BLUE WHALE: The blue whale is the largest animal that has ever lived on our planet. The largest measured by scientists, a female, was nearly 100 feet long and weighed over 180 tons. That's as big as a Boeing 737 airplane. It commonly grows to around 80 feet in length and 120 tons in weight. A typical blue whale has a heart the size of a full-grown bison, a tongue the size of an African elephant, a blowhole as wide as a person and an aorta large enough to swim through. Even at birth, the blue whale is enormous, weighing as much as an adult hippopotamus — around three tons. It drinks approximately 100 gallons of fat-rich milk every day for the first seven months of its life, gaining 200 pounds each day, or eight pounds an hour. As an adult, it feeds almost exclusively on tiny, shrimp-like crustaceans called krill, which it filters from the sea with modified teeth called baleen. A feeding blue whale will lunge into a dense group of krill, open its mouth and expand its throat like a giant pouch. It then forces the water back out through baleen plates, which catch the tiny animals. During the summer feeding season, a typical blue whale gorges on 2,000 to 9,000 pounds of food each day. The blue whale is also the loudest creature on our planet. Its low-frequency whistles can be heard for hundreds of miles underwater and are often 40 to 50 decibels louder than a jumbo jet. These powerful, highly structured sounds may help them find food or mates.