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. Mature males are obvious due to their very tall dorsal fin. 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.
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.
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. Orcas have been seen herding dolphins against a beach in Southern Tasmania, so they could attack and eat them. And though they are indeed toothed whales, killer whales technically belong to a family of oceanic dolphins. Orcas are the largest members of that family and one of the world's most powerful apex predators, feeding on seals, sea lions, even other whales.
Killer whales hunt in pods comprising up to 40 individual whales. There appear to be both resident and transient orca pods, with resident pods preferring fish while transient pods target marine mammals. All killer whale pods use cooperative hunting techniques similar to wolf packs, and each pod has its own unique noises that its members can recognize. Killer whales use echo-location to communicate and hunt, making sounds that travel through the water until they hit an object and bounce back, revealing the object's location, size, and shape.
Type A killer whales are the largest, reaching up to 9. These orcas prefer to live in open waters of the Southern Ocean, feeding mostly on minke whales. Type B killer whales are pack ice whales that are smaller than Type A killer whales, feeding on Weddell seals they manage to knock off the ice floes. Killer whales do this by using their tails and bodies to create waves that wash the seals into the water.
There is also a smaller variant of Type B killer whales known as Gerlache orcas, named after the Gerlache Strait off the Antarctic Peninsula. These orcas have an unknown diet but have been seen feeding on penguins, and they are usually spotted around penguin colonies. Type C killer whales are known as Ross Sea killer whales, a dwarf species that is the smallest of the three known Antarctic types of killer whale.
Males reach around six meters Ross Sea killer whales are typically seen around eastern Antarctica in thin pack ice. Killer whales from different eco-types don't breed with one another, which is a criterion for being classified as a different species. However, until recently scientists had not proved these different species of orcas in Antarctica existed, as they had not mapped the entire genome of killer whale mitochondria housing their DNA. But in , after sampling killer whales from the North Pacific, North Atlantic, and the oceans surrounding Antarctica, scientists were able to see clear differences between each species of killer whale.
The researchers believe that Type B and C killer whales are genetically similar, because their lineage diverged from other orcas around , years ago — just a moment in evolutionary terms. Type C killer whales are observed to have a specialized diet focusing on Antarctic toothfish, though the exact reason for this is unknown. Killer whales in the Ross Sea, near McMurdo Sound, have been commonly spotted carrying toothfish in their mouths.
A comparison of the nutrient density of toothfish with other prey shows that toothfish represent a higher-energy food source than other Ross Sea fish. Scientists don't know the extent to which toothfish forage or how deep Type C killer whales can dive, but in some studies orcas are estimated as diving to - meters - 1, feet with a maximum of around meters 2, feet. During a pilot project in McMurdo Sound in January , these researchers recorded and photographed three observations of orcas with Antarctic toothfish prey.
Because these observations occurred during the late summer break-up of fast ice over shallow coastal waters, the scientists hypothesized that toothfish are the main prey for Type C killer whales, at least during the summer.
New Zealand and Italian scientists have discovered that Type C killer whales swim 4, km 3, miles from Antarctic to northern New Zealand. The aim of the study was to determine the importance of toothfish and where killer whales feed in the Ross Sea. At the same time, km miles north of Scott Base , Italian whale experts Giancario and Simone Panigada used satellite transmitters on killer whales in Terra Nova Bay to determine orca movements.
Eisert said the two teams hit research gold when they independently verified that Type C killer whales were making long journeys between Scott Base and the warmer waters off Northland, New Zealand. The research team found that the average orca commute took 22 days. The scientists from New Zealand have collaborated with Ingrid Visser from the Orca Research Trust as well as other researchers to create the first open-access photo-ID catalogue for Antarctic killer whales from the Ross Sea.
Photo identification is the main non-invasive research tool used to study orcas. Slight differences in color, nicks on the fins, and scars on the killer whale's body uniquely identify each orca, allowing individual killer whales to be recognized wherever they go. Compilation of killer whale images into catalogues enables researchers to follow individual orcas in time and space, making estimations of their total population size. Visser is also investigating the possibility of hosting a killer whale photo ID on Antarctica New Zealand's digital asset management platform, launched in June,
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