Mule

Mule is the offspring of a male donkey and a female horse, a hybrid animal rather than a breed, valued across many agricultural traditions for combining traits from both parent species: a mule generally has the surefootedness, hardiness, disease resistance and long working life associated with the donkey alongside size, strength and speed closer to that of a horse. Mules are almost always sterile because their parent species have different numbers of chromosomes, so every mule must be bred anew from a donkey and a horse rather than from other mules, historically making mule breeding a specialized undertaking. Mules have been used for millennia across a very wide range of agricultural and transport roles, including plowing, pack and draft work, riding and military transport, and remain in active working use today in many parts of the world, particularly in mountainous or difficult terrain where their surefootedness and endurance are especially valued. The reverse cross, a hinny, produced from a male horse and a female donkey, is rarer and generally smaller than a mule, reflecting differences in maternal versus paternal genetic and developmental contribution between the two crosses.