Ecological traps for large-scale invasive species control: predicting settling rules by recolonising American mink post-culling.
Abstract
Management programmes seeking to reduce the density of invasive species must overcome compensatory processes, such as recolonisation by dispersers from non- or partially controlled areas. However, the scale and drivers of dispersal in such contexts are poorly known. We investigated the dispersal patterns of American mink re-invading 20,000 km2 of their non-native range during a culling programme led by citizen conservationists. Using multinomial models, we estimated the contributions of density dependence, proxies for patch quality and distance from the natal patch on mink settlement. Seventy-seven per cent of mink dispersed and settled in non-natal patches. Dispersal distances were large with settlement probabilities only reduced by half at c. 60 km, and 20% of mink dispersing >80 km. Females were more attracted to high-quality patches, mostly found at low altitudes. Males favoured patches with intermediate current densities and consistently high quality. Synthesis and applications. We predicted post-culling recolonisation by a non-native mobile carnivore over a large spatial scale by using information on relative densities obtained during management interventions, largely carried out by citizen conservationists. This was possible through continued monitoring of the area designed to feed into the adaptive management process of the control project. High mink mobility dictates management should take place on very large spatial scales to minimise re-invasion from uncontrolled areas. Our research shows both males and females are attracted to patches with previously consistent occupation, which provides a degree of predictability to patterns of recolonisation. Targeting control to patches that are attractive to immigrant mink requires knowledge of current mink density. Creating so-called ecological traps in the face of ongoing immigration from peripheral areas provides a promising tool to effectively control mobile invasive species.