Efficacy of raccoon removal in urban and rural sites in northern Illinois

Abstract

Raccoons ( Procyon lotor ) are opportunistic and highly adaptable mesopredators that may negatively impact avian and reptilian species. Although wildlife professionals often utilize predator control techniques to manage raccoons, information to guide management activities is lacking. We analyzed the efficacy of raccoon removal within urban and rural sites in northern Illinois, USA, during 2022–2024. We placed 109 camera traps ( n  = 204 unique camera trap placements) at 6 study sites (5 treatment and 1 control) to monitor raccoon response to removal. Collaborators removed raccoons ( n  = 771) from treatment sites. We used catch‐per‐unit effort data to calculate preremoval abundance and density estimates of raccoons and incorporated camera‐trap data to create single‐ and multi‐season occupancy models to determine raccoon response postremoval. Each year, raccoon detections decreased directly postremoval and remained below estimates observed preremoval for the rest of each camera‐trapping season (i.e., for 2–3 months) at 4 of the 5 removal sites. However, abundance and detection estimates returned closer to preremoval levels for each study site (i.e., 10–12 months following removal) each subsequent year. 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%, indicating fewer raccoons were entering the population after removal efforts occurred. In 2023 and 2024, the control site had an extinction rate close to zero and colonization rates that increased to 80% by 2024, indicating more raccoons entered the population each year when removal efforts did not occur. Our findings suggested that a successful short‐term population reduction of raccoons could aid in management efforts for sensitive species. Our results indicated that implementing biannual, multiple, or extended trapping programs could maintain reduced raccoon abundance and occupancy over longer durations where protection of prey species is needed. Expanding trapping through a long‐term program could lessen the effects of immigration and counteract any density‐dependent effects resulting from removal.