Hybrid Equines

Equid (horse, donkey, zebra) hybrids are well known and some are bred commercially. The generic term for a zebra hybrid with a horse, pony, donkey or ass is a zebroid. The generic term for a hybrid of a zebra with any type of donkey or ass is a zebrass.

The usual naming convention for hybrids is a "portmanteau word" comprising first part of male parent's name + second part of female parent's name. 

A horse/zebra hybrid foal at the Rothschild Zoological Museum, Tring, England.

Zebras that are hand-reared or reared with domestic horses or donkeys can become tame enough to be led, ridden or used as draught animals. Those raised with horses or donkeys may prefer to mate with horses or donkeys rather than with zebras.

MULES, MOLLIES AND HINNIES

Mules (donkey stallion/horse mare) are bred as draught animals. Male mules are sterile, but fertile female mules (mollies) sometimes occur and can be mated to either a horse of donkey stallion. In France, the Poitou donkey is used almost exclusively for siring large, strong mules on Poitou horse mares. Jack donkeys are reportedly often reluctant to mate with horse mares and may have to be trained to do so. Miniature mules are produced using smaller breeds of donkey and pony. An article in The New York Times, Thursday Feb 22nd, 1968 entitled "Rare Type Of Mule Kicks Up Heels At Children's Zoo" detailed the birth of a foal to a Shetland pony fathered by a burro at New York's Central Park Zoo. Although sterile, mule stallions are generally castrated to make them tractable.

The hinny (horse stallion/donkey mare hybrid) is less common. The head of a hinny is more horse-like than the head of a mule. They are harder to produce than mules as stallion/jenny matings are less likely to result in pregnancy. Hinnies are smaller and finer boned than mules. This was believed to be due to the donkey mare having a less roomy womb, but the difficulty in impregnation suggests it is largely genetic. Donkeys have 62 chromosomes while horses have 64 chromosomes; hybrids are less likely where the male has more chromosomes than the female.

In "The Variation Of Animals And Plants Under Domestication" Darwin wrote: "The ass has a prepotent power over the horse, so that both the mule and the hinny more resemble the ass than the horse; but that the prepotency runs more strongly in the male-ass than in the female, so that the mule, which is the offspring of the male-ass and mare, is more like an ass, than is the hinny, which is the offspring of the female-ass and stallion." In "The Variation Of Animals And Plants Under Domestication" Darwin elaborated: "Colin, who has given in his 'Traite Phys. Comp.' tome 2 pages 537-539, [...] is strongly of opinion that the ass preponderates in both crosses, but in an unequal degree. This is likewise the conclusion of Flourens, and of Bechstein in his 'Naturgeschichte Deutschlands' b. 1 s. 294. The tail of the hinny is much more like that of the horse than is the tail of the mule, and this is generally accounted for by the males of both species transmitting with greater power this part of their structure; but a compound hybrid which I saw in the Zoological Gardens, from a mare by a hybrid ass-zebra, closely resembled its mother in its tail."

FERTILE MULES AND HULES

Mules are generally sterile, but several female mules have produced offspring when mated to a purebred horse or ass. This is so rare that the Romans had a saying, "cum mula peperit," meaning "when a mule foals" - the equivalent of "when hell freezes over." When a mule gave birth in Albania in 1994, it was thought to have unleashed the spawn of the devil on a small village. When a mule gave birth in 2002 in Morocco five years ago, locals feared it signalled the end of the world.

Donkeys have 62 chromosomes while horses have 64 chromosomes. As well as different numbers, the chromosomes have different structures. Mules and hinnies have 63 chromosomes that are a mixture of one from each parent. The different structure and number usually prevents the chromosomes from pairing up properly and creating successful embryos. Since 1527 there have been more than 60 foals born to female mules around the world and probably additional unreported ones. However, mollies have a strong maternal drive and will kidnap foals of horses and donkeys sharing the same paddock.

