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Goryainova Z.I.,RAS Severtsov Institute of Ecology | Katsman E.A.,RAS Severtsov Institute of Ecology | Zavyalov N.A.,Rdeysky State Nature Reserve | Khlyap L.A.,RAS Severtsov Institute of Ecology | Petrosyan V.G.,RAS Severtsov Institute of Ecology
Russian Journal of Biological Invasions | Year: 2014

The results of comparative analysis of tree and shrub resources quantitative characteristics in the active and abandoned beaver habitats within the territory of the Tadenka River basin, Prioksko-Terrasny Nature Reserve, where beavers have been dwelling for more than 60 years, are presented. Using one-way ANOVA analysis with the settlement type (active or abandoned) as a factor, it was shown that long-term foraging by beaver leads to a decrease in the species richness of trees (P = 0.068). Different hypotheses of the impact produced by beaver selective foraging on various forest layers (overstorey and undestorey) are discussed. Factors promoting thinning and changes in the age structure of the overstorey and undestorey are considered. There were observed changes in the species composition, accompanied by an increase in the proportion of low preference and nonfood species. The conclusion is made that, if the foraging zone does not exceed 50 m at the beginning of habitat utilization, it extends up to 165 m in the absence of predators when the habitat is used repeatedly. This observation is confirmed by Fisher’s exact test (P = 0.005), Yates’ chisquared test (P = 0.002), and the likelihood ratio test (P = 0.0002). In the case of beavers recolonizing their abandoned habitats with unrecovered food resources in the Tadenka River basin, a distant zone within 50 to 165 m from the bank becomes the main zone for tree-shrub foraging. © 2014, Pleiades Publishing, Ltd.

Zavyalov N.A.,Rdeysky State Nature Reserve
Biology Bulletin | Year: 2013

The state of food resources for Eurasian beavers (Castor fiber Linnaeus, 1758) after several cycles of habitat colonization and abandonment has been analyzed in three beaver settlements on small rivers of Novgorod oblast. It has been shown that tree stands surrounding the settlements differ in composition and degree of damage but are similar in that they contain no forage for beavers: aspen is absent, and birch trees are large and require great efforts to cut them down and utilize. The undergrowth and understory also contain no aspen, while abundant willows and birch are represented by young, thin-stemmed plants unevenly distributed over the area. Tree species prevailing in abandoned settlements are not favored by beavers, implying that the animals must have expended extra energy for foraging. Supposedly, populations of beavers on small rivers in the southern taiga subzone, in habitats modified by their activities, will maintain their abundance far below the maximum possible level, depending on the rate of forage plant regrowth against the background of deteriorating habitat quality. © 2013 Pleiades Publishing, Inc.

Zavyalov N.A.,Rdeysky State Nature Reserve | Petrosyan V.G.,RAS Severtsov Institute of Ecology
Russian Journal of Biological Invasions | Year: 2015

Results of the long-term analysis of the Eurasian beaver (Castor fiber) and its settlements in the Pushta River basin and Moksha River floodplain lakes in the southeastern part of the Mordovia State Nature Reserve during the period of 1940–2013 are described. The numbers of beaver settlements and animals living there 73 years after they were reintroduced have stabilized in the ranges of 20–29 settlements and 65–96 individuals. The performed integrated analysis of environmental conditions, climate, hydrological network, and the effects of predators, diseases, spatial arrangement of settlements, size of the settlemetns, number of dams in settlements, specific foraging features, and food resources, as well as mathematical data processing using the classic models of population dynamics (Malthus, Beverton–Holt, and Ricker) and a time series analysis, suggests that the dynamics is at a climax stage with a fluctuation at low abundance level. A hypothetical theoretical qualitative model of the long-term beaver population dynamics is discussed for different restoration rates of food resources. Using this model, it is shown that typical of the population dynamics in the Berezinsky Biosphere Reserve and Oksky Nature Reserve as well as Allegheny National Forest is a high restoration rate of food resources (type I dynamics). On the other hand, characteristic of the population dynamics in the Lapland, Il’menskii, PechoraIlych, and Mordovia nature reserves is a low restoration rate of food resources (type II dynamics). It is inferred that the further development of the beaver population in the Mordovia Nature Reserve will mainly depend on the functional (the rate of food restoration in abandoned habitats as well as the growth scale and rate of black alder stands in the abandoned beaver settlements) and random (cold winters, winter floods, and droughts) factors influencing the beaver population dynamics in the nature reserve. © 2015, Pleiades Publishing, Ltd.

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