Mammal Society Position Statement on The Reintroduction of Beavers to Britain

Background

The beaver, Castor fiber, is native to Britain and is currently classed as Endangered on the GB Red List. The species became extinct in southern Britain and Wales by around 1300, but persisted in Scotland until around 1600 (Raye, 2015). The species was reintroduced to Knapdale, Scotland in 2009, as part of a formal pilot study. However, most of the current Scottish population is derived from unauthorised releases on the Tay catchment. In 2016 the Scottish Government announced that it had no plans to remove the two established populations.  Recent surveys show that the Tayside population is expanding into new areas, including establishing a strong presence in the city of Perth, and 251 active territories were identified.  Whilst population estimates are very uncertain, it is likely that there are now around 1,000 individuals in Scotland (including juveniles). Translocation of beavers to the Loch Lomond National Nature Reserve took place in early 2023, with Loch Lomond being only the third location in Scotland where a beaver translocation has successfully taken place since the reintroduction trial at Knapdale in 2009. In England, breeding populations are established in Devon and Kent, and there are regular signs of beaver activity on the catchments of the River Wye and the Bristol Avon. There are also signs of beavers in Wales but, as yet, no breeding population is known.  In total, the number of wild animals in England and Wales may be fewer than 100.

Benefits and risks of reintroduction

There is considerable evidence that the reintroduction of beavers brings a wide range of ecosystem services and ecological benefits. These include increasing the water-holding capacity of catchments, filtration of particulate pollution of water courses, and the creation of pools and wetlands (Puttock et al. 2017; Thomson et al. 2020).  Benefits accrue to a wide range of wildlife, including many aquatic invertebrates, amphibians, waterfowl and bats (Ciechanowski et al. 2011, Dalbeck et al. 2020; Law et al. 2016, 2019, Nummi & Holopainen 2014).  Impact on fishes have been widely studied, and while there can be some blockage of migration routes for salmonids, this difficulty can be overcome through targeted management (Malison and Halley 2020). The creation of pools and the filtration of water also bring benefits to fish breeding.  

There can also be some impacts that are less desirable, such as the flooding of valuable agricultural land or the blockage of leats and other watercourses. This can lead to ongoing mitigation costs which is a major barrier to landowner acceptance. Therefore, it is vital that a robust management plan is in place to ensure that such impacts are dealt with swiftly and effectively (for example, by removing a dam or introducing a ‘beaver deceiver’ to enable water levels to be lowered). It should be noted that the benefits and disbenefits of beavers may be experienced by different people, and therefore good communication, community consultation and an effective management strategy are vital components of any reintroduction plan. 

Beavers have the potential to carry a range of infectious diseases. Of particular concern is Echinococcus multilocularis, because this parasite could potentially become established in wild rodent populations and is potentially fatal in humans. One case of a captive imported beaver with Echinococcus multilocularis has been confirmed (Barlow et al. 2011) and an unlicenced beaver release resulting in the capture and screening of released animals on the River Otter in 2015. However, assessments have shown that provided appropriate quarantine and health-screening protocols are followed, the risks of introducing significant disease to humans, domestic animals, or wildlife are extremely low (Girling et al. 2019).  

Position on reintroductions

The Mammal Society welcomes the return of this native species across Britain, and the recent increased legal protection of this species in Scotland and England.  The Mammal Society’s update on the further legal protection for beavers can be found here.

All reintroductions should follow IUCN guidelines, including giving careful attention to the genetic composition of the population (noting that the founder breeding stock for most of the current population was extremely limited) and to appropriate disease screening.  

Reintroductions to the wild are to be preferred to those in enclosures, given that the ecological and conservation benefits of the latter are extremely limited.

We believe that there should be a national strategy and oversight of reintroductions to target areas where the greatest benefits will be obtained. All reintroductions should be accompanied by long-term monitoring and a management plan to enable potential unwanted effects of beaver reintroductions to be dealt with swiftly and effectively.

National funding should be made available for beaver reintroductions, with an avoidance of short-term projects, which will not provide the long-term management required by such projects. 

References

Barlow, A.M., Gottstein, B. & Mueller, N. 2011. Echinococcus multilocularis in an imported captive European beaver (Castor fiber) in Great Britain. Veterinary Record, 169, 339.

Campbell-Palmer, R, Puttock A, Needham RN, Wilson K, Graham H, Brazier RE. 2021. Survey of the Tayside Area Beaver Population 2020-2021. NatureScot Research Report 1274.

Ciechanowski M, Kubic W, Rynkiewicz A, Zwolicki A. 2011. Reintroduction of beavers Castor fiber may improve habitat quality for vespertilionid bats foraging in small river valleys. European Journal of Wildlife Research 57(4): 737–747.

Dalbeck L, Hatchel M, Campbell-Palmer. 2020. A review of the influence of beaver Castor fiber on amphibian assemblages in the floodplains of European temperate streams and rivers. Herpetological Journal 30: 135–146

Girling SJ, Naylor A, Fraser M, Campbell-Palmer R. 2019. Reintroducing beavers Castor fiber to Britain: a disease risk analysis.  Mammal Review 49: 300-23.

Law A, McLean F, Willby N J. 2016. Habitat engineering by beaver benefits aquatic biodiversity and ecosystem processes in agricultural streams. Freshwater Biology 61: 486–499.

Law A, Levanoni O, Foster G, Ecke F, Willby N J. 2019. Are beavers a solution to the freshwater biodiversity crisis? Diversity and Distributions 25: 1763–1772.

Malison R L, Halley, D J 2020. Ecology and movement of juvenile salmonids in beaver-influenced and beaver-free tributaries in the Trøndelag province of Norway. Ecology of Freshwater Fish. DOI: 10.1111/eff.12539

Nummi P, Holopainen S. 2014. Whole-community facilitation by beaver: ecosystem engineer increases waterbird diversity. Aquatic Conservation: Marine and Freshwater Ecosystems 24: 623–633.

Puttock A, Graham H A, Cunliffe A M, Elliott M, Brazier R E. 2017. Eurasian beaver activity increases water storage, attenuates flow and mitigates diffuse pollution from intensively-managed grasslands. Science of the Total Environment 576: 430–443.

Raye L. 2015. The early extinction date of the beaver (Castor fiber) in Britain. Historical Biology. 27:1029-41.

Thompson S, Vehkaoja M, Pellikka J, Nummi P. 2020.  Ecosystem services provided by beavers Castor spp. Mammal Review. DOI: 10.1111/mam.12220

Statement updated 20/02/2023.