The biggest heart in the animal kingdom can be found in the sea—appropriately belonging to the world’s largest animal, the blue whale. A blue whale’s heart weighs up to 400 pounds and can rival the size of a small car! A whale’s heart only beats about six times per minute— pretty remarkable considering a human heart beats about 70 times a minute.
On the flip side, it’s the fairyfly that holds the coveted title of having the tiniest heart. In fact, it’s so small, you need to use a microscope to see it. This heart is shaped like a tube and runs along the fly’s back. Fairyflies are a type of chalcid wasp, found in temperate and tropical regions throughout the world.
Blue whales may have the largest hearts and fairyflies may have the smallest, but pythons’ hearts actually grow and shrink. After eating large meals, particularly those with high amounts of fatty acids, pythons’ hearts can up to double in size! This allows the heart to pump more blood for food digestion.
And while a seal’s heart typically beats about 100 times per minute, it can slow down to beat as few as ten times per minute when the seal is diving deep in the ocean in search of food. This slower heart rate allows the seal to save oxygen and hold its breath for up to 30 minutes! Other animals, like emperor penguins and manatees, are also able to slow their heart rates down to stay underwater longer.
These aren’t the only amazing animal hearts! Learn more about the octopus’s three hearts!