The Eurasian beaver Castor fiber was once widespread in Europe and Asia. However, by the beginning of the 20^th century, over-hunting had drastically reduced both the numbers and range of the species. In Europe, only a few isolated sites remained: parts of the Rhone (France) and Elbe (Germany), southern Norway, the Neman River and Dnepr Basin (Belarus) and Voronezh (Russia). A series of management measures and reintroductions have enabled the beaver to return to much of its former range, and there are now a number of rapidly expanding populations extending from Spain and France across central and eastern Europe to European Russia, and in Scandinavia and parts of western Finland.

Free-living populations of beavers are now established or establishing in most regions of their former European range, the main exceptions to date being Portugal, Italy, the south Balkans and Great Britain (Halley and Rosell 2002, Ceña et al. 2004). Detailed information on the status and distribution of the Eurasian beaver in each range state can be found in Halley and Rosell (2002), and information on the population that was translocated to Spain in 2003 can be found in Ceña et al. (2004). It is generally a lowland species, but occurs up to 850 m in Europe (Halley pers. comm. 2006).

In Mongolia, a small population exists along the Bulgan River in northern Dzungarian Govi Desert, in the south-western corner of Mongolia. Mongolian-German Biological Expeditions carried out conservation introductions along Hovd River in Mongol Altai Mountain Range in 1974, 1975, and 1978, and along Tes River in northern Hangai Mountain Range in 1985, 1988 and 2002. In all cases Mongolian beavers from the Bulgan River were used in order to protect the gene pool in the central Asiatic hydro-geographic basin (Stubbe and Dawaa, 1982; Stubbe et al., 2005a). A separate attempt to reintroduce beavers from Voronezh Reserve (Russian Federation) was unsuccessful (M. Stubbe pers. comm.).