Raccoon Dog Population Research Articles

The evolutionary and ecological convergence of the raccoon and raccoon dog: A perfect storm of invasive species in Europe

AbstractThis paper initially describes the evolution of body shape in the raccoon (Procyon lotor) and the raccoon dog (Nyctereutes procyonoides). I explain how their similarities are the result of convergent evolution, the process by which unrelated organisms come to resemble one another in form, function, or both. This is the first examination of this phenomenon in these two species. In addition, I consider how their convergent traits and habits as omnivores have contributed to their astounding success as invasive species in Europe. Problems have arisen from these introductions, including impacts on prey species. Considering their broad adaptability as “stout” shaped mesocarnivores should aid in understanding their behavior and ecology, and could assist in addressing their management in Europe. Last, I offer suggestions for the control of raccoons given their compensatory versus additive mortality patterns, a practice that may also have implications for the regulation of raccoon dog populations.

Estimating the impact of sarcoptic mange epidemic on the population size of wild raccoon dogs (Nyctereutes procyonoides) from wildlife rescue data

The impact of infectious diseases on host populations is often not quantified because it is difficult to observe the host population and infectious disease dynamics. To address this problem, we developed a state-space model to simultaneously estimate host population and disease dynamics using wildlife rescue data. Using this model, we aimed to quantify the impact of sarcoptic mange on a Japanese raccoon dog population by estimating the change in their relative population size. We classified the status of rescued raccoon dogs into four categories: i) rescued due to infection with mange, ii) rescued due to traffic accidents without mange, iii) rescued due to traffic accidents with mange, and iv) rescued due to causes other than traffic accidents or mange. We modelled the observation process for each category and fitted the model to the reported number of raccoon dogs rescued between 1990 and 2010 at three wildlife rescue facilities in Kanagawa Prefecture, Japan. The mortality rate induced by mange was estimated to be 1.09 (95% credible interval (CI): 0.47–1.72) per year. The estimated prevalence of sarcoptic mange ranged between 4–80% in the study period. When a substantial prevalence of mange was observed (1995 to 2002), the host population size decreased by 91.2% (95% credible intervals: 86.3–94.7). We show that the impact of infectious disease outbreak on the wildlife population can be estimated from the time-series data of wildlife rescue events due to multiple causes. Our estimates suggest that sarcoptic mange triggered a substantial decrease in the Japanese wild raccoon dog populations.

Prevalence of Toxoplasma gondii Antibodies and Risk Factors in Two Sympatric Invasive Carnivores (Procyon lotor and Nyctereutes procyonoides) from Zgorzelec County, Poland.

The intracellular protozoan Toxoplasma gondii is distributed worldwide and infects many species of warm-blooded animals. Most mammals, including humans, can serve as intermediate hosts. This pathogen, with its zoonotic potential, causes toxoplasmosis, a condition that can range from subclinical to fatal in humans. It is therefore important to assess the occurrence of the pathogen, even if only indirectly through the detection of antibodies. Epidemiological data on the seroprevalence in wild animals, including invasive species, are rare in Poland. Therefore, we tested 197 wild raccoons (Procyon lotor) and 89 raccoon dogs (Nyctereutes procyonoides) from Zgorzelec County, southwestern Poland, for the presence of antibodies. Samples were collected between January 2019 and December 2020 and analysed using a commercial indirect modified agglutination test (MAT, cut-off 1:25). The statistical analysis revealed significant differences in seroprevalence between the two predatory species. Of the 197 surveyed raccoons, 96 (48.73%; 95% confidence interval (CI): 41.73-55.73%) tested positive, while 25 of the 89 raccoon dogs (28.09%; 95% CI: 18.70-37.48%) were positive. Regarding risk factors, body weight and sex influenced the presence of T. gondii antibodies in both the species, with a higher likelihood of seropositivity among heavier animals and females, respectively. For raccoon dogs, juveniles were more likely to be seropositive than adults at a given weight. Our results suggest that T. gondii infection is widespread in the regional raccoon and raccoon dog populations, indicating a high level of parasite circulation in the environment.

