Technical Report: Managing Mammal Damage in UK Woodlands

/ by Jon Smith / in Blogs

Technical Report: Managing Mammal Damage in UK Woodlands

Mammal activity is a primary driver of tree mortality and reduced timber quality in the UK. Damage typically occurs through browsing (eating shoots), bark stripping, or fraying, all of which compromise a tree’s structural integrity and health.

Profile of Common Damaging Species

Species Primary Damage Types Typical Timing & Targets
Deer Browsing, bark stripping, and fraying (antler rubbing). All ages; significant impact on seedlings and pole-stage trees.
Grey Squirrels Extensive bark stripping on main stems and branches. April–July; targets healthy, fast-growing broadleaf species.
Rabbits & Hares Basal gnawing and clipping of young shoots. Winter and Spring; prevalent in areas with tall grass cover.
Voles Precise gnawing of bark at the base (up to 5cm diameter). Winter; high risk when food sources are scarce.

 

Core Impacts on Woodland Health

The presence of high mammal populations without adequate protection leads to three primary levels of degradation:

  • Restricted Regeneration: Persistent browsing of seedlings prevents the natural replacement of older canopy trees, leading to an aging, stagnant woodland.

  • Pathogen Entry: Bark stripping creates open wounds that serve as entry points for fungal infections and decay, drastically reducing timber value and tree lifespan.

  • Biodiversity Loss: Over-browsing alters the woodland “understory” (shrub layer), removing the habitat required by nesting birds and various insect species.

Protection and Mitigation Strategies

1. Physical Barriers (Primary Defense)

  • Individual Protection: Use of tree shelters (tubes), spiral guards, or mesh guards to protect the main stem of young trees.

  • Exclusion Fencing: Utilizing deer-proof or stock fencing for large-scale planting schemes where individual guards are impractical.

2. Habitat & Environmental Control

  • Vegetation Management: Keeping grass short around the base of new plantings reduces the cover available for voles and rabbits, making them vulnerable to predators.

  • Strategic Selection: Incorporating less palatable species in high-pressure areas to discourage browsing.

3. Population Management

  • Biological Control: Supporting natural predators, such as owls (for voles) and the recovery of the pine marten (to mitigate grey squirrel populations).

  • Direct Management: Implementing humane population control measures where mammal density exceeds the land’s carrying capacity.

Management Tip: Regular monitoring is essential. Damage identified in the early stages can often be mitigated by adjusting the height or type of tree guard used.