Like most of the native Mustelidae, the European polecat (Mustela putorius) is also subject to a number of anthropogenic influences. Without the systematic survey of the species and review of potential influences on population biology, it would be impossible to make conclusions on the status of these species. However, according to the Habitats Directive of the European Commission, this is also required for the species listed in Annex V, which includes the European polecat. It is necessary that differentiated questions are to be answered and the occurrence of the species is to be documented. Additional development trends are to be assessed.
The aim of the study where to answer as many questions as possible on ecology and population status of the polecat, or at least test hypothesis with their regards to their validity. Based on existing state of knowledge, which have been unsystematically collected or were missing as well a lack of evaluation approaches, it was impossible to answer questions comprehensively, especially regarding the Habitat Directive of the European Commission. Therefore for most thematic complexes the basics have been first worked out. The conclusions of this study refer essentially on the federal state of Saxony-Anhalt. The base of the population biology thematic complex was the dissection of a total number of 162 polecats found dead or hunted from the central and northern Germany. Out of this total number of animals 122 came from Saxony-Anhalt. The focus of the research was to determine basic biological data. The age group, the participation of both sexes in reproduction, nutritional-ecological aspects, juvenile development, diseases and parasite infections, mortality and population genetics were examined via further analyses. Extensive field studies helped document the current occurrence of the species as much as possible and to verify knowledge about habitat requirements. In addition, the actual habitat quality and competitive behaviour in connection to food and habitat availability were reviewed. The anthropogenic influence on the European polecat population in Saxony-Anhalt was analysed both on field studies and by supplementing laboratory analytical methods. The focus was on traffic mortality, hunting and pollutants on the population of the polecat. In addition, the effect of land consolidation measures, water maintenance and drainage on habitat quality was investigated.

The study showed declining occurrences, large distribution gaps and a lack of reproductive participation of both sexes compared to previous comparative periods. The age structure of the sample has changed significantly since the Peaceful Revolution in 1989 1990. In the present study, the sample consisted mainly of adults that were lost to reproduction and thus the species conservation. The main cause of the examined individuals was roadkill. The genetic analysis did not reveal any segregations within the samples, which was predominantly from Saxony Anhalt. Nevertheless, the allelic diversity in the north of the study area is higher than in the south, although not significantly. A reduction in genetic diversity from north to south was also found by comparing with other European polecat populations. For the samples from Saxony-Anhalt, a differentiation of the population into two different subunits was evident. Individuals from the north had a higher allelic diversity than the south east population due to the supposed connection to north western populations. This was confirmed by landscape genetic studies. Within the northern group, the genetic allocation of single individuals from the found dead analysis and from the live capture to four neighbouring catch area was possible. Kin relationships were found, lifetime migrants detected and the suspicion of family clan like structures confirmed. Overall, the genetic results were discussed with the regards of a possible bottleneck. This has not been confirmed at present. However, the genetic structure between the northern and southern populations may lead to expect corresponding phenomena in the future. Causes for the observed population biological changes compared to earlier periods were probably mainly due to a very high pollutant load, which can be attributed to anthropogenic inputs.

The ubiquitous contribution of pollutants, their distribution in the organism and the transfer via placenta and mother´s milk to juvenile contributed to the presence of a threshold like background pollution within the sample. Partially high exposures of single individuals were found, which could neither be explained by circumstances of the find nor by regional characteristics. Especially the polychlorinated biphenyls and organochlorine pesticides enriched in the food web affect the hormonal regulation of reproduction and apparently caused massive reproduction problems. The polecat, which is particularly sensitive to these substances, reproduce quickly through many juveniles under optimal conditions as a typical r strategist. At the time of the study, these species was apparently no longer able to compensate for the deficits that as built up so far. In addition, land consolidation, drainage and water maintenance caused large scale losses of suitable habitats and connecting corridors, so that parts of the population became isolated. Conventional farming led to temporary but large scale barriers during mating season and Dismigration of the polecat. This forced fragmentation of the landscape and prevented the possible reintroduction of the species. The lack of habitats and structures led to the species shifting to corridors accompanying urban infrastructure as substitute habitats.

These findings led to four results. First, the criteria for evaluation of the conservation status were revised. Secondly, the guidelines for answering the questions of EU Habitats Directive were modified. Thirdly, monitoring instructions and species protection measures were developed. Fourth, a conservation concept for the federal state of Saxony-Anhalt was being prepared. In this way, the polecat should be enabled to repopulate suitable parts of the landscape in the future from the still existing parts of population. At the same time, the findings of the study should help to recognise the discussed anthropogenic influences in their effect on the polecat as an exemplary species. This should help to minimise problematic interventions in central German ecosystems and to develop new species concepts for handling resources and habitats.