Deer are adaptable herbivores, consuming a wide variety of plant matter crucial for their health and survival. Their diet shifts based on seasonal availability and their changing nutritional needs throughout the year. This flexibility allows them to thrive in diverse environments, from forests to agricultural landscapes.
Primary Dietary Components
Deer primarily consume three main categories of natural foods: browse, forbs, and mast, which together can constitute over 85% of their diet. Browse includes leafy parts, twigs, and buds of woody plants like shrubs and trees. Common examples are oak, maple, sumac, aspen, and dogwood. Browse is a consistent part of their diet, especially when other food sources are scarce.
Forbs are broad-leafed herbaceous plants, including wildflowers, weeds, and legumes like clover and alfalfa. These highly digestible and nutrient-rich plants are a preferred food source when available, particularly in late spring and summer.
Mast consists of fruits and nuts from trees and shrubs, divided into “hard mast” (energy-rich nuts like acorns and hickory nuts, high in fats and carbohydrates) and “soft mast” (berries, apples, pears, persimmons, and wild grapes, offering sugars and vitamins). While highly preferred, mast availability fluctuates with environmental factors. Deer also consume fungi, such as mushrooms, for protein, vitamins, and minerals.
Seasonal Variations in Diet
A deer’s diet changes significantly with the seasons, driven by plant availability and physiological demands. In spring and early summer, deer focus on new, tender growth. This period, characterized by an abundance of fresh forbs and succulent browse, meets their high protein needs for antler growth in bucks and gestation and lactation in does.
As summer progresses into fall, deer shift towards energy-dense foods to build fat reserves for colder months and the rut. Hard mast, like acorns and other nuts, becomes a primary food source due to its high fat and carbohydrate content. Soft mast, including berries and apples, also contributes to their energy intake.
During winter, when many plant sources are dormant or covered by snow, deer rely more heavily on browse, including woody stems, buds, and evergreen leaves. Their metabolism slows, reducing energy requirements, but they still need sufficient forage to maintain body temperature and survive. Leaf buds and evergreen leaves are important in northern regions during winter.
Foods to Avoid and Human Interactions
Certain plants are harmful or toxic to deer, including common ornamental species like azaleas, rhododendrons, and yew. While deer usually avoid these due to natural instincts, they may consume them if other food sources are scarce.
Feeding deer human-provided foods is discouraged and can be detrimental to their health. Their digestive systems are adapted to natural forage, and sudden dietary changes, especially with carbohydrate-rich foods like corn, can disrupt gut microbes, leading to severe digestive issues, illness, or even death. Artificial feeding sites can also cause deer to congregate in high densities, increasing the risk of disease transmission, such as Chronic Wasting Disease (CWD). Concentrating deer also makes them more vulnerable to predators and can lead to habituation to humans, increasing deer-vehicle collisions and property damage.
Deer frequently interact with agricultural lands, consuming crops like corn, soybeans, wheat, and alfalfa. This can lead to significant economic losses for farmers, with deer being responsible for a portion of wildlife crop damage. Farmers may implement various strategies, including fencing, habitat management, or controlled hunting, to mitigate crop damage.