Blue whales are able to breathe air, but they are very comfortable in the ocean waters where buoyancy helps to support their incredible bulk. These mammals are found in all the world's oceans and often swim in small groups or alone.

A blue whale calf weighs two tons (1,814 kilograms) at birth and gains an extra 200 pounds (91 kilograms) each day of its first year. These giant creatures feed on tiny shrimplike animals called krill.

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Only a few thousand blue whales are believed to swim the world's oceans. They were hunted for many years for their blubber and oil, and they were almost hunted to extinction. They were protected under the 1966 International Whaling Convention and are now considered to be an endangered species.

Blue Whale A blue whale's heart is the size of a small car! Learn more amazing facts about these amazing creatures with National Geographic Kids.