Predicting the spread of feral populations of the American mink in Italy: is it too late for eradication?

Predicting the speed and direction of the spread of alien species is one of the ways in which models can contribute to managing invasions. In Italy, the American mink is an alien invasive living in feral populations whose distribution and impacts are little known. The aim of this study was to predict the likely distribution of the American mink across Italy and the rate of population spread. An extended spatially explicit population dynamics model (SEPM) was used to simulate mink expansion in Italy across a period of 20 years. We used the current and recent distribution of mink farms as the initial points of invasion and validated the model in two ways: (1) by comparing the predicted distribution with the distribution of known populations of mink in Italy; (2) by comparing the predicted rates of spread with those observed in real populations. The application of the model to the Italian landscape highlighted the possibility that mink are already widespread in the country even though only few reports of this species have ever been made. This is of serious conservation concern considering that mink has proven to be a damaging invasive elsewhere. However, the fact that this species should mostly be restricted to north-east Italy suggests that eradication may still be possible. This study highlights the risks posed by American mink and shows that modelling, which is generally less expensive than field studies, can be used to guide surveys and future management of alien invasives.