What Is Different About a Horse & a Donkey?

Even without looking at the animal, you can tell whether it's a horse or a donkey by the sound of its voice. While horses utter smooth sounds that are termed "whinnies" or "neighs,, donkeys have a noticeably different and unique language. In her 2012 book "The Donkey Companion," Sue Weaver writes that a donkey's bray is the product of the audible intake of air followed by the forceful outflow resulting in the "hee-haw" vocalization most people are familiar with.

Donkeys and horses are similar enough in appearance that it's obvious they do come from the same family. But upon closer comparison you'll notice clear differences. Donkeys' ears are long and thick compared to horses' smaller and thinner ears. A horse's eyes are smaller and not set quite so far apart as a donkey's are, with a forehead that is narrower than a donkey’s. Horses have six vertebrae in their backs while donkeys only have five. A donkey’s hooves are smaller and have more of an upright box-like shape compared to a horse’s larger, oval and more angled hooves. Most horses have long tails with separate strands of hair, but a donkey's tail looks more like a cow's tail on the upper two-thirds, with coarse hair forming a switch on the lower part of the tail.

Horses of both genders can be temperamental on an individual basis, but you can count on male donkeys to be aggressive. It's such an innate part of their nature that male donkeys, also called "jacks," must be housed separately from other donkeys and animals unless they're breeding. Additionally, "The Encyclopedia of Applied Animal Behavior and Welfare" published in 2010 notes that donkeys react differently to fear-inducing stimuli than a horse does. Donkeys will freeze up in such situations. This reaction has given them their stubborn reputation and makes it necessary to take a different approach when handling and training donkeys.

A donkey's withers aren't as pronounced as a horse's. At first glance you might not think that's a significant difference, but if you intend to saddle up a donkey, you won't be able to use your horse's saddle. You'll need a special saddle built specifically for donkeys, because horse saddles are designed to fit horses' wide ribs and round back, not the donkey's flatter, shorter back and less broad ribs.

Chromosomes are something you can't see just by looking at a horse or a donkey, but the number of chromosomes that each carries is another difference between the two. Donkeys have 62 chromosomes and horses have 64. Horses and donkeys can interbreed, but the offspring are typically sterile. That's because in order for crossbred offspring to be fertile, both parents have to have the same number of diploid chromosomes.