Cornevin and Lesbre stated that in 1873 an Arab mule was fertilized in Africa by a horse stallion, and produced female offspring. Both parents and the offspring were taken to the Jardin d'Acclimatation in Paris where the mule had a second female colt sired by the same stallion and then two male colts, one sired by an ass and the other by a horse stallion. The female progeny were fertile, but their offspring were feeble and died at birth. Cossar Ewart gives an account of a recent Indian case in which a female mule gave birth to a male colt. The best documented fertile mule mare was "Krause" who had 2 male offspring, both sired by her own sire. In most fertile mule mares, the mare passes on a complete set of her maternal genes (i.e. from her horse/pony mother) to the foal rather than a mixture of chromosomes. A female mule bred to a horse will therefore produce a 100% horse foal.

In the 1920s, a mule mare called "Old Beck" (Texas A&M) produced a mule daughter called "Kit". When Old Beck was bred to a horse stallion she produced a horse son (he sired horse foals). When bred to a donkey, she produced mule offspring. Likewise, a mare mule in Brazil has produced two 100% horse sons sired by a horse stallion.

A molly gave birth to 2 foals in Nebraska in the mid-1980s. The event prompted the first genetic testing of a mule's offspring. Tests showed no evidence the mother passed along any genetic markers from her donkey father, who was also the father of the foals. This is called "hemiclonal transmission". She passes on only her horse DNA with no shuffling of horse and donkey genetic material.

In April 2007, a 7 year old black molly, “Kate”, owned by ranchers Larry and Laura Amos gave birth at a Grand Mesa ranch near to Colbran. Kate was one of 10 mules purchased from Pleasant Plains, Arkansas and would already have been pregnant. Genetic testing at the University of Kentucky and the University of California at Davis confirm that Kate is a mule and that the foal is her offspring. This rules out stolen foals that were donkeys or mulish-looking horses. Her son has a donkey-like appearance suggesting the father was a donkey and, because female mules usually only pass on their maternal horse DNA, that he is a mule.

A fertile hinny in China is believed to be a unique case. Her offspring was sired by a donkey. Named "Dragon Foal", one would have expected a donkey foal if the mother had passed on her maternal chromosomes in the same way as a mule. However, Dragon Foal appears to be a strange donkey with some mule-like features. Her chromosomes and DNA tests confirm she is a previously undocumented combination. In Morocco, a mare mule produced a male foal that is 75% donkey and 25% horse i.e. she passed on a mixture of genes instead of passing on her maternal chromosomes. There are no recorded cases of fertile mule stallions.

There is an unverified case of a mare mule that produced a mule daughter (this may be another report of Old Beck and Kit). The daughter was also fertile and produced a horse-like foal with some mule traits; this was dubbed a "hule". There are no reports as to whether the hule was fertile; it may have been castrated in the same way as a mule stallion.

ZEBRA/DONKEY (ZEBRA/ASS) HYBRIDS

Zedonks (zebronkeys, zonkeys, zebadonks, zebrydes) are zebra stallion/donkey hybrids. Zebrets are donkey stallion/zebra mare hybrids and are rare. Other names have been used: zenkey (Japan) and hamzab (Israel). Generic terms are zebrass, zebra mule and zebra hinny.

Zebrasses resemble donkeys with a striped pattern overlaided on the donkey's background colour. Usually there is clear striping on the legs, a dorsal stripe. There may be facial stripes and indistinct stripes on the body. According to Dorcas McClintock in "A Natural History Of Zebras," a hybrid foal from a Somali wild ass bred to a mountain zebra mare had 2 transverse shoulder stripes, leg bands and zebra-like ear stripes. Piebald zebrasses are produced when a zebra is crossed to a piebald donkey.

Zebrass males are generally sterile although Darwin wrote of a hybrid born of a horse mare and a zebras stallion.

  A zebrass foaled at Schoenbrunn in 1841.  Hybrid of Grevy's Zebra and Somali Ass(1929)

"Ass-zebra" ("Wonders of Animal Life" edited by J A Hammerton (1930)). Possibly one of the Sells-Floto Circus Hyneys.

