Hares are strict herbivores whose diet consists solely of plant matter. These swift-footed mammals are functionally designed to consume and process vegetation, aligning with the general understanding of their ecological niche. This widely accepted view raises a specific question: are hares exclusively herbivorous, or do exceptions occur under certain conditions? The answer requires examining documented instances of non-plant consumption and the biological machinery that defines their feeding habits.
The Primary Diet of Hares
The diet of a hare is overwhelmingly based on the consumption of diverse plant species, a necessity dictated by the seasonal availability of forage. During the spring and summer months, the diet is rich in herbaceous plants, grasses, and forbs, such as clover and various wildflowers. Hares exhibit a high degree of dietary flexibility, often consuming parts from dozens of plant taxa as they become available in the landscape.
As the seasons transition to autumn and winter, the available food quality and quantity decrease significantly, forcing a shift in foraging strategy. The hares transition to consuming more woody material, including the bark, buds, and small twigs of shrubs and trees. This high-fiber, cellulose-rich material is a challenging food source, but it provides the necessary bulk and residual nutrients to sustain them during periods of scarcity.
The constant need for fibrous material is a defining characteristic of their feeding ecology. This selective grazing influences the surrounding vegetation, as hares often target specific plants like legumes, which offer higher nutritional value when available. The consumption of these plant parts establishes the biological baseline for the hare as a dedicated herbivore.
Documented Instances of Non-Plant Consumption
While the diet is plant-based, there are documented instances where hares opportunistically consume non-plant matter, including animal-derived materials. This behavior is not part of their standard feeding routine but is instead a rare, supplemental action typically triggered by a specific nutritional deficit or severe environmental stress. These instances are often linked to a deficiency in protein or essential mineral salts, particularly calcium and phosphorus, which are often limited in winter vegetation.
One of the most commonly recorded non-plant consumption behaviors is osteophagia, the gnawing on bones or shed deer antlers. Shed antlers are a rich source of calcium and phosphorus. Hares will chew on them to supplement their mineral intake during periods of high demand, such as gestation or lactation. The purpose of this consumption is purely to replenish these limiting nutrients, not to gain energy or protein.
Hares have also been observed occasionally consuming animal protein in the form of carrion, eggs, or insects, especially during harsh winter conditions when plant matter is scarce or nutrient-poor. This opportunistic scavenging provides a temporary boost of protein and fat, which is otherwise difficult to obtain from a purely vegetarian diet in deep winter. These actions are considered an ecological adaptation to extreme conditions, highlighting their flexibility rather than a predatory instinct.
Specialized Digestive Adaptations
The hare’s digestive system is specifically adapted to process the high volumes of fibrous plant material that constitute its primary diet. Hares are categorized as monogastric hindgut fermenters, meaning that the bulk of their digestive work occurs in the large intestine, particularly a large pouch called the cecum. This cecum functions as an anaerobic fermentation chamber, hosting specialized microbes that break down cellulose, a complex carbohydrate that mammals cannot digest on their own.
The process requires a unique mechanism known as caecotrophy, or the reingestion of soft fecal pellets known as caecotrophs. After fermentation, the nutrient-rich material is expelled from the body as soft, mucus-covered pellets, distinct from the hard, waste pellets. The hares consume these caecotrophs directly, allowing the protein, B vitamins, and volatile fatty acids synthesized by the cecal microbes to be absorbed in the small intestine.
This complex two-stage digestion process confirms the hare’s specialization for an herbivorous diet. The biological machinery is dedicated to extracting maximum nutrition from low-quality, fibrous forage. While the digestive system can process the small quantities of protein and minerals gained from opportunistic scavenging, it is not designed for a standard meat-based diet.