Background information and definitions
The UK water vole Arvicola amphibius population has declined by 96% since 1950, which is largely thought to be due to predation by invasive non-native American mink Mustela vison. Mink also prey on fish, birds and other mammals, and can have a significant effect on local wildlife (Defra 2005). This intervention may involve controlling mink populations through trapping.
Defra (2005) Mink. Defra Rural Development Service. Rural Development Service Technical Advice Note 02.
Supporting evidence from individual studies
A 2005 systematic review investigating the effectiveness of trapping in reducing or eradicating American mink Mustela vison populations in all habitats (Tyler et al. 2005) found evidence from seven studies demonstrating that mink populations decreased but that firm conclusions could not be made because of experimental design limitations. Due to the lack of controls for comparison, decreases could not be attributed solely to trapping. There was no robust investigation into other factors that could also be acting upon the populations at the same time. A lack of available data meant that statistical analyses could not be performed.Study and other actions tested
A large-scale systematic trapping programme in an area of moorland, livestock farms and forestry centred on the Cairngorms National Park, UK (Bryce et al. 2011) found that American mink Mustela vison were eradicated over a large area, conserving upland populations of water vole Arvicola amphibius. No mink were captured in 2006 when most traps were in catchment headwaters in close proximity to water vole colonies. However, capture rate increased rapidly as traps were added downstream (below 300 m). By December 2009, 376 mink had been caught (47% female) and an area of 10,000 km² appeared to be free of breeding mink. There was some evidence of localized water vole expansions, but re-colonization of the lowlands was expected to be slow. Capture rate increased with connectivity to mink in other sub-catchments and was highest from July-December. Mink rafts were used at 2 km intervals in each sub-catchment and were systematically moved downstream from the headwaters of the five main river catchments. Rafts were also retained upstream to remove immigrants. Once mink footprints were recorded on a raft, a trap was set. The project involved 186 local volunteers, including gamekeepers, conservation professionals, residents and land managers.Study and other actions tested