Fact vs. Fiction: Do Giraffes Have Two Hearts?
A giraffe has a lot of space between its chest and head, which is probably the reason so many people wonder if the unique animal has two hearts. National Geographic confirms that these gentle giants are the tallest land mammals in the world. Their necks are 6 feet long on average, which is why they need powerful cardiovascular systems.
Unlike octopus or squid — which do have multiple hearts — giraffes only have one heart. Their anatomy and size require a lot from that single heart, which is part of what makes these animals so interesting.
Giraffes are tall animals, reaching average heights of 14 to 19 feet, with males typically growing taller than females. They weigh anywhere from 1,750 to 2,800 pounds, and their legs are around 6 feet long, similar to their necks. That large amount of body mass requires a large heart to pump blood to the extremities and the head. On average, giraffe hearts weigh around 25 pounds and are approximately 2 feet long, according to the San Diego Zoo.
The Role of the Left Ventricle
Not only is the size of the heart related to the size of the animal, but the size is also an important factor in pumping enough blood up those long necks. Additionally, other anatomical features are even more important in combating gravity than the overall size of the heart.
The right ventricle is one of four chambers of the heart and is responsible for pumping blood to the lungs. The muscle in a giraffe's right ventricle, as noted by the iGiraffe Conservation Foundation (GCF), is around 1 centimeter thick. The left ventricle is the part of the heart that pumps oxygenated blood out to the rest of the body. The muscle wall increases in thickness by 0.5 centimeters for every 15 centimeters in neck length. Africa Geographic estimates that the left ventricle can be up to 7 centimeters thick.
A giraffe’s left ventricle isn't the only thing helping to combat gravity. The heart beats 40 to 90 times per minute while resting or up to 170 beats per minute while running. Even more notable, giraffes have very high blood pressures. GCF estimates that giraffe blood pressure runs around 280 over 180. That's slightly more than twice the optimal blood pressure of humans. Researchers believe this helps pump blood efficiently to the brain.
Circulatory System Adaptations
Discover Wildlife points out that giraffes have a dense network of capillaries that stabilizes their blood pressure and protects them from the negative effects of fast blood pressure changes. They also have valves within their circulatory system to dilate and constrict as necessary. This minimizes the risk of fainting when giraffes stand up quickly or bend their necks for a drink.
Giraffes have tall, slender legs with skin that’s tight and thick. The skin on their legs works much like compression socks and keeps the giraffe's blood pressure stable. It also helps keep the blood pumping through the body instead of pooling in their long legs. According to Live Science, the combination of thick skin and an added muscle in their jugular vein helps carry blood from the head back to the heart.
Other Giraffe Facts
Giraffes only have one heart, but there are plenty of other interesting facts to delight those interested in giraffe trivia. Check out these five fun facts:
- In the wild, giraffes live about 25 years and roam freely on the woodlands and plains of their African home.
- Adult males grow to heights more than three times that of humans, allowing them to scope out the terrain for hyenas and crocodiles, their main predators, according to the San Diego Zoo.
- Giraffes spend anywhere from 16 to 20 hours eating every day and only sleep for five to 30 minutes daily.
- Giraffes eat up to 75 pounds of leaves every day, which also provides most of their hydration, so they only have to drink once every few days in the wild.
- Scientists have identified four species of giraffes: Masai, reticulated, southern and northern.