The white-tailed deer ( Odocoileus virginianus) is a highly adaptable herbivore found throughout North, Central, and South America. Understanding its dietary habits is crucial for effective wildlife management and for coexisting with these animals, especially in areas where they are abundant. White-tailed deer are commonly hunted for meat and sport.
General Dietary Habits
White-tailed deer are both browsers and grazers, meaning they consume a variety of plant materials. Their diet varies significantly depending on the habitat, season, and availability of food sources. As ruminants, deer possess a four-chambered stomach, enabling them to quickly ingest food and later digest it more thoroughly in a safe location. This adaptation allows them to eat rapidly in areas where they must remain vigilant for predators.
Seasonal Variations in Diet
A whitetail's digestive process in northern climates changes with each season.
Spring
Spring is an optimal time for white-tailed deer, as management practices stimulate new plant growth. Deer focus on regaining weight lost during the winter. Forbs are highly digestible and rich in energy, minerals, and antioxidants, making them crucial during this period. Mushrooms are also highly sought after due to their phosphorus content, essential for antler growth and developing fawns.
Summer
During the summer, deer primarily consume annual and perennial forbs and woody browse, which provide high levels of essential nutrients. Deer shift to browse plants, particularly their first-choice selections. Later in the summer, they may transition to second-choice browse plants and early fruits like grapes and berries.
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Fall
As fall approaches, deer need to consume carbohydrate-rich foods like acorns, chestnuts, apples, and pears to build up fat reserves for the winter and breeding season. Nuts and mushrooms remain important for their phosphorus content, which aids in antler mineralization.
Winter
In winter, deer diets change drastically. They shift to assimilating woody browse almost exclusively, feeding on living twigs and buds. Leaf buds and evergreen leaves are especially vital in northern regions.
Key Food Categories
White-tailed deer diets primarily consist of browse, forbs, and mast.
- Browse: This includes the leaves, buds, and twigs of woody plants like trees, shrubs, and vines. Browse is a staple food, always available regardless of weather conditions.
- Forbs: These are non-woody, broad-leaved plants, often called "weeds." Forbs are highly digestible and nutrient-rich but are an ephemeral food source, as they are sensitive to freezing temperatures and dry periods.
- Mast: This category includes nuts and fruits, which provide high-energy sources. Acorns and chestnuts are important, with acorns being high in fat and carbohydrates and chestnuts being high in protein and carbohydrates. Deer prefer chestnuts due to their lower tannin content, which can inhibit digestion.
Regional Dietary Differences
The specific plants that deer prefer vary by geographic area. Wildlife biologists classify browse plants into first, second, and third choices, and these classifications can differ from one region to another. State game agencies and natural resources conservation services often provide publications on preferred whitetail food plants specific to each state.
Nutritional Needs
Deer require a balanced intake of protein, energy, minerals, vitamins, and water to maintain their physiological functions.
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- Protein: Essential for body maintenance, growth, reproduction, lactation, and antler growth. The protein requirements vary with age and sex, with higher needs during lactation and antler development.
- Energy: Derived from nutrients in foods, energy is needed for body maintenance, reproduction, growth, and daily activities. Deer seek carbohydrate-rich foods in the fall to build fat reserves for the winter.
- Minerals: Calcium and phosphorus are crucial for skeletal and antler development. Sodium, or salt, is also important, especially during the spring and summer.
- Vitamins: While specific amounts needed are not well-defined, vitamins are important for overall health.
- Water: Critical for maintaining bodily functions, water is obtained through vegetation and direct sources.
Habitat Management for Optimal Nutrition
Managing wooded habitats to increase food and cover availability is essential for supporting healthy deer populations. Techniques include:
- Increasing Light Penetration: Opening the canopy to allow sunlight to reach the forest floor encourages the growth of beneficial plants.
- Maintaining Acorn-Producing Trees: A diversity of mature oak trees, with about 20 trees per acre averaging at least 14 inches in diameter at breast height (DBH), provides a reliable acorn supply. Preferred oak species include post, black, white, northern red, chinquapin, blackjack, and scarlet oaks.
- Creating Brush: Managed timber harvests can create brush, as harvested trees re-sprout, providing easy-to-reach forage.
- Protecting from Grazing: Preventing cattle grazing protects the area, ensuring adequate forage for deer.
- Promoting Shrubs and Vines: Encouraging the growth of shrubs and vines like blueberry, dogwoods, sumacs, grape, greenbrier, and viburnum provides additional food sources.
The Importance of Forbs
White-tailed deer thrive on palatable, nutritious, and easily digestible foods, with forbs being a highly preferred category due to these attributes. Providing a variety of forage types is critical.
Agricultural Crops
A wide variety of agricultural crops are readily used whenever available because they tend to be highly nutritious, palatable, and readily digestible.
Browse Line
Evidence of deer feeding includes the presence of a browse line on nearby trees. Think of northern white cedar growing along a lakeshore, where there are no green branches until about six feet up. In Minnesota, the browse line is typically around six feet, but with a deep snow depth and a hungry deer, the browse line could be closer to nine feet.
The Role of Supplemental Feeding
Supplemental feeding is generally not needed in areas with plentiful food sources like Illinois. In fact, feeding deer is illegal in most cases in Illinois, as it can contribute to the spread of diseases.
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