This paper is devoted to the area and abundance of pine marten in the West Siberia during XX – XXI century.
West Siberia ; Pine marten ; Area ; Numerosity
Western Siberia is an area of overlapping ranges of the two mustelid species of genus Martes — sable M . zibellina and pine marten M . martes . Traditionally ( Geptner et al ., 1967 ; Pavlinov et al ., 2002 ), sable inhabits an entire forest area of the region, from forest tundra to forest steppe. At the same time, pine marten controls the eastern boundary of the area, reaching 80° E in the Vasyugan river basin. However, with respect to the latter specie, pine martens area was specified primarily by the scientific works of I.P. Laptev (1958) and S.U. Stroganov (1962) in the mid-twentieth century. At the beginning of the twenty-first century, the literature provides data concerning population growth and expansion of the geographic area of pine martens including in the southern taiga in the eastern region ( Kiryuhin et al ., 2002 ; Shubin, 2002 ).
According to a specific point of view, the pine marten habitat depends on the spread of different types of linden Tilia sp. (Bakeev and Bakeev, 1973 ) because lime forests provide this predator with refuge in form of hollows, as well as feed resources, such as Hymenoptera (bees, wasps) and hollow-nesting birds and their eggs. However, in the southeastern region of western Siberia, lime forests appear only in the form of scattered, small area relict lime groves (Hlonov, 1965 ). Moreover, many of the lime forests have special conservation status and are under threat of degradation and extinction.
According to another hypothesis, in the early twentieth century, pine marten managed to expand its area up to the middle taiga of western Siberia as the result of a sharp reduction in the number of sable, as well as the conversion of forest landscapes by fires and logging. During this period, the Vakh river basin was the eastern boundary of the species distribution (Laptev, 1958 ).
To determine the boundaries of the geographic area and relative abundance of pine marten, collection materials recollected over the past 60 years in the southeastern forest zone of western Siberia (Tomsk region and the surrounding area) were analysed. A total of 638 skulls of the genus Martes were selected from the collections in Tomsk State University, Tomsk Institute of Agriculture (branch of Novosibirsk State Agrarian University), West Siberian branch of the Russian Scientific Research Institute of Hunting and Farming and Siberian Zoological Museum of the Institute of Animal Systematics and Ecology Siberian Branch of the Russian Academy of Sciences (Novosibirsk).
Because sable and marten have significant similarities in craniometrical parameters, there is a need for specific identification of the craniological material. When using both classical indexes of specific identification (Aristov and Baryshnikov, 2001 ) and the method proposed by A.T. Grebenik et al. (2010) , sable can be clearly distinguished from pine martens. Sample analysis has demonstrated that among males and females of M . zibellina , there are atypical individuals, occupying an intermediate position between the pine marten and typical sable. With high probability, these “anomalous” individuals can be identified as kidus, i.e., hybrids between the two species. The intermediate signs of kidus regarding parental forms were mentioned by P.B. Jurgenson (1947) . Later, these assumptions were confirmed by N.N. Grakov (1981) , who obtained hybrids in captivity. According to the results of his work, it was experimentally determined that interspecific hybrids are oligocarpous, only hybrid females can produce offspring, and males are sterile. Therefore, for further analysis, these animals were united with pine marten in the same group (“pine marten”).
The share of “pine marten” in the southeast of the forest zone of western Siberia in the 1950s amounted to 12.2 ± 3.8% of the whole sample selection of the genus Martes . That share is measured against the share of martens caught in the middle and southern taiga of the Khanty-Mansi Autonomous District (8.9 ± 0.1%), identified in the same period of harvested furs (Bakeev and Bakeev, 1970 ). These data may indicate a similar number of species in different zones of the taiga of western Siberia in the middle of the last century.
In addition, significant differences in the samples of the genus Martes from the right and left bank of the Ob River were noted. Thus, on the left bank from the 1950s until the 2000s, a significant decrease in the occurrence of “pine marten” from 12.2 to 4.8% was observed. However, in the samples of skulls from the right bank from the 1950s to the 2000s, this species was not identified. This area is known to have only rare visits of individual martens according to both literary ( Laptev, 1958 ) and modern survey data. On this basis, the large Ob River with an extensive floodplain more than 10 km in width can be a real barrier to the distribution of the species in the West Siberian Plain. A similar trend was noted not only for the Tomsk region but also for the adjacent Khanty-Mansi Autonomous District. Beginning in the 1960s, there has been an evident decline in the number of martens (Bakeev and Bakeev, 1970 ), and in the 1980s, the martens disappeared from the east of the district, in the Nizhnevartovsk region (Trenichev, 1990 ).
The overall decline in the occurrence of pine marten in a forest area over the last 60 years may indicate a decrease of this speciess population in the southern and middle taiga, despite the persistence of a broad range. Pine marten is most likely affected by the growth of the population of sable (Kassal and Sidorov, 2013 ) because these species are hostile competitors (Bakeev et al., 2003 ). Further evidence supporting this view is a recent extension of the martens' area on the southern edge of sub-taiga forests and in the forest-steppe of Western Siberia (Kiryuhin et al ., 2002 ; Inozemtsev and Ryzhkov, 2007 ; A.Y. Bondarev information), where its primary competitor is absent or highly rare.
This work was supported by the State contract No 6.657.2014/K.