1970s zebra/donkey hybrid, photographed 2006 at Colchester Zoo, England.

A Grevy’s zebra stallion was presented to USA by King Menelik of Abyssinia. President Roosevelt. It lived at the national Zoo from 1904 to 1919 and was loaned for a while to the US Dept of Agriculture for use in cross-breeding experiments with horses and asses. At least some of the hybrid offspring went to Sells-Floto circus. Sells-Floto Circus advertised one of the hybrids as:

A New Member Of The Animal Kingdom. A strange beast came into being a short time ago, and naturally it was the Sells-Floto Circus which seized upon it as thing of interest to the public at large That beast was the ‘Hyney,’ a Government animal, now being exhibited with the Circus to show the wonderful results of the propagation and breeding of entirely different animals.

For the parents of the Hyney were brought from widely separated parts of the earth. After years of experiments, in which attempts were made to cross the zebra with some other beast that might give it value as a domestic animal, the United States Government, through its division of husbandry and animal industry, decided that the burro was the proper animal. And so a Grevy Zebra, of the Galla district of Africa, the fiercest and wildest of all types of zebra, was crossed with a Rocky Mountain Burro, known as the slowest and dullest and most sluggard animal of the horse species. The result was a success.

And thus it is that a new animal enters into being – the Hyney – with a burro for a mother and a zebra for a father. The combination is perfect. As fleet, as graceful as a horse, yet the Hyney has all the strength and working power of a mule. As intelligent as its zebra forebear, still it has the docility of its burro ancestors. Five of the animals are exhibited both in the menagerie and main performance of the Sells-Floto Circus, where the extent of their intelligence and their value as farm animals is well depicted.

An article from New York Times, June 16th, 1973, announced the birth of a zebra/donkey hybrid at the Jerusalem Zoo. They called it a "hamzab" from the Hebrew for donkey-zebra and erroneously claimed it to be the first of its kind born anywhere. A breeding programme at Colchester Zoo, England in 1975 produced several zedonk hybrids from Arabian donkey mares and zebra stallions. In Christmas week of 1975 their third zedonk foal was born. Previous attempts at crossbreeding zebras with horses and donkeys had failed to produce surviving foals. The zoo's aim was to produce disease-resistant work-horses for Africa. Colchester Zoo experts believed their success was due to the use of an Arabian donkey (a variety not tried before in hybridization experiments) and had hoped that the hybrids would be viable and fertile. Their last zedonk, Shadow, is 30 years old. He shares an enclosure with zebras, but does not socialise with them.

Usually a zebra stallion is paired with a horse mare or ass mare, but in 2005, a Burchell's zebra named Allison produced a zebrass (a zebret ) called Alex sired by a donkey at Highland plantation in St. Thomas parish, Barbados.

In "Origin of Species" (1859) Charles Darwin mentioned four coloured drawings of hybrids between the ass and zebra. In his "The Variation Of Animals And Plants Under Domestication", he mentions an unusal zebra triple-hybrid: "I have seen, in the British Museum, a hybrid from the ass and zebra dappled on its hinder quarters. [...] Many years ago I saw in the Zoological Gardens a curious triple hybrid, from a bay mare, by a hybrid from a male ass and female zebra." and "a compound hybrid which I saw in the Zoological Gardens, from a mare by a hybrid ass-zebra, closely resembled its mother in its tail." If true, this is the only account of a fertile zebrass stallion.

In "Darwinism An Exposition Of The Theory Of Natural Selection With Some Of Its Applications" (1889), Alfred Russel Wallace commented on the production and appearance of hybrids: "Crosses between the two species of zebra, or even between the zebra and the quagga, or the quagga and the ass, might have led to a very different result."

ZEBRA/HORSE, ZEBRA/PONY HYBRIDS

Zorses or zebrules are zebra stallion/horse hybrids and zonies are zebra stallion/pony hybrids. Zorses are sometimes called golden zebras due to dark stripes overlaying a chestnut background, though the colour depends on the colour of the horse parent. The zetland is a one off accidental zebra/Shetland pony hybrid.

