Extinction Debt Paid Off: The Demise of the European Polecat ( <i>Mustela putorius</i> ) in NE Iberia

The global loss of individuals and populations is driving a myriad of species toward extinction, many of which are not yet recognized as threatened. The European polecat (Mustela putorius) exemplifies this trend, as throughout most of its range it is of low conservation concern despite widespread suspected, though poorly documented, population declines. For a decade, we monitored a vanishing polecat population to identify the ecological drivers behind its decline, using a combination of camera trapping (5551 trap days), roadkill data, landscape descriptors, and dietary and toxicological analyses. We documented a marked segregation between the polecat and other mesocarnivores. Polecat favored lowland farmland rich in rats and rabbits as prey, avoiding sclerophyllous forest and water bodies dominated by potential competitors like the invasive American mink, otter, and stone marten. This habitat selection likely increased the risk of rodenticide secondary poisoning (with 84.6% prevalence), road mortality (42 individuals in 10 years), and interactions with domestic cats. However, the loss of habitat heterogeneity and semi-natural vegetation, associated with agricultural intensification, led the habitat and connectivity loss that probably contributed decisively to the ultimate demise of the population. Although American mink control was implemented, large-scale conservation actions-such as hedgerow restoration, construction of faunal underpasses, or replacement of anticoagulant rodenticides-were not in place prior to the population's extinction. However, ongoing habitat restoration may support future recolonization or reintroductions and benefit other species for which the polecat could serve as an effective umbrella species in European agroecosystems.