Colloquially, the term "ass" is often used today to refer to a larger, horse-sized animal, and "donkey" to a smaller, pony-sized one. In the western United States and much of Latin America, a small donkey is sometimes called a burro. A male donkey or ass is called a jack, a female a jenny, and offspring less than one year old, a foal (male: colt, female filly).
While different species of the Equidae family can interbreed, offspring are almost always sterile. Nonetheless, horse/donkey hybrids are popular for their durability and vigor. A mule is the offspring of a jack (male) donkey and a mare (female horse). The much rarer successful mating of a male horse and a female donkey produces a hinny.
Asses were first domesticated around 3000 BCE, approximately the same time as the horse, and have spread around the world. They continue to fill important roles in many places today and domesticated species are increasing in numbers (although the African wild ass and another relative, the Onager, are endangered species). As "beasts of burden" and companions, asses and donkeys have worked together with humans for centuries.
Jennies are pregnant for approximately 11 months, and usually give birth to one foal. Twins are very rare. Only about 1.7 percent of donkey pregnancies result in twins. Both twins survive in only about 14 percent of the cases.
Donkeys vary considerably in size, depending on breed and management. Most domestic donkeys range from 0.9 to over 1.4 m tall, though the Mammoth Jack breed is taller, and the Andalucian-Cordobesan breed of southern Spain can reach up to 1.6 m high.
Donkeys are adapted to marginal desert lands, and have many traits that are unique to the species as a result. Wild donkeys live separated from each other, unlike tight wild horse and feral horse herds. Donkeys have developed very loud vocalizations, which help keep in contact with other donkeys over the wide spaces of the desert. The best-known call is referred to a "bray," which can be heard for over three kilometers. Donkeys have larger ears than horses. Their longer ears may pick up more distant sounds, and may help cool the donkey's blood. Donkeys in the wild can defend themselves with a powerful kick of their hind legs as well as by biting and striking with their front feet.
Donkeys' tough digestive system is somewhat less prone to colic than that of horses, can break down near-inedible vegetation and extract moisture from food very efficiently. As a rule, donkeys need smaller amounts of feed than horses of comparable height and weight. Because they are easy keepers, if overfed, donkeys are also quite susceptible to developing a condition called laminitis.
The ancestors of the modern donkey are the Nubian and Somalian subspecies of African wild ass. The African Wild Ass was domesticated around 4,000 BCE. The donkey became an important pack animal for people living in the Egyptian and Nubian regions as they can easily carry 20% to 30% of their own body weight and can also be used as a farming and dairy animal. By 1800 B.C., the ass had reached the Middle East, where the trading city of Damascus was referred to as the “City of Asses” in cuneiform texts. Syria produced at least three breeds of donkeys, including a saddle breed with a graceful, easy gait. These were favored by women.
Equines had become extinct in the Western Hemisphere at the end of the last Ice Age. However, horses and donkeys were brought back to the Americas by the Conquistadors. In 1495, the ass first appeared in the New World when Christopher Columbus brought four jacks and two jennys. It is from this bloodline that many of the mules which the Conquistadors used while they explored the Americas were produced. Shortly after America became independent, President George Washington imported the first mammoth jack stock into the country. Because the existing Jack donkeys in the New World at the time lacked the size and strength he sought to produce quality work mules, he imported donkeys from Spain and France, some standing over 1.63 m tall. One of the donkeys Washington received from the Marquis de Lafayette, named "Knight of Malta," stood 1.43 m and thus was regarded as a great disappointment. Viewing this donkey as unfit for producing mules, Washington instead bred Knight of Malta to his jennys and, in doing so, created an American line of Mammoth Jacks (a breed name that includes both males and females).
Despite these early appearances of donkeys in America, the donkey did not find widespread distribution in America until it was found useful as a pack animal by miners, particularly the gold prospectors, of the mid-1800s. Miners preferred this animal due to its ability to carry tools, supplies, and ore. Their sociable disposition and adaptation to human companionship allowed many miners to lead their donkeys without ropes. They simply followed behind their owner. As mining became less an occupation of the individual prospector and more of an industrial underground operation, the miners' donkeys lost their jobs, and many were simply turned loose into the American deserts. Descendants of these donkeys, now feral, can still be seen roaming the Southwest today.
By the early 20th century, donkeys began to be used less as working animals and instead kept as pets in the United States and other wealthier nations, while remaining an important work animal in many poorer regions. The donkey as a pet is best portrayed by the appearance of the miniature donkey in 1929. Robert Green imported miniature donkeys to the United States and was a lifetime advocate of the breed. Mr. Green is perhaps best quoted when he said "Miniature Donkeys possess the affectionate nature of a Newfoundland, the resignation of a cow, the durability of a mule, the courage of a tiger, and the intellectual capability only slightly inferior to man's." Standing only 32-40 inches, many families recognized the potential of miniature donkeys as pets and companions for their children.
Although the donkey fell from public notice and became viewed as a comical, stubborn beast which was considered “cute” at best, the donkey has recently regained some popularity in North America as a mount, for pulling wagons, and even as a guard animal. Some standard species are ideal for guarding herds of sheep against predators, since most donkeys have a natural wariness toward coyotes and other canines and will keep them away from the herd.
