whales are regarded as apex predators, lacking natural predators.Killer whales are highly social; some populations are composed of matrilineal family groups which are the most stable of any animal species. Their sophisticated hunting techniques and vocal behaviours, which are often specific to a particular group and passed across generations, have been anthropomorphically described as manifestations of culture. The IUCN currently assesses the orca's conservation status as data deficient because of the likelihood that two or more killer whale types are separate species. Some local populations are considered threatened or endangered due to prey depletion, habitat loss, pollution (by PCBs), capture for marine mammal parks, and conflicts with fisheries. In late 2005, the "southern resident" population of killer whales that inhabits British Columbia and Washington state waters were placed on the U.S. Endangered Species list. Wild killer whales are not considered a threat to humans, but there have been cases of captive orcas killing or injuring their handlers at marine theme parks. Killer whales feature strongly in the mythologies of indigenous cultures, with their reputation ranging from being the souls of humans to merciless killers.