Zebroid is a blanket term for zebra/horse hybrids. Any of the zebra species can be used in breeding zebroids; the colour depends on the colour of the horse; usually there is clear striping on the legs, a dorsal stripe, striped face and less distinct stripes on the body; the somewhat donkey-like attributes of zebras result in a dorsal stripe, upright mane without a forelock and large ears.

Piebald zorses are produced when a zebra is crossed to a piebald horse. Stripes are visible on the colored areas of the coat. The white patches form a startling contrast with these striped patches. A hybrid called "Eclyse" was bred in Germany in 2007 from a zebra mare and piebald or skewbald horse stallion (piebald = black-and-white, skewbald = any-other -colour-and-white e.g. brown/bay/chestnut with white). Pied zorses are not commonly bred.

Another term for zebra hybrids is zebra mule since zebra stallions (which are hand-raised or fostered on a horse mare) are used in preference to zebra mares. Zebra hinnies are rarely found. Zebroid and zebrass males are generally sterile. Although wild animals, zebras which are hand-reared or reared with domestic horses can become tame enough to be led, ridden or used as draught animals.

In "Origin of Species" (1859) Charles Darwin wrote: "In Lord Moreton's famous hybrid from a chestnut mare and male quagga, the hybrid, and even the pure offspring subsequently produced from the mare by a black Arabian sire, were much more plainly barred across the legs than is even the pure quagga..

In his "The Variation Of Animals And Plants Under Domestication", Darwin wrote: "I have seen, in the British Museum, a hybrid from the ass and zebra dappled on its hinder quarters. [...] Many years ago I saw in the Zoological Gardens a curious triple hybrid, from a bay mare, by a hybrid from a male ass and female zebra". and further described Moreton's hybrid; In the famous hybrid bred by Lord Morton ('Philosoph. Transact.' 1821 page 20.) from a chestnut, nearly purely-bred, Arabian mare, by a male quagga, the stripes were "more strongly defined and darker than those on the legs of "the quagga." The mare was subsequently put to a black Arabian horse, and bore two colts, both [...] plainly striped on the legs, and one of them likewise had stripes on the neck and body.

In "Darwinism An Exposition Of The Theory Of Natural Selection With Some Of Its Applications" (1889), Alfred Russel Wallace commented: "Crosses between the two species of zebra, or even between the zebra and the quagga, or the quagga and the ass, might have led to a very different result." 

Raymond Hook of Nanyuki, Kenya, is claimed to have bred the first zebroids by crossing a Grevy's zebra stallion with domestic mares (date unknown?). The hybrids had Grevy-like narrow stripes and a tufted tail, but were more horselike in conformation and color. The strong, sure-footed, docile and mulelike zebroids were used as pack animals by climbers on Mount Kenya's lower slopes. Grey's zebra has also been crossed with donkey mares.

Carl Hagenbeck produced zebrules (zebra/pony hybrids) at his Tierpark in Hamburg. These had dark bodies and faintly visible stripes.

1899 zebra/horse hybrid

1904 zebra/horse hybrid

Cossar Ewart, Professor of Natural History at Edinburgh (1882-1927) and a keen geneticist, crossed a zebra stallion with pony mares in order to disprove telegony, or paternal impression, a common theory of inheritance at the time. Telegony states that if a female mates with more than one male the later offspring will inherit characteristics from the earlier sires.

