Blog: Squirrel snacks and troublesome badgers: The challenges of setting up research in the field

University of Southampton and Centre for Forest Protection PhD student Alexandra Ash is investigating the bark-stripping behaviour of grey squirrels to identify future methods to prevent tree damage. Alexandra tells us about the challenges of navigating problem-solving in the field to develop the best experimental set-up for feeding trials.

This presentation was delivered by Dr Alexandra Ash, one of the project leads on CFP Phase 1 project ‘Understanding grey squirrel damage in UK woodlands’, as part of the ‘Managing mammalian pests in woodland landscapes’ session at Britain’s Forest Future: Research-Practice Exchange in Durham, UK on 18 November 2025. Alex summarised her recently completed PhD which aimed to understand the drivers of bark stripping by grey squirrels in UK woodlands. Key messages from this presentation included:

• University of Southampton and Forest Research in collaboration with The Woodland Trust, Cardiff University / Prifysgol Caerdydd and Charles Dutton (Fellow of the Institute of Chartered Foresters) tested the potential for deploying the natural defences of trees to manage the bark-stripping damage by grey squirrels in Great Britain.
• The team observed tree chemical composition to correlate with observed susceptibility of trees to grey squirrel damage. In particular, certain chemical compounds were associated with resistance and some associated with susceptibility.
• They also tested the effects of these compounds on wild grey squirrel behaviour, finding that squirrels responded negatively to compounds identified from resistant trees and positively to compounds identified from susceptible trees.
• These findings highlight the potential utility of tree chemical compounds to reduce the intensity or frequency of the behaviour in woodlands.

Britain’s Forest Future: Research-Practice Exchange was a forest and woodland research, policy and practice knowledge-exchange event organised by Defra, the Future of UK Treescapes, and the Centre for Forest Protection. It was held on the 17 & 18 November 2025 in Durham, UK.

Journal Article: Understanding Why Grey Squirrels (Sciurus carolinensis) Bark Strip in British Woodlands: A Systematic Map

Abstract

Background:

The damage to trees caused by grey squirrels in Britain undermines the UK Government’s ambitious afforestation targets for expanding woodland area to sequester carbon. The motivations of grey squirrel bark stripping are poorly understood, hindering the development of non-lethal management options that target bark stripping.

Aim:

We provide a broad synthesis of the literature on the bark-stripping behaviour of squirrel species with the specific goal of identifying methods to understand and mitigate the bark-stripping behaviour of grey squirrels in Britain.

Methods:

We searched for articles that described or investigated the bark-stripping behaviour of squirrel species. Literature searches were conducted in English, Spanish, Simplified Chinese and Traditional Chinese using relevant platforms for literature-search databases. Information extracted from the articles included coding variables defined by study meta-data, study design and contextual variables for bark-stripping behaviour.

Results:

We identified 188 relevant articles on sciurid bark-stripping behaviour in North America, South America, Europe, Asia and Africa. Most studies were observational (65%), identifying important tree and stand characteristics associated with tree susceptibility to damage. Experimental studies (15%) largely aimed to identify methods to prevent damage caused by squirrels, with none finding an effective, practical and humane solution for preventing or reducing damage. Evidence for the causes of bark-stripping behaviours remains sparse, particularly for species that cause significant economic damage.

Conclusion:

Future research should prioritise experimental designs and interdisciplinary collaborations aiming to establish causal understanding. For the grey squirrel, we propose multiple hypotheses that warrant further investigation, including nutritional deficiencies, self-medication, scent-marking and agonistic behaviours.

This research is being built upon in CFP Phase 2 project: Understanding grey squirrel bark stripping.