1. The detrimental impacts of invasive, non-native species on islands are widely acknowledged and it is often best to act rapidly against such species, even where uncertainty exists over the best way to proceed. If management actions are evaluated and refined, using information learnt from the biology of culled animals, this uncertainty can be gradually reduced, increasing the likelihood of a successful outcome.
2. American mink Neovison vison carcasses were collected as part of an eradication campaign on several islands of the Outer Hebrides, Scotland, and stable isotope analysis was used to describe ecological variation in this invasive non-native predator.
3. Isotope profiles from individual mink whiskers demonstrated how behaviour at a population level changed markedly over time. As the eradication campaign progressed, mink increased their reliance on marine food sources and focused their activity on the coastline. Stable isotope analyses also demonstrated sex-related changes in foraging and ranging behaviour in relation to food resource availability on the two main island complexes.
4. Synthesis and applications. Our findings contribute to the refinement of a campaign to extend the successful eradication of mink from Uist and Harris, to the whole of the Outer Hebrides archipelago, UK. They also highlight the potential for stable isotope approaches to provide more detailed postmortem information that can inform adaptive management of wildlife populations for conservation objectives.