In "Anomalies and Curiosities of Medicine" by George M Gould and Walter L Pyle (1896) wrote: The influence of the paternal seed on the physical and mental constitution of the child is well known. To designate this condition, Telegony is the Word that was coined by Weismann in his "Das Keimplasma," and he defines it as "Infection of the Germ," and, at another time, as " Those doubtful instances in which the offspring is said to resemble, not the father, but an early mate of the mother," - or, in other words, the alleged influence of a previous sire on the progeny produced by a subsequent one from the same mother. In a systematic discussion of telegony before the Royal Medical Society, Edinburgh, on March 1, 1895, Brunton Blaikie, as a means of making the definition of telegony plainer by practical example, prefaced his remarks by citing the classic example which first drew the attention of the modern scientific world to this phenomenon. The facts of this case were communicated in a letter from the Earl of Morton to the President of the Royal Society in 1821, and were as follows:

In the year 1815 Lord Morton put a male quagga [a type of zebra] to a young chestnut mare of seven eighths Arabian blood, which had never before been bred from. The result was a female hybrid which resembled both parents. He now sold the mare to Sir Gore Ousley, who two years after she bore the hybrid put her to a black Arabian horse. During the two following years she had two foals which Lord Morton thus describes: " They have the character of the Arabian breed as decidedly as can be expected when fifteen sixteenths of the blood are Arabian, and they are fine specimens of the breed; but both in their color and in the hair of their manes they have a striking resemblance to the quagga. Their color is bay, marked more or less like the quagga in a darker tint. Both are distinguished by the dark line along the ridge of the back, the dark stripes across the forehand and the dark bars across the back part of the legs." The President of the Royal Society saw the foals and verified Lord Morton's statement.

However, Cossar Ewart found that zebra-horse hybrids were brown with faint stripes. When the same mares were subsequently mated with a pony, the resulting foals showed none of the markings or temperamental characteristics of a zebra. Cossar Ewart found that in male zebra-hybrids the sexual cells were immature and the sperm were abnormal, however the ovaries of female zebra-hybrids appeared similar to those of a normal mare or female zebra. As well as disproving paternal impression, he wanted to produce a more resilient draught animal for South Africa; one less subject to local diseases and more tractable than a mule.

An experiment that disproved telegony. Left, a striped zebra-horse hybrid, produced by mating a mare with a zebra stallion. The same mare was then mated with a horse stallion, and produced the filly shown below, which bears no traces of any effect of the previous sire. The experiment was carried out by the US Government and reported in "Genetics in Relation to Agriculture" by E B Babcock and RE Clausen. ("The Science of Life" by H G Wells, J Huxley and GP Wells (c.1929))

In "The Science of Life" (c 1929) by H G Wells, J Huxley and GP Wells, the authors wrote "To-day it is possible to assert without any question that telegony is a mere fable, which could only have gained ground in the days when men were ignorant of the true mechanism of fertilization and reproduction. The supposed instances of telegony which are constantly being reported even to-day, invariably. Perhaps the most famous example is that of Lord Morton's mare. The mare, a pure Arabian, was mated with a zebra stallion, and produced a hybrid foal. On two later occasions, she was bred to a black Arab stallion, and gave birth to two further foals. These had legs which were striped even more definitely than those of the hybrid foal or the zebra sire himself, and one had some stripes on parts of the neck also. In addition, they had a stiff mane of very zebra-like appearance. Darwin himself accepted the evidence as sufficient proof of telegony. But when definitely planned and long-continued experiments were made, the proof escaped. Cossar Ewart, for instance, made a number of horse and zebra crosses to test the validity of the belief. When mares previously bred to zebras were afterwards mated with horse stallions, their colts were often without the least trace of zebra characters. In other cases, colts with some degree of striping were produced. But one mare gave birth to a striped colt as a result of her first mating, which was with a horse stallion ; while two later matings with other stallions, made after she had been successfully mated once and three times respectively with a zebra, gave unstriped offspring. In other cases, when striped colts were born to a mare and stallion after the mare had been previously mated to a zebra, Ewart took other mares, closely related to the first, bred them to the same Arabian stallion without having mated them previously with a zebra - and they, too, produced striped foals. In short, the production of striping (and also of erect mane) in foals is not a very uncommon occurrence in horses; it may appear whether previous impregnation by a zebra has taken place or not. The stripes of Lord Morton's foals were a mere coincidence, well illustrating the danger of drawing conclusions from single and therefore possibly exceptional cases, and the need for systematic and repeated experiments."

The King's Hybrid (1902). This seems to be the same animal Hammerton later described in 1930.

