Deer are widely perceived as gentle, plant-eating animals, often seen grazing peacefully. Many assume their diet consists solely of vegetation, leading to curiosity about whether they consume anything beyond plants.
The Herbivorous Nature of Deer
Deer are herbivores, primarily consuming plant material. They are classified as browsers, preferring leaves and twigs of woody plants, forbs, grasses, fruits, and fungi. Their diet adapts seasonally, with browse and forbs being particularly important. Acorns and other nuts provide high-energy sources, especially during autumn.
Their digestive system is adapted for processing fibrous plant matter. Deer are ruminants, possessing a four-chambered stomach, similar to cattle and sheep. The first and largest chamber, the rumen, acts as a fermentation vat where microorganisms break down cellulose and other complex carbohydrates. This process allows deer to extract nutrients from tough plant cell walls.
Deer rapidly consume food, chewing it just enough to swallow. This partially chewed food enters the rumen for initial breakdown. Later, deer regurgitate this material, known as cud, and chew it again more thoroughly. This re-chewing further breaks down plant fibers, increasing surface area for microbial action before the food passes through other stomach chambers for further digestion and nutrient absorption. This specialized process is highly efficient for a plant-based diet.
When Deer Deviate from Their Typical Diet
While deer are primarily plant-eaters, they consume non-plant matter under specific circumstances, often due to nutritional deficiencies or opportunistic behavior. These instances are anomalies to their typical herbivorous diet and do not classify them as omnivores or carnivores.
One documented behavior is osteophagia, the gnawing on bones or shed antlers. Deer do this to obtain essential minerals like calcium, phosphorus, and sodium, which may be lacking in their plant-based diet, especially during winter or periods of high demand like antler growth or lactation. The distinctive zigzagging marks left on bones result from their jaw movement.
There are rare reports of deer consuming animal matter. These instances are opportunistic, such as scavenging on carrion or the remains of other deer. Some observations also include deer eating small animals like bird eggs or nestlings. Such behaviors are not a regular part of their diet and occur when other food sources are scarce or specific nutrients are needed. Their digestive system is not designed to efficiently process large amounts of meat.