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Deer Forest Study


Background: Forests and Deer Management

Deer rely on forested habitats. Forests provide food and cover for deer and a variety of other wildlife. As a primary consumer of forest plants, deer can impact the quality of their habitat and the habitat of many other wildlife species. Because of the strong link between deer and the forests they inhabit, deer management must consider interactions between deer and forests.

For decades, the relationship between deer and forests has been a part of Pennsylvania's deer management program. In the 1950s, appeals were made to sportsmen to support antlerless deer seasons to ensure the future of deer and Pennsylvania's forests. In the 1960s and 1970s, deer management objectives described the need to balance deer populations with their food supplies (i.e., forested habitat). In the 1980s, 1990s, and early 2000s, deer management objectives were defined by the number of deer that could be supported on a square mile of forested habitat. Today, deer management is guided by a number of goals including the maintenance of healthy forest habitats. Although the specific measures have changed, the common theme through decades of deer management remains the same – deer numbers must be balanced with the food and cover provided by forests.

From the 1980s to 2004, deer management recommendations were based on deer density objectives. Field studies with deer enclosures spanning decades and feeding studies with individual deer provided the basis for these deer density objectives. Using results from these studies, deer management recommendations were designed to balance deer populations with available food.

However, deer density objectives were never achieved. Political and social pressures lead the Board of Game Commissioners to approve less than the recommended number of antlerless licenses. Consequently, deer populations increased. By the late 1990s, deer populations were nearly twice as high as the density objectives.

In 2000, the Board of Game Commissioners acted to reduce deer populations following the long standing deer density recommendations. Although there was considerable debate regarding deer impacts and regeneration during this time, the science supporting the objectives of the deer management program remained the same – deer density objectives based on results of deer enclosure and feeding studies. And in 2000, the Board of Commissioners made a concerted effort by increasing antlerless allocations to reach those deer density objectives set in the 1980s.

In 2006, deer management objectives changed. As a result of a new deer management plan in 2003 that included publicly identified and supported goals, numerous objectives related to deer health, forest habitat health, and deer-human conflicts replaced the single deer density objective. Instead of basing deer management recommendations on a forest-driven deer density objective alone, deer health factors and deer-human conflicts also were considered. The Game Commission began using data from the Pennsylvania Regeneration Study (PRS) to monitor deer-forest interactions which provide the most current and comprehensive statewide forest regeneration data available. The PRS began as a collaborative project involving the U.S. Forest Service, DCNR, and Penn State University.

The PRS represented a new source of the most current forestland data. Prior to 2006, complete statewide results of forest regeneration and deer impacts did not exist. The first complete sampling of public and private land across Pennsylvania was completed in 2005. The Game Commission used these data to make deer management recommendations as soon as they were available. Since 2006, the Game Commission has continued to work with the U.S. Forest Service and others to expand the PRS's usefulness from forestry to deer management. Prior to PRS, the agency used forest data collected in 10-year increments.

The Deer-Forest study represents the latest effort to ensure the PRS provides the best available data for making responsible deer management recommendations.


Purpose of the Study: Can We Do Better?

Pennsylvania's deer management plan clearly directs Game Commission staff to evaluate and improve the methodology behind the deer program. Research is the vehicle for this work. The Game Commission has maintained an active deer research program for decades. Research findings are incorporated into the deer program improving our management and understanding of whitetails and deer conflicts.

Game Commission research efforts have evaluated deer management measures. Deer harvest estimates, use of age ratios to monitor deer population productivity and predator impacts, methods to monitor deer population trends, methods of gathering public input, methods of collecting hunter-killed deer to monitor chronic wasting disease have all been evaluated and published in the scientific literature. Every aspect of the deer program has been subjected to external, professional scrutiny and, in most cases, published in the scientific literature. The program is sound.

Since the Game Commission began using forest regeneration data (i.e., PRS) to guide its deer management recommendations, evaluations and improvements have occurred. In 2007, personnel from the bureaus of Wildlife Management and Wildlife Habitat Management reassessed whether the PRS data set is the best to use for monitoring deer impacts on forests. After evaluating characteristics of all available data sets, the answer was clear. The PRS collects highly-detailed tree regeneration data, measures overstory stocking levels and competing vegetation, and is representative of public and private lands. As such, the PRS is still the most appropriate data set available to evaluate forest habitat health based upon adequate tree regeneration.

Since 2007, other modifications in the analysis of the data have occurred based on recommendations from an external review by Wildlife Management Institute and ongoing PGC evaluations.

Incorporating PRS data into deer management recommendations has improved our decision-making, but the question remains. Can we do better? Can we improve our sample sizes or choose alternative measures to increase our ability to detect changes in forest regeneration? How can we better assess other factors affecting forest regeneration and plant diversity? Can we fine-tune deer impact assessments to ensure they reflect actual deer browsing pressure? These questions deserve answers to ensure deer management recommendations are made in the best interest of deer, people, other wildlife species, and forested habitats. These questions also require data from field studies to provide answers. The Deer-Forest Study is designed to provide these answers.

The Deer-Forest Study is a complex study. Since 2006, when the Game Commission began using measures of forest regeneration, it has recognized that deer are not the only factor affecting regeneration. To better understand the effect of deer on the forest, these other factors must be investigated. Consequently, the Deer-Forest Study will explore how forest management activities (i.e., timber harvesting, prescribed fire, herbicide treatments, etc.) can influence deer impacts on the forest.

The Deer Management Assistance Program (DMAP) is an important part of the deer management program. DMAP helps landowners to reach their forest and deer management goals. DCNR is a primary user of DMAP and the state's largest forested landowner. As a result, it is important that the science behind DCNR's requests for DMAP permits is as strong as the science behind the Game Commission's deer management recommendations. For this reason, the Game Commission and DCNR have decided to work together with the U.S. Geologic Survey and Penn State University to complete this comprehensive study of deer and forest interactions.

The Deer-Forest Study represents the next step in improving the deer program. By completing the Deer-Forest Study, the Game Commission is working to achieve objectives in its Strategic and Deer Management plans to evaluate and improve management measures and programs.

Study Areas


Hunter Benefits

A primary concern and consideration for the Game Commission is that the data we use accurately reflect the effects of deer on forests. Deer are not the only factor affecting forest regeneration. But deer impact assessment is the most important measure used in deer management recommendations. By evaluating the role of deer, as measured by the deer impact assessment, and making improvements, this study will benefit hunters in three ways.

First, this large-scale project allows us to monitor the effect of deer on forest regeneration under real conditions. Deer are often an easy target when it comes to lagging forest regeneration, given their browsing in the understory. Deer also are easier to manage than many of the other factors affecting forest regeneration. However, if deer are not the cause, then further deer population reductions will not lead to the ultimate goal – healthy and sustainable forest habitats that support abundant wildlife populations. By furthering our understanding of the role of deer and other factors on forest regeneration, misplaced blame does not fall on deer.

Second, recommendations to reduce deer populations have significant impact on hunters. A high deer impact assessment leads to a recommendation to reduce deer populations. By critically evaluating the deer impact assessment under real-world conditions, the Game Commission is ensuring that recommendations to reduce deer populations are truly necessary and responsible. Recommendations to reduce deer populations are not taken lightly, and this study is designed to strengthen the data upon which future recommendations are based.

Finally, DMAP is available for landowners to manage deer to achieve their objectives. DCNR is the largest, and most scrutinized, user of DMAP. This study will investigate the role of DMAP and the influence of forest management on deer populations and associated impacts. By clarifying these relationships, DCNR can apply DMAP in the most effective manner.