Zonkey

A zonkey (also known as zebrass, zebronkey, zeedonk, zedonk, zebadonk, zenkey, zebrinny, or deebra) 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. Donkeys are closely related to zebras and both animals belong to the horse family. Zonkeys are very rare.

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In South Africa they occur where zebras and donkeys are found in proximity to each other. Like mules, however, they cannot usually 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.

Genetics

Donkeys and wild equids have different numbers of chromosomes. A donkey has 62 chromosomes; the zebra has between 44 and 62 (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.

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 has to 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.

In captivity

Though zonkeys are rare, zoos have succeeded in producing them. Colchester Zoo in Essex claimed, erroneously, to have produced the first zonkey in 1971. Zebra-ass hybrids dating back to 1815 were reported by Charles Darwin in 1859. A breeding program at the zoo in 1975 resulted in several hybrids. In Christmas week of 1975 Colchester Zoo's third zonkey foal was born, the result of mating a donkey with different male zebras. 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 were hopeful that the hybrids would be viable and fertile. A zonkey is still exhibited at Colchester, but they now have a policy of preventing interbreeding and so will not be breeding more. In the United States, the Tupelo Buffalo Park and Zoo in Mississippi exhibits one as a zedonk.

Colchester Zoo were, knowingly or unknowingly, repeating an experiment made by the Boers during the South African War when zonkeys were bred as work animals. In that earlier experiment, Chapman's zebras and ponies were crossed to evolve a new animal for transport work.

In Origin of Species (1859) Charles Darwin mentioned four colored drawings of hybrids between the ass and zebra, including the famous cross made in 1815 by Lord Moreton of a donkey and a quagga. In The Variation Of Animals And Plants Under Domestication[1], published first in 1868 and a revised second edition in 1883, Darwin wrote: "I have seen, in the British Museum, a hybrid from the ass and zebra dappled on its hinder quarters." Darwin continued, "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 expanded on his early report of Lord Moreton's quagga cross. Both works pre-date the claim from Colchester Zoo.

An "ass-zebra" is shown and described in Wonders of Animal Life (1930) edited by J A Hammerton. Crosses between Grevy's Zebra and the Somali Ass are reported from the same period.

Exotic animal breeders who house zebras sometimes breed zonkeys.

See also

• Donkey
• Mule
• Zorse
• Zebra
• Tijuana Zebra