Density dynamics and changes in habitat use by the European mink and othernative mustelids in connection with the American mink expansion in Belarus

Changes in spatial structure of the native riparian mustelid guild includin g the European mink Mustela lutreola, otter Lutra lutra, polecat M. putoriu s and stoat M. erminea in connection with the expansion of the American min k M. vison were analysed on the basis of a radiotracking and snowtracking s tudy in the upper reaches of the Lovat river, NE Belarus. Four main questio ns were investigated: (1) how does habitat selection differ between the nat ive mustelids in the absence of American mink? (2) does habitat use change following the arrival of American mink and, if so, how? (3) does habitat se lection differ between the two mink species? (4) how does European mink den sity before American mink arrival compare with American mink densities afte r the disappearance of European mink? Before American mink naturalization, European mink density was highest at s mall rivers and brooks, otter density was highest at larger rivers, polecat s were found to inhabit all types of river banks and shores at a similar de nsity. No changes in otter habitat use were found after the American mink e xpansion. Gradually, during four years of the American mink expansion, Euro pean mink became rare at small rivers. However, at brooks used less frequen tly by American mink there was little change in European mink density. Radi otracking data showed that American mink drive European mink away from rive rs. European mink are still found at brooks, however, such small streams ar e used more frequently by European mink males than by females, because ther e is not enough food to rear a litter. Following the American mink expansio n, the polecat population along the banks and shores was reduced by approxi mately half. In riparian habitats American mink seems to be a more competit ive species than the polecat and as a result, polecat populations tend to d ecline there. Furthermore, as with European mink, polecat females are at an even greater competitive disadvantage due to their smaller body size. The most important difference in habitat selection of the native mink and n aturalized mink is that the European mink inhabited banks and shores and us ually stayed close to aquatic ecosystems, whereas the American mink fairly frequently inhabited marshes, pools and even dry forest.