A horse's neigh may be unique in the animal kingdom. Now scientists know how they do it

Horses whinny to find caller friends, shake hands aged ones and observe happy moments for illustration feeding time.

How precisely horses nutrient that unique sound — besides called a neigh — has agelong eluded scientists.

The whinny is an different operation of some precocious and debased sounded sounds, for illustration a transverse betwixt a grunt and a squeal — that travel retired astatine nan aforesaid time.

The low-pitched portion wasn't overmuch of a mystery. It comes from aerial passing complete bands of insubstantial successful nan sound container that make sound erstwhile they vibrate. It's a method akin to really humans speak and sing.

But nan high-pitched portion is much puzzling. With immoderate exceptions, larger animals person larger vocal systems and typically make little sounds. So really do horses do it?

According to a caller study, they whistle.

Researchers slid a mini camera done horses' noses to movie what happened wrong while they whinnied and made different communal equine sound, nan softer, subtler nicker. They besides conducted elaborate scans and blew aerial done nan isolated sound boxes of dormant horses.

The whinny's mysterious high-pitched tones, they discovered, are a benignant of whistling that starts successful nan horse's sound box. Air vibrates nan tissues successful nan sound container while an area conscionable supra contracts, leaving a mini opening for nan whistle to escape.

That's different from quality whistling, which we do pinch our mouths.

“I'd ne'er imagined that location was a whistling component. It's really interesting, and I tin perceive that now,” said Jenifer Nadeau, who studies horses astatine nan University of Connecticut. Nadeau was not progressive pinch nan study, which was published Monday successful nan diary Current Biology.

A fewer mini rodents for illustration rats and mice whistle for illustration this, but horses are nan first known ample mammal to person a knack for it. They're besides nan only animals known to beryllium capable to whistle done their sound boxes while they sing.

“Knowing that a ‘whinny’ is not conscionable a ‘whinny’ but that it is really composed of 2 different basal frequencies that are created by 2 different mechanisms is exciting,” said Alisa Herbst pinch Rutgers University's Equine Science Center, of nan study successful an email.

A large lingering mobility is really horses' two-toned calls came to be. Wild Przewalski’s horses tin do thing similar, arsenic tin elks. But much distant equine relatives for illustration donkeys and zebras can't make nan high-pitched sounds.

The two-toned whinnies could thief horses convey aggregate messages astatine nan aforesaid time. The otherwise sounded neighs whitethorn thief them definitive a much analyzable scope of feelings erstwhile socializing, said study writer Elodie Mandel-Briefer pinch nan University of Copenhagen.

“They tin definitive emotions successful these 2 dimensions,” Mandel-Briefer said.

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Associated Press video journalist James Brooks contributed to this report.

The Associated Press Health and Science Department receives support from nan Howard Hughes Medical Institute’s Department of Science Education and nan Robert Wood Johnson Foundation. The AP is solely responsible for each content.