population decline – Zoology by Vadim Sidorovich

Declines in mountain hares in Naliboki Forest, central west of Belarus: hypotheses and arguments

Before, in 1950s-1970s the mountain hare was common species in Naliboki Forest. According to the local hunter’s words in those winters the species tracks covered snow cover densely and more or less evenly in each fragment of this forested terrain. In the late 1990s and beginning of 2000s it looked like the mountain hare local population density in Naliboki Forest was evidently in a decline; there were censused only 0.2-0.8 inds per one square km. In 2005-2010 the evident growth of the local population of mountain hare was registered, and more or less high number of the species continued till 2014 (2.9-6.1 inds per one square km). Then during the each next winter we faced with fewer and fewer number of mountain hares in Naliboki Forest.

Recovering of the badger local population in Naliboki Forest, NW Belarus in connection with winter warming and predation of lynxes and wolves

Historically, the badger was fairly common species in Naliboki Forest that is in the north-western part of Belarus. Besides the respective information that was obtained from the locals (e.g. Baliaslaw Sadowski, Lianard Jurevich, Edzik Khmara), who lived and was familiar with the forest in the 1930s-1960s, also presence of numerous former badger setts suggests about the commonness of badgers. Approximatelly, the density of main setts, where badger families lived before, was not lower than 15 per 100 km² in the most ecologically rich southern part of Naliboki Forest and about 4 per 100 km² in the central and central-northern parts of the terrain, where habitat carrying capacity for badgers is markedly lower. It means that the former density in more or less undisturbed badger population in Naliboki Forest ranged approximately between 20 and 120 individuals per 100 km² in relation to the habitat carrying capacity of the terrain.

Rapid decline in the local population of lynx in Naliboki Forest, NW Belarus: density-dependent regulation or disease?

First, briefly about history of lynxes in Naliboki Forest during several last decades. In the early and mid-1990’s, after the Soviet Union crash, perhaps in conditions of relatively weak nature protection, the majority of lynxes were poached in Naliboki Forest. In the 1980’s there was a dense lynx population in the terrain, but by the late 1990’s lynxes occurred sporadically there. In the early 2000’s lynxes began recolonizing Naliboki Forest. The severe snow conditions in the late winter and early spring of 2013 seemed to impact lynxes negatively, and the local lynx population number dropped from 35 to 22 the next winter. Indeed, during the spring of 2013, as far as we learned, local forestry workers and antler searchers found at least three lynx carcasses. All of them seemed to be subadults or kittens, because they looked relatively small.

The causes of long-term decline in the polecat population in Belarus

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.

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