“I have once come across audible vocalisation reminiscent of recordings, again in a captive giraffe,” he says. John Doherty, at Queen’s University Belfast, studies giraffes in Samburu Reserve in northern Kenya. But vocalisations in other species with similar social structure is known to convey information about things like age, gender, sexual arousal, dominance or reproductive states, she says.
Unfortunately, Stöger says, she and her colleagues were not able to observe the giraffes mid-hum, so we don’t know about the behaviours associated with the sounds. Alternatively, it could be a way for giraffes to communicate with each other in the dark, when vision is limited, to say, “hey, I’m here”, she adds. “It could be passively produced – like snoring – or produced during a dream-like state – like humans talking or dogs barking in their sleep,” she says. Why the humming?īashaw says she can imagine a few potential roles for this humming. “This new vocalisation could add a piece to that puzzle,” she says. Giraffes have a socially structured system, and for a long time scientists have been trying to figure out how they communicate, says Meredith Bashaw at the Franklin & Marshall College in Lancaster, Pennsylvania. Stöger and her colleagues say the hum varies in duration and contains a rich combination of notes. That’s not infrasound – we can still just about hear it unaided. The “hum” turned out to be a low frequency sound, of about 92 hertz. “I was fascinated, because these signals have a very interesting sound and have a complex acoustic structure,” she says.
Others have suggested giraffes use low frequency “infrasonic” sounds – sounds below the level of human perception – much like elephants and other large animals do for long-range communication.Īfter reviewing almost 1000 hours of sound recordings in three European zoos, Angela Stöger at the University of Vienna, Austria, found no evidence of infrasonic communication – but she did pick up a weird humming coming from the giraffe enclosures in all three zoos at night. People had earlier speculated that giraffes are unable to produce any substantial sounds because it is physically difficult for them to generate sufficient airflow through their long necks to produce vocalisations. We are familiar with many animal sounds – a lion’s roar, a dog’s bark, a parrot’s squawk – but what sound comes to mind when you think of a giraffe? The long-necked beasts make basic sounds like snorts or bursts through their nose, but nothing you could identify with a nice label – until now.īiologists say they have discovered that giraffes hum.
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