Bighorn sheep are iconic animals of North America, known for their impressive curved horns and ability to thrive in rugged, mountainous terrains. Understanding their diet provides insight into their survival strategies and ecological role. Their ability to extract nutrients from often-sparse vegetation highlights their adaptability.
Core Dietary Components
Bighorn sheep are primarily herbivores, with their diet largely consisting of grasses, forbs, and shrubs. Grasses, including species like bluegrass, sedges, wheatgrass, bromes, and fescues, form a significant portion of their intake, especially during warmer months. These provide essential fiber for their digestive system. Forbs, which are broad-leafed herbaceous plants, are also consumed, particularly for their higher protein and nutrient content. Examples of forbs include clover, vetch, cinquefoil, and phlox, which are often sought out in spring and summer.
As seasons change or in areas where grasses and forbs are less abundant, bighorn sheep rely more on woody browse. Shrubs like willow, sagebrush, bitterbrush, and serviceberry become important food sources. Desert bighorn sheep, for instance, frequently consume shrubs such as acacia, catclaw, encelia, sweetbush, and krameria. They may also utilize cacti, such as prickly pear, especially when other forage is scarce, sometimes breaking them open with their horns to access the moist interior. This diverse consumption helps meet their nutritional needs.
Dietary Adaptations to Environment
The diet of bighorn sheep exhibits significant variations based on the season and their specific geographical location. During the lush spring and summer months, their diet often shifts towards abundant grasses and nutrient-rich forbs. As fall and winter approach, and vegetation becomes less available or dormant, they transition to more fibrous options like dry grasses and woody shrubs. Their ability to adapt to snow cover and scarcity is evident in their foraging behavior, seeking out areas where snow is less deep.
Regional differences also influence their diet. Rocky Mountain bighorn sheep, for example, tend to graze more on grasses and alpine plants. In contrast, desert bighorn sheep are more reliant on desert shrubs and even cacti due to the arid conditions of their habitat. Regardless of the specific plant types, bighorn sheep are opportunistic feeders, selecting the most nutritious forage available. Their specialized ruminant digestive system, with a four-chambered stomach, efficiently breaks down tough, fibrous plant matter, maximizing nutrient absorption.
Hydration and Mineral Consumption
Beyond solid forage, bighorn sheep acquire water through various means, adapting to environmental availability. They drink directly from streams and springs or consume snow in colder climates. For desert subspecies, extracting moisture directly from plants is a key adaptation, allowing them to sustain themselves for extended periods without surface water, sometimes solely on plant moisture and temporary pools.
Bighorn sheep also seek essential minerals, such as sodium, which are often scarce in their diet. They visit natural mineral licks, geological formations rich in salts and other vital minerals. These licks provide micronutrients like calcium, phosphorus, and zinc, important for bone health and physiological function. This strong drive for minerals sometimes leads them to areas with human infrastructure, such as roads where de-icing salts are present.