Distribution of introduced raccoons Procyon lotor on the Queen Charlotte Islands: implications for burrow-nesting seabirds Original Research Article

Information on the occurrence of introduced raccoons was collected for 62 islands of the Queen Charlotte archipelago, to determine their current and potential distribution relative to colonies of native, burrow-nesting seabirds. Raccoons or their sign were found on 32 of 37 islands (86%) requiring crossings of up to 400 m, six of 21 islands (29%) requiring crossings of 400–800 m, and one of four islands surveyed beyond this distance, located 950 m offshore. An estimated 83% of burrow-nesting seabird colonies, and 80% of burrow-nesting seabirds are potentially accessible with over-water crossings of 950 m or less. Evidence of raccoons has been found on three islands that historically contained seabird colonies, and on 11 active colony islands, on which 14% of the regionʹs seabird population breeds. A logistic regression model using island isolation and size as predictors indicated that 55% of burrow-nesting seabirds occur on islands with a probability of raccoon occurrence greater-or-equal, slanted0.5. A second model incorporating oceanic exposure as well provided a better fit to the raccoon occurrence data and reduced the above value to 22%. However, the data set used contained relatively few exposed (west coast) sites, thus the true influence of exposure warrants further investigation. Future management efforts should include continued, standardized monitoring, quantitative evaluation of monitoring techniques, and research into effective control methods.