This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (February 2009)

Look up Equus, equus, or equine in Wiktionary, the free dictionary.

Equus is a genus of animals in the family Equidae that includes horses, donkeys, and zebras. Within Equidae, Equus is the only extant genus. Like Equidae more broadly, Equus has numerous extinct species known only from fossils. This article deals primarily with the extant species.

The term equine refers to any member of this genus, including any horse. The word comes from Latin equus, "horse",^[1] cognate with Greek "ἵππος" (hippos)^[2], Ionic "ἴκκος" (ikkos), "horse"^[3][4] (the earliest attested form of the word is the Mycenaean Greek i-qo, written in Linear B syllabic script^[5]).

Characteristics

Equines are medium to large mammals, with long heads, and necks with a mane. Their legs are slender and end in a single, unguligrade toe, protected by a horny hoof. They have long, slender tails, either ending in a tuft, or entirely covered in flowing hair. They are adapted to generally open terrain, from plains and savannas, to mountains or deserts.

The range of equine monocular vision. Shaded areas represent blind spots.

The pinnae (outer ears) of equines are mobile, enabling them to easily localise the origin of sounds. They have two-color, or dichromatic vision. Their eyes are set back far on the head, giving them a wide angle of view, without entirely losing binocular vision. Equines also have a vomeronasal organ, that allows males to use the flehmen, or 'lip-curling' response to assess the sexual state of potential mates. Equines are one of only two mammals (the other is the human) capable of producing copious sweat perspiration for thermoregulatory cooling, enabling fast running over long distances.

Equines are herbivores, and feed predominantly on tough, fibrous food, such as grasses and sedges. When in need, they will also eat other vegetable matter, such as leaves, fruits, or bark, but are normally grazers, not browsers. Unlike ruminants, with their complex stomachs, equines break down cellulose in the "hindgut" or caecum, a part of the colon. Their dentition is almost complete, with cutting incisors to crop food, and grinding molars set well back behind a diastema. The dental formula for equines is:

A feral horse herd in the western United States

Mounted fossil of Equus occidentalis from the La Brea Tar Pits

Equines are social animals, living in herds or bands. Horses, along with Plains and Mountain Zebras, have permanent herds generally consisting of a single male and a band of females, with the remaining males forming small "bachelor" herds. The remaining species have temporary herds, lasting only a few months, which may be either single-sexed or mixed. In either case, there are clear hierarchies established amongst the individuals, usually with a dominant female controlling access to food and water resources and the lead male controlling mating opportunities.

Females, usually called mares in horses and zebras, or, in the case of asses and donkeys, jennies, usually bear a single foal, after a gestation period of approximately 11 months. Young equines are able to walk within an hour of birth, and are weaned after four to thirteen months (animals living in the wild naturally wean foals at a later date than those under domestication). Depending on species, living conditions and other factors, females in the wild may give birth every year or every other year.^[6][7]

Equines which are not in foal generally have a seasonal estrous cycle, from early spring into autumn. Most females enter an anestrus period during the winter and thus do not cycle in this period. The reproductive cycle is controlled by the photoperiod (length of the day), with estrus triggered when the days begin to lengthen. Anestrus prevents the female from conceiving in the winter months, as that would result in her foaling during the harshest part of the year, a time when it would be more difficult for the foal to survive.^[8] However, equines who live near the equator, where there is less change in length of day from season to season, have no anestrus period, at least in theory.^[9] Further, for reasons that are not clear, about twenty percent of domestic mares in the Northern Hemisphere will cycle the year round.^[10]

Classification

Family Equidae (in addition to Equus, the family includes approximately 35 other genera, all extinct)

