Date of Award
8-1-2025
Degree Name
Master of Science
Department
Forestry
First Advisor
Nielsen, Clayton
Abstract
Raccoons (Procyon lotor) are an opportunistic and highly adaptable mesopredator that negatively impact several vulnerable avian and reptilian species. While predator removal has been used for decades, wildlife managers require more information about the efficacy and long-term feasibility of using predator removal to control raccoon populations. I determined the efficacy of raccoon removal within an urban-rural gradient by placing 109 camera traps (n=204 unique camera trap placements) across 6 study sites during February-August 2022-2024 to monitor raccoon occupancy before, during, and after trapping efforts were performed. During April-June 2022-2024, collaborators removed raccoons (n=771). Based on pre-removal abundance estimates, collaborators removed 81-100%, 38-100%, and 57-100% of raccoons from each study site from 2022-2024, respectively. Each year, 4 out of the 5 removal sites exhibited a decrease in raccoon detections directly after removal and remained below the estimates observed prior to removal for the rest of each camera trapping season (i.e., for 2-3 months). However, each subsequent year displayed abundance and raccoon detection estimates that returned closer to pre-removal levels for each study site (i.e., 10 to 12 months following removal). Each year, single-season occupancy models indicated detection and occupancy probabilities were highest before removal and decreased after removal for the following 2 to 3 months. From 2023 to 2024, multi-season occupancy models indicated colonization rates decreased across all removal sites from 49 to 8% and extinction rates increased by 9%. In 2023 and 2024, the control site had extinction rates close to zero and colonization rates that increased to 80% by 2024. My results were generally similar across all removal sites for all years, suggesting that the observed results were not influenced by site-specific factors and thus generalizable across larger landscapes. These findings demonstrated a successful short-term population reduction, and provided evidence for long-term feasibility, as indicated by a decrease in colonization and an increase in extinction at the removal sites. Establishing a long-term trapping program (i.e., 5 to 10 years) with bi-annual or multiple trapping periods per year could benefit long-term reductions in raccoon populations. When possible, sites should expand their effective trapping area to cover the entire study site, especially in regions of concern for vulnerable populations. Expanding the effective trapping areas could help minimize raccoon colonization within the study site and from neighboring areas by covering a larger region.
Access
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