The giraffe is the world’s tallest land mammal. For centuries, the towering animal was popularly believed to be virtually silent, communicating only through body language. This perception is a misconception, as giraffes possess a complex, though infrequent, vocal repertoire. Their sounds range from sharp, audible warnings to mysterious, sustained low-frequency tones. Scientific investigation has begun to uncover the surprising nature of their unique communication system.
Range of Audible Daytime Sounds
Giraffes produce a variety of distinct sounds typically used for immediate, short-range communication. These sounds are sporadic and tied to specific behavioral contexts, but are generally high-frequency enough to be heard by humans. A sharp snort is often used as a signal of alarm or warning, alerting nearby giraffes to a perceived danger.
During aggressive interactions, males may emit grunts, moans, or hissing sounds, especially when challenging a rival for dominance or mating rights. A loud, forceful cough is a specific male vocalization sometimes observed during courtship rituals. Female giraffes use loud bellows and whistle-like cries when a mother is separated from or searching for her calf.
Young calves produce bleats and mews, which are similar to the sounds made by goats and sheep. These higher-pitched vocalizations allow mothers and offspring to maintain acoustic contact, particularly when visual cues may be temporarily obscured.
The Mystery of Nocturnal Humming
The most scientifically compelling discovery about giraffe vocalization centers on a sustained, low-frequency sound that occurs almost exclusively after dark. In a significant 2015 study, researchers analyzed nearly 1,000 hours of audio recordings collected from giraffes in European zoos. This extensive acoustic monitoring revealed a previously undocumented sound: a harmonic humming.
The nocturnal hum is a sustained vocalization with a rich, complex acoustic structure, recorded at an average frequency of approximately 92 hertz. This frequency is at the lower end of the human hearing range. Researchers noted that these humming episodes were concentrated during the nighttime hours, suggesting a potential communicative function when visual contact is limited.
One leading hypothesis proposes that this sustained humming serves to maintain cohesion among herd members in the dark. Since giraffes rely heavily on eyesight for communication during the day, a vocal mechanism would help monitor locations and ensure the group stays together overnight. Alternatively, the sound could be a passive physiological byproduct, similar to a snore or a sound made during a deep state of rest. Further studies employing video and audio correlation are necessary to definitively link the humming to a specific behavior or intent.
Why Giraffes Are Considered Mute
The perception that giraffes are mute stems from a combination of anatomical constraints and behavioral adaptations. A major factor is the sheer length of the neck, meaning the windpipe, or trachea, can measure over 13 feet long. This length presents a significant physiological challenge in generating enough sustained airflow to vibrate the vocal cords and produce loud sounds.
The sounds giraffes make are either extremely infrequent, like daytime snorts and grunts, or they fall on the edge of human perception, such as the low-frequency nocturnal hum. While the hum is low, it is still within the human audible range, yet its quiet nature and low pitch make it easily missed against background noise.
Giraffes also rely heavily on visual communication due to their height and keen eyesight, which allows them to see each other across vast distances of the open savanna. This reliance on visual cues reduces the need for constant, loud vocalizations necessary for other social species.