Killer Whales in the Antarctic Prefer Weddell Seals

Written by on April 22, 2011 in Marine Life
Killer Whales and calf in the Ross Sea

Killer Whales and calf in the Ross Sea

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.

Illustration by Matt Rosen. www.cartoonsbymatt.deviantart.com

Illustration by Matt Rosen. www.cartoonsbymatt.deviantart.com

 

Copyright ©  2011 by Marine Science Today, a publication of OceanLines LLC

About the Author

About the Author: Emily Tripp is the Publisher and Editor of MarineScienceToday.com. She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .

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