Blue whales weigh approximately 200 tons and can grow to a length of between 82 and 105 feet. They are the largest mammals to have ever lived on earth.
The heart of an adult blue whale alone can weigh as much as a car. Blue whale calves are born already weighing 3 tons and at a length of about 25 feet. A blue whale calf gains about 200 pounds every day for the first year of its life. Blue whales reach this enormous size with a diet comprised mostly of tiny animals called krill, which they eat at a rate of up to four tons per day.