Penn State Cooperative Extension advises on deer balancing act

University Park, Pa. -- Penn State Cooperative Extension is offering several programs this spring on deer and habitat management. According to Dave Jackson, extension forester, deer populations larger than the habitat can support pose serious problems for homeowners, agricultural producers, woodland owners and the public. Safety -- from Lyme disease to deer-vehicle collisions -- is one issue affecting many people.

"A recent Maryland survey found that one out of six citizens knows someone who hit a deer with a car," he said. "Deer browsing reduces farm crop yields, damages landscape plantings and reduces forest plant diversity. Managing deer populations so they are in balance with the available habitat is essential."

Research has repeatedly documented deer impacts on tree regeneration and forest herbaceous plant diversity, Jackson said. The ability of a forest to support deer is a function of both deer density and forage availability. By selectively browsing preferred palatable plants, deer influence tree seedling numbers, species composition and seedling height growth.

"Because deer are free to move, it is important to consider their management at a landscape level and to understand how concentrated preferential feeding can shift plant communities," he said. "As deer feed on one species, another species that is not preferred can become increasingly common. Research findings indicate that when deer numbers exceed what the land is capable of supporting, deer can severely impact the forest's ability to regenerate itself following natural or man-made disturbances."

In regions where over-browsing for decades has severely depleted food species, even very few deer have major impact and the habitat can only support very few animals, Jackson said. In landscapes with little preferred forage, deer numbers in balance with available habitat must be kept low.

"To sustainably increase the number of healthy deer the habitat can support, landscape forage availability must increase," he said. "It is possible to increase desirable forage through management activities such as controlling undesirable vegetation and harvesting trees. When deer numbers are out of balance with their habitat, look for obvious browse lines, evidence of severe browsing on nonpreferred species such as American beech, striped maple and black cherry, and forest understories dominated by species deer avoid, such as hay-scented fern, striped maple, American beech, hophornbeam, mountain laurel, blueberry and spicebush."

"Across Pennsylvania it is relatively easy to recognize areas where the deer-habitat balance has been upset for years: nonpreferred plant species, such as hay-scented fern, cover the forest floor. Many Pennsylvanians have never seen a healthy forest understory."

The question is whether these habitats can recover over time. Jackson suggested that cooperative extension specialists can advise landowners on creating better deer habitat. Web seminars and hands-on workshops offered this spring by Penn State educators and partners will address the issue.

The first "webinar," titled "Regenerating Hardwood Forests: Managing Competition, Deer, and Light," is on Feb. 9 at noon and 7 p.m. The second webinar, "Deer Habitat Management," is on March 9 at noon and 7 p.m. For webinar details or to register to participate, visit

Penn State also will offer a hands-on series of events titled "Deer Density and Carrying Capacity Workshops." These workshops are open to landowners, hunters and anyone interested in learning more about deer and their habitat. During each session, participants learn how to evaluate a given habitat and how its condition relates to deer biology, density and carrying capacity.

For a listing of dates and locations for these workshops, visit the Renewable Natural Resources Extension Web page at and click on the "Calendar" link on the right side of the page.

The Pennsylvania Forest Stewardship Program provides publications on a variety of topics related to woodland management. For a list of free publications, call 800-234 9473, send an e-mail to, or write to Forest Stewardship Program, Forest Resources Extension, The Pennsylvania State University, 416 Forest Resources Building, University Park, PA 16802.

For more information, contact Dave Jackson, extension forester, at 814-355-4897 or

Media Contacts: 
Last Updated November 18, 2010