Zebroid

Zebroid is the term generally used for all zebra hybrids. The different hybrids are generally named using a portmanteau of the sire's name and the dam's name. Generally, no distinction is made as to which zebra species is used. Many times, when zebras are crossbred, they develop some form of dwarfism. Breeding of different branches of the equine family, which does not occur in the wild, generally results in infertile offspring. The combination of sire and dam also affects the offspring phenotype.

A zorse is the offspring of a zebra stallion and a horse mare. This cross is also called a zebrula, zebrule, or zebra mule. The rarer reverse pairing is sometimes called a hebra, horbra, zebrinny, zebret, or zebra hinny. Like most other animal hybrids, the zorse is sterile.[1]

A zony is the offspring of a zebra stallion and a pony mare. Medium-sized pony mares are preferred to produce riding zonies, but zebras have been crossed with smaller pony breeds such as the Shetland, resulting in so-called "Zetlands".[2]

A zebra-donkey hybrid

A cross between a zebra and a donkey is known by many terms, including: zonkey,[3] (a term also used for donkeys in Tijuana, Mexico painted as zebras for tourists to pose with them in souvenir photos)[4] zebonkey, zebronkey, zebrinny, zebrula, zebrass, zedonk, and zebadonk. Donkeys are closely related to zebras and both animals belong to the horse family. These zebra/donkey hybrids are very rare.[5][6] In South Africa, they occur where zebras and donkeys are found in proximity to each other. Like mules and hinnys, however, they are generally genetically unable to breed, due to an odd number of chromosomes disrupting meiosis.

Living equids show wide variation in the number of chromosomes, ranging from a diploid number of 32 chromosomes in the mountain zebra to 66 in Przewalski's horse. This is due to number of chromosomal fusion and fission events during the evolution of equids.[7] The zebra has between 32 and 46 chromosomes depending on the species.

In spite of this difference, viable hybrids are possible, provided the gene combination in the hybrid allows for embryonic development to birth. A hybrid will have a number of chromosomes exactly halfway between that of its parents; for example, a cross between a horse (64 chromosomes), and a plains zebra (44 chromosomes), will produce a zebroid offspring with 54 chromosomes. The chromosome difference makes female hybrids poorly fertile and male hybrids generally sterile, due to a phenomenon called Haldane's rule. The difference in chromosome number is most likely due to horses having two longer chromosomes that contain similar gene content to four zebra chromosomes.[8]

Just as male mules and hinnies are infertile so are male zebroids. And just as female mules and hinnies only very rarely produce offspring the same appears to be true of zebroids. Considering zebroids are much less common as mules the chances of a fertile zebroid mare are very slim. Only ONE case of such a mare was reported : The zebroid mare of a zebra mare x draft horse stallion produced a foal when she was bred back to her sire but the foal died of lightning and she did not survive it much longer.

A zorse

Zebroids physically resemble their nonzebra parent, but are striped like a zebra. The stripes generally do not cover the whole body, and might be confined to the legs or spread onto parts of the body or neck. If the nonzebra parent was patterned (such as a roan, Appaloosa, pinto/paint, piebald, or skewbald), this pattern might be passed down to the zebroid, in which case the stripes are usually confined to non-white areas. The alternative name "golden zebra" relates to the interaction of zebra striping and a horse's bay or chestnut colour to give a zebra-like black-on-bay or black-on-chestnut pattern that superficially resembles the extinct quagga. Zebra-donkey hybrids usually have a dorsal (back) stripe and a ventral (belly) stripe.

The hebra Eclyse

Zorses combine the zebra striping overlaid on colored areas of the hybrid's coat. Zorses are most often bred using solid-color horses. If the horse parent is piebald (black and white) or skewbald (other color and white), the zorse may inherit the dominant depigmentation genes for white patches. The tobiano (the most common white modifier found in the horse) directly interacts with the zorse coat to give the white markings. Only the nondepigmented areas will have zebra striping, resulting in a zorse with white patches and striped patches. This effect is seen in the zebroid named Eclyse (a hebra rather than a zorse) born in Stukenbrock, Germany, in 2007 to a zebra mare called Eclipse and a stallion called Ulysses.

Zebroids are preferred over zebras for practical uses, such as riding, because the zebra has a different body shape from a horse or donkey, and consequently it is difficult to find tack to fit a zebra. However, a zebroid is usually more inclined to be temperamental than a purebred horse and can be difficult to handle. Zebras, being wild animals, and not domesticated like horses and donkeys, pass on their wild animal traits to their offspring. Zebras, while not usually very large, are extremely strong and aggressive. Similarly, zorses have a strong temperament and can be aggressive.

