AUTHORS: Jennifer Schultze, Southern Illinois University; Ashley McDonald, Southern Illinois University; Clayton Nielsen, Southern Illinois University
ABSTRACT: Raccoons (Procyon lotor) are an opportunistic and highly adaptable mesopredator that negatively impact several vulnerable avian and reptilian species. Wildlife managers require more information about the efficacy and long-term feasibility of using predator removal to control raccoon populations. We determined the efficacy of raccoon population reduction via trapping on 6 study sites in northern Illinois. Camera traps (n=109) were placed afield during February-August 2022-2024 to monitor raccoon occupancy before, during, and after trapping efforts were performed. During April-June 2022-2024, collaborators removed 680 raccoons to determine the intensity of trapping effort needed to reduce raccoon populations and to estimate pre- and post-trapping abundance of raccoon populations. We ran single-season occupancy models during these 3 temporal periods and multi-season colonization-extinction occupancy models were conducted before and after raccoon removal to determine the efficacy of trapping efforts in the long-term. Single-season occupancy estimates indicated a decrease in occupancy during removal; this reduced occupancy level remained for the duration of the study season. During 2022-2024, multi-season occupancy colonization rates decreased by 43% and extinction rates increased by 13%. In contrast, our control site with no raccoon removal had an increase in colonization by 66% and extinction rates reached nearly 0%. Further, we estimated raccoon abundance using the Leslie depletion method and following trapping, populations declined >32% on each study site. These results suggest that with enough trapping effort at the levels observed in our study, continuous removal programs may be a successful method for reducing and maintaining lower raccoon densities.
