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Learn More
In Learn More the National Geographic magazine team shares some of its best sources and other information to expand your knowledge of our featured subjects. Special thanks to the Research Division.
Vanishing Sea Ice
By Neil Shea, National Geographic Staff

Did You Know?

Like hippos, walruses are sometimes thought of as blubbery lumps—content to eat clams, lie on chunks of ice, and soak up the sun. But the big beasts can move rapidly through the water and aggressively defend their territory against intruders—including polar bears and humans in boats. They’ve also been known to eat more than shellfish.

Walruses usually consume mollusks and other invertebrates found in bottom sediments, their mustache of facial bristles helping them detect prey. But scientists and travelers have observed walruses killing seals and sometimes ducks, ripping them to pieces in their powerful jaws. No one is sure what drives the walrus to hunt other mammals and birds. It seems seal hunting is generally the domain of older, larger males, and seal meat does not appear to be a major source of protein for most walruses. It’s possible that walruses could stalk seals to augment their diets when shellfish are less plentiful—or it could merely be one more adaptation in a realm where extreme cold makes every mouthful, no matter what it comes from, count.

Related Links


  • Arctic Climate Impact Assessment.” Cambridge University Press, 2005.
  • Intergovernment Panel on Climate Change. "Climate Change 2007: The Physical Science Basis. Summary for Policymakers." United Nations World Meteorological Organization and Environment Program, February 2007.
  • Lopez, Barry. Arctic Dreams. Bantam Books, 1986.
  • Richter-Menge, J., and others. “State of the Arctic Report.” National Oceanic and Atmospheric Administration, 2006.

NGS Resources

  • Del Giudice, Marguerite. “Arctic Dreams & Nightmares.” National Geographic (January 2007), 130-49.
  • Geiger, Beth. Earth's Changing Land. National Geographic Books, 2006.
  • Johnson, Rebecca. Antarctic Adventure. National Geographic Books, 2006.
  • Ehrlich, Gretel. “Last Days of the Ice Hunters.” National Geographic (January 2006), 78-101.
  • Kramer, Nash. Ice. National Geographic Books, 2005.
  • Holland, Jennifer Steinberg. &ldquoNorthern Exposure.” National Geographic (January 2004), 100-17.