Orcas are the largest dolphin, and the largest delphinoid. Their distinctive black and white markings and tall dorsal fins make them instantly recognizable. Often called killer whales, orcas will prey on large marine mammals from seals to other dolphins to baleen whales. Not all orcas eat other mammals, some populations eat entirely fish, while others specialize in seals, or whales. There is some evidence that orcas may actually comprise several different species that look identical but do not interbreed.
Orcas live in matrilineal groups of about half a dozen related individuals. Several matrilines may form loose affiliations as a larger pod for a time. Orcas have a complex social structure, with strong bonds and cultural traditions passed down through the generations. Populations of orcas with similar habits and dialects, made up of many pods, are known as clans.
Orcas are known for their curiosity, playfulness, and high intelligence. They exhibit good problem solving skills, which can include cooperating with humans (for example, hunting whales in cooperation with whalers) or foiling them (for example, stealing fish from their lines and nets). There are reliable records of unprovoked attacks by wild orcas on humans, but they are very rare. On the other hand, captive orcas can be quite dangerous to their handlers.