NOAA’s Fisheries Service scientists discovered that killer whales in Antarctic waters prefer a specific species of seal over all other food choices.
Robert Pitman and John Durban, researchers from NOAA’s Southwest Fisheries Science Center in La Jolla, California, observed killer whales feeding off the west Antarctic Peninsula in January 2009. While documenting the whales’ method of creating waves to wash seals off ice floes, they noticed that the whales targeted Weddell seals over any other available prey, including the more abundant crabeater seals.
“These killer whales would identify and then attack Weddell seals almost exclusively, even though they made up only about 15 percent of the available seal population,” said Pitman.
Multiple whales, sometimes as many as seven, charge the ice floe creating a wave that can either wash the seals off the ice or break the ice into smaller pieces that are more easily attacked. This behavior had only been observed in the Antarctic a few times before. A previous study that included the authors of this study suggested that this distinctive killer whale population, which they call “pack ice killer whales,” is a separate species.
Once the seal is washed off the ice, the whales work together to keep it away from the safety of other ice floes. It appears that the whales try to confuse the seal by disturbing the water; they create turbulence with their flukes and blow bubbles through their blowholes. Eventually the seal is overcome with exhaustion and is divided up among the pod members.
Copyright © 2011 by Marine Science Today, a publication of OceanLines LLC