The blue whale holds the distinction of being the largest animal known to have ever existed on Earth. Reaching lengths exceeding 100 feet and weighing up to 200 tons, this colossal marine mammal navigates the vast oceans. Its anatomy reveals how internal systems are adapted to support its scale, particularly one organ that stands out for its magnitude.
The Astonishing Scale of the Blue Whale Heart
The heart of a blue whale is an organ of remarkable proportions, reflecting the immense size of the animal it serves. This powerful muscle typically weighs around 400 pounds (approximately 180-200 kilograms) and can stand up to five feet tall. Its size is often compared to that of a small car or a golf cart. For a human, whose heart weighs about one pound, the blue whale’s heart represents an immense scale.
The major arteries branching from this colossal heart are also impressive. The aorta, the largest artery, can measure about 9 inches (23 centimeters) in diameter. While popular anecdotes suggest a human could swim through these vessels, they are comparable to the size of an infant or small child. With each beat, this powerful heart can pump approximately 60 gallons (about 220 liters) of blood throughout the whale’s massive body.
Powering a Colossal Body: Function and Significance
The blue whale’s massive heart is adapted to meet the physiological demands of its enormous body and deep-diving lifestyle. Unlike human hearts, which beat between 60-100 times per minute, a blue whale’s heart rate varies dramatically depending on its activity. At the surface, its heart rate typically ranges from 25 to 37 beats per minute. However, during deep dives, this rate can slow considerably, often dropping to between 2 and 10 beats per minute, with recordings showing lows of just two beats per minute.
This ability to slow its heart rate, known as bradycardia, is an adaptation for conserving oxygen during prolonged underwater excursions. The blue whale’s aortic arch, a part of the heart that moves blood to the body, possesses an elasticity that allows it to continue contracting and maintaining some blood flow between these slow beats. This mechanism helps ensure that blood and oxygen reach distant tissues even when the heart is beating minimally.
Compared to other large mammals like the African elephant, whose heart weighs around 44-66 pounds, the blue whale’s heart is much larger, supporting a body mass that can be many times greater.