Removal of American mink (Neovison vison) from the Uists, Outer Hebrides, Scotland

Since escaping from fur farms in the 1950s, American mink had colonised the 2800 km² archipelago of the Outer Hebrides of Scotland. Between November 2001 and June 2006 the species was removed from a total of 850 km² of the southernmost islands, collectively named the Uists, as part of a pilot study exploring the feasibility of large scale eradication throughout the archipelago. Animals were also controlled in neighbouring South Harris (255 km²) to reduce the risk of recolonisation. The project used two main methods, the operation of coastal and riparian cage traps; and trapping at breeding dens located using trained dogs. In the Uists this resulted in 100,824 trap nights over 4 years. Den searches were carried out over 500 handler-days. Overall a total of 228 mink was caught in The Uists, with the last capture in March 2005. After this date, despite a further 7 months of intensive trapping and searching effort, no further signs of mink were found and they were considered likely to have been removed from this region. In the buffer area of South Harris, 41,674 trap nights over 4 years resulted in 240 captures with few animals being caught by the end of the project. This effort greatly reduced the risk of recolonisation from this region, although there was still a possibility of extant isolated populations remaining within the region, particularly on offshore islets, which would then be detected and trapped by a follow up programme. An adaptive management process resulted in significant increases in trapping efficiency. Improvements included optimisation of trap spacing and the frequency and duration of trap-line operation; improvements in the cage designs and use of lures. The protocols developed here were used in the subsequent eradication campaign in the remainder of the Outer Hebrides.