Context

Bark-stripping by grey squirrels (Sciurus carolinensis) costs the UK forestry industry up to £37 million a year in lost yield. This has led the Royal Forestry Society (RFS) to identify grey squirrel damage as the “number one threat” to broadleaf woodland health and creation, ranking above deer damage and introduced diseases. 

Efforts to reduce grey squirrel impacts mainly use lethal control (methods designed to kill), which is costly, resource-intensive, and often challenging to carry out due to public opposition and conflicting management objectives across landscapes. Non-lethal alternatives remain limited due to a lack of understanding of the underlying causes of bark-stripping behaviour. 

This project will investigate the chemical deterrents that damage-resistant trees use against bark-stripping and characterise the bark-stripping behaviours on susceptible trees.  

Research aims and objectives

Aim:

Understand the chemical defences available to trees, and the behavioural strategies available to squirrels. 

Objectives:

• Identify which chemicals in tree bark help to protect against bark-stripping by separating the complex mixture of chemicals found in bark into simpler fractions (groups or compounds) which can then be tested separately to see which are least appealing to squirrels.  

• Characterise bark-stripping behaviours in grey squirrels, and design and develop radio tags for tracking squirrel movement within tree canopies in 3D. 

• Develop a machine-learning model to automatically recognise squirrel movements and body positions linked to bark-stripping behaviour. 

Expected outcomes

• Natural chemical compounds found in bark that defend trees against bark-stripping will be identified and extracted.  

• A functional collar capable of tracking bark-stripping behaviour in 3D will be developed.  

• A toolkit for studying grey squirrel behaviours related to bark-stripping will be established.  

• A stakeholder workshop will be held to discuss and plan non-lethal methods of controlling grey squirrel damage using insights into squirrel behaviour and tree chemical deterrents.