Wild horses thrive in some of the world’s most challenging landscapes, from arid plains to high deserts. Unlike their domesticated counterparts, these animals must rely entirely on the vegetation available in their environment, which often provides a low-quality, high-fiber diet. This dependence forces them to adopt specialized eating habits and physiological mechanisms for survival.
Primary Forage: The Staple Diet
The foundation of the wild horse diet is grass, classifying them as graminivores. They graze consistently on a variety of grass species, including desert grasses, bluegrass, and wheatgrass, depending on their geographic location. Grass species make up the vast majority of their diet, often exceeding 80% of their total intake. This includes both green, actively growing forage and cured, dry grass, which still provides the necessary fiber.
Wild horses are non-selective grazers, consuming a large volume of available grasses to maximize intake in sparse environments. When conditions are favorable, they also consume forbs, which are broad-leafed flowering plants like clover and dandelions. These forbs serve as a high-quality supplement, offering a concentrated source of protein, vitamins, and minerals that grass alone may lack. This continuous grazing requires them to spend up to 16 hours a day foraging to meet their energy needs from this low-calorie, fibrous material.
Dietary Adaptations for Roughage
The equine digestive system is adapted to process the large volumes of abrasive, fibrous forage. The horse possesses hypsodont teeth, characterized by a high crown that continues to erupt throughout life. This allows the teeth to withstand the constant wear caused by grinding tough plant material like silica-rich grasses and woody browse. The extensive chewing reduces the forage into small particles, a necessary step for digestion.
Horses are classified as hindgut fermenters, relying on a massive fermentation vat located in the large intestine and cecum. Specialized microbes within this hindgut break down cellulose and hemicellulose, structural carbohydrates that the horse’s own enzymes cannot digest. This microbial process generates volatile fatty acids, which the horse absorbs and uses as its primary energy source.
Seasonal Shifts and Survival Foraging
When preferred grasses become scarce, the wild horse diet shifts dramatically to incorporate survival forage. This change involves a transition from grazing to browsing, where they consume less palatable, tougher plant materials. They may turn to woody plants like sagebrush, juniper, rabbitbrush, twigs, and tree bark, especially from species like aspen, willow, and cottonwood.
These less digestible resources, while low in nutrients, provide enough fiber to keep the digestive system functioning until better forage returns. This adaptability allows them to maintain body condition even when the primary food source is compromised. Water is a limiting factor in arid environments, and wild horses travel long distances between feeding grounds and water sources like springs or seasonal streams. In extreme conditions, they have been observed to eat certain cacti, which offer a small amount of moisture, or dig for shallow groundwater.