Monkeys are the world's best yodelers, and that includes humans

Latin America’s rainforest inhabitants have long surprised scientists with their varied calls. Now, research shows that when it comes to yodeling, some monkeys outperform even the famed Alpine singers of Austria and Switzerland.

This work provides fresh information about primate vocal abilities and offers new clues about how their unique anatomy shapes the way they produce sounds.

Experts from Anglia Ruskin University (ARU) and the University of Vienna spearheaded the study, which examined monkeys’ intricate calls through a mix of CT scans, computer simulations, and field observations.

The findings indicate that special throat structures called vocal membranes – once present in human ancestors – give these animals an extra gear for producing surprising frequency shifts.

Understanding yodeling – the basics

Yodeling is that wild, echoing singing style where the voice flips rapidly between a low chest voice and a high head voice. It started in the Swiss Alps as a way for herders to communicate across mountains.

Yodeling works by quickly switching between two vocal registers: the chest voice (your normal speaking or singing voice) and the head voice (a lighter, higher voice often used for falsetto).

That flip between the two is called a register break, and it creates the signature “yo-de-lay-ee-hoo” sound.

Instead of smoothing over the transition like most singers try to do, yodelers emphasize it -leaning into that sudden, jumpy switch to create the bouncing, echo-like effect.

Physically, it’s all about control and timing. The vocal cords stretch and tighten to hit those high head voice notes, then loosen again for the chest voice.

It takes breath support from your diaphragm, clear enunciation, and a bit of vocal agility to bounce back and forth fast enough.

Yodeling monkeys and vocal membranes

Primates such as monkeys and apes have thin vocal membranes above their vocal folds, which humans lost over time. Researchers have long wondered how these membranes benefit non-human primates.

The new study shows that these delicate tissue bands introduce “voice breaks” that pop up when sound production shifts from the vocal folds to the membranes.

This feature results in rapid changes in pitch, reminiscent of Alpine yodeling or Tarzan’s iconic yell.

Click here to listen to the world’s best yodelers…

New World monkeys from Mexico to Argentina appear to have the largest vocal membranes of all primates, indicating a key role in their communication.

The study captured the calls of species like black and gold howler monkeys, tufted capuchins, black-capped squirrel monkeys, and Peruvian spider monkeys at La Senda Verde Wildlife Sanctuary in Bolivia.

The data revealed that these vocal membranes add dramatic leaps in pitch that are rarely matched by humans.

Wider ranges and “ultra-yodels”

“These results show how monkeys take advantage of an evolved feature in their larynx – the vocal membrane – which allows for a wider range of calls to be produced, including these ultra-yodels,” explained Dr. Dunn from ARU.

Some of these calls cross frequency intervals up to five times larger than what the human voice can achieve.

While people who yodel typically stay within one octave, the study found that certain New World monkeys can exceed three octaves.

“This might be particularly important in primates, which have complex social lives and need to communicate in a variety of different ways,” Dr. Dunn continued.

“It’s highly likely this has evolved to enrich the animals’ call repertoire, and is potentially used for attention-grabbing changes, call diversification, or identifying themselves.”

Vocal variety of monkey yodeling

“This is a fascinating example of how nature provides the means of enriching animal vocalization, despite their lack of language,” noted Dr Herbst from the University of Vienna.

“The production of these intricate vocal patterns is mostly enabled by the way the animals’ larynx is anatomically shaped, and does not require complex neural control generated by the brain.”

In basic terms, the vocal membranes introduce a kind of instability that makes way for abrupt changes in pitch. By switching between membranes and folds, monkeys add a unique flair to their vocal repertoire.

This could help them communicate across thick rainforest environments, where distant calls must pierce a chaotic soundscape.

How humans do it differently

“Our study shows that vocal membranes extend the monkey’s pitch range, but also destabilize its voice. They may have been lost during human evolution to promote pitch stability in singing and speech,” explained Professor Tecumseh Fitch, also from the University of Vienna.

Humans prioritize a steady tone, which is crucial for clear speech. These membranes might have vanished from our lineage because, while they allow dramatic pitch shifts, they also create less consistent vocalization.

By losing them, our ancestors may have gained better control over speech patterns and articulation.

Why does monkey yodeling matter?

The investigation offers a fresh perspective on the relationship between anatomy and communication. Researchers highlight how small structures in the larynx can produce unexpectedly large acoustic effects.

That knowledge could inform future studies on how primate species negotiate dense habitats with loud, competing noises.

It also highlights that monkeys rely on more than simple vocal folds to make themselves heard. In the wild, these calls can travel large distances, allowing social groups to stay in contact or mark their territory.

What have we learned?

Because of this discovery, scientists now better understand why monkeys in the Americas are capable of surprising pitch changes that exceed standard human vocal ranges.

The presence of expanded vocal membranes sets these species apart and explains how yodel-like calls evolved outside of the Alpine region.

At the same time, the research adds to ongoing work on how speech and language developed in our own evolutionary line.

There is still much to learn about these remarkable calls. Each insight brings us closer to appreciating the astonishing variety in primate communication and offers another reminder that humans, for all our talk, are not the only animals with vocal tricks up our sleeves.

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Click here to listen to the world’s best yodelers…

Senior author Dr Jacob Dunn, Associate Professor in Evolutionary Biology at Anglia Ruskin University (ARU) in Cambridge, England, was joined by colleagues at the University of Vienna, including lead author Dr Christian T. Herbst of the Department of Behavioural and Cognitive Biology and Professor Tecumseh Fitch, an expert in human vocal evolution.

The full study was published in the journal Philosophical Transactions of the Royal Society B Biological Sciences.

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