Giraffes Hum: The Discovery of Nocturnal Vocalizations

For decades, the giraffe wore a peculiar crown in the animal kingdom: the title of the "silent giant." While lions roared, elephants trumpeted, and birds sang, the world’s tallest land animal seemed to glide through life in utter stillness, communicating only through body language and subtle glances. Visit any zoo, and you might watch a giraffe for hours, waiting for a sound, and hear nothing more than the soft crunch of leaves or the thud of its heavy hooves on the ground.

But silent giants don't really exist. Nature always has secrets waiting to be uncovered. And in 2015, a team of researchers made a discovery that turned everything we thought we knew about giraffes on its head—or rather, on its long, graceful neck.

They hum.

Not loud, not obvious, but hum. A low, rich, humming sound, so subtle that it had been overlooked for centuries. And they do it mostly at night, when the world is quiet and no one is listening.

The Discovery That Shook Zoo Biology

The story begins at the Tierpark Berlin and the Zoo Berlin, two of Europe’s most respected wildlife parks. Biologist Angela Stöger and her colleagues were studying the acoustic behavior of captive giraffes. They placed sensitive microphones near giraffe enclosures, hoping to capture any sounds that a human ear might miss.

For weeks, they recorded. They analyzed hundreds of hours of audio. At first, nothing seemed extraordinary. Then they listened more carefully, filtering out background noise from wind, zookeepers, and other animals.

And there it was: a low-frequency hum, typically around 92 hertz—that's deep, just within the range of human hearing, but easy to ignore. The sound was not constant. It came in bursts, mostly during the night. The researchers published their findings in the journal BMC Research Notes, and suddenly, the "silent" giraffe had a voice.

The hum has been described as a "tonal, rich, and harmonic" sound. Some compare it to a lullaby, others to the distant drone of a didgeridoo. It's not a roar, not a chirp, not a bark. It's something entirely its own, and it was hiding in plain (and audible) sight.

What Does the Hum Mean?

So, why would a giraffe hum at night? Scientists don't have a definitive answer yet, but they have several compelling theories.

Communication in the Dark

Giraffes live in loose, fluid social groups. They don't form tight herds like wolves or elephants, but they do watch out for each other. At night, when visibility is low, visual signals like necking or tail flicks become useless. A low hum could be a way to keep in touch—a "I'm over here" or "everything's fine" signal. It could help mothers find their calves, or allow a group to stay loosely connected while they browse in the dark.

This idea makes sense: many other ungulates (hoofed animals) use low-frequency sounds to communicate over long distances. African elephants, for example, use infrasound—sounds below human hearing—to call across kilometers. Giraffes might be doing something similar, but in a range we can just barely hear.

A State of Contentment?

Another possibility is that the hum is a sign of relaxation or drowsiness. Stöger noted that the sounds often occurred during quiet, resting periods. Could it be the giraffe equivalent of a cat's purr? Or the soft humming a person does while drifting off to sleep?

This is harder to prove, but it's a charming thought. Maybe those long-necked giants are simply humming themselves to sleep under the stars.

A Sexual Signal?

There is also speculation that the hum could be a mating call. In many animals, males produce low, resonant sounds to attract females or to establish dominance. The nighttime hum could be a giraffe's version of a lion's roar or a bird's dawn chorus—a serenade designed to carry through the darkness.

However, the recordings so far suggest both male and female giraffes hum, so it might not be strictly a male behavior. More research is needed.

Why It Matters: Seeing the Unseen

The discovery of giraffe humming is more than a cool fact to share at dinner parties. It's a reminder of how much we still have to learn about the natural world—even about the largest, most visible animals on the savanna.

For a long time, scientists assumed giraffes were silent because they lacked the right vocal anatomy. Giraffes have a larynx (voice box), but it was thought to be too small to produce complex sounds given the long neck. The hum proves that assumption wrong. Giraffes can produce sounds, and they do so consistently.

This matters for conservation, too. If giraffes rely on sound to communicate at night, then noise pollution from roads, cities, or tourism could disrupt their social lives. Understanding their vocal behavior helps us create better environments for them, both in zoos and in the wild, where their numbers are quietly declining. Giraffe populations have dropped by nearly 40% in three decades, a crisis that often goes unnoticed because they seem so ubiquitous. Every new insight into their behavior is a tool for protecting them.

It also opens up a whole new field of inquiry. Now that we know giraffes hum, we can ask: What do they say? Do different groups have regional dialects? Do mother giraffes use a special hum for their calves? Do giraffes in the wild hum more or less than those in captivity? The research has only just begun.

What We Still Don't Know

Science often works this way: a discovery leads to a hundred new questions. The giraffe hum is a puzzle with many missing pieces.

We don't know if all giraffes hum. The study was done on captive animals in two Berlin zoos. Do wild giraffes in the African savanna also hum? Perhaps, but no one has recorded them systematically at night. Wild giraffes are more spread out, and the background noise of insects, wind, and other animals might mask the sound.

We don't know what triggers the hum. Is it a response to something? A specific time of night? A social cue? The Berlin study found that the humming was not associated with any obvious behavior like eating, walking, or fighting. It seemed to happen spontaneously.

We don't know how they produce the sound. Do they use their larynx? Or is it produced by air moving through the long trachea? The mechanics are still mysterious.

We don't know if the hum carries meaning. Is it a simple "I'm here" or does it convey complex information like identity, mood, or intention?

These are the kinds of questions that keep zoologists up at night—and it turns out, they might keep giraffes awake too.

Key Takeaways

• Giraffes are not silent. They produce a low-frequency humming sound, especially at night, that was only confirmed in scientific literature in 2015.
• The hum is a social signal. Researchers believe it is used for communication, likely to keep in touch when visibility is low. It may also be a sign of contentment or part of courtship.
• We are just beginning to understand giraffe communication. The discovery challenges long-held assumptions and opens up new avenues for research on a species that is more complex than we thought.
• This matters for conservation. Understanding giraffe behavior—including their vocalizations—helps us protect them from threats like habitat loss and noise pollution. Giraffe populations are declining, and every insight helps.
• Nature is full of hidden sounds. The giraffe hum reminds us that we often miss the quiet stories happening all around us—if only we take the time to listen.

So next time you visit a zoo, stand quietly near the giraffe enclosure as dusk falls. Don't expect a roar or a trumpet. But if you're patient, and the night is still, you might just catch a whisper from the giants.

Giraffes hum. And now you know their secret.