Researchers solved how horses make a whinny that has both a low tone and a much higher tone at the same time. Horse vocal communication was not well understood, even though domesticated horses have lived closely with humans for over 4,000 years.
The team studied vocal anatomy, clinical records and sound recordings. They showed the low frequency comes from vocal‑fold vibration, the same basic mechanism humans use, while the high frequency comes from a laryngeal whistle formed inside the larynx.
To prove the whistle mechanism, the researchers used excised larynx experiments and alternated the gas between air and helium. Because sound travels faster in helium, the whistle tones shifted higher while vocal‑fold vibration did not, as predicted. William Tecumseh Fitch said the frequency shift was immediately obvious and confirmed the solution to the mystery.
The study suggests biphonation may let horses send multiple messages at once. Przewalski’s horses also show biphonation, while donkeys and zebras appear to lack the high component. The work was published in Current Biology.
Difficult words
- biphonation — producing two different sound tones at once
- vocal-fold — thin tissue that vibrates to make low soundsvocal‑fold
- larynx — the organ in the throat for producing voice
- frequency — how often a sound wave repeats each second
- excise — to remove or cut out tissue or partsexcised
- domesticate — to keep and breed animals for human usedomesticated
- whinny — the long high-pitched sound a horse makes
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- How could biphonation help horses send multiple messages at the same time? Give one or two examples.
- Have you ever heard a horse whinny? Describe the sound and the situation when you heard it.
- Why did the researchers use helium in the experiments, and what did the change of gas show?
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