Put 22 elephants on one side of a balance scale and the blue whale on the other, and the blue whale will weigh more. It is the largest and heaviest animal that has ever existed. Each day, it eats 2 ton of small shellfish called krill. Even though it so big and heavy, the blue whale can jump out of the water, swim on its back, and dive very deep. What's more, this heavyweight swims at speeds of up to 20 miles per hour. When whalers got fast boats and harpoon guns, blue whales became major targets. As a result, these giant whales became very rare. Today, there is an international ban on hunting them and all other whales. This ban is working, but it may be to late.

Once found in all the oceans, the blue whale today lives in the Antartic waters. In winter, it travels north, but it avoids the tropical regions. The mating season is around July. There is usually only 1 offspring. Born in the ocean, the calf knows how to swim and dive as soon as it is born. For the first 6 months, it eats 150 pounds each day of a very thick milk that is produced by its mother's body.

Blue whales are part of a family of whales called rorquals. After the blue whale, the most familiar rorqual is the humpback whale, frequently seen on whale-watching expeditions off America's east coast or off Hawaii. It is also famous for its songs, which have been recorded and featured on record albums.