Deer are herbivores, but describing their diet simply as “plants” overlooks their complex foraging habits. As ruminants, deer possess a four-chambered stomach with specialized microbes designed to break down fibrous plant matter. Their diet is highly adaptable and opportunistic, changing constantly based on the availability of nutrient-dense forage. Rather than having a single “favorite” food, deer prioritize items that provide the most calories, protein, and minerals necessary for survival, growth, and reproduction.
Categorizing the Deer Diet
The natural diet of deer is generally separated into three main categories that vary in importance throughout the year. Deer are classified as “browsers,” meaning they preferentially select individual leaves, twigs, and fruits over grazing on ground-level grass like cattle. This selective feeding is possible because their narrow muzzle and digestive system require higher-quality, more digestible plant parts.
The first category, browse, consists of the leaves, buds, and tender new growth of woody plants and shrubs. Browse serves as a critical food source, especially during winter months. Forbs are broad-leaved weeds and flowering plants that are highly digestible and rich in protein and nutrients. These are sought out during the spring and summer when rapid growth and high nutritional demands occur.
The final category is mast, which includes hard mast like acorns and hickory nuts, and soft mast such as berries and wild fruits. While browse and forbs make up the majority of the annual diet, mast is highly preferred for its concentrated energy content. This combination allows the deer to balance its nutrient intake to meet changing physiological demands.
The Most Highly Preferred Foods
The foods deer seek out most aggressively are those that provide a dense nutritional punch, often surpassing the quality of common browse. Acorns are consistently ranked as a top preference due to their high content of carbohydrates and fat, essential for building energy reserves. Although low in protein, the caloric density of hard mast is a powerful motivator for consumption in the fall.
Certain cultivated and native plants are also highly favored for their protein content. Agricultural crops like alfalfa and clover are rich sources of protein, vital for antler growth in males and lactation in females. Wild fruits such as apples, wild grapes, and persimmons are consumed rapidly because they offer a concentrated burst of sugar and energy. Deer prioritize these items when available, demonstrating a strong preference for foods that quickly satisfy a high-energy need.
Seasonal Shifts in Foraging
A deer’s nutritional requirements and food selection change drastically with the seasons, aligning with their reproductive and metabolic cycles. During spring and early summer, the focus shifts to maximizing protein intake to support body development and reproduction. Deer primarily seek high-protein forbs and the tender new growth of woody plants to fuel lactation for does and rapid antler growth for bucks.
Late summer and fall mark a period for energy storage in preparation for the breeding season and winter. During this time, deer switch their preference to high-energy mast and fruits like acorns, which are converted into the fat reserves needed to survive the colder months. In winter, when high-quality food is scarce, the diet shifts almost entirely to lower-quality woody browse, such as twigs and buds. The deer’s metabolism slows down, allowing them to rely on fat reserves and the small amount of energy extracted from this fibrous forage.
Foods Deer Should Never Consume
Introducing high-carbohydrate foods to a deer can have fatal consequences due to their specialized digestive system. Deer are ruminants, relying on a delicate balance of microbes in the rumen to break down a high-fiber diet. A sudden influx of readily fermentable carbohydrates, such as that found in corn, bread, or pastries, quickly disrupts this microbial community.
This radical dietary change can lead to lactic acidosis, where the rapid fermentation of starches produces excessive lactic acid. The acid lowers the pH of the rumen, destroying beneficial microbes and causing severe dehydration. This process stops the deer’s ability to digest food, causing it to functionally starve even with a full stomach.
Furthermore, feeding deer concentrates them in unnaturally high numbers, which increases the risk of disease transmission. Chronic Wasting Disease (CWD) is easily spread through saliva, urine, and feces at communal feeding sites. Habituation to human feeding also causes deer to lose their natural fear, increasing their vulnerability to vehicle collisions and potential aggression toward people.