Under conditions of domestication it is possible to obtain hybrids
between
equid species. There are records of onager/ass, onager/horse and zebra/horse (zebroids)
crosses, but the cross that has been most significant in human history is one
between horses and donkeys. Breeding a male donkey to a female horse results in
a mule; breeding a male horse to a female donkey produces a hinny.
Offspring from either cross, although fully developed as males or females,
are almost always sterile. Hence, a line of horses and a line of domestic asses
must be maintained to perpetuate mule or hinny production.
The mule in most circumstances has been the preferred product of
the
horse/ass cross. (The breeding is also easier to manage.) The mule has greater
endurance and is stronger and less excitable than a horse. Depending on the
need, different breeds of horses can be used to produce fine riding mules, heavy
draft mules or medium-sized pack animals. In Medieval Europe, when horses were
bred large to carry armored knights, mules were the preferred riding animal of
gentlemen and clergy. In 1495, Christopher Columbus brought four jacks and two
jennies to the New World. They would produce mules for the conquistadores'
expeditions onto the American mainland. Ten years after the conquest of the
Aztecs, the first shipment of twelve jennies and three jacks arrived from Cuba
to begin breeding mules in Mexico. Female mules were preferred as riding
animals, whereas the males were used as pack animals along the trails that tied
the Spanish Empire together. Both mules and hinnies were used in the silver
mines. Along the frontier each Spanish outpost had to breed its own supply of
mules, and each hacienda or mission maintained as least one stud jack.
On the Iberian Peninsula, Catalonia and Andalucia each developed a large
breed of ass, putting Spain in the forefront of the mule-breeding industry.
Exportation of Spanish jacks was prohibited until 1813. However, the King of
Spain presented George Washington with a large black jack in 1785. This animal,
"Royal Gift," is considered the father of the mule industry in the
United States.
Mules were once used to pull fire-fighting equipment and were often
employed
by armies to pull artillery and to remove the wounded from the battlefield. The
twenty-mule team that hauled borax from Death Valley and other mining centers in
the West has become part of American legend. Indeed, some western towns were
originally laid out with extremely wide streets to allow the mule teams to turn
around.
The main mule-breeding centers in the United States developed in Tennessee,
Kentucky and Missouri to provide work animals for the
cotton fields of the Old South. After the American Civil War and the development
of tenant farming throughout the South, the mule continued as the major draft
animal in American agriculture. "Forty acres and a mule" was all one
needed for self-sufficiency. The importance of the mule declined rapidly in the
1940s and 1950s, however, as gasoline-driven tractors became widespread, and
mules all but disappeared from the American scene.
Today there is renewed interest in mules for recreation and competition. In
the Southeast mules are used for nighttime raccoon hunting, and the mules'
ability to jump over fallen trees or fences is exploited in jumping
competitions. Pulling contests using heavy draft mules have created a new demand
for large mules. Particularly popular are large red mules produced by crossing
American Mammoth Jackstock with Belgian mares.
