The domesticated donkey, known scientifically as Equus asinus, is a member of the horse family that has been a working animal for thousands of years. The common question of whether all donkeys are male often arises from confusion about their proper names and their relationship with other equine hybrids. Donkeys follow the same reproductive biology as nearly all mammals, existing as both males and females. Understanding the true nature of the donkey requires separating the biological facts of the species from the specialized terminology used in animal husbandry.
Biological Reality of Donkey Sexes
Donkeys are a distinct species and naturally reproduce through sexual reproduction, requiring both a male and a female. The male donkey produces sperm, and the female donkey, or dam, produces the egg and provides the environment for gestation.
Female donkeys are polyestrous and non-seasonal breeders, meaning they can cycle and become pregnant throughout the year. Their reproductive activity may be influenced by factors like light, nutrition, and temperature. Once pregnant, the female has a prolonged gestation period, which typically ranges from 333 to 395 days. The average duration is approximately 371 days, resulting in the birth of a single offspring.
Proper Terminology for Donkeys
The confusion surrounding donkey sexes is often rooted in the specific, non-scientific names used for them. A mature male donkey is universally referred to as a “jack.” This term is used for the breeding male regardless of whether he has been castrated.
The female donkey is called a “jenny,” or sometimes a “jennet.” The offspring of either sex is called a “foal,” similar to the young of a horse. A male that has been castrated to prevent reproduction and improve temperament is commonly referred to as a “gelding,” a term shared with castrated horses. The use of these unique terms, instead of the more general “male donkey” and “female donkey,” can make the species’ sexual reality seem more complex than it is.
Distinguishing Donkeys from Mules
The most significant source of public confusion regarding donkey sexes is the mule, which is often mistakenly viewed as a type of donkey. A mule is not a species but a hybrid animal, resulting from the mating of a male donkey (jack) and a female horse (mare). The opposite cross, a male horse (stallion) and a female donkey (jenny), produces a hinny.
The biological difference lies in their genetics, specifically their chromosome count. Donkeys have 62 chromosomes, while horses have 64. Their hybrid offspring, the mule or hinny, receives an uneven count of 63 chromosomes. This odd number is the primary reason for their sterility.
During meiosis, the process of creating reproductive cells, chromosomes must pair up precisely. The 63 chromosomes in the mule, which consist of an unmatched set from two different species, cannot align correctly. This failure in pairing disrupts the formation of viable gametes, rendering nearly all mules and hinnies unable to reproduce.