The dynamics of the temporal and geographical distribution of the beaver

Spread beaver in the Oligocene and Miocene, especially in connection existed contributed Eurasia to North America in the Bering Strait (watch article numbered 1.2). M. Menzbir suggested (cited in Dzyakava, 1975a), which in the Miocene between Europe and North America there is a direct link through the "Atlantic Bridge" (watch article numbered 1.3). According to this "bridge" Beavers could enter Europe, creating forms here, united in the genus Steneofiber.

Beavers quickly occupied the central zone of the Eurasian continent and differentiated into two kinds of endemic and Propalaeocastor Steneofiber. In the Neogene probably existed very favorable conditions for the beavers — that are known to all the families of the Neogene of the family. In the upper Miocene, somewhere in the south-eastern part of Europe differentiate species of the genus Castor. Due to the cooling of the family Castoridae, formed in a soft and even hot climate Oligocene, were forced to adapt to the harsh climatic conditions of the upper Pliocene and Pleistocene. Managed to beaver Castor Eucastoroides labor and delivery giant beavers Trogontherium, Paradlpoides and Castoroides (Dyakov, 1975a).

Outlining the history of the species, L. Lavrov (1981) writes that, according to R. Gorshtetteru in Tertiary North America, Eurasia and Africa zoogeographic were one. Repeatedly occurred overland connection between the continents have determined exchange fauna. Leading to American researchers Taylor that genus Castor appeared in North America during the Pliocene, ie, a little later than the first discoveries of this kind in Europe, L. Lavrov added that it was the original home of the area with a warm climate and intense resumption drevespo-shrub and herbaceous vegetation, especially the Mediterranean region. Adapting to life in the freezing waters began to develop from the time of the Lower Pliocene. In the north, with rich water system are unfavorable and limiting edaphic and climatic factors — severe winters, rocky soil and frozen to the bottom. Consequently, it is the Tertiary with its mild climate and movement of the continents contributed to the development and dissemination of genera of Castoridae, including the kind of Castor. At the end of this period, they were forced to adapt to the more severe conditions of the Pleistocene, and the number of genera of Castoridae significantly reduced.

The most important factor shaping the flora and fauna is the movement of glaciers, which took place in Eurasia and North America repeatedly and asynchronously (watch article numbered 1.4). The onset of ice at a rate of 3 to 73 cm a day made it possible for the majority of land animals to migrate south. The retreat of the glaciers, also numbering in centuries, and its melting entailed the formation of high-water river systems and great water flow, which seized large areas and often have had disastrous consequences for the animals, especially the semi-aquatic, not adapted to prolonged movement by land and by a long stay in the water . They could be beneficial for the beavers.

Rather complete picture of the past distribution of the genus Castor in the Old World gives SI Ognev (1947). Based on extensive data analysis of literature and archival documents, he wrote that the entire continent of Western Europe during the Quaternary period was inhabited by beavers and not only evidence of their existence ever in Ireland. He considers questionable information about the existence of a beaver in Greece, Egypt, northern Iran, Asia Minor, and in the valleys of the Tigris and Euphrates rivers (in spite of the information from the "Avesta" — Alikhanov, 1984). Note also that in Afghanistan there is a river Kunduz — the left tributary of the Amu Darya — and the city of Kunduz. VN Rock (1951) writes that in the translation of Kunduz means "beaver", although the words with the root "kunda" may be associated with the term "beaver". VN Rock provides comprehensive information and analysis of the material for the dissemination of the beaver in North Asia, emphasizing that the beaver not only had the widest distribution in Siberia (watch article numbered 1.1 and below, watch Article at No. 1.10), but was an important game animals of outstanding economic value.

North limit of the beaver in Eurasia by Dzyakava V. (1975a), almost everywhere coincides with the boundary of the forest-tundra, and sometimes — in Scandinavia and on the Kola Peninsula, the floodplains of the Northern Dvina and other rivers — extended to the shores of the Arctic Ocean. The southern boundary of the area came to North Africa, Mesopotamia, Northern India (V. Dyakov references Khlebovich and Fedyushin), which, in our view, it is likely because a related area Castor canadensis mexicanus (see watch article numbered 1.1) also extends south to 25 ° c. sh.

Northern border of the Canadian beaver basically corresponds to latitudes range Castor fiber L. in northern Eurasia. The southern boundary of this species is now on the line, close to 25 °. sh., ie by 1.5 thousand kilometers to the south. On a recent wealth of beaver resources of North America data indirectly indicate that about a hundred years ago, only one factory can annually purchase 20 thousand beaver skins (this is approximately equal to the product of the Soviet Union in 1985). Beaver skins were two thirds of total exports of furs (Wilsson, 1966). Beaver in Europe has been so popular that the Hudson Bay Trading Company in the period from 1857 to 1877 could be sent to a London auction of more than 3 million beaver pelts (Aulaire dE., Au-laire dO., 1973), or 150 thousand year. Number of beavers in North America around 1600, is estimated at 60-100 million head (Sedlag, 1983, S. 79). Yet the vast wealth of beaver in North America at the end of XIX century. have been exhausted. According to Theodore Roosevelt (Roosevelt, 1908), the beavers were caught from all the rivers, and their number has decreased to such an extent that not even justified by labor placed traps. By this time, the inhabitants of large areas of the Old World had not the slightest idea of beaver, because these animals were killed at least a hundred years ago (watch article numbered 1.2, see also below, watch Article at No. 1.11).

As follows from the driven material in some Western European countries beaver was in the Middle Ages, and the destruction of the last beaver northwest dates back 1866-1871 years. The whole of history was the destruction of a unique animal. Huge negative impact on the environment is truly revealed only recently.

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