A donkey is a long-eared equine that looks similar to a horse, shares the genus Equus with the horse, but is a completely different species.
Donkeys (Equus asinus) have 62 chromosomes while horses (Equus caballus) have 64 chromosomes. Crossing donkeys with horses results in hybrids called mules or hinnies, each of which ends up with 63 chromosomes. The male mules are always sterile, but on rare occasions, a fertile female can occur. The chromosomes between the two species have different structures and with the difference in number, too, this usually prevents the chromosomes from pairing up properly and creating successful embryos.
However, donkeys bred to donkeys always produce donkeys. You may hear many of the following terms: donkey, burro, ass, jackass, jennet, miniature donkey, mammoth, jackstock, standard, Mexican burro, and all of them are terms for donkeys. "Burro" is a colloquial term for the Spanish or feral type of donkey (wild burros). The term is used almost exclusively in the West and is correct only when referring to donkeys that are feral.
So where does the donkey come from, if not from a horse?
Well, after collecting and analyzing skin samples from donkeys in 52 countries in Europe, Asia, and Africa; and the dung from wild asses in Sudan, China, and Mongolia; scientists have concluded from mitochondrial DNA that African wild asses in Northeast Africa are the true ancestors of modern donkeys. These findings suggest that two populations of wild asses in Africa were the first to be domesticated about 6,000 years ago: the Nubian ass (Equus africanus africanus) and the Somali ass (Equus africanus somaliensis). Both of these wild asses are listed as critically endangered on the IUCN Red List. These two sub-species are thought to have had a role in the development of the modern donkeys that traveled with humans to other parts of the world.
The earliest domesticated donkey bones date to 4600-4000 BC, at El-Omari, a predynastic Maadi site in Upper Egypt near Cairo. Bones also have been discovered at sites in Syria, Iran and Iraq between 2800-2500 BC. In addition, donkey burials have been found at some sites which may reflect the value of a trusted domestic animal. Analysis of the skeletons revealed that they had been used as pack animals, judging by the signs of strain on their vertebrae. And the body morphology was midway between that of wild asses and modern donkeys, leading to the argument that the domestication process continued as a slow process over periods of several centuries. Interestingly, domestic donkeys are smaller than the wild ones, and in particular they have smaller feet.
The history of donkeys is tied to human history because when and where they were first used tends to mark the shift to more a mobile, trade-oriented society. But despite the critical role that it played in transportation throughout human history, the donkey is the least studied of all domesticated animals. Donkeys are desert-adapted and can carry heavy loads through arid lands allowing shepherds to move their households along with their herds. In addition, donkeys were ideal for the transport of food and trade goods throughout Africa and Asia.
Donkeys range in size from the Miniature Mediterranean that is less than 36 inches to the elegant Mammoth Jackstock that is 14 hands and up. The rare French Poitou donkey, which is characterized by a huge head and ears, and a very thick, shaggy, curled black coat, can stand 14 to 15 hand high. Unfortunately, there are estimated to be about 400 purebred Poitous left in the world today.
Donkeys in the USA are not grouped by "Breed" but rather by type. The only exception to this is the Miniature Donkey. As of May 2008, they may now be recognized as a breed since they pass their unique breed traits on to their offspring consistently. The types of donkeys are labeled by their sizes; 36" and under are Miniature Mediterranean, 36.01-48" are Standard, 48.01" to 54" are Standard jennets or 56" for Large Standard, and 54/56" and over, Mammoth stock.
Donkeys differ from horses in conformation and the most noticeable difference is the ears. A donkey's ears are much longer in proportion to their width than a horse's. The necks are straighter than in horses, and most donkeys and all zebras lack a true wither. The croup and rump are also a different shape in the donkey since they lack the double-curve muscled haunch. Hoof shape varies as well; donkey hooves are rounder with more upright pasterns. The tail resembles a cow's; covered with short body hair and ending in a tassel of course hair. The coarse mane hair is stiffly upright, rarely laying over. Donkeys do not have a true forelock, although sometimes the mane grows long enough to comb down the face between the ears. Show donkeys wear their manes clipped short or shaved close to the neck.
Donkeys come in most of the same colors and patterns that horses do, but they look just a bit different. The colors of true pinto, horse aging gray, appaloosa, palomino and buckskin do not occur in the donkey or the mule or hinny. They also have a few unusual colors that are unique to the species such as dappled roan, blue-eyed ivory, frosted spotted and a unique spotting pattern called tyger spot that is similar to Appaloosa. Most donkeys have dark ear marks; dorsal stripes and shoulder crosses; as well as the light points of white muzzle and eye rings, and white belly and inner leg. Leg barring may be present as well. Occasional small dark spots at the throatlatch are called collar buttons and are good identifying markings. These typical donkey markings may be passed on in part or whole to mule or hinny offspring.
Donkeys can also perform all the gaits horses or mules do, and some are even gaited and can perform a single-foot gait.
Donkeys (geldings) can be wonderful guard animals for an entire herd of cattle, sheep or goats, or even a flock of chickens, geese or ducks. Their natural aversion to predators and inborn dislike of dogs will inspire the donkey to severely discourage any canine or coyote attacks on the herd. Dogs and donkeys usually don't mix, although they can be trained to leave the family dog alone. Only large Standard geldings, at least 3 years old, are recommended for guard duty. Miniatures are not suitable as guard donkeys.
Donkeys characteristically get by on less food than a horse of similar size, and need a lower protein content in their feed. Good grass hay and pasture is usually all a donkey needs.
Donkeys can be used just like horses under saddle and in harness, although donkeys are more laid back. . Donkeys are not really stubborn; they simply will not put themselves in danger. That stubborn streak is the donkey's way of telling humans that something is not right. It is not a good idea to abuse a donkey, for they are clever and seem intelligent enough to plot revenge. However, treated kindly, they will do their best for their owner and with the utmost patience, unless you are asking them to get their feet wet.
Otherwise, they are very friendly, and their versatile nature makes them excellent for children.