Ponies and horses are more similar than they are different. The one thing that ponies are not, that many people are mistaken about, is that they are not baby horses. Both horses and ponies are of the same species (Equus caballus) and come from the exact same family tree. However, ponies stay small their whole life, maturing more quickly than horses. Pony foals are tiny and will rapidly mature to the approximate size of their parents. Horses are slower growing, some not attaining full mature size until they are six or seven years of age.
The most obvious difference between a horse and a pony is size. For most purposes, a pony is under 14.2 hands high if you ride English, and under 14 hands if you’re a western rider. This size distinction varies between places too and often they are arbitrary sizes set for the show ring. Some horses are more pony-ish in their behavior and physiology, and some ponies more horse-like. In fairness to the riders and these mounts, these size standards help prevent ponies and small horses from showing against larger animals, whose size might give them an advantage. It also isn’t safe to have very small children on tiny ponies riding around the same ring with larger horses.
Some breeds that are under the 14.2/14 hand mark are considered horses. Examples would be the Miniature Horse and the Icelandic Horse. Both are the size of ponies but are called horses. In the case of the Miniature Horse, most will have small ponies, such as Shetlands in their pedigrees, and it’s unlikely to find any actual horse breeds. Others like the Welsh Pony will have individuals above the pony height standards, but may still be regarded as a pony. Some horse breeds have individuals of pony size, such as the Morgan Horse, American Quarter Horse, and many gaited breeds such as the Paso Fino and Kentucky Mountain Horse.
Some differences between horses and ponies may not be as easy to spot as the size. Horses and ponies often have very different temperaments. Ponies tend to be more stoic and intelligent than larger horses. It’s a mistake to see this as docility. They can be quite wily, which is why it’s sometimes easier to find a quiet horse for a child than a reliable pony. Ponies are very adept at avoiding work and withstanding the consequences. Horses can be quieter, and often the larger the breed, the more docile they are. This depends largely on what the horse breed was developed for.
Ponies are incredibly strong for their size. They can pull or carry heavy loads with more strength than a horse, relative to their size. They are hardier than horses and can withstand greater ranges in temperature. Their coats tend to grow thicker in the winter, which often doesn’t shed out until the hottest days of summer. They begin to grow back their thick coats as soon as the days start to shorten. Ponies have thicker manes and tails. Their hooves tend to be tougher. They are heavier boned and shorter legged in proportion to their bodies compared to horses.
Ponies can eke out nutrition from a pasture that a horse would starve on. In fact, it’s very easy to overfeed a pony, which makes them more prone to founder and laminitis than horses. Feeding a pony takes a slightly different approach than feeding horses. While some horses can be ‘hard keepers’ most ponies are the extreme opposite, apparently putting on weight just looking at the grass on the other side of the fence. A pony that is a hard keep is rare, and it may be an indication of a health problem.
Ponies also tend to live longer than horses. It’s not unusual for ponies to live beyond thirty years of age, and many world record holders for the oldest equines are ponies. Many ponies are still used for riding and driving into their late 20s.