Physical description and related species
Unlike the baleen whales, orcas or killer whales are 'toothed' whales, with true teeth rather than fibrous plates for filter-feeding. They catch single prey, ranging from fish, squid, penguins, seals, dolphins, porpoises, and even whales, including the largest whale of all, the blue whale.
Usually black and white, in Antarctic waters their skins are covered with a film of plankton called diatoms, which gives them a brownish and yellowish hue.
Male orca whales (9.75 m) grow significantly larger than females (8.5 m). Mature males are obvious due to their very tall dorsal fin.
Orca whales are found almost everywhere throughout the earth's oceans.
Previously thought to live on the outer fringe of the pack ice, we now know that they can live deep in the ice, even in winter.
It was also thought that they migrated away from Antarctica in winter, but there have been some rare sightings of them deep inside the pack ice in the heart of winter. Furthermore, small calves have been sighted in mid winter, indicating that orcas are the only species of whale to breed in Antarctic waters.
They are common in Antarctic waters, with a population estimated at about 70 000.
Conservation status: data deficient
Diet and feeding
Orcas are born into a family group and remain with that group for the rest of their lives. As a result, they form very highly co-ordinated hunting packs, which are comparable to wolves or African wild dogs. Once they decide to tackle a prey animal, it often has little chance of escape.
Large males will often take on the most dangerous jobs when tackling potentially dangerous prey, but females appear to be responsible for teaching hunting techniques to their young.
Recently they were seen herding dolphins against a beach in Southern Tasmania, so they could attack and eat them.
In Patagonia, South America, and at the remote Crozet Islands in the Southern Indian Ocean orca whales have learned to feed on young seals by pursuing them to the water's edge. They will even pursue until they are half out of the water on the beach, they then wriggle back into the water, often with a hapless seal pup in their jaws.
Orca whales appear to use their calls extensively to keep in touch with each other and to coordinate their hunting behaviour.