Donkeys have a reputation for stubbornness, but this is due to some handlers' misinterpretation of their highly-developed sense of self-preservation. It is difficult to force or frighten a donkey into doing something it sees as contrary to its own best interest..
Although formal studies of their behaviour and cognition are rather limited, donkeys appear to be quite intelligent, cautious, friendly, playful, and eager to learn. They are often pastured or stabled with horses and ponies, and are thought to have a calming effect on nervous horses. If a donkey is introduced to a mare and foal, the foal will often turn to the donkey for support after it has been weaned from its mother.
Once a person has earned their confidence they can be willing and companionable partners and very dependable in work. For this reason, they are now commonly kept as pets in countries where their use as beasts of burden has disappeared. They are also popular for giving rides to children in holiday resorts or other leisure contexts.
The vast majority of donkeys are used for the same types of work that they have been doing for 6000 years. Their most common role is for transport, whether riding, pack transport, or pulling carts. They may also be used for farm tillage, threshing, raising water, milling, and other jobs. Other donkeys are used to sire mules, as companions for horses, to guard sheep, and as pets. A few are milked or raised for meat
The number of donkeys in the world continues to grow, as it has steadily throughout most of history. Some factors that today are contributing to this are increasing human population, progress in economic development and social stability in some poorer nations, conversion of forests to farm and range land, rising prices of motor vehicles and gasoline, and the donkeys' popularity as pets.
In prosperous countries, the welfare of donkeys both at home and abroad has recently become a concern and a number of sanctuaries for retired and rescued donkeys have been set up. The largest is the Donkey Sanctuary of England, which also supports donkey welfare projects in Egypt, Ethiopia, India, Kenya, and Mexico.
According to British food writer Matthew Fort, donkeys were until recently used in the Italian Army. The Mountain Fusiliers each had a donkey to carry their gear and in extreme circumstances, the animal could be eaten. In 2006, security forces in Afghanistan prevented a man taking a donkey which he had laden with 30 kg (66lb) of explosives and a number of landmines, which would have been set off by a remote controlled detonator, from entering a town in Zabul Province.
The Spanish brought donkeys, called "burros" in Spanish, to North America, where they were prized for their hardiness in arid country and became the beast of burden of choice by early prospectors in the Southwest United States. In the western United States the word "burro" is often used interchangeably with the word "donkey" by English speakers. Sometimes the distinction is made with smaller donkeys, descended from Mexican stock, called "burros," while those descended from stock imported directly from Europe are called "donkeys."
The wild burros (or more accurately, feral burros) on the western rangelands descend from animals that ran away, were abandoned, or were freed. Wild burros in the United States were protected by , the Wild Free-Roaming Horses and Burros Act of 1971 (see also Kleppe v. New Mexico). These animals, considered to be a living legacy, are periodically at risk when there are severe drought conditions. To reduce herd populations and preserve grazing land, the Bureau of Land Management conducts roundups of burro herds and holds public auctions.
Wild burros can make good pets when treated well and trained properly. They are clever and curious. When trust has been established, they appreciate, and even seek, attention and grooming.
Horse-donkey hybrids are almost always sterile because horses have 64 chromosomes whereas donkeys have 62, producing offspring with 63 chromosomes. Mules are much more common than hinnies. This is believed to be caused by two factors, the first being proven in cat hybrids, that when the chromosome count of the male is the higher, fertility rates drop (as in the case of stallion x jennet). The lower progesterone production of the jenny may also lead to early embryonic loss. In addition, there are less-scientific reasons: Due to different mating behavior, jacks are often more willing to cover mares than stallions are to breed jennys. Further, mares are usually larger than jennys and thus have more room for the ensuing foal to grow in the womb, resulting in a larger animal at birth. It is commonly believed that mules are more easily handled and also physically stronger than hinnies, making them more desirable for breeders to produce, and it is unquestioned that mules are more common in total number.
The offspring of a zebra-donkey cross is called a zonkey, zebroid, zebrass, or zedonk; zebra mule is an older term, but still used in some regions today. The foregoing terms generally refer to hybrids produced by breeding a male zebra to a female donkey. Zebra hinny, zebret and zebrinny all refer to the cross of a female zebra with a male donkey. Zebrinnies are rarer than zedonkies because female zebras in captivity are most valuable when used to produce full-blooded zebras. There are not enough female zebras breeding in captivity to spare them for hybridizing; there is no such limitation on the number of female donkeys breeding.
For at least the past century, a few donkeys and burros in Mexico have been painted with white stripes to amuse tourists. These are not hybrids.
An animal which may look like a zebra-donkey hybrid because of its distinctly striped hindquarters and hind legs is the okapi, which has no relationship to either of those species. Okapi are most closely related to the giraffe. In addition to the rear stripes, okapi have some striping near the top of their forelegs.
There were several other, now extinct (sub)species called the Yukon Wild Ass (Equus asinus lambei) and the European Wild Ass(Equus Hydruntinus)which became extinct during the Neolithic. In the wild the asses can reach top speeds equalling zebras and even most horses.
The long history of human donkey use has created a rich store of cultural references.
Any number of donkeys appear in world literary works.