Deer are herbivores that primarily consume plant matter. Their diet is remarkably diverse, adapting to seasonal availability, geographic location, and different plant species.
Their Natural Diet: A Diverse Menu
Deer are classified as concentrate selectors, preferring high-quality, easily digestible foods rich in nutrients. Over 400 plant species have been documented as part of a deer’s diet in the Southeast alone.
A significant portion of their intake comes from “browse” (leaves, twigs, and tender shoots of woody plants). Examples include young growth from raspberry, black cherry, honeysuckle, maple, and willow. They also consume “forbs” (broad-leaved herbaceous plants like clover, alfalfa, buttercup, Solomon seal, dandelions, and various wildflowers).
Fruits and nuts, collectively known as “mast,” are important. Deer seek out soft mast such as apples, pears, persimmons, and wild berries. Hard mast, like acorns, beechnuts, and hickory nuts, is favored for its high fat and oil content. Deer also consume fungi, such as mushrooms, for nutritional value.
Seasonal Shifts and Habitat Influences
A deer’s diet changes significantly with the seasons, driven by the availability and nutritional content of plants. In spring, deer prioritize fresh, nutrient-rich vegetation like young forbs and tender green growth to support antler development in males and lactation in females. As summer progresses, their diet expands to include a wider variety of leaves, early fruits, and agricultural crops like soybeans and alfalfa, which offer high protein.
During autumn, deer shift their focus to building fat reserves for the upcoming winter and the breeding season. This period sees increased consumption of high-energy foods such as acorns, other nuts, and ripened fruits like apples and corn from agricultural fields. In winter, when other food sources are scarce, their diet primarily consists of woody browse, including the buds and twigs of shrubs and trees, and evergreen leaves.
The specific habitat also plays a significant role in shaping a deer’s diet. Deer in forested areas rely heavily on browse and mast from trees. Those in agricultural landscapes often incorporate cultivated crops, such as corn and soybeans, into their diet. In suburban environments, deer may consume ornamental plants and certain grasses if other preferred foods are limited.
Foods That Harm Deer
Providing human-sourced foods to deer can be detrimental to their health, despite good intentions. Their specialized digestive system, a four-chambered stomach, relies on a specific balance of microbes to break down natural plant fibers. Introducing foods like corn, bread, birdseed, or pet food can disrupt this delicate microbial balance, leading to digestive issues such as acidosis, severe diarrhea, and dehydration.
Sudden changes in diet, especially during winter when their digestive system is adapted to woody browse, can be particularly harmful, potentially leading to starvation even with a full stomach of indigestible food. These inappropriate foods can also cause physical ailments, including foundering hooves, which impair their mobility. Furthermore, artificial feeding sites can concentrate deer, increasing the risk of disease transmission among them.
Certain plants commonly found in gardens and natural habitats are also toxic to deer. These include foxglove, monkshood, bleeding heart, spurge, yew, and rhubarb leaves, which contain compounds that can cause serious illness or even be fatal. While deer generally avoid plants with strong scents, fuzzy textures, or bitter tastes, they may consume these toxic plants if food sources are extremely scarce.