Castor

Today, beaver populations in Europe are expanding rapidly, and there are no major threats (e.g. threats of a magnitude likely to cause decline at the regional level). Competitive exclusion of the native European beaver C. fiber by its American cousin C. canadensis may be a threat in parts of Finland and north-west Russia, but it is not a major threat regionally. In Europe North American beavers are now confined entirely to Finland and north-west Russia, where populations are increasing only slowly (due to heavy harvesting). The former population at a reservoir near Paris has been removed, and populations introduced to Poland and Austria have apparently gone extinct in competition with C. fiber, the opposite of what has tended to happen in Finland and north-west Russia (it has been suggested that, due to differences in the life history of the two species, Eurasian beavers may have a competitive advantage at more southerly latitudes, whilst North American beavers may be more successful further north: D. Halley pers. comm. 2006). There are no serious prospects of further introductions (Halley and Rosell 2002, D. Halley pers. comm. 2006). The two species do not interbreed (Tattersall 1999). Road kill is an important source of mortality for some populations (Tattersall 1999). Rapidly expanding beaver populations may come into conflict with humans in some areas, as they do some damage to forestry and crops. Such damages should be put into perspective: they tend to be less severe than those caused by other species such as deer and voles, but are noticed because beavers are a new and unfamiliar species in areas where they have been recently introduced (Halley and Rosell 2002).

In Mongolia, illegal hunting for skins, meat and castoreum still occurs in some areas such as the Tes River. Habitat loss through selective clear-cutting of willow, upon which this species relies for food and shelter is also a threat; this is known to be occurring along the Bulgan River and is leading to isolation of small populations and inbreeding. Pollution of water systems is also a threat. A hydroelectric dam in the Chinese section of the Bulgan River prevents migrations in this area (M. Stubbe pers. comm.).

In China, firewood gathering has depleted much of the forest on which the beavers need to subsist; additionally heavy grazing pressure has further reduced vegetation needed by beavers.