What Do Deer Eat? White-Tailed Deer Diet Through the Year

Browsers, not grazers

Herbivores that eat mostly grass are called grazers, like cattle and bison. Animals that pick leaves, buds and twigs from bushes and trees are called browsers. The white-tailed deer is mainly a browser and a selective one: instead of mowing whatever is in front of it, it picks out the most nutritious plants and plant parts.

Studies across North America have recorded white-tails eating many hundreds of different plant species. The main food groups are:

• Browse: leaves, buds and twig tips of trees and shrubs such as maple, oak, aspen, sumac, dogwood, greenbrier and blackberry.
• Forbs: broad-leaved non-woody plants, including many wildflowers, clovers and other legumes.
• Mast: acorns, beechnuts and other nuts, plus soft fruits such as apples, persimmons and berries.
• Grasses and sedges: mainly young green growth in spring.
• Fungi and other foods: mushrooms, lichens and, in deserts, cactus pads and tough shrubs.
• Crops: corn, soybeans, alfalfa, winter wheat and orchard fruit.

How deer digest their food

Deer are ruminants, like cattle, sheep and goats. Their stomach has four chambers. The first and largest, the rumen, holds billions of microbes that break down tough plant fiber that the deer could not digest on its own.

A deer feeds quickly, filling its rumen, then moves to cover to lie down and chew its cud. It brings small lumps of food back up into the mouth, chews them again with saliva and swallows them, breaking the plants into ever smaller particles. This lets a deer spend less time exposed in open feeding areas, which helps it stay safe from predators.

The microbe community in the rumen changes as the diet changes through the seasons. A sudden switch to an unfamiliar food can upset this balance, which is one reason deer are adapted to gradual seasonal shifts in what they eat.

What deer eat through the year

Spring and summer are the time of plenty. Does need extra protein and minerals to produce milk for their fawns, and bucks need it to grow antlers.

Autumn is dominated by mast. In good acorn years deer may spend much of their time under oaks, building up fat that will see them through winter and, for bucks, through the rut, when they eat very little.

Winter is the hard season in the north. Deer slow their metabolism and move less, living partly on stored fat. Many gather in sheltered conifer stands called deer yards and feed on twigs within reach. In very deep snow they may struggle to find enough food.

How deer change forests

Where deer are very numerous, their feeding reshapes whole forests. In parts of eastern North America, high densities of white-tailed deer have stripped the understory of young trees, shrubs and wildflowers. A clear “browse line” may appear, below which almost no leaves remain, at about the height a deer can reach standing on its hind legs, around 1.5–1.8 m (5–6 ft).

Because deer prefer some plants, such as young oaks, maples, hemlock and many wildflowers, heavy browsing lets less tasty plants, ferns and some invasive species take over. This can reduce habitat for ground-nesting birds and other wildlife. At moderate densities, though, deer browsing can increase plant variety by keeping dominant plants in check.

Why deer visit gardens and farms

White-tailed deer love edges, where woods meet open land, and suburbs and farms are full of edges. Gardens, lawns and crops offer fertilized, well-watered plants that are tender and rich in nutrients, often close to cover. In areas without large predators and with little hunting, deer populations can grow high enough that natural food runs short and gardens become a regular part of their diet.

Crop damage from deer costs US farmers hundreds of millions of dollars a year, and deer eating ornamental plants are one of the most common wildlife complaints in suburban North America.

Other deer, other diets

Not every deer eats the same way. The moose feeds heavily on willow, birch and aquatic plants, wading into lakes to graze, as explained in what do moose eat? Reindeer rely on lichens in winter. Red deer and elk eat much more grass than white-tails and can switch between grazing and browsing depending on season.