The Heart of a Blue Whale Is the Size of a Golf Cart

Powering the largest animal ever to have lived requires an engine of truly epic proportions. The blue whale's heart is a biological marvel, a muscular pump weighing up to 1,300 pounds that must circulate around 6,000 gallons of blood throughout a body that can stretch nearly 100 feet. Its main artery, the aorta, is so wide that a human could theoretically crawl through its walls, a testament to the immense volume of blood it transports with every single, powerful contraction. This scale is a direct evolutionary response to the demands of such a colossal body, ensuring oxygen can reach the furthest tips of its flukes and flippers.

The rhythm of this massive heart is just as remarkable as its size. For many years, scientists could only study the anatomy of beached whales, but recent technological advances have allowed them to monitor living ones. By attaching temporary electrocardiogram (EKG) sensors via suction cups, researchers discovered that a blue whale’s heart rate is incredibly variable. While at the surface, it may beat up to 34 times per minute, but during deep dives for food, it can slow to an astonishingly low two beats per minute. This extreme slowdown is a critical adaptation for conserving oxygen in the crushing depths of the ocean, and the force of each beat is so great that its pulse can be detected by sonar from two miles away.