Yodel-ay-hee-hoo! Monkeys are better yodelers than humans, study finds Voice breaks in Latin American monkey calls resemble human yodeling, but over a much wider frequency range. Jennifer Ouellette Apr 3, 2025 3:10 pm | 9 Black and gold howler monkeys (Alouatta caraya) Credit: Jacob Dunn, Anglia Ruskin University Black and gold howler monkeys (Alouatta caraya) Credit: Jacob Dunn, Anglia Ruskin University Story textSizeSmallStandardLargeWidth *StandardWideLinksStandardOrange* Subscribers only Learn moreHumans have practiced some form of yodeling since at least the 13th century, when Marco Polo encountered Tibetan monks on his travels who used the vocal technique for long-distance communication. It's since morphed into a distinctive singing style. But can animals also yodel? According to a new paper published in the Philosophical Transactions of the Royal Society B, Biological Sciences, several species of monkey dwelling in the rainforests of Latin America employ "voice breaks" in their calls that acoustically resemble human yodelingi.e., "ultra-yodels" that boast a much wider frequency range.Many years ago, I wrote about the bioacoustics of human yodeling for New Scientist. In many respects, yodeling is quite simple. It merely involves singing a long note subjected to repeated rapid sharp shifts in pitch. It's the unique anatomy of the human vocal tract that makes it possible, notably the larynx (voice box) located just behind the Adam's apple. The larynx is comprised of cartilage and the hyoid bone that together support the vocal cords, which are attached to muscles on either side of the larynx.When air flows through the trachea, the vocal cords vibrate at frequencies ranging from 110 to 200 Hz. We have the capability of contracting the muscles to change the shape, position, and tension of our vocal cords, thereby altering the pitch of the sound produced. Stiffer vocal cords result in faster vibrations, which produce higher pitches.Prior research has shown that human vocal cords share the same two principal vibration modes as a guitar, and human singers rely on both when performing. It's well-known that we have two distinct ranges: a "head voice" and a "chest voice." There is a gap when shifting between them, which trained singers learn how to smooth over. Yodelers accentuate that gap instead.Monkey see, monkey yodel?That's how it works for humans, but when it comes to the question of yodeling animals, it depends on how you define yodeling, according to bioacoustician Tecumseh Fitch of the University of Vienna in Austria, who co-authored this latest paper. Plenty of animal vocalizations use repeated sudden changes in pitch (including birds), and a 2023 study found that toothed whales can produce vocal registers through their noses for echolocation and communication.There haven't been as many studies of vocal registers in non-human primates, but researchers have found, for example, that the "coo" call of the Japanese macaque is similar to a human falsetto; the squeal of a Syke monkey is similar to the human "modal" register; and the Diana monkey produces alarm calls that are similar to "vocal fry" in humans. Tufted capuchins (Sapajus apella) Jacob Dunn, Anglia Ruskin University Tufted capuchins (Sapajus apella) Jacob Dunn, Anglia Ruskin University Peruvian spider monkey (Ateles chamek) Jacob Dunn, Anglia Ruskin University Peruvian spider monkey (Ateles chamek) Jacob Dunn, Anglia Ruskin University Tufted capuchins (Sapajus apella) Jacob Dunn, Anglia Ruskin University Peruvian spider monkey (Ateles chamek) Jacob Dunn, Anglia Ruskin University It's known that non-human primates have something humans have lost over the course of evolution: very thin, light vocal membranes just above the vocal folds. Scientists have pondered the purpose of those membranes, and a 2022 study concluded that this membrane was crucial for producing sounds. The co-authors of this latest paper wanted to test their hypothesis that the membranes serve as an additional oscillator to enable such non-human primates to achieve the equivalent of human voice registers. That, in turn, would render them capable in principle of producing a wider range of callsperhaps even a yodel.The team studied many species, including black and gold howler monkeys, tufted capuchins, black-capped squirrel monkeys, and Peruvian spider monkeys. They took CT scans of excised monkey larynxes housed at the Japan Monkey Center, as well as two excised larynxes from tufted capuchin monkeys at Kyoto University. They also made live recordings of monkey calls at the La Senda Verde animal refuge in the Bolivian Andes, using non-invasive EGG to monitor vocal fold vibrations.The results showed that New World monkeys had evolved the largest primate vocal membranes, supporting the hypothesis that they play a critical role in vocal production, specifically voice breaks that transitioned rapidly in frequency, which they achieved by switching sound production from their vocal folds to their vocal membranes. It's technically a yodel, even though it might not sound much like the human version (cf. the recording of a tufted capuchin above).The monkeys' "ultra-yodels" had frequency leaps that were five times larger than human frequency changes, often exceeding three octaves. (Human yodelers are limited to one octave.) While the monkeys' vocal membranes serve to extend their pitch range, the tradeoff is a lack of pitch stability.These results show how monkeys take advantage of an evolved feature in their larynxthe vocal membranewhich allows for a wider range of calls to be produced, including these ultra-yodels," said co-author Jacob Dunn, an evolutionary biologist at Anglia Ruskin University in Cambridge, England.This might be particularly important in primates, which have complex social lives and need to communicate in a variety of different ways. Its highly likely this has evolved to enrich the animals call repertoire, and is potentially used for attention-grabbing changes, call diversification, or identifying themselves.Philosophical Transactions of the Royal Society B, Biological Sciences, 2025. DOI: 10.1098/rstb.2024.0005 (About DOIs).Jennifer OuelletteSenior WriterJennifer OuelletteSenior Writer Jennifer is a senior writer at Ars Technica with a particular focus on where science meets culture, covering everything from physics and related interdisciplinary topics to her favorite films and TV series. Jennifer lives in Baltimore with her spouse, physicist Sean M. Carroll, and their two cats, Ariel and Caliban. 9 Comments