Red squirrels (Sciurus vulgaris) have declined dramatically in England, largely due to squirrelpox virus and competition from invasive grey squirrels (Sciurus carolinensis) and habitat loss. To support their recovery, this project used a structured decision making (SDM) approach to evaluate 18 alternative strategies against several core objectives relating to red squirrel recovery, cost, public acceptability, animal welfare, non-target species bycatch, and socio-economic factors such as tree damage.
Strategies included various combinations of lethal grey squirrel management, red squirrel translocations, and potential future tools (grey squirrel fertility control and a squirrelpox vaccine). Over 60 stakeholders from diverse sectors shaped the objectives and strategies.
To evaluate strategy performance, we combined several methods, including: a biological model projecting squirrel population dynamics and disease spread over 25 years; a welfare elicitation exercise to assess impacts of different methods on squirrel welfare; and survey-based modelling to predict public opposition to grey squirrel management techniques.
Doing nothing, continuing with the current status quo, and switching from lethal management of grey squirrels to fertility control alone if it becomes available all fail to deliver red squirrel recovery, with a high chance of red squirrel extinction across mainland England over the next 25 years. England-wide grey squirrel suppression strategies offer the best chance for large-scale red squirrel recovery, but with high monetary costs, high species bycatch potential, welfare concerns, and predicted low public support. The regional strategies we modelled for Northern and South West England that incorporate red squirrel translocations also show promise for red squirrel recovery, with a preference expressed among stakeholders towards the Northern England strategies. Targeted regional strategies may be more feasible and incur fewer costs to other objectives.
This report offers a transparent, evidence-based framework to guide red squirrel conservation with the next step being a decision on a national strategy to take forward. Additionally, the approach is iterative and can be reapplied at smaller spatial scales to support more nuanced local decision-making.