Cooperative Fish and Wildlife Research Units Program: Pennsylvania
Education, Research and Technical Assistance for Managing Our Natural Resources

Pennsylvania Project

Deer abundance and its relationship to factors that affect forest vegetation conditions

January 2013 - June 2026


Participating Agencies

  • Cooperative Research Units
  • Pennsylvania Game Commission
  • Pennsylvania Bureau of Forestry
  • Department of Conservation and Natural Resources
  • PA Dept of Conservation and Natural

In the last decade, deer densities were reduced in many Wildlife Management Units (WMU) in Pennsylvania. These decisions to reduce deer densities were based on the assumption that forest conditions, especially regeneration, would improve with lower deer populations. Primarily anecdotal observations suggest forest regeneration has improved but the large-scale, quantitative Forest Inventory Analysis (FIA) monitoring program has failed to provide strong evidence for changes in tree regeneration. Consequently, the Pennsylvania Game Commission (PGC) has developed a decision model for deer harvest allocations based on deer browsing impact as measured by the FIA in addition to estimates of tree seedling density.

The ability to explain the lack of change in tree regeneration despite deer population reductions is critical to the credibility of the Pennsylvania Game Commission’s deer management program. In recent years, deer population reductions have caused the deer program to be sued by a sportsmen's group and audited by the legislature. Additionally, the application of the Deer Management Assistance Program (DMAP) on state forest lands has been questioned because DMAP has been used by the Pennsylvania Bureau of Forestry (BOF) to attempt to reduce the effect of deer browsing on forest vegetation.

The PGC needs a better understanding of how the deer browsing impact measure is related to deer densities and whether this measure is valuable for making deer harvest decisions. Similarly, the BOF needs to better understand how the application of the DMAP affects deer harvest and hunter behavior. Both agencies require a better understanding of how vegetation responds to changes in deer density in the context of existing monitoring programs and management activities.

This research proposes to stabilize deer populations at different densities on four study areas and quantify changes in vegetation with respect to other forest conditions (seed production, advanced tree regeneration, etc.) and management actions (e.g., herbicide to remove competing vegetation).

Research Publications Publication Date
Begley-Miller, D. R., D. R. Diefenbach, M. E. McDill, C. S. Rosenberry, and E. H. Just. 2018. Evaluating inter-rater reliability and statistical power of vegetation measures assessing deer impact. Forests 9:669. | Download October 2018
Begley-Miller, D. B., D. R. Diefenbach, M. McDill, P. Drohan, C. Rosenberry, and E. Just. 2019. Soil Chemistry, not short-term (2 year) deer exclusion, explains occupancy of several understory plant taxa in forests affected by acid deposition. AoB Plants 11:1-15 | Download August 2019
Theses and Dissertations Publication Date
Begley-Miller, D. 2018. Shaping Pennsylvania's Forests: Effects of white-tailed deer, soil chemistry, and competing vegetation on oak-hickory forest understory plant community composition. Dissertation, Pennsylvania State University, University Park, PA. May 2018