The term jackass is used to signify a male donkey. A donkey is a domesticated ass. The ass is a species related to the horse and zebra and part of the Equiid family that is found wild in Africa and Asia. The male ass is called "a jack," thus the term jackass.
When a jackass is bred to a female horse, called a mare, the result is a mule. The mule retains characteristics of both horses and donkeys. Mules were popular animals to breed for farm labor before the age of mechanized farming equipment. Mules can be born both male and female, but cannot reproduce. The burro is a wild donkey found in the southwestern region of the United States and Mexico. Spanish conquistadors brought donkeys from Asia to the region in the 15th century. Some of these were released into the wild and became the modern burro. Burro is the Spanish word for donkey.
Humans domesticated asses in Africa long before the horse was domesticated. Mules gained their reputation for stubbornness because their natural self-preservation instincts required them to be independent-thinkers, often putting their own welfare before that of the human. Mules were often thought to be stronger and require fewer daily calories, making them a better choice for labor animals.