Study finds horses' whinny includes a whistle.

Researchers found the high-pitched component of a horse's whinny comes from a whistle-like mechanism in the voice box, while the low tones arise from vibrating tissues in the larynx.

Scientists report that the familiar horse whinny combines two sound mechanisms produced at the same time. The low-pitched part comes from air moving over vibrating tissues in the larynx, similar to human speech. The high-pitched element is a whistle that originates inside the voice box when an area above the vibrating tissues narrows to create a small opening. The study, published in Current Biology, used endoscopic video, detailed scans, and airflow tests on isolated voice boxes to reach these conclusions. Key findings: - A horse's whinny contains simultaneous low and high fundamental frequencies. - Low tones are produced by vibrating bands of tissue in the larynx, like human vocal folds. - The high tones are produced by a whistle-like mechanism that starts in the voice box when a small opening is formed above the vibrating tissues. - Researchers used a small camera passed through the nose, imaging scans, and airflow experiments on isolated larynges to observe the mechanism. - Horses are the first known large mammals observed to whistle through the voice box while producing voiced sounds; some close relatives like donkeys and zebras do not produce the high-pitched component. Summary: The study clarifies how horses produce their two-toned whinny and suggests the combination of mechanisms could allow more complex signals during social interactions. How this two-part call evolved and its full communicative role remain undetermined at this time.