The white-tailed deer (Odocoileus virginianus) is the most widespread mainland ungulate herbivore across the Americas, ranging from Canada through Central and into South America. This adaptability is largely due to its digestive system, which classifies it as a ruminant. Possessing a four-chambered stomach allows the deer to process a wide array of plant matter, defining its selective foraging strategy.
Primary Natural Diet: Browse, Forbs, and Mast
White-tailed deer are classified as “concentrate selectors,” meaning they prioritize consuming small amounts of highly nutritious, easily digestible plant parts over large quantities of coarse, low-quality bulk forage. Their diet focuses on three main categories: browse, forbs, and mast. This selective feeding allows them to maximize the intake of protein and energy with each bite, which is necessary for their relatively quick digestive process.
Browse makes up a substantial part of their annual intake, consisting of the tender leaves, buds, and twigs of woody plants, shrubs, and vines. Examples of preferred browse include new growth from species like maple, oak, and sumac. Although browse has a higher fiber content than other foods, it remains a reliable food source, especially during winter when other vegetation is scarce.
Forbs are often the most preferred food category because they are highly palatable, nutrient-rich, and easily digestible. These non-woody, broad-leaved plants, commonly referred to as weeds or wildflowers, include clover and ragweed. Forbs are a major component of the diet during the growing season, providing high levels of protein and water content necessary for growth and development.
Mast refers to nuts and fruits, which provide concentrated bursts of energy seasonally. Hard mast, primarily acorns and hickory nuts, are rich in fats and carbohydrates, making them a crucial food source in the autumn. Soft mast includes fruits and berries like apples, grapes, and plums, offering high sugar and vitamin content, supplementing the diet during summer and fall.
Seasonal Variation in Nutritional Needs
The nutritional needs of the white-tailed deer fluctuate throughout the year, driven by life-cycle events like reproduction and antler growth. Their diet must align with these changing metabolic demands and the seasonal availability of forage. In the spring and summer, the deer requires a diet high in protein, often needing between 16% to 20% crude protein for optimal health.
This high-protein demand is necessary for does supporting late-term pregnancy and lactation, which imposes the greatest strain on their reserves. Bucks require substantial protein for the rapid growth of antlers, and all deer need it to rebuild muscle mass lost over the winter. The abundance of new forbs and tender browse naturally provides the high-quality forage required during this period.
As fall approaches, the focus shifts to energy and fat storage in preparation for the breeding season (rut) and the colder months. Carbohydrate-rich hard mast, particularly acorns, becomes a primary target for building fat reserves. This fat sustains the deer through the intense activity of the rut, when bucks may lose up to 30% of their body weight, and provides insulation during winter.
During winter, when snow covers ground forage, the deer’s metabolic rate slows, and they primarily rely on fat reserves and the more readily available, but less nutritious, woody browse. Although protein requirements are lower for maintenance, energy remains important for regulating body temperature. Fawns, in particular, need high-energy food due to their low body fat.
Agricultural and Suburban Foraging
In areas where natural habitat meets human development, white-tailed deer become opportunistic foragers, readily exploiting agricultural fields and suburban landscapes. This behavior results from the deer’s preference for concentrated, high-nutrient food sources. Agricultural crops provide a dense, easily accessible food supply that often exceeds the nutritional quality of native forage.
Deer frequently target crops such as corn, which offers concentrated carbohydrates, and soybeans, which are extremely high in protein and fat. They will also forage on wheat, alfalfa, and other commercial crops, adapting their diet based on the planting and harvesting cycles. This reliance can lead to significant conflicts with farmers due to crop damage.
In suburban and residential settings, deer treat gardens and ornamental plantings as readily available food plots. Common targets include high-value garden vegetables like beans, lettuce, and tomatoes. They also consume ornamental shrubs and flowers, such as hostas, impatiens, and arborvitae.
The availability of human-supplied food alters the deer’s natural movement patterns, causing them to concentrate in smaller areas. While these sources provide immediate energy, they can increase the risk of disease transmission and habitat damage due to over-browsing. This often makes the deer less wary of people, leading to increased human-wildlife conflict.
Foods to Avoid or Limit
Providing supplemental feed for white-tailed deer, particularly processed items, poses a significant danger to the animal’s health. The deer’s four-chambered stomach relies on a delicate balance of specialized microbes to break down their naturally high-fiber diet. Introducing large amounts of low-fiber, high-carbohydrate foods rapidly disrupts this microbial ecosystem.
Foods like corn, bread, donuts, or moldy grains can cause a severe digestive condition known as acidosis. In this scenario, the sudden influx of simple carbohydrates causes an overgrowth of acid-producing bacteria in the rumen. This shift leads to a rapid pH drop, which kills the beneficial microbes needed for digestion.
A deer afflicted with acidosis may develop severe diarrhea and dehydration, effectively starving to death because it can no longer digest any food. Sudden changes in diet are especially harmful during winter when the deer’s system is adapted to processing woody browse. Well-intentioned feeding can be fatal, and wildlife management agencies advise against supplemental feeding of deer with processed foods.
While deer possess adaptations to safely consume small amounts of mildly toxic plants, certain common ornamental plants, such as yew, can be highly poisonous if consumed in quantity.