Killer Whales Create Waves to Wash Seals Off Ice Floes
Posted on March 30, 2011
NOAA's Fisheries Service scientists studying the cooperative hunting behavior of killer whales in Antarctic waters discovered that the animals favor one type of seal (Weddell seals) over all other available food sources. The findings were reported in a study published in the journal Marine Mammal Science. The researchers also discovered that the killer whales hunt together and create waves to wash their victims off the ice.
Researchers Robert Pitman and John Durban from NOAA's Southwest Fisheries Science Center in La Jolla, Calif., observed killer whales hunting in ice floes, off the western Antarctic Peninsula during January of 2009. The whales were observed deliberately creating waves to wash seals off ice floes and into the water where they could be eaten. The whales (in groups as large as seven) charge the ice floe creating a wave that either washes the seal off the ice or breaks the ice into smaller pieces.
Once the seal was washed off the ice, the killer whales worked as a group to keep it from escaping onto another ice floe. The researchers say the whales tried to confuse the seal by causing turbulence in the water with their flukes and blowing bubbles under the water through their blowholes. The whales also tire and drown the seal by pulling it under water by its hind flippers.
Once the seal has succumbed from exhaustion, the researchers say it is usually divided up among the pod members underwater. The researchers said, "In most cases, little of the seal's remains float to the surface, but in one instance the carcass rose to the surface and appeared to have been methodically skinned and dismembered before being eaten."
The researchers also noticed Weddell seals were the killer whales' primary target, despite the availability of other prey species. Killer whales appear to have a big preference to hunt and eat Weddell seals.
The research conducted on killer whale cooperative hunting methods will be the subject of an upcoming documentary by the British Broadcasting Corporation entitled, Frozen Planet.