White-tailed deer are adaptable herbivores found across North America, adjusting their diet based on local availability. As ruminants, deer possess a specialized four-chambered stomach that allows them to efficiently process plant material through microbial fermentation. They are classified as concentrate selectors, prioritizing highly digestible, nutrient-dense foods over low-quality roughage. This opportunistic and selective feeding strategy allows them to seek the most palatable and nutritious forage available as seasons change.
Browse and Forage (Woody Plants and Forbs)
The deer’s diet is built upon two categories of vegetation: browse and forbs. Browse consists of the tender leaves, stems, and buds of woody plants, such as shrubs and trees. It serves as a consistent source of bulk and moderate protein throughout the year. Species like sumac, maple, aspen, cedar, and honeysuckle are frequently consumed, with the growing tips offering the highest nutritional value. In winter, when herbaceous growth is scarce, deer rely heavily on the lower-quality twigs and stems of woody browse for survival, sometimes comprising up to 60% of their diet.
Forbs are broad-leafed herbaceous plants, such as weeds or wildflowers, highly desired due to their exceptional nutritional content. Unlike grasses, forbs remain highly digestible and often contain crude protein levels exceeding 13%. Deer actively seek out forbs like common ragweed and partridge pea. The availability of these nutrient-rich plants is important during warmer months when deer have high demands for growth, antler development, and nursing.
Mast Crops (Nuts and Fruits)
Mast crops are seasonal, high-energy food sources that deer actively target to build up fat reserves. These foods are divided into hard mast and soft mast, each providing a different nutritional boost. Hard mast refers to nuts produced by trees, with acorns from various oak species being the most important component across many regions.
Deer prefer white oak acorns because they contain lower levels of bitter tannic acid, making them sweeter and more palatable than red oak varieties. Other hard mast, including hickory nuts and beechnuts, are also consumed, providing high concentrations of fats and carbohydrates essential for pre-winter conditioning. Focusing on hard mast in the fall allows deer to accumulate the stored energy needed to endure winter.
Soft mast includes wild fruits and berries, such as wild apples, persimmons, grapes, and blackberries, which provide necessary sugars and readily available carbohydrates. These fruits are primarily available during the late summer and fall, helping to fill nutritional gaps when summer forbs begin to dry out. Consuming both hard and soft mast maximizes the deer’s ability to store body fat before cold weather arrives.
Dietary Shifts Across Seasons
The deer’s diet changes significantly with the seasons, driven by fluctuating nutritional needs and plant availability. In the spring and early summer, the focus is on growth and reproduction, leading to a prioritization of high-protein forbs and new plant shoots. Does require this protein for lactation and fawns for rapid development, while bucks need it for antler growth, which is composed of up to 80% protein.
By fall, the dietary goal shifts to energy storage, prompting a search for high-calorie mast crops, like acorns and persimmons, to build fat reserves. The deer’s digestive system adapts to these changes, with the microbial community adjusting to efficiently process the current food source.
During winter, deer enter a survival phase, reducing their metabolism and voluntary food intake by as much as 30% to conserve energy. They rely on the low-quality, high-fiber woody browse that remains available, supplemented by stored body fat. The rumen microbes are adapted for this fibrous diet, which is why a sudden switch to highly digestible food during this time can be detrimental.
Mineral Intake and Water Sources
Beyond caloric intake, deer require specific minerals for physiological functions, bone health, and reproduction. Calcium and phosphorus are important, making up a significant portion of hardened antler mass and necessary for skeletal growth. While calcium is often sufficient in the natural diet, phosphorus levels in forage can sometimes be low, especially in certain soil types.
Deer acquire these elements, along with sodium, through geophagy, the consumption of mineral-rich soil at natural licks. Sodium is highly sought after during spring and summer because the high water and potassium content of fresh forage can dilute the body’s sodium levels, driving deer to seek concentrated salt sources. Water intake is also met through free water sources like streams and ponds, as well as the moisture found in the vegetation they consume. Their need for free water decreases significantly in the winter months.