While white-tailed deer are ruminants like cows, but their diet selection is much different. Cattle are grass-roughage eaters, have a relatively large rumen compared to body size and depend heavily on grasses for their diet.
Grasses are relatively low in crude protein and digestibility when compared with legumes, forbs (broadleaf weeds) and the new-growth of browse plants. To a white-tailed deer, browse consists of the leaves and twigs of trees, shrubs (brush) and vines.
Deer Eat High Quality Foods
Because grass is relatively low in nutrition, grasses need a longer residence time in animal’s rumen. Longer residence time increases rumen microflora (bacteria and protozoa) degradation and digestion of the forage. Thus, for grass-roughage eaters like cattle and sheep, residence time is quite long and rate of food passage is slow.
Deer can’t go slow! They have higher physical demands for energy and can not afford to carry around extra, dead-weight. Instead, white-tailed deer focus only on the most palatable, most-easily digested food items found in their habitat. This ensures that they get the most energy possible with the lowest amount of food intake. Besides, eating takes energy.
What do Deer Eat Then?
White-tailed deer are what people in the diet business call “concentrate selectors.” Their rumen is small relative to their body size. Thus, their diet must be higher in nutritive value and capable of being rapidly degraded in the rumen.
Therefore, white-tailed deer rely primarily on the good stuff, the forb and browse plants that are found growing in their environment — which are usually much higher in crude protein and digestibility than just about every species of grass.
Keep this in mind: grasses comprise only a very small part of the overall diet of the white-tailed deer, usually less than 10%. I think this important to point out because so often I hear people say, “the deer have so much grass to eat.” Yes, you may see them in a field but it is not the grass they are eating. They are instead searching for interspersed forbs/weeds that are much easier for them to digest and loaded with protein.
Warm season perennial grasses that supply livestock with most of their nutrients will not meet the nutrient and consumption requirements of white-tailed deer. In fact, a white-tailed deer will not survive in a field of grasses.
Only grasses that are rapidly degraded in the rumen, such as the small grains and ryegrass, are used to any extent by deer. This is why winter food plots for white-tailed deer containing these grasses can work. Other useful introduced forages include both warm and cool season legumes. Deer will use these small grains and legumes, but not even they are able to comprise a complete deer diet.
Deer Eat A Diversity of Foods
Good diverse plant communities, possibly even combined with supplemental feeding for those interested in maintaining deer body condition, should always be considered for proper deer herd health. Deer are very selective feeders so they require a diverse environment, a diverse diet to remain healthy. White-tailed deer prefer high quality habitat.
For several reasons, deer are often observed feeding along field edges. First, deer are very difficult to see in dense woods so we rarely see them there, even though they are there. Second, there is always a greater diversity of food available at the intersection of field and the edge of a woodland. This is because forb diversity is low in woodlands, but browse diversity is low in grasslands. Put them together and you have a deer buffet!
More Resources on Deer Diet
- What do deer eat and why?
- Foods of Northern Deer
- Deer Feeding Habits in Missouri
- Whitetail Food Habits Central Texas
A Wild Deer’s Diet
The complete list of native plants used by white-tailed deer include browse, forbs, soft and hard mast (fruits, acorns), and mushrooms. Deer are not classified as grazers, but rather are commonly referred to as browsers. Each day, a deer’s mission is to get high quality food with as little effort as possible.
Forbs and mast, while providing good nutrition, may not be available each year or at certain times of the year. Forbs are often abundant during the rainy seasons such as during the spring and fall. Deer will consume these readily when available because they are very high in protein levels.
Browse plants tend to be more stable, so they lend themselves to being termed the “bread and butter” of a deer’s diet. Again, browse plants are trees, shrubs and vines. These types of plants are deeply rooted and can persist through the summer. During the winter, when natural foods are low, deer will also eat old, dead leaves directly off the forest floor. They are low in nutrition at this point, but they may be the best food available to them at that time.
Browse is the most important source of deer nutrition because of year-round availability. Important browse plants include greenbriar, poison ivy, grape vines, honeysuckle, hackberry, elm species, oak species and a variety of other trees and shrubs that are palatable in the area/region where the deer live.