• Genus Equus
  • Subgenus Equus
    • Equus ferus Wild horse^[11][12]
      • Equus ferus caballus Domestic horse
      • †Equus ferus ferus Tarpan (historically extinct)
      • Equus ferus przewalskii Przewalski's Horse or Mongolian Wild Horse or takhi
      • †Equus algericus (Pleistocene of Algeria)
      • † North American caballid horses (Pleistocene; most likely synonymous with E. ferus):
        • †Equus lambei Yukon Wild Ass (or Yukon Wild Horse)
        • †Equus niobrarensis
      • Subgenus †Amerhippus Hoffstetter, 1950 (jr synonym subgenus Tomolabis Cope, 1892) (this subgenus and the species therin are possibly synonymous with E. ferus)^[13]
        • †Equus andium
        • †Equus neogeus
        • †Equus fraternus Leidy, 1860 (North America)
        • †Equus santaeelenae
        • †Equus scotti Owen
        • †Equus niobrarensis
        • †Equus conversidens Owen, 1863 ("Mexican Horse") (North America)
    • †New World stilt-legged horse (all following species within the group may be synonyms or regional races of a single species)^[14]
      • †Equus francisci Hay, 1915
      • †Equus semiplicatus Cope, 1893 (North America)
  • Subgenus Asinus
    • Equus africanus African Wild Ass^[12][15]
      • Equus africanus africanus Nubian Wild Ass
      • Equus africanus asinus Domestic Donkey, Ass or Burro
      • †Equus africanus atlanticus Atlas Wild Ass
      • Equus africanus somalicus Somali Wild Ass
    • Equus hemionus Onager or Asiatic Ass
      • Equus hemionus hemionus Mongolian Wild Ass, Dziggetai or Gobi Kulan
      • †Equus hemionus hemippus Syrian Wild Ass
      • Equus hemionus khur Indian Wild Ass or Khur
      • Equus hemionus kulan Turkmenian Kulan
      • Equus hemionus onager Persian Onager
    • Equus kiang Kiang
      • Equus kiang chu Northern Kiang
      • Equus kiang kiang Western Kiang
      • Equus kiang holdereri Eastern Kiang
      • Equus kiang polyodon Southern Kiang
    • †Equus hydruntinus European Ass (late Paleolithic of southern Europe)
    • †Equus altidens (middle Pleistocene of Tadjikistan)
    • †Equus tabeti (early middle Pleistocene of Algeria, known only from teeth and limb bones)
    • †Equus melkiensis (late Paleolithic of Algeria, based on teeth and limb bones)
    • †Equus graziosii (late Pleistocene of Italy)
  • Subgenus Dolichohippus
    • Equus grevyi Grevy's Zebra
    • †Equus koobiforensis Eisenmann, 1983 (East Africa, ~2 million years (late Pliocene), similar but more derived than E.simplicidens and E.sanmeniensis
      • †Equus oldowayensis Hopwood, 1937 (East Africa, late Pleiocene, early Pleistocene, likely conspecific with E.koobiforensis
  • Subgenus Hippotigris
    • Equus quagga Plains Zebra
      • Equus quagga boehmi Grant's Zebra
      • Equus quagga borensis Maneless Zebra
      • Equus quagga chapmani Chapman's Zebra
      • Equus quagga crawshayi Crawshay's Zebra
      • Equus quagga burchellii Burchell's Zebra
      • †Equus quagga quagga Gmelin, 1788 Quagga (South Africa, extinction in early 20th century)
      • Equus quagga selousi Selous' Zebra
    • Equus zebra L.,1758 Mountain Zebra
      • Equus zebra hartmannae Hartmann's Mountain Zebra
      • Equus zebra zebra Cape Mountain Zebra
    • †Equus mauritanicus Pomel, 1897 (Pleistocene transitional form between E. (Dolichohippus) and E. (Hippotigris), possibly via E.koobiforensis)
  • Subgenus †Parastylidequus
    • †Equus parastylidens Mooser’s Horse
  • incertae sedis
    • †Equus simplicidens Hagerman Horse (North American Pleiocene - earliest known species of genus Equus) (perhaps closest to Dolichohippus^[16])
    • †Equus cumminsii Cope, 1893 (North America; based on a single, 3 million year old tooth)
    • †Equus livenzovensis Baihusheva, 1978 (southern Russia and western Europe, Pleiocene - highly similar to E. simplicidens
    • †Equus sanmeniensis Teilhard&Piveteau, 1930 (south China, late? Pliocene; similar but more derived than E.livenzovensis
    • †Equus teilhardi Eisenmann, 1975 (south China, late(?) Pliocene; similar to E.sanmeniensis but smaller, likely synonym)
    • †Equus numidicus Pomel, 1897
    • †Equus plicidens Owen, 1844 (late Pliocene, only teeth known)
    • †Equus stenonis group
      • †Equus stenonis Cocchi, 1867 (Europe to China, late Pleiocene)
        • †Equus stenonis guthi (late Pliocene, France)
        • †Equus stenonis senezensis (late Pliocene)
        • †Equus stenonis pamirensis (=Hippotigris pamirensis) (late Pliocene, central Asia)
        • †Equus stenonis petraloniensis Tsoukala (Greece - Petralona cave)
        • †Equus stenonis vireti (late Pliocene)
      • †Equus sivalensis (late Pleiocene (?), India; similar to E.stenonis in skull shape)
      • †Equus stehlini (early Pleistocene, ~1 million years ago; similar but smaller than E. stenonis
      • †Equus bressanus (early Pleistocene, ~1 million years ago; similar but much larger than E. stenonis
      • †Equus sussenbornensis Wüst, 1901 (early middle Pleistocene of Europe)
      • †Equus verae Sher, 1971 (middle Pleistocene of north eastern Asia)
      • †Equus namadicus (middle paleolithic sites in India)
    • †subgenus Allozebra & Hesperohippus (N. American lineage of middle to late Pleistocene)
      • †Equus idahoensis
      • †Equus (A.) occidentalis
      • †Equus (A.) excelsus
      • †Equus (H.) pacificus
    • †Equus complicatus
    • †Equus fraternus
    • Equus major Boule (nomen dubium)
    • †Equus giganteus group
      • †Equus giganteus
      • †Equus pectinatus
      • †Equus crinidens