Predicting future distributions and dispersal pathways for precautionary management of human-raccoon dog conflicts in metropolitan landscapes

Human-wildlife conflicts in cities are becoming increasingly common worldwide and are a challenge to urban biodiversity management and landscape planning. In comparison to compensatory management, which often focuses on addressing emergency conflicts, precautionary management allows decision-makers to better allocate limited resources on prioritized areas and initiate long-term actions in advance. However, precautionary approaches have rarely been developed or applied in biodiversity conservation. Since 2020, human-raccoon dog conflicts in Shanghai, one of the largest cities in the world, have tripled in reported number due to the rapid spread of the species in the city from 70 residential districts in 2020 to 249 residential districts in 2022. Here, we use ensemble and circuit modeling to predict suitable raccoon dog habitat and identify their potential dispersal pathways to aid the development of precautionary management strategies. We find that raccoon dog distribution is positively associated with several anthropogenic factors, including residential buildings and nighttime light, which could be signs that the species’ foraging behavior has adapted to the urban environment. We find that raccoon dogs only occupy 10.1% of its suitable habitat, and thus there is a high potential for the expansion of the raccoon dog population and more frequent human-raccoon dog conflicts in the near future. We predict 60 potential dispersal pathways across Shanghai, seven of which cross densely human populated areas and are likely to trigger excessive conflicts. Based on our findings, we propose priority areas where precautionary management strategies, such as constraining stray animal feeding and wildlife-vehicle collision prevention, would potentially alleviate human-raccoon dog conflicts. We present the first study on the precautionary approach of human-wildlife conflict in China’s major cities, and provide a practical example of how comprehensive modeling approaches can be used as the foundation of precautionary management in urban landscapes.

Raccoon dog (Nyctereutes procyonoides) phylogeography including the Polish population: local and global aspects

The raccoon dog (Nyctereutes procyonoides) is a representative of Canidae and is closely related to red fox-like canids, although the species exhibits high distinctiveness in the family. These animals were farmed for fur products, but thousands were intentionally released into the wild in western Russia. This newly established alien species in Europe has spread rapidly into many European countries. The aim of the study was to determine the origin of Polish populations by comparing the mitochondrial molecular marker cytochrome b (cytb) sequences of Polish wild and farm individuals with wild raccoon dogs from the western Russia and Asian specimens whose sequences were obtained from GenBank resources. The results of our phylogenetic analysis support the previous suggestions on the existence of two main clades clearly referring to continental and Island populations. Polish individuals were classified into a highly diverse continental group. The relationships between the haplotypes within the clade together with estimated values of genetic diversity parameters indicate that the Polish raccoon dog populations exhibit high genetic similarity to the Russian population. In combination with the history of introduction of the species to Europe, this suggests the most probable assignment of the Polish populations to the subspecies N. procyonoides ussuriensis. Our results indicate the presence of two Japanese haplotypes within the continental group, which is inconsistent with the assumed scenario of post-glacial expansion of raccoon dogs excluding gene flow between continental and Island populations.

Roadkills as a Method to Monitor Raccoon Dog Populations.

Simple SummaryThe raccoon dog (Nyctereutes procyonoides) is a highly invasive species, therefore knowledge regarding the population size, trends and spatial distribution is important for species assessment and for the planning of control measures. In Lithuania, however, as such surveys would require the concerted action of many hunting clubs, raccoon dog surveys have not been carried out since 1997. In this study, we investigated whether roadkill data for the species could be used as a means for monitoring the population. For the period in which surveys were conducted, we found a strong correlation between the numbers surveyed and the numbers of animals hunted and between those hunted and the number of roadkills. Therefore, we consider that roadkill counts may be used as a proxy for a survey at the countrywide scale. Practical implementation of the method is proposed.The raccoon dog (Nyctereutes procyonoides) is one of the most frequently killed species on Lithuanian roads. As an invasive species, up-to-date knowledge of population size, trends and spatial distribution is critically important both for species assessment and for the planning of control measures. In Lithuania, however, raccoon dog surveys have not been carried out since 1997. We investigated, therefore, whether roadkill counts on predefined routes could be used as a proxy for a survey. Our dataset includes survey numbers for the period 1956–1997, hunting bag sizes for 1965–2020 (including the spatial distribution of the hunting bag in 2018–2020) and roadkill data relating to 1551 individuals between 2002–2020. At the most local scale, that of the hunting areas of hunting clubs, correlations between the numbers of hunted and roadkilled individuals were negative and insignificant or absent. At the country scale, however, we found significant correlation both between the numbers surveyed and hunted in 1965–1997 (r = 0.88), and between those hunted and the number of roadkills in 2002–2020 (r = 0.56–0.69). Therefore, we consider that roadkill counts on predefined and stable routes may be used as a proxy for a survey at the country scale. Practical implementation of the method is proposed.

