The mule is a hybrid animal that results from breeding a male donkey and a female horse. It is more common than the hinny, which is the offspring of a male horse and a female donkey. Mules are robust animals used for various purposes, and their existence highlights the intriguing possibilities of interspecies breeding.
A 1939 article in the Journal of Heredity documented the case of "Old Bec," a fertile mare mule owned by Texas A&M University. "Old Bec" produced two offspring, one sired by a jack and the other by a Saddlebred stallion. While her female offspring proved sterile, her male offspring exhibited no donkey characteristics and further sired foals with no donkey traits, raising questions about the heritability of hybrid traits.
In 1995, researchers at the Federal University of Minas Gerais in Brazil reported on a mare mule that had experienced multiple pregnancies, showcasing the potential for repeated fertility in these hybrids. The mule had given birth to offspring sired by both donkeys and horses, with varying chromosome counts and physical characteristics.
In early 2002, a rare event was observed in Morocco: a mare mule giving birth to a foal. This occurrence, considered an ill omen in ancient times, added to the limited but growing documentation of fertile mare mules.
In a groundbreaking scientific achievement in May 2003, a mule named Idaho Gem was born at the University of Idaho, marking the first successful cloning of both an equid and a hybrid animal. This significant milestone demonstrated the advancement of cloning technology.
In 2003, the Food and Agriculture Organization of the United Nations identified China as the leading market for mules, followed by Mexico and various Central and South American countries. This data point underscored the ongoing global significance of mules in agriculture and transportation, particularly in developing nations.
Despite advancements in transportation, mule trains remained relevant in logistical operations as late as 2005. Organizations like the World Food Programme utilized these animals for transporting goods in areas with challenging terrain, highlighting the continued practicality of mules in specific contexts.
Further evidence of mare mule fertility emerged in 2007 when a mare mule in Colorado gave birth to a colt. Blood and hair analysis confirmed the biological relationship between the mule mother and her foal, adding to the scientific understanding of this unusual phenomenon.