Genetic Scorecard Indicator - Eurasian beaver

No populations are more than 25 years old, and all are growing to some extent, rather than declining.  However, some populations such as Beauly remain very small, others such as Knapdale are currently at carrying capacity, while Tayside shows a continuing trend of population growth. There remains a significant risk of genetic diversity loss through drift in the smaller isolated populations, although at present, diversity in beavers across Scotland is comparable to that seen in mainland Europe. 

Population definitions:

Populations in Scotland and Great Britain are geographically disparate and currently unconnected. As such the populations have been defined based on geography. However, dispersal can be high within watersheds and connectivity may increase over time.

Ne500: The proportion of populations that have an effective population size of more than 500. 

• Proportion of populations with Ne > 500 in Scotland = 0/5
• Proportion of populations with Ne > 500 in UK = 0/6

PM: Proportion of populations that existed in 2000 that still exist in 2025.

• Proportion of populations maintained in Scotland = 5/5
• Proportion of populations maintained in UK = 6/6

all populations maintained only since recent introductions (>2000).

Functional variation

As beavers in Scotland originate from a reintroduction and subsequent translocations the genetic diversity is a subset of mainland European diversity, and there has been no opportunity for local adaptation, therefore there is no risk of loss of functional variation at present. 

Divergent lineages

As beavers in Scotland originate from a reintroduction and subsequent translocations genetic diversity is a subset of mainland European diversity and no known or suspected distinct lineages are present. 

Hybridisation/Introgression

Eurasian beavers do not hybridise with American beavers (C. canadensis) which are not present within Scotland or Great Britain. Hybridisation has not been deemed a threat to Eurasian beavers.

Low turnover - constraints on adaptive opportunities

Species reproduces annually with sufficient fecundity for rapid mammalian population growth.

The Beaver population in Tayside continues to increase alongside the capacity to expand further. Other populations in Scotland are already at carrying capacity and unable to expand further (i.e. Knapdale) and some are too small to maintain diversity without further intervention. Translocations are ongoing in both Scotland, with potential to be expanded to wider Great Britain, to mitigate this risk. Overall genetic diversity in Scotland is low but comparable to diversity available across the species range.  

Scotland

• Risk: Serious
• Mitigation: Partially effective

GB/UK

• Risk: Serious
• Mitigation: Not in place

Overall Genetic Health status explanation

Classified as serious as all populations have an Ne < 500 with only one population (Tayside, Scotland) expanding and large enough to be self-sustaining in the long term. Mitigation is actively being carried out in Scotland with translocations from Tayside to other populations to increase population sizes. Translocations to wild living populations in England is possible but not currently managed.  

In situ genetic threat level

• In situ Risk for Scotland: Serious

Relatively low genetic diversity, fragmented populations, no populations with Ne > 500. 

• In situ Risk for UK: Serious

Relatively low genetic diversity, fragmented populations, no populations with Ne > 500. 

Confidence in in situ threat level

• Confidence score for Scotland: High

The population in Knapdale is at carrying capacity (~20-30 individuals) with all suitable habitat occupied by beavers. The population in Beauly has been surveyed in 2017, 2019 and 2021 and numbers have remained low suggesting the population is not likely to be viable without reinforcement. The population in Tayside has been surveyed three times with the most recent survey completed in 2020-2021. This most recent assessment showed considerable expansion in territories and range with an estimate population size of 954 (range 602 – 1381). Although the numbers continue to increase in Tayside it likely does not yet constitute a population with Ne > 500.

• Confidence score for UK: High

The population of beavers in the River Otter, Devon is estimated to be comprised of 15 family groups which is significantly below an Ne of 500. While the rest of the potential populations of wild living beavers in England have not been effectively surveyed, they most likely will not constitute a population with Ne > 500.

Not widely bred in zoos with only 71 individuals kept across European Association of Zoo and Aquaria (EAZA) establishments although none of these are in the UK. A studbook for beavers translocated from Tayside to other Great British populations and enclosures is managed by The Beaver Trust. There are currently 27 licensed sites in England where beavers have been released into an enclosure.

Population

Demographic

Population in Tayside, Scotland has been surveyed in 2012, 2017-2018, and 2020-2021 with other populations surveyed sporadically. More routine monitoring of Scottish populations outlined as a required action in Scotland’s Beaver Strategy. 

N pops assessed/monitored in Scotland = 5/5
N pops assessed/monitored in UK = 6/6

Genetic

The most recent genetic assessment was undertaken in 2021 which surveyed Tayside, Scotland (n=65), Knapdale, Scotland (n=37), and Devon, England (n=5). 

N pops assessed/monitored in Scotland = 2/5
N pops assessed/monitored in UK = 3/6

Population surveys of all wild living populations in Scotland and Great Britain, genetic monitoring of all populations in Scotland and Great Britain, better understanding of adaptive potential, improve estimates of Ne for the species, and feasibility studies for development of additional populations across Great Britain.