The colony of Castor fiber in the nature reserve “Dnieper-Orelsky”
Abstract
Under conditions of intensive anthropogenic and recreational pressure on the ecosystem, the existence of a natural reserve “Dnieper-Orelsky” is a condition of preservation of variety of flora and fauna of all Dnipropetrovsk region. Almost disappeared by the beginning of the twentieth century species of the castor fiber due to natural dispersion gradually settles in the most suitable for its existence reservoirs, restoring its prior area. Its absolute abundance in the territory during 1992–2008 was increased from 5 to 28 individuals. The aim of the work is to study the settlement of beavers in the nature reserve “Dnieper-Orelsky” their forage reserve, environment-forming role, and to work on new safe methods for their registration.Accounting work was carried out by perambulation of the shoreline of the river and the lake with boat in october–november 2013. Coordinates of the found animal tracks fixed with the help of GPS-navigator, were recorded in the field book and photographed for the further identification. In geostatistical analysis, these data act as a training sample on which probabilistic models are built which link the species’ area of living with preferred environmental conditions.Hot scent of vital activity of beavers namely holes, crawlways to the water, nibbled trees found on the northern and southern shores of the lakes “Solone” and “Solonenke”, in the coastal area of the lake “Sokilki”. Forage base of beavers in the territory of the reserve in 80 % of cases consists of white poplar (Pópulus alba L), in 12 % – of black poplar (Pópulus nigra L.), sometimes there occur sporadically fallen oaks (Quercus robur L.), amorphous (Amorpha fruticosa L.), elm (Úlmus laévis Pall) and alder (Alnus glutinosa L.). Bavers’ forage area spreads for no more than25 metersfrom the water's edge. The average diameter of felled trees is20 cm, 82 % of the trees has a diameter from 5 to40 cm. The diameter of the largest tree, felled by the beavers, is72 cm. 88 % of the trees have sections of the removed cortecs, which start at the level from 0 to50 cmover the land, in 11 % of the cases these sections start at the level from 50 to60 cm. On one tree the lower bound of the nibble located at the rate of70 cm. The upper boundary of nibbles was 35–90 cm from the ground. The width of the nibble prints on fallen trees ranged from 3 to8 cm, but in most cases ranged from 5–6 cm, indicating that the beavers’ families, which live in the explored area, have progeny both of the previous and current year.Remote sensing data helped produce factor analysis of the ecological niche of animals. The results of analysis were used to identify the characteristics of the environment, which make the place suitable for the existence of the species. Received data of the area of animals’ living were used as a training sample on which probabilistic models were built which link the species’ area of living with preferred environmental conditions. It was found out that similar ecological conditions of areas in which the presence of beaver is noted, has a number of other places of the reserve.References
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