Water vole Arvicola amphibius population under the impact of the American mink Neovison vison: Are small midfield ponds safe refuges against this invasive predator?

The American mink Neovison vison is an invasive carnivore which may significantly affect populations of the water vole Arvicola amphibius. However, its impact on this rodent species depends on the abundance, dispersion and configuration of the habitats suitable for water voles and their accessibility for the mink. Using live-trapping, we studied the water vole and American mink populations inhabiting midfield ponds located in the vicinity of a large lake. In the same area, the mink diet was described after collecting and analysing scats. During four spring seasons, the water vole density gradually increased and no population peaks or crashes were observed. The maximum recorded density was 9.0 individuals/1 km of pond shoreline. Water voles displayed high year-to-year population turnover: less than 5% of the marked individuals were recaptured in the following year. In April-July, the exchange of individuals in the population during one-month periods was also high and usually exceeded 50%. Water vole remains were found in mink scats in all seasons, and the highest overall percentage biomass of water vole in mink diet for a two-months period reached 52.2% in May-June 2012. The results of our study show that at small water bodies adjacent to a large lake, the water vole population may withstand the impact of the invasive American mink. (C) 2018 Deutsche Gesellschaft fur Saugetierkunde. Published by Elsevier GmbH. All rights reserved.