Donkeys are hardy members of the horse family whose diet is shaped by their ancestral home: the arid and semi-desert regions of North Africa and the Arabian Peninsula. Most donkeys living without human management are feral populations, retaining the physiological adaptations of the African wild ass. Their survival depends on their ability to thrive on low-quality forage and manage with minimal resources. Because high-nutrient vegetation is scarce, they spend a significant portion of their day foraging to meet their daily energy needs.
The Primary Diet of Coarse Vegetation
The wild donkey’s diet centers on tough, highly fibrous plant material, as their native environment offers little lush, calorie-dense forage. They are classified as both grazers and browsers, consuming a wider variety of plants than the typical horse, which is primarily a grazer. This broad consumption includes low-nutrient grasses, hardy scrub, woody plants, and flowering herbaceous plants known as forbs.
Donkeys can subsist on vegetation considered too coarse for cattle or horses. Their diet consists of dry, bladed grasses, the stems and leaves of shrubs, and desert plants like Opuntia species. They are highly efficient at extracting nutrients from this low-quality intake, often spending up to 18 hours a day slowly foraging to maximize their intake of scarce calories and fiber.
Foraging Strategies in Arid Environments
Wild donkeys have developed specific behavioral strategies that allow them to find sustenance in resource-poor landscapes. They travel vast distances, sometimes up to 19 miles daily, searching for scattered forage and water sources. During extreme drought, when grasses are unavailable, donkeys turn to emergency forage, including twigs, bark, and roots.
Donkeys possess an exceptional memory for water sources and will dig wells, sometimes up to six feet deep, in dry riverbeds to access subterranean water. These “equine wells” provide water for the donkeys and become a source for dozens of other species. The ability of donkeys to tolerate significant dehydration, losing up to 30% of their body weight in water, allows them to range farther from permanent water sources than most other large mammals.
The Digestive System Advantage
The donkey’s ability to survive on a low-quality diet is rooted in the unique efficiency of its digestive system. Like horses, donkeys are hindgut fermenters, relying on microbial action in their large intestine and cecum to break down plant fiber. However, the donkey’s digestive process is significantly more thorough than that of the horse, allowing them to extract nutrients from material that other equids would pass undigested.
The primary difference lies in the mean retention time, which is the amount of time food stays in the digestive tract. Donkeys have a slower passage rate, keeping the feed in contact with the gut microbes for a longer period, which allows for greater fermentation and absorption of nutrients from highly fibrous material.
Furthermore, donkeys are capable of recycling nitrogen, making them highly efficient at utilizing low levels of protein found in their desert diet, a mechanism that helps them maintain metabolic health on sparse forage. This efficiency means donkeys require less food by weight, needing only about 1.5% of their body weight in dry matter daily, compared to the 2% to 2.5% consumption rate common for horses.