Key facts
- site Holnicote Estate, West Somerset
- size 5,059 hectares of which 600 hectares is woodland
- establishment method planting and natural regeneration
- type lowland broadleaved woodland, coniferous woodland, mixed (established and recent) plantation, riparian woodland, ancient woodland, natural regeneration, wood pasture, parkland or orchard, coppice
- funding Landscape Recovery Scheme, Higher Tier Capital Grant, Countryside Stewardship Higher Tier
- key objective nature conservation
Tree protection
- main mammals causing damage or risk to trees squirrel and deer
- main tree protection method shooting, enhancing natural predation, sheep’s wool and lanolin-based products
- duration of main tree protection methods 3 to 5 years
The diverse landscape of Holnicote Estate
Holnicote Estate spans 5,059 hectares of Exmoor National Park in West Somerset. Much of the estate is access land under the Countryside and Rights of Way Act (2000), with 150 miles of public footpaths and bridleways.
Owned and managed by the National Trust, it has a contrasting landscape that includes the rugged moorland of Dunkery Hill, the shingle beaches of Selworthy and Bossington and a variety of woodland habitats. Among these is Horner Wood National Nature Reserve – a designated Site of Special Scientific Interest – which includes 351.8 hectares of ancient oak woodland.
Managing grey squirrels in woodland accessible to the public
Grey squirrels pose the most significant risk to woodland habitats across the estate. The grey squirrels strip bark from both young and mature trees, especially from the tree canopy. In some cases, they can remove up to 60-70% of the bark, weakening the trees and making them more vulnerable to wind damage.
The discovery of pine martens on the estate has complicated grey squirrel control operations. Since their presence has been confirmed, the use of lethal traps for grey squirrels is no longer permitted to protect the pine martens.
While alternatives such as live trapping remain impractical due to the size of the estate and the resource required. For effective results, it would require establishing extensive trapping lines consisting of 40 to 50 individual traps, which then require a minimum of three to four checks daily over the course of a month before any noticeable impact can be observed.
To address this ongoing issue, the estate works alongside neighbouring landowners as part of a broader grey squirrel control initiative within Exmoor National Park, working to set up a syndicate of trained volunteers using low powered air rifles.
At present, a trained volunteer culls grey squirrels at fixed bait stations, and between October 2024 and June 2025, has successfully removed approximately 150 grey squirrels from an area that had been experiencing considerable damage. Health and safety are paramount given the woods are open to the public, receiving many visitors.
Simon Powne, a Wildlife Biologist for the National Trust, says
We need to be mindful of the fact that people are using air rifles on publicly accessible land and use risk assessments to determine where we locate bait stations. At this level, a 16.27 joules air rifle presents a low risk. Moreover, when set up on a fixed bait station, the operator is positioned well away from any public footpaths and where the very steep valley side forms a suitable backstop.
In addition to culling, the estate is closely monitoring the local populations of pine martens and Eurasian goshawks, both known to predate on grey squirrels. As part of a broader reintroduction scheme, plans are underway to release another 10 pine martens into Exmoor National Park within the next year.
Deer in the landscape. Credit Simon Powne/National Trust
Rethinking traditional fencing
While deer fencing is a common approach to protecting young trees, Holnicote Estate ultimately decided against it after weighing up its limitations. Though the fencing might offer short-term protection, it risked simply shifting browsing deer to surrounding areas. The estate was concerned about the long-term implications fencing requires regular maintenance and a clear plan for removal within 10 years.
In addition, the cost of fencing the 17-hectare Riverlands Wood at Porlock Vale to protect against deer would have been equivalent to employing a full-time Wildlife Manager for an entire year, including the initial cost of necessary equipment. This prompted a reassessment of priorities.
Rather than investing in expensive fencing, the estate opted for a more flexible, adaptive strategy supported by government grants. These funds help cover the costs of targeted deer and squirrel control. By combining this with overplanting of certain tree species, the estate has been able to reduce reliance on guards and fencing all together.
Combining strategies to manage deer populations
Whilst red deer are a significant factor in the tourism trade for the area, the browsing roe deer threatens young trees and coppice regeneration – particularly in areas where Eurasian beavers are present. To mitigate this impact, the estate uses Trico®, a deer repellent spray derived from emulsified sheep fat.
Roe deer amongst young trees. Credit Simon Powne
Trico® is being applied in Riverlands Wood, where deer fencing and tree guards would be costly and impractical. Each tree is manually sprayed twice a year – once in early spring and again in autumn. Initial results indicate that this approach has been highly effective, reducing roe deer browsing damage to below 20% within the first year of application. However, this success may also be partially due to the deliberate overstocking of trees in the woodland.
Holnicote Estate plans to assess the relative impact of these factors using the Forest Research ‘nearest neighbour’ technique for new tree plantings to calculate percentage of damage.
To further support deer management, glades and rides with highly palatable flora are being maintained along woodland edges to provide alternative browsing habitat. Historically these areas made up a low percentage of the woodland, whereas all plans now have glades and rides factored in, with deer management as the main motivator. This has also resulted in an increase in the biodiversity value of these areas.
Lethal control is selectively implemented to ensure that deer populations remain at healthy and sustainable levels, which is currently around 8 deer/kilometre2.
Simon Powne, Wildlife Biologist, National Trust
The combination of habitat management, tree species selection, non-lethal management and lethal management need to be considered in equal parts. It’s important to understand what your objectives are for the woodland, how much damage you can tolerate and what your objectives are for wildlife, too.
Useful links
For additional information, consider the following resources
- National Trust – for further information about the Holnicote Estate
- Confederation of Forest Industries – for a two-year review of Trico® as a deer repellent
- Scottish Forestry – for a woodland herbivore impact assessment to identify and evaluate the damage deer pose to trees in your woodland
- Forest Research – for the ‘nearest neighbour’ method to quantify wildlife damage to trees in your woodland
