Mammoth Jackstock

Scientific NameEquus africanus asinus
Common NameMammoth Jackstock
Care LevelModerate to High
Lifespan30-35 years
Adult Size56-66 inches at the withers
DietHerbivore (grass and hay)
OriginUnited States
TemperamentGentle, Stubborn, Alert

History & Domestication

The history of the Mammoth Jackstock traces back to the early days of the United States. These magnificent animals were the brainchild of George Washington, who, with the help of King Charles III of Spain, envisioned creating a breed of donkeys large enough to mate with horses to produce draft mules. The King sent him large Andalusian donkeys which were then crossbred with large American jennies to produce the first Mammoth Jackstocks.

The resulting breed played a vital role in agriculture, transportation, and industry in the 19th and early 20th centuries. Their strength, stamina, and ability to breed large mules made them incredibly valuable. However, with the advent of modern machinery, their numbers started to decline. Today, the Mammoth Jackstock is considered a rare breed, with enthusiasts and breeders working hard to preserve their lineage and legacy.


One of the defining characteristics of the Mammoth Jackstock is its size. To be classified as a “Mammoth,” jacks (males) must stand a minimum of 56 inches, and jennies (females) must be at least 54 inches tall at the withers. However, many specimens surpass these measurements, with some reaching up to 66 inches or more.

This impressive size, coupled with their solid build and muscular structure, provides them with the strength and stamina they are known for. Their legs, strong and well-proportioned, are perfect for both draft work and covering long distances.


On average, Mammoth Jackstocks can live up to 30-35 years, although this can vary depending on factors such as genetics, care, and overall health. With their size comes a greater need for attention to their health and well-being, especially as they age. Joint problems, heart conditions, and other age-related ailments can manifest, but with proper care, regular veterinary check-ups, and a balanced diet, these animals can lead long and healthy lives.


Breeding Mammoth Jackstocks is a careful endeavor. Given their size and value, many breeders focus on lineage, genetics, and health screenings to produce the best offspring. The gestation period for a jenny is about 12 months, typically resulting in a single foal. Twin births are rare and often come with complications.

Breeders usually wait until jennies are at least four years old before breeding to ensure they are mature enough to carry and birth offspring without complications. Jacks, on the other hand, can start breeding as early as two years but are often held off until they are more mature and have been health and temperament tested.

Unique Features

Apart from their impressive size, Mammoth Jackstocks possess a variety of unique features. Their ears are notably large, even in comparison to their size, and can measure up to 33 inches in length. These large ears are more than just distinctive; they provide the Jackstock with enhanced hearing capabilities and help regulate body temperature in hot conditions.

Their coat colors can range from black, brown, gray, to sorrel, and they often have white points – white markings on their muzzle, belly, and the insides of their legs. Their voice is also distinctive; a deep, resonant bray that can be heard from a considerable distance.

Behavior and Temperament

Mammoth Jackstocks are known for their calm and gentle temperament. However, they still possess the classic donkey trait of stubbornness or, more accurately, a keen sense of self-preservation. This means they will often refuse to follow commands if they perceive a situation as unsafe or uncomfortable.

They are intelligent and can be trained for various tasks, but this requires patience, consistency, and positive reinforcement. Building a relationship based on trust and respect is essential when working with these animals. They also thrive in social settings, so they often benefit from having companions, either of their kind or other livestock.


Given their size and strength, proper handling techniques are crucial for the safety of both the handler and the animal. It’s essential to be firm yet gentle, always approaching them in a calm and confident manner. Early socialization and training are crucial, especially for jacks, which can become aggressive if not properly managed.

Using tools like halters, lead ropes, and training sticks can aid in handling, but it’s essential always to use these tools humanely. Establishing dominance while maintaining trust is the key to a successful relationship with a Mammoth Jackstock.

Grooming Needs

Like other donkeys, Mammoth Jackstocks require regular grooming to maintain their health and appearance. Their thick coats should be brushed to remove dirt, debris, and loose hair. Given their size, checking their hooves can be a task, but it’s essential for preventing infections and ensuring they are free from cracks or overgrowth. Regular trimming, usually every 6-10 weeks, is necessary.

Dental care is also crucial. Ensuring their teeth are free from sharp edges or overgrowth can prevent eating difficulties and digestive problems.

Diet & Nutrition

Being herbivores, the primary diet of Mammoth Jackstocks consists of grass and hay. Their larger size means they require more food, but care must be taken not to overfeed, as they can become overweight, leading to health issues.

A balanced diet may include quality hay, fresh pasture, and specific grains or pellets tailored for large donkeys or mules. It’s also essential to provide them with mineral and salt blocks to cater to their dietary needs. Fresh water, available at all times, is a must.


While Mammoth Jackstocks are hardy and can adapt to various temperatures, they need protection from extreme conditions. In hot climates, shade and ample water are essential. In colder conditions, providing them with a well-insulated shelter, free from drafts, and possibly even blankets can help them maintain body heat.

Common Health Issues

Due to their size, Mammoth Jackstocks can be prone to joint issues, especially as they age. Regular health check-ups can catch early signs of arthritis or other joint problems. Other concerns might include respiratory issues, dental problems, and the risk of obesity-related conditions.

Habitat Requirements

A spacious pasture for grazing, a sturdy shelter, and a clean and dry resting area constitute an ideal habitat for Mammoth Jackstocks. Due to their size, ensuring that fences are strong and tall enough is crucial. They also require protection from potential predators and other threats.

Cost of Care

Caring for a Mammoth Jackstock can be a considerable investment. The initial purchase price can be high, especially for well-bred specimens. The recurring costs include food, regular veterinary care, grooming, and potential boarding or housing expenses if the owner does not have adequate facilities. As with any large livestock, the financial commitment should not be underestimated. Proper planning and understanding of the requirements can ensure a happy and healthy life for these magnificent animals.

Mammoth Jackstock FAQs (Frequently Asked Questions)