Food Availability—Seasonal availability determines which foods are consumed.
Browsing—Deer nibble off the tender shoots, twigs, and leaves of trees, shrubs, and other plants using their lower front teeth.
Grazing—Deer will eat grasses, especially in suburban areas. In winter, they paw through the snow to expose edible grasses.
Foods Eaten—Deer eat a wide variety of foods based on their nutritional needs and the seasonal availability of plants. For example, during the summer and fall they search for plants that are high in protein to prepare for rut and to help them survive the winter. Below are some examples of food that deer will eat.
- Forbs such as geum, buttercup, Solomon seal, and trillium
- Twigs, buds, and leaves of woody plants such as elms, honeysuckle, raspberry, black cherry, maple, basswood, grape, and hawthorn
- Apples, crabapples, and other fruits
- Sweet corn and other vegetables
- Landscape and ornamental plants such as arborvitae and hostas
- Agricultural crops such as corn and soybeans
- Acorns are high in fats and oils, providing an accumulation of fat reserves to help deer through cold midwestern winters.
- Acorn production is often cyclical, with higher yields occurring every 2 to 5 years depending on the tree species, rainfall, and location.
- Deer may shift their range in the fall and winter to take advantage of good acorn production. In years when acorn production is low, browsing becomes more important.
- Where cultivated crops are readily available, the lack of acorns does not pose a threat to survival. But in areas of extensive woodlands, lack of available acorns may influence the general health of local deer.
Deer obtain water from three sources: open water, vegetation consumed, and metabolism from oxidation of fats, carbohydrates, and proteins.
In summer deer require about 1½ quarts of water per hundred pounds of body weight each day.
In winter, when water sources are frozen, deer consume snow; although deer require less water in cold weather.
During a drought deer may gather in areas that still have open water. They are attracted there by the water and the forbs that remain in the moister soil. These wet areas also attract insects that can carry epizootic hemorrhagic disease, which increases the chance for deer to become infected.
During the summer, drought can hinder a female’s ability to hide her fawn since there is less dense vegetation.
When vegetation suffers from drought conditions, palatability and digestibility may be decreased. And drought conditions can cause tree nuts to drop early, reducing the amount of oak acorns, hickory nuts, and walnuts available to deer in the fall and early winter.
A deer’s ability to move long distances can reduce the impacts that drought has on the deer.
In Illinois there is plenty of food for deer. Supplemental feeding is not needed. In fact, feeding deer in Illinois is illegal in most cases. Strict rules on feeding wildlife, including deer, are set in the Illinois Administrative Code: https://www.dnr.illinois.gov/adrules/documents/17-635.pdf
The Illinois Digest of Hunting and Trapping Regulations also lists the current rules and exceptions on supplemental feeding.
Many deer diseases are transmitted through saliva or fecal contamination by animals sharing common feeding sites. The discovery of chronic wasting disease among deer in 2002 led the Illinois Department of Natural Resources to ban all deer feeding to reduce the spread of this fatal deer disease.