A Zebroid (also zedonk, zorse, zebra
mule, zonkey, and zebmule) 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.
Zebroid is the
generic name for all zebra hybrids. The different hybrids are generally named
using a portmanteau of the sire's name and the 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 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 horbra, hebra, zebrinny or zebret. Like most other
animal hybrids, the zorse is sterile.
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".
A cross between a zebra and a donkey is known by many terms including: zonkey, 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. 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. Horses have 64 chromosomes, while most zebroids
end up with 54 chromosomes.
Common wisdom states
that hybrids occur only 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.
Zonkeys are inter
specific 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
Zebroids physically
resemble their non zebra 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 non zebra 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 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 quagge. In
zebra-donkey hybrids, there is usually a dorsal (back) stripe and a ventral
(belly) stripe.
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. 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 non depigmented 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 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. 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.
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. 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).
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. One
adult and a foal remain at the tourist attraction of Groombridge
Place 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; 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 donkey 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. In 2007, a
stallion, Ulysses, and a zebra mare, Eclipse, produced a zebroid named Eclyse,
displaying an unusually patchy color coating. The Wild Animal Safari
in Springfield, Missouri, and its sister location in Pine Mountain,
Georgia, have several zedonks as of 31 March 2010. In July 2010, a zedonk
was born at the Chestatee Wildlife Preserve in Dahlonega, Georgia. Another
zebra–donkey hybrid, like the Barbados zonkey sired by a donkey, was born 3
July 2011 in Haicang Safari Park, Haicang, Xiamen, China. A
zonkey, Ippo, was born 21 July 2013 in an animal reserve,
in Florence, Italy. Khumba, the offspring of a zebra dam and a
dwarf albino donkey sire, was born on 21 April 2014 in the zoo of
Reynosa in the state of Tamaulipas, Mexico.
Popular culture
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) 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.
The video
game Red Dead Redemption has the "Zebra Donkey" available
as a multi-player mount.
HINNY
The word hinny is
also a term of endearment used in North East England, equivalent to honey; see Geordie and Mackem.
A hinny is a domestic equine hybrid that is the
offspring of a male horse, a stallion, and a female donkey, a
jenny. It is the reciprocal cross to the more common mule, which
is the product of a male donkey (jack) and a female horse, amare.
Description
Hinnies on average are slightly smaller than mules in part because donkeys are generally smaller than horses, and growth potential of equine offspring is influenced by the size of the dam's womb. There is debate over whether this is the only reason for the size variances between the two types of hybrid equines. Some fanciers believe this size difference is only physiological, owing to the smaller size of the donkey dam, as compared to mares, which are generally much larger.
Others claim
it is a natural consequence of the reciprocal cross. The position of
the American Donkey and Mule Society (ADMS) is: "The genetic
inheritance of the hinny is exactly the same as the mule."
Like mules, hinnies
do come in many sizes. This is because donkeys come in many sizes, from
miniatures, as small as 24 inches (61 cm; 6 hands) at the withers,
to American Mammoth Jacks that may be over
15 hands (60 inches, 152 cm) at the withers. Thus, a hinny
is restricted to being about the size of the largest breed of donkey. Mules,
however, have a female horse as a parent, so they can be as large as the size
of the largest breed of horse, such as those foaled from work horse
mares such as the Belgian.
Other than size, some
additional minor differences occur that can be used to distinguish between
mules and hinnies. The head of a hinny is said to resemble that of a horse more
than it does a mule's, with shorter ears (although these are still longer than
those of horses), and more horse-like manes and tails than mules. A male hinny
is properly called a horse hinny, and a female hinny is properly called a mare
hinny. In England, a hinny is commonly called a jennet.
Hinnies are difficult
to obtain because of the differences in the number of chromosomes of
the horse and the donkey. A donkey has 62 chromosomes, whereas a horse has
64. Hinnies, being hybrids of those two species, have 63 chromosomes and
are sterile. The uneven number of chromosomes results in an
incomplete reproductive system.
According to the
ADMS: "The equine hybrid is easier to obtain when the lower chromosome
count, the donkey, is in the male. Therefore breeding for hinnies is more
hit-and-miss than breeding for mules."
The male hinny or mule
can and will mate, but the emission is not fertile. Male hinnies
and mules are usually castrated to help control their behavior by
eliminating their interest in females.
Female hinnies and
mules are not customarily spayed, and may or may not go through estrus.
Female mules have been known, on rare occasions, to produce offspring when
mated to a horse or donkey, although this is extremely uncommon. Since 1527,
more than sixty cases of foals born to female mules around the world have been
documented. In contrast, according to the ADMS, there is only one known
case of a female hinny doing so.
Namely,
in China, in 1981, a hinny mare proved fertile with a donkey sire. When
the Chinese hinny was bred to a jack, she produced the so-called "Dragon
Foal," which resembled a donkey with mule-like
features. In Morocco, in 2002, a mule mare bred to a donkey sire
produced a male foal. DNA testing revealed the foal has a
mixed karyotype hybrid like the Chinese hinny offspring "Dragon
Foal."
Hinnies are rare for
many other reasons. Jennies and stallions can be choosier about their mates
than horse mares and donkey jacks. Thus, the two parties involved may not care
to mate. Even if they do cooperate, female donkeys are less likely to conceive
when bred to a horse than horse mares are when bred to a
donkey. Breeding large hinnies is an even bigger challenge, as it
requires stock from a jenny of large size, such as the Baudet de
Poitou or American Mammoth Donkey. Mammoth donkey stock is becoming
increasingly rare and has been declared an endangered domestic breed. Fanciers
are unlikely to devote a Mammoth jenny's valuable breeding time to producing
sterile hinny hybrids, when Mammoth females are in high demand to produce
fertile pure-bred Mammoth foals.
