a Penn State Forest Stewards series article – written by Dave Jackson, Forest Resources Educator, Penn State Extension and Matt Russell, Associate Professor/Extension Specialist, University of Minnesota
Many woodland owners take to their woods in October to begin scouting for deer season. A good way to learn more about where white-tailed deer might be found is by understanding what they’re eating. A deer’s diet consists of a variety of crops, herbaceous and woody vegetation, fruits, and nuts. A healthy diet will consist of a variety of different foods. A deer requires an estimated 6 to 8 percent of their body weight daily in forage to stay healthy. For a 150-pound deer, that’s up to 12 pounds of food every day!
Too much browsing pressure, eating twigs and young shoots, from deer can kill or limit the growth of tree seedlings, a fact that foresters and woodland owners know very well. Over decades, deer populations can greatly impact the look of woodlands. Knowing which tree seedlings are growing in your woods and which ones are browsed can give you more details on a deer’s diet.
In Pennsylvania, tree species that rank high on a deer’s list include a number of hardwood trees. Red and white oaks are two of the primary hardwood species that deer prefer to browse, while blackgum, hickory, and yellow poplar are also very high on the preference list. As you move north, species like maple (red and sugar), white ash, and basswood become more preferred species where they are more abundant.
While deer prefer these tree species, they also avoid certain plants. Deer will start by browsing the most preferred or palatable trees first. If there are high populations of deer in an area, preferred plants will see more browsing which can lead to other plants, that deer don’t prefer, taking over.
So what does it mean if deer are browsing beech seedlings/sprouts? Likely that deer are getting desperate and other food sources are limited. Evidence of high deer populations can be seen in a woodland that is dominated by beech brush, striped maple, black birch, black cherry, mountain laurel, ferns (primarily hayscented and New York) and invasive exotic plants. Deer avoid browsing these plants because they are not as digestible compared to other vegetation.
More evidence of deer browse impacts is the presence of a browse line on all understory trees, where there are no green branches until about five or six feet up. Another sign may include the presence of seedlings that are severely hedged and not able to grow above 1-foot in height, as well as understories dominated by species that deer avoid. Deer do not readily eat species like ferns, striped maple, beech, ironwood, mountain laurel, blueberry, and spicebush. As a result, we see these species dominating the forest understory in many areas.
To have a healthy woodland, tree seedlings need to develop into healthy, mature trees. As an example, consider a browse-sensitive species like oak. First, it can take over thirty years for an oak tree to produce acorns. Second, acorn crops only occur every two to five years and truly “bumper” crops much less often. In these good crop years, acorns can make up the majority of a deer’s diet in the late fall. If oaks can never make it from acorn, to seedling, to sapling, to healthy mature tree, the habitat quality for deer can suffer in the long term as oaks are replaced by other, potentially less desirable, species.
Knowing which species are being browsed can also give you insight into which methods can be used to protect seedlings. Although costly, fencing can be constructed around individual trees or larger areas several acres in size. Protecting tree seedlings ensures that you have healthy trees for the future while steering deer towards other food sources.
You may also consider harvesting additional antlerless deer. The Pennsylvania Game Commission’s Deer Management Assistance Program (DMAP) helps landowners meet their forest management goals by allowing hunters to harvest additional antlerless deer from a property during the regular hunting seasons.
Areas with low deer browsing pressure provide diverse wildlife habitats. They support healthy understories, preparing the forest for future replacement following natural tree mortality or planned timber harvests. Habitat repeatedly damaged by over-browsing continues to decline, losing its ability to support additional deer and other wildlife. It is important to reach a proper balance between desired habitat conditions and deer populations.