The blue whale is the largest animal on the planet, and the heaviest known to have ever existed, weighing as much as 200 tons - for reference, that's approximately 33 elephants. Their heart is the size of a Volkswagen Beetle. Their stomach can hold up to one ton of krill, and they need to eat four tons a day to survive. As the loudest animal on Earth, with their calls reaching up to 188 decibels - louder than a jet engine at 140 decibels. Their sub frequency whistle can be heard several hundred miles away and is likely used to attract other whales.