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

1. American mink in Britain are an invasive alien species, with significant impacts on native prey species. There have been suggestions that mink in Britain have declined since the 1990s. 2. Three nationwide datasets 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. National Biodiversity Network data suggest an increase in mink numbers but this can be explained by a concomitant increase in mammal recording. 3. 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. Culling can have an impact on mink populations, but currently neither implementation nor monitoring is sufficient to generate national-level effects or to assess the national-level impact of cumulative local efforts. 4. We conclude that, at a national level, it is not possible, on the basis of currently available data, to ascertain the current 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 Britain.