© Hans Hillewaert via Wikimedia Commons

What sound does a giraffe make? Dogs bark, lions roar, cats meow, and giraffes? Well, they have long necks. And they eat leaves. (They also get into intense fights with those long necks.) They can snort and grunt, but they don’t “talk.” Even zoologists didn’t think giraffes could speak.

Giraffes have all the equipment to “talk,” vocalize to use the technical term, but they were considered mute. One theory suggested giraffes’ necks were too long, so they couldn’t produce enough airflow velocity to vibrate the vocal folds and create audible sounds. The air just couldn’t make it all the way up to their mouths and out over their big tongues. And those tongues are big! The snorts and grunts giraffes produce are more like the bursts of air when you sneeze or cough, rather than vocalizations.

Scientists at the University of Vienna thought we might be missing something with the giraffe. This is kind of crazy because people have been acquainted with giraffes for thousands and thousands of years. Researches collected almost 950 hours of audio from giraffes at the Copenhagen Zoo, Berlin Tierpark, and Vienna Zoo. When they started analyzing this data, they discovered a strange noise, which they decided to call a hum.

The hum scientists picked up in this study was a low rumble, near the bottom end of what humans can hear. In these hundreds of hours of audio, researchers identified 65 instances of “humming vocalizations.” These noises are labeled “humming,” but we wouldn’t really call them that. They’re more like a whale song, a fog horn, or a groan. Well, summing up this sound in a word isn’t so easy.

The University of Vienna came up with “humming” because there wasn’t a word in scientific literature for “giraffe speak.” We have a long list of words to describe different animal sounds. But nothing on this list really seems to capture the bizarre noise giraffes make. Hum may not be great, but that’s what we’ve got.

Before the humming discovery, some speculated that giraffes communicated in the infrasonic range–sounds below 20 Hz and outside the human hearing range. (Learn all about them here in our infrasonic episode). This has never been proven, and regardless these hums aren’t infrasonic. They are well in the human range. So if you stand next to a giraffe and it hums, you can hear it. But you might need to be around the giraffe at night. The humming was only detected then. Why, is yet another mystery.

We now know giraffe’s vocalize, but we don’t know much beyond that. The University of Vienna scientists believe giraffes use these hums to communicate. One theory is these so-called hums help a group stay in touch when they can’t see each other, but researchers need corresponding video recordings to make that conclusion.

For right now, we’ll have to just be content knowing that giraffes really do speak. Or rather, hum.

-Episode co-produced by Marylee Williams