The giraffe is one of the world’s most recognizable animals, known for its towering height and distinctive patterned coat. While its silhouette is familiar across the African savanna, the physiological and behavioral adaptations that allow this mammal to thrive are complex. This exploration highlights five extraordinary facts about the giraffe, covering everything from its circulatory system to its communication habits.
The Unique Physiology of the Long Neck
The giraffe’s neck, despite its length, contains only seven cervical vertebrae, the same number found in almost all other mammals, including humans. This immense vertical distance requires a specialized circulatory system to ensure blood reaches the brain against gravity. Consequently, the giraffe maintains high blood pressure, nearly double that of an average human.
Maintaining this pressure requires a powerful heart, which can weigh up to 25 pounds. Mechanisms prevent the animal from fainting or suffering brain damage when it lowers its head to drink. When the head is down, a dense network of small arteries and veins, known as the rete mirabile, acts as a pressure regulator. This “wonderful net” increases resistance to blood flow, slowing the rush of blood to the brain and protecting cerebral tissue from the sudden change in hydrostatic pressure.
Sleep Patterns and Behavior
Giraffes possess some of the shortest sleep requirements among all mammals. They average less than two hours of sleep per day, broken up into numerous short naps lasting only a few minutes each. This intermittent rest allows them to remain vigilant, ready to react quickly to predators.
Most of their resting is done standing up, an alert posture that minimizes the time needed to flee. To achieve deep, rapid eye movement (REM) sleep, a vulnerable state, a giraffe will lie down with its legs folded beneath its body. It then curls its neck backward, often resting its head on its rump. This deep rest is only taken in short bursts, balancing the need for restorative sleep with the imperative for safety.
Ossicones and Their Purpose
The bony, horn-like structures atop a giraffe’s head are not true horns or antlers but are called ossicones. They are formed from ossified cartilage that remains covered in skin and fur throughout the animal’s life. Ossicones are present on both males and females from birth, initially lying flat and fusing to the skull later in life.
In males, the ossicones become thicker and serve as powerful weapons during dominance contests, where males engage in ritualized “necking” combat. The impact often rubs the fur from the tips of the male ossicones, leaving them bald. Beyond combat, the structures are highly vascularized, containing a dense network of blood vessels that scientists believe function in thermoregulation, helping the giraffe dissipate excess heat.
Surprising Communication Methods
For a long time, the giraffe was considered nearly silent, as its great height and long trachea were believed to make vocalization difficult. However, acoustic research confirmed that giraffes are not mute and communicate using specific, low-frequency sounds. The most notable vocalization is a sustained, harmonic humming sound that occurs at night.
Recordings show this nocturnal hum registers at an average frequency of approximately 92 hertz, within the lower range of human hearing. The exact function of this humming is still being investigated, but researchers hypothesize it may be used to maintain contact or coordinate movement within the herd when low visibility limits visual communication.
The Specialized Tongue
The giraffe’s prehensile tongue is an adaptation allowing it to navigate the thorny branches of acacia trees. This organ can reach up to 53 centimeters (21 inches) long, acting as a grasping tool to strip leaves from vegetation. The tongue’s toughness is aided by thick, protective papillae, which shield it from sharp thorns.
The unusual bluish-black or purple coloration of the tongue is another specific adaptation. This dark pigment is caused by a high concentration of melanin, the same compound that protects human skin from ultraviolet radiation. Since giraffes spend many hours feeding with their tongue extended into the sunlight, the melanin is believed to act as a natural sunscreen, protecting the tissue from UV damage.