• 

  Przewalski's Horse, the only remaining type of "wild" horse that has never been domesticated

• 

  A domesticated horse

• 

  An onager, one type of wild ass

• 

  A pair of kiangs

• 

  Quagga (now extinct)

• 

  Plains zebra

• 

  Grévy's zebra

• 

  Equus conversidens (extinct)

Cross-breeds

Different species of Equus can crossbreed, though the ensuing offspring are usually infertile. Hybrids include:

a mule

• Mule, a cross between a male donkey and a female horse. Mules are the most common type of hybrid equine and are renowned for their toughness, surefootedness, and working ability.
• Hinny, a cross between a female donkey and a male horse. Considered a less desirable cross than a mule, generally smaller in size and not as hardy.

Any equine with partial zebra ancestry is called a zebroid.

See also

• Domestication of the horse
• Evolution of the horse

References

Sources

• Burke, et al. 2003. The systematic position of Equus hydruntinus, an extinct species of Pleistocene equid. Quaternary Research 59(3):459-469.
• Duncan, P. (ed.). 1992. Zebras, Asses, and Horses: an Action Plan for the Conservation of Wild Equids. IUCN/SSC Equid Specialist Group. IUCN, Gland, Switzerland.
• Equid Specialist Group 1996. Equus ferus. In: IUCN 2004. 2004 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 21 January 2006.
• Equid Specialist Group 1996. Equus ferus ssp. przewalskii. In: IUCN 2004. 2004 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 21 January 2006.
• Groves, C.P.; Bell, H.B. (2004). "New investigations on the taxonomy of the zebras genus Equus, subgenus Hippotigris". Mammalian Biology 69: 182–196. doi:10.1078/1616-5047-00133. 
• Higuchi RG, Wrischnik LA, Oakes E, George M, Tong B, Wilson AC (1987). "Mitochondrial DNA of the Extinct Quagga: Relatedness and Extent of Postmortem Change". Journal of Molecular Evolution 25 (4): 283–287. doi:10.1007/BF02603111. PMID 2822938. 
• International Commission on Zoological Nomenclature. 2003. Opinion 2027 (Case 3010). Usage of 17 specific names based on wild species which are pre-dated by or contemporary with those based on domestic animals (Lepidoptera, Osteichthyes, Mammalia): conserved. Bull.Zool.Nomencl., 60:81-84.
• Moehlman, P.D. 2002. Equids. Zebras, Assess and Horses. Status Survey and Conservation Action Plan. IUCN/SSC Equid Specialist Group. IUCN, Gland, Switzerland. (http://www.iucn.org/themes/ssc/publications/actionplans.htm#Equids2002)
• Orlando, L; Mashkour, M; Burke, A; Douady, CJ; Eisenmann, V; H�nni, C (2006). "Geographic distribution of an extinct equid (Equus hydruntinus : Mammalia, Equidae) revealed by morphological and genetical analyses of fossils". Molecular Ecology 15 (8): 2083–2093. doi:10.1111/j.1365-294X.2006.02922.x. PMID 16780426. 

v t e Equine Equine science and management Equine anatomy Equine nutrition Horse behavior Horse care Horse breeding Equine conformation Equine coat color Horse gait Equestrianism and sport Glossary of equestrian terms List of Equestrian Sports Horse tack Bit Bridle Saddle Harness English riding Western riding Driving Horse training Horse racing Equestrian at the Summer Olympics (medalists, venues) Horse show Equitation Evolution and history Domestication In warfare In the Middle Ages Horses in East Asian warfare History of the horse in South Asia Horses in the Napoleonic Wars Horses in World War I Horses in World War II History of the horse in Britain Horse breeds, types and other Equidae Horses List of horse breeds Wild horse Feral horse Stock horse Gaited horse Draft horse Warmblood Sport horse Other Equus List of donkey breeds Donkey Zebra Onager Hybrids Hinny Mule Zebroid Category: Equidae

A zebroid (also zedonk, zorse, zebra mule, and zebrule) is the offspring of any cross between a zebra and any other equine: essentially, a zebra hybrid. In most cases, the sire is a zebra stallion. Offspring of a donkey sire and zebra dam, called a zebra hinny, or donkra, do exist but are rare. Zebroids have been bred since the 19th century. Charles Darwin noted several zebra hybrids in his works.

