Zoroastrianism (which also revered otters), and there were laws in place for unlawful killing of these animals. In China, a few hundred beavers live in the basin of the Ulungur River near the international border with Mongolia. The Bulgan Beaver Nature Reserve (; ) was established in 1980 to protect the creatures. Conservation The Eurasian beaver Castor fiber was once widespread in Europe and Asia but by the beginning of the 20th century both the numbers and range of the species had been drastically diminished, mainly due to hunting. At this time, the global population was estimated to be around 1,200 individuals, living in eight separate sub-populations. Conservation of the Eurasian Beaver began in 1923 in the USSR, with the establishment of the Voronezh Nature Reserve. From 1934 to 1977, approximately 3,000 Eurasian Beavers from Voronezh were reintroduced to 52 regions of the USSR, from Poland to Mongolia. In 2008, the IUCN granted the Eurasian Beaver a status of least concern, with the justification that the species had recovered sufficiently with the help of global conservation programmes. Currently the largest numbers can be found across Europe, where reintroductions have been successful in 25 countries and conservation efforts are ongoing. However, populations in Asia remain small and fragmented, and are under considerable threat. Reintroduction into Scotland The first sustained and significant population of wild-living beavers in the United Kingdom became established on the river Tay catchment in Scotland as early as 2001, and spread widely in the catchment, numbering from 20 to 100 individuals. Because these beavers were either escapees from any of several nearby sites with captive beavers, or illegal releases, Scottish Natural Heritage initially planned to remove the Tayside beavers in late 2010. Proponents of the beavers argued that no reason existed to believe that they were of "wrong" genetic stock, and that they should be permitted to remain. One beaver was trapped by Scottish Natural Heritage on the River Ericht in Blairgowrie, Perthshire, in early December 2010, and was held in captivity in the Edinburgh Zoo. In March 2012 the Scottish Government reversed the decision to remove beavers from the Tay, pending the outcome of studies into the suitability of reintroduction. In 2005, the Scottish government had turned down a licence application for unfenced reintroduction. However, in late 2007, a further application was made by the Royal Zoological Society of Scotland, Scottish Wildlife Trust and Forestry Commission Scotland