The giraffe has one of the highest blood pressures among mammals, reaching up to 280/180 mm Hg, double that of humans (120/80 mmHg). This exceptional pressure is necessary to overcome the gravitational challenge of delivering sufficient blood and oxygen to the brain, given that the giraffe’s head is typically 2 meters above its heart.
The giraffe’s heart weighs around 11 kilograms and, like all mammals, is divided into two halves: the right and left ventricles, each responsible for circulating blood throughout the body. The right ventricle has the relatively easy task of pumping blood to the lungs.
In contrast, the left ventricle faces the arduous task of propelling blood throughout the rest of the body, including the giraffe’s towering neck and head. To accomplish this remarkable feat, the heart must not only battle gravity but also counter the hydrostatic pressure of the blood already present in the elongated vertical artery, requiring an immense amount of force.
Previously, it was believed that giraffe had significantly larger hearts relative to their body size to generate this force. However, recent research has revealed that the giraffe’s body cavity lacks the space to accommodate a larger heart. Instead, the left ventricle boasts incredibly thick, muscular walls and a small chamber radius, enabling each heartbeat to generate sufficient power to circulate blood effectively.
However, this reduced chamber size presents additional challenges. To ensure adequate blood flow, the giraffe’s heart exhibits an altered electrical rhythm, allowing more time for the left ventricle to fill with blood between beats. Additionally, the average resting heart rate is slightly higher than expected for an animal of its size, ranging from 40 to 90 beats per minute. For reference, this rate is comparable to the average human heart rate (60-100 bpm) and significantly faster than an elephant’s (30 bpm).
In summary, while the giraffe’s heart is not notably larger compared to most mammals, its left ventricle possesses thicker muscles that generate ample force to overcome gravity. The slightly elevated heart rate and altered heartbeat work in tandem to optimize blood filling, resulting in an overall efficient circulatory system.
