Big Blue, king of the Seas The biggest living animal in the world is the blue whale. It weighs about 150 tons, the same as 40 big trucks. It is over 30 meters long, the length of three buses one behind the other. Just the whale's tongue weighs 3.8 tons, and its heart is about 450 kilograms. A baby blue whale weighs more than 3 tons when it is born, and gains 90 kilors a day during its first year. An adult whale eats between 900 and 4,100 kilograms of food each day. The whale swims slowly through the water with its mouth open, and thousands of tiny fish and plankton swim into it. But the whale can't swallow anything larger than a shrimp. Whales live in the water, but they are not fish. They are mammals, and they cannot stay under water for too long. Blue whales can dive for an hour, to a depth of 105 meters, but they need to come to the surface to breathe. When thay come to the surface, they blow a wet stream 8 to 10 meters up in the air. Blue whales are the loudest animals on Earth. Their call is louder than a jet, and it can travel for hundreds of miles in the ocean. They use their calls and songs to communicate with other blue whales.