Expansion and population dynamics of a non-native invasive species: the 40-year history of American mink colonisation of Poland.

The American mink, an invasive mammal introduced to Europe, severely impacts native biodiversity. The history of its invasion has been poorly investigated in central and eastern Europe, and the current variations in densities of mink populations are not well studied, thus making a reduction of its impact difficult. Here we analyse the temporal dynamics and spatial distribution of the American mink population in Poland, which began to establish itself at the beginning of the 1980s and originated from Polish farm escapees and immigrants from Lithuania and Belarus. Mink dispersal started in the north and continued to the south and in 2016 mink occurrence was recorded across ca. 75% of the country. By about 1997 mink had colonised half of Poland, and in 2016 the only mink-free area was in the south and south-east of the country. The rate of expansion showed accelerating and decelerating patterns, and reached its maximum 12 years after the beginning of the expansion. Mink farming in western Poland developed rapidly after 2000 and probably influenced acceleration of mink range expansion rates in years 2006–2008. Indices of mink densities showed significant nonlinear change over time since local populations were established and were highest in populations estimated to be 10–15 years old. The prediction of non-native species invasion rates and population dynamics should be incorporated into management actions curbing their negative impact on native fauna. Introduction