Population decline of carnivore species may happen suddenly, develop rather fast and proceed short-term. For instance, such demise character was known for the European mink in Belarus and Russia (Macdonald et al., 2002; Sidorovich, 2011). Population decline of other carnivore species may pass gradually and less evident, and a considerable decrease in population density may take many more years.
The situation that is characterized by gradual and long-term decline is fairly hard to notice, while manipulating short-term data only. It takes much time to establish a right hypothesis on the decline and to prove the hypothesis. Usually, in such a case, when a population decline appeared to be evident, it is already too late to get a complete dataset to analyze the declining process and to reveal the factors that impacted the population. The polecat Mustela putorius population decline in Belarus was characterized by the mentioned features of gradual and long-term decline (see Sidorovich, 2011). Our results of the study on the polecat demise suggest the following negative factors that are responsible for the population decline.