EFFECT OF RACCOON (PROCYON LOTOR) REDUCTION ON BLANDING’S TURTLE (EMYDOIDEA BLANDINGII) NEST SUCCESS

Abstract

The Lake County Forest Preserve District has monitored a state-endangered Blanding’s Turtle (Emydoidea blandingii) population at two adjoining nature preserves along the Illinois–Wisconsin border since 2004. Prior to predator management, 92.3% of documented and unprotected natural Blanding’s Turtle nests (12 of 13) and 88% of monitored artificial nests have been at least partially depredated. The goal of this study was to determine the efficacy of subsidized Raccoon (Procyon lotor) removal efforts in increasing the nest success of Blanding’s Turtles. During April–May 2013 and 2014, we captured and euthanized 78 Raccoons from our 2 km2 study area. We estimated pre-removal abundance estimates using the Leslie depletion method; it appeared that we removed 83–89% of the Raccoons from the study area each year and pre-removal density estimates were 37.5% lower in 2014 than 2013. During the study period, we monitored 22 Blanding’s Turtle in situ unprotected nests. In 2013, one of seven (14%) Blanding’s Turtle nests was partially depredated and no nests were completely depredated, indicative of a successful impact of Raccoon removal on Blanding’s Turtle nest success. However in 2014, nine of 15 (60%) Blanding’s Turtle nests were depredated. Our results provide some evidence that removal of Raccoons may have increased Blanding’s Turtle nest success but other factors, such as a functional response of surviving Raccoons or depredation by other subsidized predators may be contributing to decreased nest success.