The Siberian flying squirrel (Pteromys volans) in south of Eastern Europe: distribution boundaries and its changes

Abstract

Information on the former and current distribution of the Siberian flying squirrel on the plains of Eastern Europe was analysed, with special attention to the south-western segment of the species range, which in ancient times entered the territory of Ukraine (in the sense of its modern borders). The study, as a starting point of analysis, is based on the reports of researchers of the 18th and 19th centuries (mainly J. Güldenstedt and D. Bagaliy), repeated in a number of later publications, about the findings of the species in Sumy Oblast and its probably wider distribution in Polissia, in the Forest Steppe, or even in Podillia. Detailed descriptions of all former and modern records of the species with a cadastre of locations are given. This cadastre covers the entire south-western segment of the area, including the Dnipro and Volga basins. Information on finds of the species in the region is summarized in two sets of data, before and after 1960; they are all marked on the respective maps. The points of finds of the species are unevenly distributed, which may indicate unequal availability of data from different regions. However, the author believes that such unevenness is related to the peculiarities of the distribution of the species, since the absence of the species was shown for some of the locations in the data-absence zones, despite its detailed searches, and the dynamics of distribution limits were shown for some places. The south-western segment of the range of the flying squirrel can be described as a continuous wedge, in which the south-western border runs through the territory of Belarus along its north-eastern borders and the corresponding parts of neighbouring countries, through Polotsk, Baran, further along the border from the Russian Federation to Trubchevsk and further to the Bryansk Forest reserve, which is the southernmost location of the species. The eastern border of this segment goes to the Volga, reaching it in the area of Nizhny Novgorod, however, data indicate a large winding of the range boundary in this part to the north, to Safonovo, Rzhev, Mozhaisk, Obninsk, Pushchino and further to Ryazan. In Pushchino, the species is listed as an introducer. This loop of geographic range may indicate the isolated status of the western segment, from Berezina in the west to Desna in the east. It is assumed that this area of the range was formed as a result of the recent (15–18 centuries) expansion of the distribution limits of the species and their new reduction over the last 100 years (19–20 centuries), with a rate of reduction of about 100–160 km per century. There is a high the probability of finding the species in the north-east of Ukraine.