Phylogenetic relationships between different raccoon dog (Nyctereutes procyonoides) populations based on four nuclear and Y genes.

The raccoon dog (Nyctereutes procyonoides), endemic to East Asia, is classified as six subspecies according to their geographical distribution including a population introduced to Europe. Studies on phylogenetic relationship or population genetics in both native and introduced areas have been carried out recently. Lately, opinions that Japanese raccoon dogs should be classified as a different species were asserted based on several studies using karyotypes, morphometric characters, mtDNA, and microsatellites analysis. However, no data pertaining to the nuclear DNA (nDNA) or Y chromosome are available. To estimate the relationship among the species using different genes is necessary in understanding of the history of this species. Therefore, we investigated nDNA and Y chromosomes in our study to define relationships: (1) between continental raccoon dog populations, (2) between original and introduced groups, and (3) between continental and Japanese groups. The analysis of four nuclear (CHRNA1, VTN, TRSP, WT1) and ZFY genes indicated that there had been no genetic differentiation among the continental populations. However, significant differences were observed between continental and Japanese raccoon dogs in VTN and ZFY genes implying genetic differentiation has been going between them. To better understand the phylogenetic relationship among raccoon dog populations, further study will be necessary.

Genetic Diversity and Population Structure of East Asian Raccoon Dog (Nyctereutes procyonoides): Genetic Features in Central and Marginal Populations.

The raccoon dog (Nyctereutes procyonoides) is endemic to East Asia but has been introduced in Europe. Its high adaptability enabled its rapid colonization of European countries, where population growth has been raising concerns regarding ecosystem disturbance and the spread of zoonotic diseases. The genetic diversity and structure of endemic, source, and introduced populations from seven locations across South Korea, China, Russian Far East, Finland (spread to Finland after introduction to European part of Russia from Russian Far East), Vietnam, and Japan (Honshu and Hokkaido) were examined based on 16 microsatellite loci. Two major and significantly different (FST = 0.236) genetic clusters were found: continental (South Korean, Chinese, Russian, Finnish, and Vietnamese) and island (Japanese) populations. The continental raccoon dog population comprises three subpopulations (Chinese_Russian_Finnish, South Korean, and Vietnamese) and the Japanese population consists of Honshu and Hokkaido subpopulations. The genetic diversity and geographic structure of raccoon dogs in East Asia has been influenced by natural barriers to gene flow and reveals a typical central-marginal trend in genetic diversity (continental vs. island, and central vs. marginal or source vs. introduced within continental populations). The detected differences between continental and island populations agree with those reported in previous studies that considered these populations as different species.

The diet of feral raccoon dog (Nyctereutes procyonoides) and native badger (Meles meles) and red fox (Vulpes vulpes) in Denmark

The raccoon dog (Nyctereutes procyonoides) is an East Asian Canid that has been introduced in Europe. Introduction of alien species is an increasing conservation issue. We examined the diet of a recently established raccoon dog population in Denmark by analysing stomach content in 249 carcasses collected in 2008–2016. Raccoon dog diet was compared to the diet of native badger (Meles meles) and red fox (Vulpes vulpes) in Denmark. The most common food for raccoon dogs were invertebrates (frequency of occurrence, FO 69%), small mammals (FO 68%), birds (FO 41%), fruits (FO 38%), amphibians (FO 36%) and carrions (FO 34%). The occurrence of invertebrates was highest during spring and summer, while fruits, cereals and carrions were eaten most often during autumn and winter. As expected, raccoon dog shared the major food categories with badger and red fox, but generally, it had a wider dietary niche. Overall, dietary overlap between raccoon dog and badger was 0.74 (Pianka index, Ojk). The dietary overlap with red fox was relatively high in all seasons, peaking in summer (Ojk 0.87) and dropping in winter (Ojk 0.79). Despite the dietary overlap between the alien racoon dog and native red fox and badger, the species may coexist due to partitioning of feeding habitats and/or because the red fox is limited by other factors, e.g. diseases and anthropogenic activities. The introduced raccoon dog seems to fit a dietary niche between badger and red foxes in human-dominated landscapes in north-western Europe.

