The blue whale is the largest animal that has ever lived, and its heart weighs as much as a small car.
Blue whales reach about 30 metres and can weigh close to 200 tonnes, heavier than any known dinosaur. A blue whale heart weighs roughly 180 kilograms.
Why is this true?
Living in water removes the limits that gravity places on land animals, and a diet of tiny krill is available in enormous quantities. A large whale can eat several tonnes of krill a day.
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More about animals
Animals are the easiest place to find facts that sound invented. Three hearts, blue blood, cube-shaped droppings, a punch fast enough to boil water for an instant — every one of these is ordinary biology to the animal doing it. The collection here leans on well-documented behaviour and anatomy rather than folklore, so each entry comes with a short explanation of why the trick actually works and a source you can read next.