|Species:||Equus asinus x Equus caballus|
Most mules are sterile. Sterile hybrids are not species in their own right.
A mule is the offspring of a male donkey and a female horse. Horses and donkeys are different species, with different numbers of chromosomes. Of the two F1 hybrids between these two species, a mule is easier to obtain than a hinny (the offspring of a male horse and a female donkey). While there is no known instance of a male mule siring offspring, female mules have on very rare occasion given birth to viable offspring. The size of a mule and work to which it is put depends largely on the breeding of the mule's dam. Mules can be lightweight, medium weight, or even, when produced from draught horse mares, of moderately heavy weight.
It has been claimed that mules are "more patient, sure-footed, hardy and long-lived than horses, and they are considered less obstinate, faster, and more intelligent than donkeys."
A female mule that has estrus cycles and thus, in theory, could carry a fetus, is called a "molly" or "Molly mule," though the term is sometimes used to refer to female mules in general. Pregnancy is rare, but can occasionally occur naturally as well as through embryo transfer. One of several terms for a gelded mule is a "John mule."
The median weight range for a mule is between about 370 and 460 kg (820 and 1,000 lb). Although it depends on the individual animal, an army mule can "carry up to 72 kg and walk 26 km without resting." In general, a mule can be packed with "dead weight" of up to 20% of its body weight, or approximately 90 kg (200 lb). The average equine in general can carry up to approximately 30% of its body weight in "live" weight, such as a rider. However, while a few mules can carry live weight up to 160 kg (350 lb), the superiority of the mule becomes apparent in their additional endurance.
One of the virtues of the mule is that a mule has the size and ground-covering ability of a horse, but is comparatively stronger than a horse of similar size and inherits the endurance and disposition of the donkey father. Mules also tend to be more independent than most other domesticated equines other than the donkey. Mules also tend to require less food than a horse of similar size.
With its short thick head, long ears, thin limbs, small narrow hooves, and short mane, the mule shares characteristics of a donkey; in height and body, shape of neck and croup, uniformity of coat, and teeth, it appears horse-like; the mule comes in all sizes, shapes and conformities. There are mules that resemble quarter horses, huge draft mules, fine-boned racing mules, shaggy pony mules and many more types.
A mule does not sound exactly like a donkey or a horse. Instead, a mule makes a sound that is similar to a donkey's but also has the whinnying characteristics of a horse (often starts with a whinny, ends in a hee-haw). Sometimes, mules whimper. The coats of mules come in the same varieties as those of horses. Common colors are sorrel, bay, black, and grey. Less common are white, roans (both blue and red), palomino, dun, and buckskin. Least common are paint mules or tobianos.
The mule possesses the even temper, patience, endurance and sure-footedness of the donkey, and the vigor, strength and courage of the horse. Operators of working animals generally find mules preferable to horses: mules show more patience under the pressure of heavy weights, and their skin is harder and less sensitive than that of horses, rendering them more capable of resisting sun and rain. Their hooves are harder than horses', and they show a natural resistance to disease and insects. Many North American farmers with clay soil found mules superior as plow animals.
Mules are generally less tolerant towards dogs than horses are. They are also capable of striking out with any of their hooves in any direction, even sideways if needed.
Mules exhibit a higher cognitive intelligence than their parent species. This is believed to be the result of hybrid vigor, similar to how mules acquire greater height and endurance than either parent.
Mules are highly intelligent. They tend to be curious by nature. A mule generally will not let the rider put it in harm's way.
Color and size variety 
Mules come in a variety of shapes, sizes and colors, from minis under 50 lb (20 kg) to maxis over 1,000 lb (500 kg), and in many different colors. Mules from Appaloosa mares produce wildly colored mules, much like their Appaloosa horse relatives, but with even wilder skewed colors. The Appaloosa color is produced by a complex of genes known as the Leopard complex (Lp). Mares homozygous for the Lp gene bred to any color donkey will produce an Appaloosa colored mule.
The Food and Agriculture Organization of the United Nations (FAO) reports that China was the top market for mules in 2003, closely followed by Mexico and many Central and South American nations.
Mules and hinnies have 63 chromosomes, a mixture of the horse's 64 and the donkey's 62. The different structure and number usually prevents the chromosomes from pairing up properly and creating successful embryos, rendering most mules infertile.
There are no recorded cases of fertile mule stallions. A few female mules have produced offspring when mated with a purebred horse or donkey. Herodotus gives an account of such an event as an ill omen of Xerxes' conquest of Greece in 480 BC: "There happened also a portent of another kind while he was still at Sardis,—a mule brought forth young and gave birth to a mule" (Herodotus The Histories 7:57).
Since 1527 there have been more than 60 documented cases of foals born to female mules around the world. There are reports that a mule in China produced a foal in 1984. In Morocco, in early 2002, a mare mule produced a rare foal. In 2007 a mule named Kate gave birth to a mule son in Colorado. Blood and hair samples were tested verifying that the mother was a mule and the colt was indeed her offspring.
A 1939 article in the Journal of Heredity describes two offspring of a fertile mare mule named "Old Bec", which was owned at the time by the A&M College of Texas (now Texas A&M University) in the late 1920s. One of the foals was a female, sired by a jack. Unlike its mother, it was sterile. The other, sired by a five-gaited saddlebred stallion, exhibited no characteristics of any donkey. That horse, a stallion, was bred to several mares, which gave birth to live foals that showed no characteristics of the donkey.