Two mitochondrial genes are associated with performance traits in farmed raccoon dogs (Nyctereutes procyonoides)

The relationships between chosen mitochondrial genes polymorphisms and performance traits in raccoon dogs were determined. The study involved 354 farmed raccoon dogs. Blood collected from the animals was the analysed biological material. Mitochondrial DNA genes, i.e. MT-CO1 (mitochondrially encoded cytochrome c oxidase I), MT-CO2 (mitochondrially encoded cytochrome c oxidase II), and MT-CYB (mitochondrially encoded cytochrome b) were amplified using the polymerase chain reaction method. The amplicons obtained were sequenced and subjected to bioinformatics analysis. Based on the nucleotide sequences, three haplotypes for the MT-CO1 gene fragment and two haplotypes for the MT-CO2 gene fragment were identified. The sequence of the MT-CYB gene was monomorphic. Based on the haplotypes, five previously undescribed mitochondrial haplogroups were determined. Statistical analysis revealed significant differences between the values of three of the five investigated performance traits of raccoon dogs and the identified haplotypes and mitochondrial haplogroups, taking into account predictors of direct additive effects, additive maternal effects, and fixed specific maternal environmental effects. The new mitochondrial haplogroups identified in the farmed raccoon dog population may imply constant emergence of adaptive mutations that are conserved in subsequent generations. The results of the association study indicate a statistically significant association between haplotypes and mitochondrial haplogroups of farmed raccoon dogs and their body weight, body size, and colour type, which allows considering MT-CO1 and MT-CO2 genes as candidate genes encoding these traits in raccoon dogs. The results of the molecular analyses can be applied to improve the performance traits in farmed raccoon dogs.

Population structure of the raccoon dog (Nyctereutes procyonoides) using microsatellite loci analysis in South Korea: Implications for disease management.

The prevention and control of infectious diseases transmitted by wildlife are gaining importance. To establish effective management strategies, it is essential to understand the population structure of animals. Raccoon dogs (Nyctereutes procyonoides) in South Korea play a key role in the maintenance of food web stability and possess genetic compositions that are unique compared to those in other areas. However, wild raccoon dogs play another role as the main host of various infectious diseases. To establish long-term strategies for disease management, we investigated the genetic structure and possible geographic barriers that influence the raccoon dog population in South Korea by analyzing 16 microsatellite loci. The present study showed that mountains were the major factors responsible for genetic structuring, along with distance. We proposed potential management units (MUs) for raccoon dogs based on the genetic structuring and gene-flow barrier data obtained in this study. Four MUs were suggested for the Korean raccoon dog population (Northern, Central, Southwestern, and Southeastern). The Korean raccoon dog population structure determined in this study and the proposed MUs will be helpful to establish pragmatic strategies for managing Korean raccoon dog population and for preventing the transmission of infectious diseases.

Using Viral Gene Sequences to Compare and Explain the Heterogeneous Spatial Dynamics of Virus Epidemics.

Rabies is an important zoonotic disease distributed worldwide. A key question in rabies epidemiology is the identification of factors that impact virus dispersion. Here we apply new analytical methods, based on phylogeographic reconstructions of viral lineage movement, to undertake a comparative evolutionary-epidemiological study of the spatial dynamics of rabies virus (RABV) epidemics in different hosts and habitats. We compiled RABV data sets from skunk, raccoon, bat and domestic dog populations in order to investigate the viral diffusivity of different RABV epidemics, and to detect and compare the environmental factors that impact the velocity of viral spread in continuous spatial landscapes. We build on a recently developed statistical framework that uses spatially- and temporally-referenced phylogenies. We estimate several spatial statistics of virus spread, which reveal a higher diffusivity of RABV in domestic dogs compared with RABV in other mammals. This finding is explained by subsequent analyses of environmental heterogeneity, which indicate that factors relating to human geography play a significant role in RABV dispersion in domestic dogs. More generally, our results suggest that human-related factors are important worldwide in explaining RABV dispersion in terrestrial host species. Our study shows that phylogenetically informed viral movements can be used to elucidate the factors that impact virus dispersal, opening new opportunities for a better understanding of the impact of host species and environmental conditions on the spatial dynamics of rapidly evolving populations.

Home ranges of raccoon dogs in managed and natural areas.

