Volkswacht Bodensee - Revealed: Why monkeys are better at yodelling than humans

When monkeys howl -- or yodellers yodel -- they rapidly switch back and forth between low and high frequency sounds.

This is in contrast to opera singers, who are trained to precisely control how they gradually move from note to note, in a way that is pleasing to listen to.

Yodellers and monkeys, however, make bigger jumps far more abruptly, creating vocal breaks that sound like Tarzan's yell.

When yodelling, a human might be able to jump an octave, which doubles the frequency.

Monkeys can manage three and half octaves, according to a new study.

A "cheap trick" in their larynx means these monkeys will always beat humans, senior study author Jacob Dunn of the UK's Anglia Ruskin University told AFP.

Both humans and monkeys have a pair of vocal folds in their larynx which vibrate to create sound.

But monkeys have an additional pair of membranes that gives them a far wider pitch range, the international team of researchers discovered.

This is thought to give monkeys, which are social creatures, a more complex way of communicating with each other.

All other primates, and even ancient human ancestors, appear to have this special tissue, Dunn said.

At some during our evolution, humans seem to have lost these membranes, he added.

But the shame of being inferior yodellers may have been worth the trade-off.

To be able to speak clearly, humans needed a "streamlined" larynx -- and these membranes would have gotten in the way, Dunn explained.

"If you put a human brain on the primate larynx" it would struggle to speak intelligibly because of the membranes and other things like air sacs, he said.

For the study, the researchers put sensors on the necks of some monkeys at Bolivia's La Senda Verde Wildlife Sanctuary.

This allowed them to see what was going on in the larynx of black and gold howler monkeys, tufted capuchins, black-capped squirrel monkeys and Peruvian spider monkeys.

The spider monkey was the best yodeller, managing around four octaves, Dunn said.

The researchers also studied the larynges of dead monkeys and used computer modelling to analyse the frequencies.

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

R.Buehler--VB