In "Animal Life and the World of Nature" (1902-1903), WP Dando (Fellow of the Zoological Society, London) writes: Much interest has been aroused at the Zoo by the presentation by His Majesty the King of a hybrid Zebra, a cross-breed between a stallion horse and a Burchell's zebra mare. This animal was sent over to England by Lord Kitchener, who discovered it among the remounts placed at his disposal in the Transvaal during the war. The zebra markings are fairly distinct on all four legs, also slightly across the loins and at the root of the tail, continuing a few inches up the centre of the buttocks. These markings (and the tail itself, which it will be noticed is more like a donkey's than a horse's) are the only characteristics of the zebra which are prominent, the animal lacking the erect mane and other distinguishing features. Since the animal has been in captivity he has become most ferocious and savage - no doubt from the want of proper exercise. By the courtesy of the Society's officials I was enabled to get my pictures in the yard adjoining the stables, the animal being securely held; and I took my position at a respectful distance."

German zebroid (1929)

In "Wonders of Animal Life" (1930), J A Hammerton, it noted that crosses were made between Chapman's zebras and a ponies during the South African War.

In "Wonders of Animal Life" (1930) edited by J A Hammerton, it notes: During the South African War, an attempt was made by the Boers to evolve a new animal to supplement the supply available for transport work. A cross was obtained between a Chapman's zebra and a pony and a specimen was captured by the British and presented to King Edward VII by Lord Kitchener. The animal was produced chiefly for hauling guns. It was photographed by W S Berridge. WP Dando FZS, in the 1902/03 encyclopedia "Animal Life and the World of Nature" described the same hybrid as a cross with a Burchell's zebra.

McClintock noted that a Chapman's zebra stallion, kept by Friedrich von Falz-Fein at Askania-Nova in southern Russia actually preferred to mate with domestic mares rathter than with a Chapman zebra mare. Eventually the stallion killed his zebra mate by biting her to death.

Today, zorses and zonies are relatively common. Zebra hybrids are considered better suited (through better temperament and more horse-like/donkey-like conformation) than pure zebras to being ridden or used for draught. They are resistant to some of the diseases that afflict horses and donkeys, hence they have been used use in Africa for trekking and draught. In the USA they are bred as riding and show animals, because of their interesting appearance.

ZORSE/ZONY COLOURS

Zebras are normally bred to solid colour horses/ponies to produce offspring with striping over the whole body. The interaction of chestnut and zebra striping gives rise to the alternative name "golden zebra". The striping pattern depends on the type of zebra used. When bred to a piebald (black-and-white) horse (US: piebald pinto) or to a skewbald (brown/bay/chestnut-and-white) horse (US: skewbald pinto) or to particoloured USAnian breeds known as "Paint" and "Appaloosa", the offspring have a mix of striped coloured areas and unstriped white areas. Grey horses are not used as the offspring will be grey, becoming white with age, albeit having the conformation of a zorse/zony.

DARWIN ON HYBRID EQUIDS

In "Origin of Species" (1859) Charles Darwin mentioned four coloured drawings of hybrids between the ass and zebra. He noted "In Lord Moreton's famous hybrid from a chestnut mare and male quagga, the hybrid, and even the pure offspring subsequently produced from the mare by a black Arabian sire, were much more plainly barred across the legs than is even the pure quagga. Lastly, and this is another most remarkable case, a hybrid has been figured by Dr. Gray (and he informs me that he knows of a second case) from the ass and the hemionus." Darwin described the latter hybrid in "The Variation Of Animals And Plants Under Domestication": The Equus indicus [onager] a hybrid, raised at Knowsley ('Gleanings from the Knowsley Menageries' by Dr. J.E. Gray.) from a female of this species by a male domestic ass, had all four legs transversely and conspicuously striped, had three short stripes on each shoulder and had even some zebra-like stripes on its face! Dr. Gray informs me that he has seen a second hybrid of the same parentage, similarly striped.

