Photo credit: pixabay.com

New research shows that giraffes aren’t as tight-lipped as we thought — as night falls, they burst into a harmony of humming.

We have specific words to describe the sounds made by all kinds of animals, but nothing really comes to mind when you consider the giraffe. At most, people have only ever heard giraffes snort through their nostrils. In fact, zoologists have speculated that their long necks make it hard for giraffes to generate enough airflow all the way from lungs to mouth to vibrate their vocal chords. But scientists from the University of Austria now have evidence that giraffes do indeed make noise — we just never paid close enough attention.

Angela Stoger’s team of researchers had faith in the giraffe’s vocal abilities, so they spent eight years recording almost a thousand hours of audio from giraffes at three zoos. If that sounds like a strenuous task, the researchers would agree. “As expected, exploring giraffe vocal communication turned out to be time consuming, tedious and very challenging,” the authors wrote in their paper. But the work paid off — they discovered that the giraffes produce a deep, spooky humming noise, almost like tantric chanting.

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They found a distinctive pattern of harmonic humming at an average frequency of 92 Hz, but only at nighttime. Although this frequency isn’t low enough to be considered “infrasonic,” or below the range of human hearing, the recordings still came as a surprise to zookeepers and giraffe managers. In fact, the strength of their humming exceeded expectations based on the giraffe’s lengthy windpipes, and the data may challenge our existing knowledge of giraffe physiology.

The hum’s varying duration and combination of notes may represent a rich form of communication. According to Meredith Bashaw at the Franklin & Marshall College, giraffes have a complex social structure that would normally require some type of communication. The humming could be an intentional communication used when darkness impairs their vision — a way of alerting each other of their presence. The authors of the study noted that in each zoo, at least one of the giraffes had been separated from the others.

In order to really pinpoint the reasons behind giraffe vocalization, researchers need to observe the giraffes’ behavior as they hum, which will require intense night-vision instruments. It’s possible that they’re simply singing themselves to sleep, given the meditative and rhythmic quality of their humming. Or we may discover that giraffes have a culture of elaborate nocturnal symphonies. The paper concludes that we still know very little about giraffe behavior and society, and tuning in to their vocalizations could reveal stunning insights.

You can listen to the mysterious humming in this video: