Despite their immense size and their communal nature, giraffes aren’t known for being particularly talkative. In fact, they are pretty much silent most of the time. But these gentle giants do make the occasional vocalization, and it’s not what you would expect.
Before we dive into the complexities of giraffe vocalization, it’s worth mentioning that yes, there is anecdotal evidence that giraffes make sound, though it’s not yet known if these sounds are used as a form of communication. While they have been known to snort, grunt, hiss, and even moo, hearing these sounds is incredibly rare – instead, these lanky introverts appear to be opting for a more complex form of dialogue.
Due to their suspiciously quiet nature, much of the research into giraffe vocalization worked under the assumption that they are able to communicate using infrasonic sound. Many large animals from sub-Saharan Africa, like elephants and some large cats, use infrasonic sound to communicate within their groups.
Infrasonic sound is produced at a lower frequency than the lower limit of human hearing. While humans typically can’t hear below 20 hertz, sound is considered to be infrasonic when it occurs between 1.5 hertz and 20 hertz.
A longitudinal study into giraffes’ infrasonic abilities was published in 2013 and claimed that giraffes produce infrasonic vocalizations using Helmholtz resonance – picture blowing across the neck of a bottle. Researchers observed both audible and inaudible vocalizations that coincided with movements of the head and neck. They were also only observed producing these sounds when in close proximity to one another, suggesting the noises were an intentional form of communication.
The specific shape of the giraffes’ necks during these movements is what led the researchers to believe the sound was produced using Helmholtz resonance. But these ridiculous necks are also thought to be the reason giraffes prefer to remain silent.
While giraffes do have a larynx, or voice box, their small lung capacity and narrow trachea make it difficult to produce enough airflow to vibrate their vocal cords. That combined with the fact that air has to travel between 2 and 2.4 meters (6.6-7.9 feet) down their ridiculous neck means that choosing not to speak is usually a lot easier.
In an interesting contradiction to the 2013 study, however, came research published in 2015 that claims giraffes in fact don’t use infrasonic sound, or at least not perceivably often, instead opting for a midnight hum.
The study was conducted across three European zoos and collected over 947 hours of audio recordings. By analyzing the animals’ acoustic signals, the team found no evidence for infrasonic communication, but they did catch the giraffes using a humming noise to communicate with their herd.
A total of 65 harmonic, sustained, and frequency-modulated humming vocalizations were observed occurring at night, with an average frequency of 92.01 hertz. Though it is unclear what these vocalizations were communicating, the team speculate that giraffes may be using visual communication during the day, switching to audible communication at night when their vision is impaired.
However, much of the research into how giraffes communicate is contradictory and needs further investigation, so as of yet we don’t have a definitive answer to the question “what does the giraffe say?”.