Sourcing Beavers for Projects in Britain
Beavers could potentially be obtained from a variety of European range states. Small numbers of captive bred beavers of Bavarian origin are probably already available from wildlife collections in the UK. A recent genetic study which focused on the collection of DNA from historic and prehistoric skeletal material in Europe up to the channel coast with Britain suggests that the remains nearest to Britain were similar in type to the modern Elbe population (Halley 2010). However a study undertaken by the National Museum of Scotland (Kitchener & Lynch, 2000) suggests that from a skeletal perspective the beavers once found in Britain are nearest in type to the relict Scandinavian population. This study prompted the importation of Norwegian beavers for the Knapdale trial. Overexploitation by humans reduced the western European beavers to tiny relict populations in Norway, France and Germany in historic times. These now have a genetic difference of around 0.1% and instances have arisen of physical abnormalities arising in populations drawn from single founder stocks alone (Halley, 2010). At one point the western populations were all interconnected and there has been recent discussion amongst the statutory conservation bodies nationally regarding the case for allowing the inclusion of further western European genes. Although eastern European beavers are more genetically variable than their western counterparts they are believed to be distinct as clades. However the recent analysis of DNA in Bavaria from a – probably Russian origin – beaver population which is identical to that of the Elbe population casts doubt on this assumption. As the beaver population in Europe continues to rise rapidly with both clades mixing throughout their range a credible case could therefore be made within the IUCN criteria for –
- Re-stocking from Scandinavia alone.
- A mixed western European population
- A mixed western and eastern European population
At the time of writing SNH (Gaywood M. personal communication) have indicated that their position is that they would still only wish to see Norwegian/Scandinavian animals used in UK projects at this moment. SNH may change their position on this once a DNA profile of captive British and wild Bavarian samples has been completed by the spring of 2012. At this point they may support the inclusion of other western European stocks in British trials. The population of beavers which are present and expanding in range on the Tay are likely to be of Bavarian (mixed eastern and western founders) and Polish origin. The recent DNA analysis of a beaver captured on the Tay in January of 2011 identified it as being of French descent. There may well be a strong seam of western European genetics in the captive beaver population in Britain which are largely drawn from Bavarian stocks. This could be verified through genetic analysis.
Natural England would consult with SNH on this issue and a decision would be made based on the outcome of those discussions at the time of any licence application (Wilson C. personal communication). Natural England have however made it clear that they are more concerned about the establishment of the fox tapeworm Echinococcus multiloculariswhich is currently absent in Britain from imported beavers than they are about their country of origin. One way to avoid this issue completely would be to only utilise captive bred beavers from populations which are already established in Britain.
Halley, D. J. (2010) Sourcing Eurasian beaver Castor fiber stock for reintroductions in Great Britain and Western Europe.Mammal Review, 32, 153-178.
Rosell, F., Campbell-Palmer, R., Parker, H. (2012) More genetic data are needed before populations are mixed: response to “Sourcing Eurasian beaver Castor fiber stock for reintroductions in Great Britain and Western Europe”. Mammal Review