This creature has a tongue that weighs as much as an elephant and a tail as wide as an airplane. The blue whale is the largest mammal in the world and the largest animal ever known to have lived on Earth. Calves weigh two tons (1,814 kilograms) at birth and gain about 200 pounds (91 kilograms) every day during the first year of their lives.

Blue whales breathe air, but they are at home in the water, where buoyancy helps to support their massive bulk.

These mammals are found in all the world's oceans, swimming in small groups or alone. They often spend the summers feeding in polar waters, and undertake lengthy migrations towards the equator as winter arrives. Migrating blue whales are often spotted off the coasts of California and Mexico.

The blue whale nurtures its massive body with tiny shrimplike animals called krill. It is a baleen whale, and feeds through a comblike strainer of some 400 plates equipped with bristles to ensnare tiny morsels of food as the whale swims. An adult blue whale can eat some 4 to 8 tons (3.6 to 7.3 metric tons) of krill per day.

Only a few thousand blue whales are believed to swim the world's oceans. For many years they were aggressively hunted for their blubber and oil, and their numbers were dramatically reduced. In the 1930-'31 season alone, whalers killed almost 30,000 blue whales. They finally came under protection with the 1966 International Whaling Convention.

Like many large animals, whales reproduce slowly. Females carry their young for a year before giving birth to a single calf.

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