Zebra-horse hybrid foal with quagga-like markings, Walter Rothschild Zoological Museum, Tring, England

In 1815, Lord Morton mated a quagga stallion to a chestnut Arabian mare. The result was a female hybrid which resembled both parents. This provoked the interest of Cossar Ewart, Professor of Natural History at Edinburgh (1882–1927) and a keen geneticist. Ewart crossed a zebra stallion with pony mares to investigate the theory of telegony, or paternal impression. In Origin of Species (1859), Charles Darwin mentioned four coloured drawings of hybrids between the ass and zebra. He also wrote

In Lord Morton'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.[12]

In his book The Variation of Animals and Plants under Domestication, Darwin described a hybrid ass-zebra specimen in the British Museum as being dappled on its flanks. He also mentioned a "triple hybrid, from a bay mare, by a hybrid from a male ass and female zebra" displayed at London Zoo. This would have required the zebroid sire to be fertile.

During the South African War, the Boers crossed Chapman's zebras with ponies, to produce animals for transport work, chiefly for hauling guns. A specimen was captured by British forces and presented to King Edward VII by Lord Kitchener, and was photographed by W. S. Berridge.[13] Zebras are resistant to sleeping sickness, whereas purebred horses and ponies are not, and zebra mules hopefully would inherit this resistance.

Grevy's zebra has been crossed with the Somali wild ass in the early 20th century. Zorses were bred by the US government and reported in Genetics in Relation to Agriculture by E. B. Babcock and R. E. Clausen (early 20th century), in an attempt to investigate inheritance and telegony. The experiments were also reported in The Science of Life by H G Wells, J Huxley, and G P Wells (around 1929).

Interest in zebra crosses continued in the 1970s. In 1973, a cross between a zebra and a donkey was foaled at the Jerusalem Zoo. They called it a "hamzab". In the 1970s, the Colchester Zoo in England bred zedonks, at first by accident and later to create a disease-resistant riding and draft animal. The experiment was discontinued when zoos became more conservation-minded. A number of hybrids were kept at the zoo after this; the last died in 2009.[14] One adult still remains at the tourist attraction of Groombridge Place[15] near Tunbridge Wells in Kent.

Zorses have appeared in several TV shows and movies. In the Viva La Bam episode "Groundhog Day". in the final race, Brandon Dicamillo's sled is a zorse. It was colored pink, blue, purple. and red. On the 'uncommentary' on the DVD seasons of Viva La Bam, Tim Glomb says, "If you send me a list of all the episodes where the zorse is, I'll give you a dollar". The 2007 movie I'm Reed Fish features a zorse named Zabrina. In the movie Racing Stripes, an animated zorse appears in the alternate ending. He is the son of Stripes, a zebra stallion and Sandy, a grey Arabian mare.

Zorses have also appeared in books. They are briefly mentioned several times in George R.R. Martin's A Song of Ice and Fire series of fantasy novels.[25] Sutton Coleman wrote a sonnet about zorses and published it in his 2007 book, Ligers, Tigons, and Zorses, Oh My! In Roald Dahl's book Going Solo, several other characters and he speculate on how nice it would be to own a zorse, although they admit it would be difficult to train.

The fantasy setting Glorantha has a magical fertile breed of horses crossed with zebras based on the city of Pavis. This small population is extended by breeding stallions of these breeds with ordinary horses, creating an infertile breed called Cavalry Zebras.

The video game Red Dead Redemption has the "Zebra Donkey" available as a multiplayer mount, however this is a Mexican donkey painted to appear as a zebra, so is not an actual hybrid breed.

In El Tigre: The Adventures of Manny Rivera, the characters' school's mascot is the famed Zebra Donkey.

Wikimedia Commons has media related to Zorses.

• Hybrid Equines Information and images of different zebroids
• Eclyse - Photo of a zebroid named Eclyse
• "Zenkey foal a hybrid star". Sydney Morning Herald. Agence France-Presse. 29 August 2003.
• BBC News (26 June 2001): "Zebra Hybrid is Cute Surprise"
• Metro (28 June 2007): "A single-zorsed story"
• Dorsett, Katherine. "What the heck is a zedonk?" CNN. 23 September 2010.
• The International Zebra Zorse Zonkey Association
• Video of a Zorse
• Rare zebra-donkey mix born in Florence animal reserve: The zonkey named Ippo only one in Italy