In his "The Variation Of Animals And Plants Under Domestication", Darwin wrote: "I have seen, in the British Museum, a hybrid from the ass and zebra dappled on its hinder quarters. [...] Many years ago I saw in the Zoological Gardens a curious triple hybrid, from a bay mare, by a hybrid from a male ass and female zebra. and further described Moreton's hybrid; In the famous hybrid bred by Lord Morton ('Philosoph. Transact.' 1821 page 20.) from a chestnut, nearly purely-bred, Arabian mare, by a male quagga, the stripes were "more strongly defined and darker than those on the legs of "the quagga." The mare was subsequently put to a black Arabian horse, and bore two colts, both [...] plainly striped on the legs, and one of them likewise had stripes on the neck and body.

In that book, Darwin concluded: "The ass has a prepotent power over the horse, so that both the mule and the hinny more resemble the ass than the horse; but that the prepotency runs more strongly in the male-ass than in the female, so that the mule, which is the offspring of the male-ass and mare, is more like an ass, than is the hinny, which is the offspring of the female-ass and stallion." In "The Variation Of Animals And Plants Under Domestication" Darwin elaborated: "Colin, who has given in his 'Traite Phys. Comp.' tome 2 pages 537-539, [...] is strongly of opinion that the ass preponderates in both crosses, but in an unequal degree. This is likewise the conclusion of Flourens, and of Bechstein in his 'Naturgeschichte Deutschlands' b. 1 s. 294. The tail of the hinny is much more like that of the horse than is the tail of the mule, and this is generally accounted for by the males of both species transmitting with greater power this part of their structure; but a compound hybrid which I saw in the Zoological Gardens, from a mare by a hybrid ass-zebra, closely resembled its mother in its tail.)"

In "Darwinism An Exposition Of The Theory Of Natural Selection With Some Of Its Applications" (1889), Alfred Russel Wallace commented: "Crosses between the two species of zebra, or even between the zebra and the quagga, or the quagga and the ass, might have led to a very different result."

OTHER EQUID HYBRIDS

According to Dorcas McClintock in "A Natural History Of Zebras," Grevy's zebra has 46 chromosomes; plains zebras have 44 and mountain zebras have 32. The domestic horse has 64 chromosomes. Although all 3 zebra species have been crossed with domestic horses, the 2 dissimilar sets of chromosomes inherited by a zebra hybrid cannot mix because of differences in number, size and shape. As a result, almost all zebra hybrids are sterile. In captivity, plains zebras have been crossed with mountain zebras. The hybrid foals had no dewlap and, except for their larger ears and their hindquarters pattern, they resembled the plains zebra parent. Attempts to breed a Grevy's zebra stallion to mountain zebra mares resulted in a high rate of abortion. In the wild, zebra species don't interbreed even where their ranges overlap or they graze together. This was was also true when the quagga and Burchell's race of plains zebra shared the same area. A hybrid foal from a Somali wild ass bred to a mountain zebra mare had 2 transverse shoulder stripes, leg bands and zebra-like ear stripes.

According to Crandall, some hybrids ("racial intergrades") were foaled by a Hartmann's mare and sired by a Cape stallion between 1924 and 1931; one of these was sent to London Zoological Gardens and figured by Antonius (1951:196). Crandall noted that Gray (1954) listed many crosses between zebras and both horses and asses, wild and domestic. In most cases the male hybrids seemed to be sterile, but there was some evidence indicating that females may sometimes be sterile. Several of these hybrids were figured by Antonius (1954). Additionally, Prezwalski's horse (a primitve wild species) interbreeds freely with domestic horse and has produced hybrids, probably sterile, with zebras, but did not produce offspring when mated with donkeys (Gray 1954). Although Crandall did not state where these Prezwalski hybrids were produced, they may have been at Hagenbeck's Tierpark. As a result, there may be a very low level of domesticated horse blood in some Prezwalski's horses today. The herd at the National Zoo's breeding farm at Front Royal, Virginia is known to contain domesticated horse blood.

Source: Messy Beast