Cracking the mystery of red squirrel decline

Mathematical modelling research by Professor Andy White has been used to direct policy and practice to conserve red squirrels – a protected species in the UK – from squirrelpox virus-carrying, invasive grey squirrels.

The research demonstrated that the red squirrel conservation policy used up to 2015 would not be sufficient to contain squirrelpox in the UK. Working with stakeholders, his research was the trigger for a radical change in policy to protect red squirrels in priority areas in the UK, directly informing the ‘Scottish Strategy For Red Squirrel Conservation (2015)' and the Red Squirrel Survival Trust policy to protect red squirrels on Anglesey.  

Prof. White's research has also evaluated red squirrel population viability under different forest management scenarios. This research underpins commissioned reports he produced for the Forestry Commission that have had a direct impact on current and future forest management practice in the UK that balance timber production and red squirrel conservation. 

Prior to this work, conservation policy had focussed on control in regions where grey squirrels tested positive for squirrelpox. This had reduced grey numbers in local areas but had not prevented disease spread or increased red squirrel numbers. The work showed that it is extremely challenging to prevent the spread of the squirrelpox into areas where grey squirrels are already well-established and, importantly, that squirrelpox will not persist in red squirrel (only) populations.

Saving Scotland's Red Squirrels (SSRS), the body responsible for red squirrel conservation in Scotland, stated that this work “had impact both on policy through inclusion in the Scottish Strategy for Red Squirrel Conservation (2015) and practice as SSRS recognised the difficulty in containing squirrelpox as the trigger for a radical change of strategy that protects remaining red squirrel populations in Priority Areas for Red Squirrel Conservation (PARCs) in southern Scotland”. 

Impact on Forest Management Practice in Northern England 

The modelling research was also extended to answer specific red squirrel conservation issues faced by forest management practitioners. Working with Stakeholders in the Forestry Commission, future felling and restocking scenarios for Kidland and Uswayford forest were used to drive the mathematical model and led to predictions of red squirrel population viability.

The Planning and Environment Manager for the North England Forest District of the Forestry Commission stated “The findings….highlighted how the (original) proposed forest design plans could lead to a risk of red squirrel extinction (particularly in Uswayford). As a result alternate felling and restocking regimes were developed by the Forestry Commission and tested in the model. The model results had a direct impact on the final forest design plans for the Uswayford and Kidland forest (for 2017 - 2041) which are outlined in the Cheviot Forest Plan (FC 2015) and which represent the optimum in terms of silviculture and red squirrel viability. The combined FC and Maxwell Institute modelling study therefore played a key role in the red squirrel conservation strategy in these forests.