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This paper reports the results of stationary studies on the ecology of the American mink (Neovison vison Schreb.) on three small rivers of the Sikhote-Alin region from 2003 to 2018. The population density in the field stations range from 0.4 to 2.2 individuals per 1 km of watercourse. Cyclic changes in the density of the mink population were found to occur with a period of about six years (rS = 0.68, P = 0.01). Hunting of low intensity did not affect the number and growth of the mink population. The correlation between floods and annual precipitation and dynamics of density was weak and unreliable. In the predator’s diet, three main forage groups (mammals, frogs, and fish) were singled out, the ratio of which varied in the basins of different rivers and according to the seasons of the year.

Changes in distribution of six mammal species, viz. Procyon lotor, Nyctereutes procyonoides, Neovison vison, Cervus nippon, Dama dama, Ovis aries musimon in SW Poland (42000 km2), since their introduction till 2008, have been analyzed. A rough estimate of their numbers is also provided for seven regions in SW Poland (Silesia). Detailed maps of distribution of the American mink and fallow deer in SW Poland during 2004–2008 are also presented. The alien ungulates, as long-established species in SW Poland, are not considered as particularly destructive to indigenous flora and fauna. They are not invasive, and have never been regarded as such. On the other hand, the alien carnivores are regarded in SW Poland as destructive to the indigenous fauna. Counter-measures for the rapidly increasing carnivores are proposed.

Analysis of the fragment of mtDNA D-loop (369 bp, n = 48) in wild and domestic American minks harvested in Caspian-Baltic watershed in the European part of Russia reveals a relatively high level of genetic polymorphism for introduced specimens. The values of haplotype and nucleotide polymorphism are correspondent to the level found in populations of the species inhabiting Eastern Europe (Poland). The tendency of differentiation of haplogroups is noted against the background of weak geographical or breeding structure of populations. Observed patterns of polymorphism are probably connected with peculiarities of introduction history as well as with the pool of initial DNA set of ancestors introduced in Eurasia. The domesticated form of the American mink does not differ from wild populations of the species on the basis of the used DNA marker. In wild populations of the species located at a short distance from a mink farm, haplotypes typical of domesticated minks are found.

Lake Glubokoe (Moscow oblast, Russia) is one of the most investigated water bodies of Europe. We detected new parasite species for the ecosystem of the lake (alien for territory of Europe): coccidian Goussia obstinata (in invasive alien fish Perccottus glenii) and copepod Neoergasilus japonicus (on aboriginal ruff Gymnocephalus cernuus). The given coccidian is host-specific for P. glenii and was introduced in the lake together with its host. Participation of P. glenii in circulation of recorded heteroxenous helminthes (Isthmiophora melis, Azygia lucii, and Raphidascaris acus) was revealed. This is confirmed by the data on trophic links of their obligatory definitive hosts (American mink Neovison vison and northern pike Esox lucius) with P. glenii in Lake Glubokoe.

Craniometrical variation is studied using 441 American mink Neovison vison Baryshnikov and Abramov, 1997 (Schreber, 1777) skulls from nine geographically isolated populations and subpopulations, including domestic minks from a fur farm, with the aim to assess the factors underlying morphological diversity. The geographic origin of populations and potential hybridization between wild minks and domesticated individuals escaping from fur farms are regarded as the main hypotheses of morphological diversity. Sexual size dimorphism is leveled by using nonparametric multidimensional scaling. The results do not show any statistically significant effect of domestic animals from fur farms on the morphological variation in wild minks. The mechanisms limiting wide-range hybridizations based on morphogenetic differences between wild and domestic populations as a result of different selection vectors (stabilizing natural selection in wild populations and breeding) are postulated. Along with such biases, wild mink populations display certain patterns that limit morphological diversity corresponding to well-known biogeography laws and modifying variation. The morphological heterogeneity of introduced populations should be considered taking into account the latest history of formation of prapopulations.

On the basis of our materials for the period of more than 40 years and published data, the territorial aspect of muskrat (Ondatra zibethicus) and American mink (Neovison vison) invasion is characterized in dynamics. Special attention is paid to the state of their number and economic importance.

Data on current habitat ranges of five species of semiaquatic mammals are given in the article. The data were collected in various parts of Sikhote-Alin in 2002–2012. Four of the species, American mink (Neovison vison Schreb.), muskrat (Ondatra zibethicus L.), Eurasian beaver (Castor fiber L.), and Canadian beaver (C. canadensis Kuhl), are introduced. A native species is the otter (Lutra lutra L.). The stages of introduction and peculiarities of distribution of the semiaquatic species populations are described. The spatial distribution of the animals on the Obor and Durmin rivers selected as the model ones by us previously is analyzed (Oleinikov, 2007). The middle reaches of these rivers demonstrate the greatest variety of semiaquatic species, and their density is maximal in the lower reaches, which is mainly due to the muskrat. The spatial dissociation as a mechanism of alleviation of interspecific relationships is revealed.

The morphological variability of 367 skulls of the American mink from Tver, Pskov, and Novgorod oblasts (Caspian-Baltic watershed) are investigated using quantitative and qualitative traits. Out of the six investigated samplings, five represent feral populations and one represents ranch minks. It is shown that significant morphological differences between feral mink populations exist within a relatively small area (about 250 × 350 km). Differences in the phenotype are determined by different history of the populations and by the degree of affection of escaped ranch animals. The possible consequences of interactions between the feral and ranch mink populations, which may influence the phenotype, are discussed. The morphological differences observed between the feral mink populations are lower than those theoretically expected when taking into account the considerable influence of domesticated animals. Among the possible reasons of morphological stability of skulls of feral populations of the American mink, we specify naturalization of sizes of ranch escapees under pressure of environmental conditions, as well as possible elimination of the first-generation hybrids between feral and domesticated minks owing to outbreeding depression.

Environmental changes have created conditions for expansion of the ranges of hoofed and carnivore game mammals in a northerly direction. The data on the changes of range boundaries of the Manchurian deer (Cervus elaphus Linnaeus, 1758), the Siberian roe deer (Capreolus pygargus Pallas, 1771), the Siberian musk deer (Moschus moschiferus Linnaeus, 1758), the Asian badger (Meles leucurus Hodgson, 1847), the American mink (Neovison vison Schreber, 1777), and the sable (Martes zibellina Linnaeus, 1758) in Irkutsk oblast (Eastern Siberia) are given.