Blue whales are the largest animals that have ever existed on Earth โ larger than any dinosaur that ever lived. This animal, which can reach a length of 30 meters and weigh 200 tons, requires a biological system of appropriate scale, and no organ is more amazing than its heart.
The heart of a blue whale can weigh almost 200 kilograms โ equivalent to the weight of two full-grown humans. Its size is approximately that of a Mini Cooper car โ large enough for a human to crawl into its main pumping chamber. It is the largest heart ever recorded in any animal.
This large heart pumps blood through a network of blood vessels that is also of gargantuan scale. The blue whale's aorta โ the largest blood vessel that carries blood from the heart โ has a diameter of about 23 centimeters. A full-grown human could fit their entire body through this blood vessel if it were flexible and elastic enough.
However, despite its enormous size, the blue whale's heart beats very slowly โ between 2 to 8 times per minute when the animal is diving. This contrasts with the human heart rate, which is approximately 60-100 times per minute. When a blue whale dives, its heart rate can drop to just 2 beats per minute in an amazing diving bradycardia process, allowing it to dive deeper and longer by using oxygen more efficiently.
The sound of a blue whale's heartbeat can be heard from a distance of up to 3 kilometers with the right detection equipment โ a deep and slow sound like that of a giant's pulse.