The largest living mammal on earth is a blue whale, or Balaenoptera musculus, as it is known scientifically. They weigh more than 200 tonnes and are about 100 feet long. An elephant weighs more than the tongue of a blue whale. They are carnivorous by nature and eat krill, which are tiny creatures. They could eat up to 4 tonnes of krill in a single day. The Blue Whales underwater appear to be an actual blue color, but when they are above the water's surface, they seem more grayish blue. The blue whale's head is flat and broad, and its long, tapered body widens at the end. Except for the Arctic, they can be found in every ocean in the world. They can hear and talk to the other whale nearly a thousand miles away.