Deer are adaptable herbivores, with a diverse diet primarily consisting of plant matter. Their feeding habits are influenced by their environment and the availability of various plant types. This adaptability allows them to thrive in numerous habitats, adjusting their consumption based on abundant and nutritious resources. Understanding these preferences reveals how deer sustain themselves in the wild.
Primary Food Sources
The majority of a deer’s diet is composed of four main categories: browse, forbs, mast, and to a lesser extent, grasses. Deer are primarily browsers, preferring the tender shoots and leaves of woody plants over other vegetation types. Browse includes the leaves, buds, and ends of twigs from trees, shrubs, briars, and vines, such as honeysuckle, greenbrier, blackberry, and young saplings like ash. These woody plants are a consistent food source, even when leaves are lost during drought or cold, as their stems and twigs retain some nutritional value.
Forbs, non-woody, broad-leaved plants like wildflowers and certain agricultural crops, are highly digestible and rich in nutrients. Examples include clover, alfalfa, and soybeans, readily consumed in spring and summer.
Mast refers to fruits and nuts, providing significant energy. Hard mast, such as acorns, chestnuts, hickory nuts, and pecans, is especially high in carbohydrates and fats. Soft mast, like berries, apples, and plums, offers sugars and vitamins.
Grasses make up a small portion of their diet, typically less than 10%, as they are less digestible and contain lower nutrient content. Deer primarily eat young, green grasses or cereal grains like oats, wheat, and rye.
Seasonal Dietary Changes
A deer’s diet changes throughout the year, reflecting seasonal availability and varying nutritional needs. In spring, as new growth emerges, deer seek highly digestible, protein-rich forbs and young browse to regain winter weight. This period is important for antler growth in bucks and preparing does for fawning and lactation. As spring transitions into summer, their diet diversifies, including foliage, soft mast like berries, and agricultural crops. During summer, deer consume up to 10 pounds of vegetation daily to support growth and replenish energy reserves.
Fall is a period of focused feeding, where deer accumulate fat reserves for colder months and the rut. Hard mast, particularly acorns and chestnuts, becomes a primary food source due to its high fat and carbohydrate content. White oak acorns are often preferred due to their lower tannin content. As winter arrives, food options become limited, and deer primarily rely on woody browse, such as twigs and buds, along with any remaining mast or agricultural remnants. Their metabolism slows, and they utilize stored fat to survive until spring.
Essential Non-Plant Nutrients
Beyond plant matter, deer require other elements for their health and bodily functions. Water is important for their health, obtained from open sources, consumed vegetation, and metabolic processes.
Minerals are a necessary component of their diet. Calcium and phosphorus are important for bone development and antler growth, while sodium plays a role in water metabolism and nutrient absorption. Deer acquire these minerals from specific soil types, water sources, or by consuming mineral-rich items like mushrooms. Mineral licks, whether natural or supplemental, are another way they obtain these trace elements.
What Not to Feed Deer
Feeding deer human food or processed items can be detrimental to their health and alter natural behaviors. Foods like corn, bread, and other processed carbohydrates can cause a severe digestive condition called rumen acidosis. This occurs because their digestive system, adapted for fibrous plant matter, cannot properly process large amounts of easily digestible sugars and starches. Such an imbalance can lead to dehydration, stomach lining damage, and even death.
Artificial feeding congregates deer in high densities, increasing the risk of disease transmission, including conditions like Chronic Wasting Disease. It can also cause deer to lose their natural fear of humans, leading to more vehicle collisions and potential aggression. Feeding deer in winter, especially with unsuitable foods like hay, can be harmful as their digestive systems are adapted to fibrous browse, and sudden dietary changes can lead to starvation.