How does a giraffe manage such flexibility in its neck, considering it has only seven vertebrae?

Giraffes stand as the tallest mammals on Earth. As they stride across the African savannas with their long, spindly legs, adult male giraffes can soar to a height of 19 feet (6 meters) [source: National Geographic]. But only about half of that height comes from their legs—the rest is all neck. And if that wasn't enough, these giants also have a secret weapon: their tongues, which can stretch up to 18 inches (46 centimeters), helping them reach even the highest leaves [source: San Diego Zoo].

Scientists are still trying to piece together the evolutionary journey that led to the giraffe's long neck. One of the most puzzling aspects is that, despite the great length, a giraffe's neck only contains seven vertebrae—just the same number found in humans and most other mammals.

Many attribute the giraffe's elongated neck to its preference for acacia leaves, which requires the ability to reach the tops of 20-foot (6-meter) trees. Yet, giraffes also spend significant time feeding on grasses and shrubs, especially later in the day, with their legs spread wide apart [source: Dagg and Foster].

Or maybe it evolved to impress the females with shorter necks. Male giraffes, known as bulls, engage in intense neck-to-neck battles to win the favor of a mate. Similar to rams clashing with their horns, the bulls use their powerful necks to deliver devastating blows. In the wild, the fittest—those with the longest and strongest necks—are most likely to prevail.

Whatever the reason, those seven vertebrae are far larger than the ones in our own necks. Each vertebra in a giraffe's neck can measure up to 10 inches (25 centimeters) [source: San Diego Zoo]. This adds up to a heavy load, with the total weight of the neck and head reaching around 600 pounds (272 kilograms) [source: San Diego Zoo].

How do these towering animals support their massive necks and move them with such ease? Keep reading to uncover the secrets behind the mechanics of nature's longest neck.

Anatomy of a Giraffe

Several features of a giraffe's neck contribute to its impressive flexibility, rivaling that of a Slinky. One such feature is the way the cervical vertebrae, or neck bones, are connected. Like humans, giraffes have seven cervical vertebrae. However, theirs are linked by ball-and-socket joints [source: Owen], which are the same types of joints that connect your arm to your shoulder, offering a full range of motion. Additionally, the joint between the giraffe's neck and skull allows it to tilt its head nearly perpendicular to the ground.

As we move down the neck toward the back, we encounter another key anatomical feature that enhances the giraffe's flexibility. The vertebrae in the top portion of our backs are known as thoracic vertebrae. In humans, these vertebrae are fused in the middle, adding stability, while the cervical vertebrae are fused at the front and back for increased mobility. In giraffes, however, the first two thoracic vertebrae are connected in the same way as the cervical ones—by ball-and-socket joints [source: Dagg and Foster]. This provides the giraffe with an extra degree of flexibility and contributes to its iconic hump [source: Encarta].

This highly flexible, yet heavy, neck plays a crucial role in the giraffe's movement. When you observe a giraffe walking, you’ll notice its neck moves in harmony with its stride. This motion, combined with the weight of the neck, helps direct the giraffe's center of gravity [source: Dagg and Foster]. The giraffe also swings its neck to assist in rising to a standing position from its long legs, much like how we use our arms to push ourselves out of bed in the morning.

The giraffe's long neck also means its blood must travel a considerable distance. As a result, giraffes have an extraordinary cardiovascular system that ensures adequate blood flow to the brain and heart, even when the neck and head are in motion. This allows the giraffe to bend down for a drink of water without experiencing a dangerous head rush [source: Dagg and Foster]. Their blood vessels have valves that prevent blood from flowing backward due to gravity [source: Wood and Johansen], and they possess more red blood cells, larger hearts, and tighter skin around their legs, which aid in better circulation [source: Dagg and Foster].

To keep everything running smoothly, the giraffe also breathes at a relatively slow pace. Its large lungs help offset the vast length of the trachea, ensuring air can travel up that long neck with ease.