Types

Zebroid is the generic name for all zebra hybrids. The different hybrids are generally named using the portmanteau convention of sire's name + dam's name. There is generally no distinction 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.

A zorse is the offspring of a male zebra and a female horse. This cross is also called a zebrula, zebrule, zebra mule or golden zebra. The rarer reverse pairing is sometimes called a horbra, hebra, zebrinny or zebret. 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 zonkey is a cross between a zebra and a donkey. "Zonkey" is not the technically correct name for such a cross. The most commonly accepted terms are zebonkey (or zebronkey), zebrinny, zebrula, zebrass, and zedonk (or zeedonk). Another name that is sometimes used is "zebadonk". Donkeys are closely related to zebras and both animals belong to the horse family. Zonkeys are very rare.^[3] In South Africa, they occur where zebras and donkeys are found in proximity to each other. Like mules, however, they are generally genetically unable to breed, due to an odd number of chromosomes disrupting meiosis.

Genetics

Donkeys and wild equids have different numbers of chromosomes. A donkey has 62 chromosomes; the zebra has between 32 and 46 (depending on 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 has a number of chromosomes somewhere in between. 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.^[4] Horses have 64 chromosomes, while most zebroids end up with 54 chromosomes.

Common wisdom states that hybrids only occur when the zebra is the sire, but the Barbados hybrid demonstrates otherwise. Two other known zebra hinnies have been foaled, but did not survive to adulthood. The rarity of zebra hinnies indicates the smaller number of chromosomes must generally be on the male side if a viable hybrid is to be produced. Before this comes into account, a successful mating needs to be accomplished in the first place. As courtship in horses involves the mare kicking at the stallion's head for some time before allowing him to mount, and as this behavior is stronger in wild equids than in domestic horses, it is difficult enough to get a horse stallion to mate and not be put off by the rough behavior of the non-horse mare.

Zonkeys are interspecific hybrids bred by mating two species from within the same genus. The offspring have traits and characteristics of both parents. Zonkeys vary considerably depending on how the genes from each parent are expressed and how they interact.

Physical characteristics

This unreferenced section requires citations to ensure verifiability.

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 horse, paint, piebald, or skewbald), this pattern might be passed down to the zebroid, in which case the stripes are usually confined to nonwhite 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 quagga. In zebra-donkey hybrids, there is usually a dorsal (back) stripe and a ventral (belly) stripe.

Zebroid 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) (these are known in the United States as pinto), the zorse may inherit the dominant depigmentation genes for white patches, it is understood that 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 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 zebra 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.^{[citation needed]} Zebras, while not usually very large, are extremely strong and aggressive. Similarly, zorses have a strong temperament and can be aggressive.

Historical and notable zebroids

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." 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 the Chapman's zebra with the pony, to produce an animal 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.^[5] Zebras are resistant to sleeping sickness, whereas purebred horses and ponies are not, and it was hoped that the zebra mules would inherit this resistance.

Grevy's zebra has been crossed with the Somali 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 (c. 1929).

The 1970s continued the interest in zebra crosses. A New York Times article from 16 June 1973 mentioned the birth of a cross between a zebra and a donkey 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.^[6] One adult and a foal remain at the tourist attraction of Groombridge Place^[7] near Tonbridge in Kent.

21st century

Today, various zebroids are bred as riding and draft animals, and as curiosities in circuses and smaller zoos. Zorses are bred in Africa and used for trekking on Mount Kenya;^[8] the zebra parent gives resistance to the nagana pest disease. A zorse (more accurately a zony) was born at Eden Ostrich World, Cumbria, England in 2001 after a zebra was left in a field with a Shetland pony. It was referred to as a Zetland. Usually, a zebra stallion is paired with a horse mare or ass mare, but in 2005, a Burchell's zebra named Allison produced a zonkey called Alex sired by a donkey at Highland plantation in the parish of Saint Thomas, Barbados. Alex, born 21 April 2005, is apparently the first zonkey in Barbados.^[9] In 2007, a stallion, Ulysses, and a zebra mare, Eclipse, produced a zebroid named Eclyse, displaying an unusually patchy color coating.^[10][11] The Wild Animal Safari in Springfield, Missouri, and its sister location in Pine Mountain, Georgia, have several zedonks as of 31 March 2010.^{[citation needed]} In July 2010, a zedonk was born at the Chestatee Wildlife Preserve in Dahlonega, Georgia.^[12] Another zebra–donkey hybrid, like the Barbados zonkey sired by a donkey, was born 3 July 2011 in Haicang Safari Park, Haicang, Xiamen, China.^[13]

