Current status of American mink Neovison vison in Great Britain: a review of the evidence for a population decline

The American mink Neovison vison in Great Britain is an invasive alien species, with significant impacts on native prey species. There have been suggestions that populations of mink in Britain have declined since the 1990s. Three nationwide data sets include data on mink distribution and abundance. Scat surveys and the National Game Bag Census suggest population declines, but the latter does not take account of survey effort (which may also have declined) and the former is misleading because there is evidence that mink change their marking behaviour in the presence of otters Lutra lutra. National Biodiversity Network data suggest an increase in mink numbers, but this can be explained by a concomitant increase in mammal recording. Although intra-guild competition between invasive mink and native otters is likely, there is no evidence that otters have caused a decline in mink numbers. There is little information on the impact of disease, or exposure to rodenticides, on wild mink - both warrant further attention. Eradication efforts can have an impact on mink populations, but currently neither implementation nor monitoring is sufficient to generate effects throughout Great Britain or to assess the impact of cumulative local and regional efforts. We conclude that it is not possible, on the basis of currently available data for Great Britain, to ascertain the status of mink or assess the underlying trend in their population. We stress the importance of collaboration, coordination, and record keeping (and sharing) in future, proper interpretation of existing data, and the use of alternative data sources. We call for greater, and better, effort in both mink management and monitoring of management in Great Britain.