What is a Mule?

Mary McMahon
Mary McMahon

A mule is a sterile cross between a male donkey, or jack, and a female horse. When a stallion is mated with a female donkey, or jenny, the result is a hinny. Mules have been bred for centuries as riding, work, and driving animals, and were widely used throughout Europe and the New World until the automobile began to replace equines as a transportation method. Breeders continue to raise mules as pleasure animals, and many ranches continue to have a working force of mules.

Mules are very intelligent animals.
Mules are very intelligent animals.

The mule is prized as a work animal because it is intelligent, surefooted, and rugged. Mules can endure hot weather and difficult working conditions which could injure horses, but they are not as difficult to manage as donkeys. Especially in the American West, the durability of the mule was a very valuable trait, as weather and trail conditions could sometimes be extreme. Mules are also known for being stubborn, but they are unusually patient and gentle with beginning riders.

Mules may be used for carrying heavy loads.
Mules may be used for carrying heavy loads.

In appearance, a mule superficially resembles a donkey, with a few horse-like traits. Mules have long ears, short manes, and partially hairless tails. They come in a range of sizes, depending on breeding, and are also available in an assortment of colors. Because of their versatility, mules are used in many of the same sports horses are, and sometimes outperform horses in competition. In addition, mules are often chosen as work animals by trail riding vacation companies, as they can carry a great deal of weight and tolerate less skilled riders.

Although a few rare instances of fertile mules have been recorded, the majority of mules are sterile. This is because donkeys have 62 chromosomes, while horses have 64, resulting in 63 chromosomes in a mule. As the chromosomes cannot be split, the mule will be unable to produce offspring. As a general rule, male mules, also called johns, are gelded to reduce behavioral problems. Female mules are known as mollies.

Because mules themselves are sterile, mule breeders maintain stocks of horses and donkeys to breed with, taking note of particularly good crosses and replicating them. Most breeders prefer to breed mules, as they are larger than hinnies, and also easier to breed in general, as female donkeys do not impregnate easily. Mule breeders select for attractive, strong mules with amenable dispositions, and are pleased to match their mules with prospective owners.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


As a mule owner, I'd like to point out a few things. First, the photo is of a nice donkey. Some mules have the white muzzle, but most do not. Also, the eye ridges of a donkey are much bigger than a mule's, which are more like a horse's. Mules have nicely haired tails, much the same as most horses' tails. If the tail is partly hairless, the problem is fly bies and itching, which can cause any equine to rub its tail hairless.

Next, the biggest advantage of mules is hybrid vigor. Mules don't get sick as much as horses do. Mules are smarter than either of their parents. Mules are stronger (by weight) and need less to eat and/or poorer quality fodder than horses. Mules generally won't get themselves hurt because they consider whether what they are asked to do is a good idea. Sometmes this takes a bit of time, and sometimes they decide, no it's not a good idea -- that's why people think mules are stubborn. Also, you can't beat a mule into submission, and they sharply remember who did the beating. But you can change their minds with kindness.


@pastanaga - Yeah, it makes sense even if you are a farmer to keep horses and donkeys as breeding stock and mules as workers, since you probably wouldn't be able to change up those two roles all the time.

I don't think mules as nearly as popular as they used to be though because society has changed so much they don't have as much of a place in it. I knew some people once who kept a mammoth mule as part of their petting zoo lifestyle farm, but that was for the novelty value. He was absolutely enormous too, but very gentle.


@Iluviaporos - Well, I think mules were used by travelers and merchants more often than by farmers. A traveler isn't going to want their only means of transportation to get pregnant because it will take time away from the road. Pregnant animals would also eat more and foals would be difficult to take care of and train.

It might seem like you're getting free money out of nowhere if you've got breeding animals, but they usually don't work that way. And, besides, a mule will live for several decades, so with good care the average person wouldn't need to replace them often.


I've always kind of wondered why mules were so popular back in the days when livestock was so important to the average person's life and resources. I would have thought that it would make more economic sense to keep animals which could be bred, as they would produce offspring to replace themselves as well as others to sell.

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