Popular culture

Zorses have appeared in several TV shows and movies. In the Viva La Bam episode Groundhogs Day in the final race, Brandon Dicamillo's sled is a zorse. It was colored pink, blue, purple and red and 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". Also, 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. It is the son of Stripes (a zebra) 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. 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, he and several other characters speculate on how nice it would be to own a zorse, although they admit it would be difficult to train.

References

Wikimedia Commons has media related to: Zorses

The Atlas wild ass (Equus africanus atlanticus), also known as Algerian wild ass is an extinct animal. It was last shown in a villa mural in AD 300 in Bona, Algeria, and went extinct after Roman sport hunting.

Taxonomy

Fossils have been found in a number of rock shelters across Morroco and Algeria by paleontologists including Alfred Romer (1928, 1935) and Camille Arambourg (1931).^[1]

Description

Based on ancient drawings, the Atlas wild ass had stripes on its legs as well as a shoulder cross.^[2]

Range and ecology

The Atlas wild ass was found in the region around the Atlas Mountains, across modern day Algeria, Tunisia and Morocco.^[3]

References

This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. Please help to improve this article by introducing more precise citations. (March 2012)

A zonkey is a cross between a zebra and a donkey. The generic name for crosses between zebras and horses or asses is zebroid or zebra mule. "Zonkey" is not the technically correct name for such a cross. The most commonly accepted terms are zebrinny, zebrula, and zedonk. Donkeys are closely related to zebras and both animals belong to the horse family. Zonkeys are very rare.^[1]

In South Africa they occur where zebras and donkeys are found in proximity to each other. Like mules, however, they are genetically unable to breed, due to an odd number of chromosomes disrupting meiosis. However, in The Origin of Species, Charles Darwin reported a case of a zonkey that apparently bred with a bay mare to produce a "triple hybrid".

Usually a zebra stallion is paired with a horse mare or ass mare, but in 2005, a Burchell's Zebra named Allison produced a zonkey called Alex sired by a donkey at Highland plantation in the parish of Saint Thomas, Barbados. Alex, born April 21, 2005, is apparently the first zonkey in Barbados.^[2]

Breeding of different branches of the equine family, which does not occur in the wild, results in infertile offspring. The combination of sire and dam also affects the offspring. A zebrinny is the offspring of a male horse and a female zebra; a zebrula is the offspring of a male zebra and a female horse; a zedonk is the offspring of any zebra and any donkey.

A number of hybrids, described as Zeedonks, were kept at Colchester Zoo, the product of accidental mating; the last died in 2009.^[3] One adult and a foal remain at the tourist attraction of Groombridge Place ^[4] near Tonbridge in Kent.

The Wild Animal Safari in Springfield, MO has several zedonks as of March 31, 2010.

Genetics

A zeedonk which was kept at Colchester Zoo.

Donkeys and wild equids have different numbers of chromosomes. A donkey has 62 chromosomes; the zebra has between 32 and 46 (depending on 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 has a number of chromosomes somewhere in between. The chromosome difference makes female hybrids poorly fertile and male hybrids sterile due to a phenomenon called Haldane's Rule. The difference in chromosome number is most likely due to horses having 2 longer chromosomes that contain similar gene content to 4 zebra chromosomes.^[5]

Common wisdom states that hybrids only occur when the zebra is the sire, but the Barbados hybrid demonstrates otherwise. Two other known zebra hinnies have been foaled but did not survive to adulthood. The rarity of zebra hinnies indicates that the smaller number of chromosomes must generally be on the male side if a viable hybrid is to be produced. Before this comes into account, a successful mating needs to be accomplished in the first place though: As courtship in horses involves the mare kicking at the stallion's head for some time before allowing him to mount, and as this behavior is stronger in wild equids than in domestic horses, it is difficult enough to get a horse stallion to mate and not be put off by the rough behavior of the non-horse mare.

Zonkeys are interspecific hybrids bred by mating together two species from within the same genus. The offspring have traits and characteristics of both parents. Zonkeys vary considerably depending on how the genes from each parent are expressed and how they interact.

See also

• Donkey
• Mule
• Zorse
• Zebra
• Tijuana Zebra

References