A horse is a horse, of course of course—except when it’s not. Horses and ponies are members of the same species, Equus caballus. The creatures share a lot of similarities. In general, you can ride them, drive them, and most importantly, pamper them like spoiled pets. Horses and ponies alike have shaped human society, letting people make agricultural and industrial advancements and helping civilizations wage wars and fight battles.
They aren’t quite the same, though. As any barn rat will tell you, the main difference between a horse and a pony is height. Horses are measured in hands, with one hand equaling 4 inches. An equine that measures 14 hands, 2 inches at the withers (the ridge between their shoulder blades) is considered a horse, whereas those that fall below this threshold are known as ponies.
"The height of an individual horse or pony will always determine whether or not the animal is a horse or pony, regardless of the name of their breed or the stereotypical standards," Emily Thomas, museum assistant at the International Museum of the Horse in Lexington, Kentucky, tells Mental Floss in an email.
But despite the strict height distinction, how people refer to certain horses and ponies is a bit fluid. This is where the semantics can get muddier than a spring paddock. Take the Arabian Horse, for instance: According to the Arabian Horse Association, the standard height for this elegant breed ranges from 14.1 to 15.1 hands, with some individuals standing under or over the average [PDF]. This means that some Arabian Horses are pony-sized, even though they’re often still called horses. And then there’s the Connemara Pony, which is still widely considered a pony even though its average height clocks anywhere between 13 and 15 hands.
Miniature horses are the most confusing example. The American Miniature Horse Association only registers minis that measure 34 inches (the breed is so small, they’re measured in inches rather than hands) or below. Yet despite their pint-sized proportions, these tiny equines are still called horses rather than ponies. This is because, as Horse Illustrated reports, a breed’s conformation can also influence whether we consider something a horse or a pony. Minis were essentially designed to resemble their much-larger counterparts, just drastically smaller, as if they'd been shrunk in the evolutionary dryer.
Tradition can also play a role in whether an animal is called a horse or a pony. The Icelandic Horse averages a height of 13 to 14 hands and has a heftier build. But breeders and registries still refer to the thick-maned Nordic steeds as horses. It’s said this is not only because of the animals' strength and weight-carrying abilities, but also because the centuries-old, Viking-era breed has always been called a horse. As Élise Rousseau writes in Horses of the World, the concept of a pony in places with shorter breeds doesn’t exist at all; equines in these areas, no matter how small, are simply known as horses.
Tradition is also why all polo mounts are called ponies. As The Horse Rider's Journal reports, the Manipuri Pony of India was considered the original polo breed. But today, a variety of horse breeds are used in the sport, though all polo mounts—regardless of height or type—are still referred to as ponies.
Basically, nailing the difference between when to call something a horse or a pony can be as tricky as naming one. One thing a pony is not, however, is a baby horse—that would be a foal. A person may call their horse a pony in the same way the owner of a full-grown dog may refer to their pooch as a puppy, but it’s a term of affection rather than an acknowledgement of age.
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