White-tailed deer harvest success and its impact on forest understory vegetation: Evaluating management program efficacy in southeastern New York

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Ralph H. Green III, Graduate Student, Pace University, Pleasantville, NY and Danielle R. Begley-Miller, Director of Science and Stewardship, Teatown Lake Reservation, Ossining, NY

Background/Question/Methods
In southeastern New York, white-tailed deer (Odocoileus virginianus) populations have increased over the last 50 years from a lack of natural predation, increase in food resources from land use changes, and restrictive hunting regulations. Unmanaged deer populations have severe negative impacts on understory plant communities, a key contributor to forest regeneration and biodiversity, affecting other plant and animal species. Numerous strategies are employed by land managers throughout the Hudson Valley region of New York to manage deer via lethal means. This study aims to better understand the effectiveness of different white-tailed deer removal programs (i.e., culling, archery, and firearms seasons) compared to no management in improving forest understory conditions across 7 nature preserves in the Hudson Valley. To assess each site, we used multiple linear regression to correlate long-term (4+ year) understory vegetation characteristics (species diversity, seedling density, and seedling height) with changes in deer density estimates by management program type. Data were from pre-existing permanent forest monitoring plots at 5 sites with ongoing deer management and 2 with no management. We also compared harvest rates across sites and program types to determine harvest efficiency (hours per successful harvest).
Results/Conclusions
Deer density estimates decreased or stabilized across all program types in the first 4 years of management (F(4,18) = 2.3, p = 0.098), and harvest efficiency (number of deer harvested per hour effort) decreased at all sites with time (F(3,23) = 8.974, p < 0.001). Culling (5.32 deer/per hour) was the most efficient harvest strategy compared to archery (0.22 deer/per hour) and firearms (0.02 deer/per hour) programs. While management programs did reduce deer densities, those changes did not correlate consistently with seedling density (F(1,16) = 0.483, p = 0.49), and seedling height (F(1,13) = 1.131, p = 0.72), but did positively correlate with understory diversity (F(1,43) = 11.184, p = 0.002). Vegetation responses appear site-specific and driven by additional site limitations beyond deer density, but data analysis was limited by inconsistent data collection strategies across sites. We recommend regional coordination among land managers to establish consistent protocols to assess and monitor the impacts of deer density on local forested ecosystems prior to starting a deer management program.