Knowledge of space use is central to understand animals’ role in ecosystems. The raccoon dog Nyctereutes procyonoides is considered as one of the most influential alien mesopredator species in Europe, having the potential to cause loss of local biodiversity and act as a vector for zoonotic diseases. We collared 12 animals to study their home range and habitat use in two areas with different management regimes in Estonia: in a protected natural area and in an intensively managed area. From May to October raccoon dogs inhabiting the natural area had considerably smaller home ranges compared to the managed area, 193.3ha±37.3SD and 391.9ha±292.9SD, respectively. This result contradicts somewhat earlier findings in other European raccoon dog populations, where the home range sizes in natural areas in summer and autumn period have usually been larger compared to managed areas. In both study areas raccoon dogs preferred watersides, where amphibians and other semi-aquatic prey are abundant, to other habitats available in their home ranges. We also studied movements of a raccoon dog pair in the managed study area in winter period. Due to mild weather conditions during the study period, raccoon dogs changed their resting sites quite often, covering a relatively large 599 ha area from November 2012 to January 2013, indicating the absence of usual winter lethargy during the mild winters.

Population genomics of the raccoon dog (Nyctereutes procyonoides) in Denmark: insights into invasion history and population development

The raccoon dog (Nyctereutes procyonoides) has a wide distribution in Europe and is a prominent example of a highly adaptable alien species. It has been recorded sporadically in Denmark since 1980 but observations since 2008 suggested that the species had established a free-ranging, self-sustaining population. To elucidate the origin and genetic patterns of Danish raccoon dogs, we studied the population genomics of 190 individuals collected in Denmark (n = 141) together with reference captive individuals from Poland (n = 21) and feral individuals from different European localities (Germany, Poland, Estonia and Finland, n = 28). We used a novel genotyping-by-sequencing approach simultaneously identifying and genotyping a large panel of single nucleotide polymorphisms (n = 4526). Overall, there was significant indication for contemporary genetic structuring of the analysed raccoon dog populations, into at least four different clusters, in spite of the existence of long distance gene flow and secondary admixture from different population sources. The Danish population was characterized by a high level of genetic admixture with neighbouring feral European ancestries and the presence of private clusters, non-retrieved in any other feral or captive populations sampled. These results suggested that the raccoon dog population in Denmark was founded by escapees from genetically unidentified Danish captive stocks, followed by a recent admixture with individuals migrating from neighbouring Germany.

Population Structure of the Raccoon Dog on the Grounds of the Imperial Palace, Tokyo, Revealed by Microsatellite Analysis of Fecal DNA.

The raccoon dog (Nyctereutes procyonoides, Canidae, Carnivora) is highly adaptable to urban environments. Populations of carnivorans inhabiting urban areas sometimes differ ecologically and genetically from those in rural areas. However, there is little information on urban raccoon dogs. This study focused on raccoon dog populations in Tokyo, one of the most highly urbanized cities in the world. We examined the genotypes of 10 microsatellites for 101 fecal samples from raccoon dogs inhabiting the grounds of the Imperial Palace, a green space in central Tokyo. We successfully genotyped 58 samples originating from 31 individuals. We also analyzed muscle tissue samples from raccoon dogs from the grounds of the Imperial Palace, the Akasaka Imperial Grounds (a green space close to the Imperial Palace), and the surrounding urban area, and then investigated the genetic structure and diversity of these populations, and the genetic differentiation among them. The population on the grounds of the Imperial Palace was genetically differentiated from that in the Akasaka Imperial Grounds, suggesting that the roads and buildings act as barriers to gene flow. In addition, the population on the grounds of the Imperial Palace showed greater genetic difference from that in the surrounding area than that in the Akasaka Imperial Grounds. We speculate that the moats around the Imperial Palace restrict individual ranges within the palace grounds and limit migration and gene flow to other areas.

Reaction of carnivorous animal populations on environmen tal measures

In the context of Chernihiv region for 21 years the total area of protected areas has increased by 189%. The presence of a strong correlation between the increase in the area of territories with environmental status and the number of raccoon dog population, which has grown by 277% is ascertained. At the same time there is no direct correlation between the in- crease in protected areas and number of wolf and fox population. These differences, in our opinion, are due to the peculiarities of ecology animal species studied and the nature of human pressure on them during the hunt and destruction as «harmful» animals. In the absence of national biological monitoring to assess the ecological status of ecosystem stability, it is advisable to use a multi-year inventory of theriofauna.

First findings of Trichinella spiralis and DNA of Echinococcus multilocularis in wild raccoon dogs in the Netherlands.