Modern mules 
In the second half of the 20th century, widespread usage of mules declined in industrialized countries. The use of mules for farming and transportation of agricultural products largely gave way to modern tractors and trucks. However, in the United States, a dedicated number of mule breeders continued the tradition as a hobby and continued breeding the great lines of American Mammoth Jacks started in the United States by George Washington with the gift from the King of Spain of two Catalan donkeys. These hobby breeders began to utilize better mares for mule production until today's modern saddle mule emerged. Exhibition shows where mules pulled heavy loads have now been joined with mules competing in Western and English pleasure riding, as well as dressage and show jumping competition. There is now a cable TV show dedicated to the training of donkeys and mules. Mules, once snubbed at traditional horse shows, have been accepted for competition at the most exclusive horse shows in the world in all disciplines.
Mules are still used extensively to transport cargo in rugged roadless regions, such as the large wilderness areas of California's Sierra Nevada mountains. Commercial pack mules are used recreationally, such as to supply mountaineering base camps, and also to supply trail building and maintenance crews, and backcountry footbridge building crews. There are still at least sixteen commercial mule pack stations in business in the Sierra Nevada. The Angeles chapter of the Sierra Club has a Mule Pack Section that organizes hiking trips with supplies carried by mules.
Amish farmers, who reject tractors and most other modern technology for religious reasons, commonly use teams of six or eight mules to pull plows, diskers, and other farm equipment, though they use horses for pulling buggies on the road.
During the Soviet war in Afghanistan, the United States used large numbers of mules to carry weapons and supplies over Afghanistan's rugged terrain to the mujahideen. Use of mules by U.S. forces has continued during the War in Afghanistan (2001-present), and the United States Marine Corps now conducts an 11-day Animal Packers Course at its Mountain Warfare Training Center located in the Sierra Nevada near Bridgeport, California.
Mule clone 
In 2003, researchers at University of Idaho and Utah State University produced the first mule clone as part of Project Idaho. The research team includes Gordon Woods, UI professor of animal and veterinary science, Kenneth L. White, USU professor of animal science, and Dirk Vanderwall, UI assistant professor of animal and veterinary science. The baby mule, Idaho Gem, was born May 4. It is the first clone of a hybrid animal. Veterinary examinations of the foal and its surrogate mother showed them to be in good health soon after birth. The foal's DNA comes from a fetal cell culture first established in 1998 at the University of Idaho.
See also 
- "Mule Day A Local Legacy". Library Of Congress.
- Ensminger, M. E. (1990). Horses and Horsemanship: Animal Agriculture Series (Sixth ed.). Danville, IL: Interstate Publishers. ISBN 0-8134-2883-1. pp. 85–87.
- Jackson, Louise A. The Mule Men: A History of Stock Packing in the Sierra Nevada, p. 5 (Mountain Press Publishing Co, Missoula, Montana, 2004). ISBN 0-87842-499-7
- "Mule". The Encyclopaedia Britannica: A Dictionary of Arts, Sciences, and General XVII. Henry G. Allen and Company. 1888. p. 15.
- "Beasts ease burden of quake victims". BBC News. 2005-10-19. Retrieved 2010-04-06.
- "More With Wayne Carlton On Elk Hunting" Hunter Specialties. Web site accessed June 1, 2009.
- American Endurance Ride Conference (November 2003). "Chapter 3, Section IV: Size". Endurance Rider's Handbook. AERC. Retrieved 2008-08-07.
- Proops, Leanne; Faith Burden, Britta Osthaus (2008 -07-18). "Mule cognition: a case of hybrid vigor?" (PDF). Animal Cognition 12 (1): 75. doi:10.1007/s10071-008-0172-1. PMID 18636282. Retrieved 2008-08-10.
- of case of genetically verified female mule offspring
- "Morocco's miracle mule". BBC News. 2002-02-05. Retrieved 2009-02-05. mirror
- A C Chandley, C A Clarke (1985 October). "Cum mula peperit" 78 (10). Journal of the Royal Society of Medicine. pp. 800–801. Retrieved 2009-02-05. mirror
- R. Rong, A.C. Chandley, J. Song, S. McBeath, P.P. Tan, Q. Bai, R.M. Speed (1988). "A fertile mule and hinny in China" 47 (3). Cytogenetics and Genome Research. Retrieved 2008-09-28. mirror
- "Befuddling Birth: The Case of the Mule's Foal". National Public Radio. 2007-07-26. Retrieved 2009-02-05.
- Nancy Lofholm (2007-09-19). "Mule's foal fools genetics". Seattle Post Intelligencer. Retrieved 2008-09-02-05. mirror
- W. S. Anderson (1939). "Fertile Mare Mules". Journal of Heredity. Retrieved 2012-11-03.
- Louise A. Jackson, The Mule Men: A History of Stock Packing in the Sierra Nevada, (Mountain Press Publishing Co., Missoula, MT, 2004) ISBN 0-87842-499-7
- Eastern Sierra Packers Association
- Mule Pack Section, Angeles Chapter, Sierra Club
- Bearden, Milt (2003) The Main Enemy, The Inside story of the CIA's Final showdown with the KGB
- "Project Idaho". University of Idaho. 2009-05-29. Retrieved 2009-09-14.
|Wikimedia Commons has media related to: Mules|
|Look up mule in Wiktionary, the free dictionary.|
- British Mule Society
- A case of a mule giving birth
- Supply Mules in Kashmir
- Project Idaho
- Western Mule Magazine
- The American Donkey and Mule Society, registers mules of all types/educational information. Also some fertile mule information in FAQ.
- Mule Production (pub.1948) hosted by the UNT Government Documents Department