A Systematic Map of Research Exploring the Ecological Modifiers and Consequences of Bark Damaging Behaviour in Squirrel Species

Bark-stripping and browsing by mammals in woodlands can cause widespread damage to trees, inhibiting tree growth and leading to whole tree or canopy death. Sciurid species worldwide are known to incorporate inner bark or cambium tissue into their diets, and outer bark can additionally be used as nesting material. The drivers and causes of bark-stripping behaviour have been investigated and determined for some species; for others this remains largely unexplained, including the eastern grey squirrel Sciurus carolinensis. For all squirrel species there is good understanding of tree susceptibility to damage as well as impacts of damage on tree health. However, much less is known about the drivers and modifiers of bark-stripping behaviour, which hinders the development of effective mitigation and management efforts. To address this knowledge gap, we aim to produce a systematic map, by collating, organising and categorising knowledge clusters and gaps on motivators of bark-stripping behaviour in squirrels, and the consequences of bark damage by squirrels in woodlands globally. Literature searches will be conducted in English, Spanish, Simplified Chinese, and Traditional Chinese using relevant scientific databases (ISI Web of Science, Scopus, SciELO, Wanfang, NDLTD and NCLTPL). The relevant search terms are defined by a primary question: what are the correlates and consequences of bark-damaging behaviour caused by squirrel species in woodlands, and what are the recommended management strategies? Papers will be screened for inclusion criteria at two stages: (1) abstracts and titles, and (2) full-texts. Information extracted from the studies will include study location, publication date, publication type, length of study, regional scope of study, data type, sampling strategy, study design, and intervention methods. Further coding variables will be used to extract relevant data, recording the modifiers and consequences of bark-stripping behaviour at different spatial scales. Results will be presented visually and narratively, summarising key characteristics of the systematic map database and identifying areas for new evidence syntheses and primary research.