The recent invasion of the raccoon dog in the Netherlands may be associated with the risk of introduction and spread of zoonotic pathogens. The aim of this study was to assess whether Echinococcus multilocularis and Trichinella spp. infections are present in Dutch raccoon dogs. Between 2013 and 2014, nine raccoon dogs, mainly road kills, were collected for necropsies. One raccoon dog tested repeatedly positive in the qPCR for E. multilocularis. The positive raccoon dog was collected in the province of Flevoland, which is not a known endemic region for E. multilocularis. Another raccoon dog tested positive for Trichinella spiralis by the digestion of the forelimb musculature and the tongue. Trichinella spiralis has not been reported in wildlife since 1998 and thus far was not found in wild carnivores in the Netherlands. It shows that despite the small raccoon dog population that is present in the Netherlands and the limited number of raccoon dogs that were tested, the raccoon dog may play a role in the epidemiology of E. multilocularis and Trichinella spp. in the Netherlands.

Polymorphism of a DCT gene fragment sequence between the dog and the raccoon dog and its potential effect on binding of transcription factors – in silico analysis of a sequenced fragment

Domestication of dogs involved strong artificial selection. After their introduction into the human environment, dogs were exposed to factors that were not encountered in the wild. The skin and hair are barriers separating the organism from the environment, and melanin plays a significant role in their protective function. The study compared a fragment of the sequence of the DCT gene, which is involved in melanin synthesis, between two species: the dog, which is exposed to similar carcinogenic factors as humans, and the raccoon dog, a species related to the dog but less exposed to anthropogenic factors.A fragment of the DCT gene 443 base pairs in length was obtained. Two genotypes were distinguished within the raccoon dog population, differing in one nucleotide in the intron sequence (145A>G). Between the DNA profile of the dog and the consensus sequence of the raccoon dog, 18 polymorphic sites were found – 15 in the intron sequence and 3 in the exon sequence. One change in the exon (191G>A) caused an ami...

Study on the occurrence of Trichinella spp. in raccoon dogs in Brandenburg, Germany

In recent years the raccoon dog population in Germany has risen dramatically and a steady westward expansion can still be seen. In addition to the highest Trichinella prevalence in wild boar and the most reported Trichinella cases in domestic swine from backyard farms, the North-Eastern part of Germany also has the highest raccoon dog density in the country. Due to their distinct scavenging behavior, raccoon dogs play a significant role as Trichinella reservoir. Therefore, to increase the knowledge on Trichinella spp. in raccoon dogs, we performed a study on the occurrence of Trichinella in the North-Eastern federal state of Brandenburg. In total 1527 raccoon dogs were examined between 2000 and 2014. An average of 1.9% of the raccoon dogs were Trichinella spp. positive. 90% of the positive animals were infected with Trichinella spiralis and one animal each with Trichinella britovi and Trichinella pseudospiralis. In T. spiralis infected animals, the number of larvae found in the muscle tissue ranged between 0.5 and 235 larvae per gram (lpg), with a median of 14 larvae. A tentative temporal increase in Trichinella occurrence was seen between the time periods 2008 to 2010 and 2011 to 2014.Based on the size of the raccoon dog hunting bags of the past decade, the species spread in westerly and north-westerly direction is evident. An interesting question is how the raccoon dog will influence the Trichinella prevalence in the sylvatic cycle in these regions in the years to come.

Homogenous Population Genetic Structure of the Non-Native Raccoon Dog (Nyctereutes procyonoides) in Europe as a Result of Rapid Population Expansion.

The extent of gene flow during the range expansion of non-native species influences the amount of genetic diversity retained in expanding populations. Here, we analyse the population genetic structure of the raccoon dog (Nyctereutes procyonoides) in north-eastern and central Europe. This invasive species is of management concern because it is highly susceptible to fox rabies and an important secondary host of the virus. We hypothesized that the large number of introduced animals and the species’ dispersal capabilities led to high population connectivity and maintenance of genetic diversity throughout the invaded range. We genotyped 332 tissue samples from seven European countries using 16 microsatellite loci. Different algorithms identified three genetic clusters corresponding to Finland, Denmark and a large ‘central’ population that reached from introduction areas in western Russia to northern Germany. Cluster assignments provided evidence of long-distance dispersal. The results of an Approximate Bayesian Computation analysis supported a scenario of equal effective population sizes among different pre-defined populations in the large central cluster. Our results are in line with strong gene flow and secondary admixture between neighbouring demes leading to reduced genetic structuring, probably a result of its fairly rapid population expansion after introduction. The results presented here are remarkable in the sense that we identified a homogenous genetic cluster inhabiting an area stretching over more than 1500km. They are also relevant for disease management, as in the event of a significant rabies outbreak, there is a great risk of a rapid virus spread among raccoon dog populations.