Good Practice Guide – Protecting Hazel Dormice during woodland management and forestry operations
The Hazel Dormouse (Muscardinus avellanarius) is a protected and priority species in Wales, listed under both UK and European legislation due to significant declines in its population and range over the past century. Hazel Dormice are now considered one of Wales’ most vulnerable mammals, with their numbers having dropped by around 70–80% in Britain since 2000. In Wales, however, they still retain much of their historic range, although populations remain fragmented and at risk.
The species is classified as ‘Vulnerable’ on the British Red List for Mammals, but may now meet the criteria for being listed as ‘Endangered’ due to the severity of its decline.
Hazel Dormice will use a range of woodland types. They are most often associated with well-structured broadleaved woodland, hedgerows and scrub, but they are also found in other habitats including conifer woodland. Coppiced woodland and woodlands containing areas prior to canopy closure, and especially areas with different ages and types of woodland structure, are more likely to provide the best conditions. Dormice may also be found in conifer plantations, especially those containing ride edges, shrubby glades, scrub and thick hedgerows connected to woodland or well-vegetated open areas.
In spring and summer, breeding nests are found within dense shrub layers, young woodland and species-rich hedgerows where hazel, honeysuckle, bramble, and other tangled vegetation provide cover and food. Typically, summer nests are 0.5–2 m above ground but may be found higher within tree holes and amongst dense climbers like honeysuckle.
In winter, dormice hibernate at ground level. They use locations that are relatively dry, protected from frost, and free from disturbance. They may hibernate in leaf litter, moss, under logs, at the base of hedgerows, or under tree roots.
Habitat loss, fragmentation and the reduction in suitably managed woodland are thought to be key reasons for their decline. Climate change resulting in warmer and wetter winters is also likely to be impacting populations.
Providing good habitat conditions is the foundation of dormouse recovery in Wales and will also benefit many other species. Conservation efforts in Wales focus on habitat restoration, improving connectivity along with research and expanding survey effort.
How are hazel dormice protected?
Hazel Dormice are European Protected Species (EPS), protected under the Habitats Regulations and the Wildlife and Countryside Act. This means you must avoid impacting dormice in a way that would be an offence, such as deliberately killing or injuring them, or deliberately or recklessly disturbing them, particularly to the extent that impairs their ability to survive, breed or hibernate or significantly impacts on the local population.
You must also avoid damaging or destroying the breeding sites and resting places of dormice and this could be an offence even if you do not do it deliberately. It is difficult to identify individual nests, however dormice will rely on an area of habitat for both breeding and hibernation, so the protections are applied to this ‘functional area’ of habitat that the local population uses for both these purposes.
Appropriate woodland management is critical to maintaining the habitat conditions that dormice require, but management activities can also have a negative impact on the local population if not managed sensitively. Even if the ultimate result of these works creates more favourable habitat, if the local population has been lost because of the management activity, then they will not benefit. For this reason, maintaining ‘ecological functionality’ will mean managing your woodland in a way that maintains or enhances the habitat favourability in the long term, whilst ensuring there is sufficient suitable and undisturbed habitat nearby, so that the local population continues to thrive whilst management is taking place. Maintaining sufficient undisturbed habitat is a necessary element of working lawfully.
Because dormice are present within woodland for every stage of their lifecycle, there is no clear ‘safe period’ when work can happen without risk. However, they tend to build their breeding nests in trees, shrubs and hedges and hibernation nests on the ground, so activities can sometimes be timed to avoid significant impacts during critical periods; particularly by avoiding works affecting trees and shrubs during the breeding season.
Once a woodland is well structured, facilitating active woodland management whist supporting dormouse populations and avoiding offences should be more straightforward, because the areas you need to work are unlikely to be the areas that are most suitable for dormice.
If you cannot avoid an offence by following this guidance, a competent ecologist may be able to develop alternative, site-specific, ways of working to enable you to keep within the law. If that is not possible, NRW may be able to issue a licence to enable you to carry out your work lawfully, but we can only do that if we are confident that there is no satisfactory alternative and that it will not harm the favourable conservation status of the species. EPS licences can only be issued as a last resort.
Are dormice using your woodland?
Our guide, ‘Surveying your woodland for protected species’ provides essential advice on how to look for records and carry out surveys to check for protected species.
Checking for records
If there are any records of Hazel Dormice within 2km of your woodland, you should anticipate that dormice are likely to be present in areas of suitable habitat.
If you apply for a felling licence, NRW will check for records. If we find records that suggest their presence, we will usually add an environmental condition to your felling licence requiring that you follow the measures in this guide.
If you want to be more certain whether Hazel Dormice are present, you can commission a competent surveyor to carry out a survey. If you already know that they use your woodland, you should just proceed on that basis.
Walkover survey
If Hazel Dormice are likely to be using your woodland, you will need to assess the habitat favourability of your site using our Good Practice Guide ‘Surveying your woodland for protected species’. Your woodland may be made up of areas with different favourability, in which case you should map these as accurately as possible.
Even if you do not anticipate dormice to be present, you should still be vigilant for signs that they are.
Before you can implement the preventive measures in the next section, you will need to have established the following:
1. Whether records, surveys, or other information indicate that Hazel Dormice are likely to be using your woodland, if so -
2. The areas of your woodland which consist of highly favourable and moderately favourable habitat for dormice following our Good Practice Guide ‘Surveying your woodland for protected species’. You should have calculated the area of each and recorded them on a map.
3. The total area of favourable habitat – this is the total area of highly and moderately favourable habitat under your control within the whole forest/woodland (whether being worked or not).
If you cannot confidently assess habitat favourability, you will need to bring in a competent ecologist to advise you. Alternatively, you can take a precautionary approach and assume that the habitat is favourable.
Preventative measures to protect hazel dormice
If you are relying on following this good practice to keep within the law, you will need to adhere to the following measures. If you cannot do this, a competent ecologist may be able to suggest site-specific mitigations that may allow you to deviate from these standard measures without causing an offence. If this is not possible, you may need to change your plans or consider applying for an EPS licence.
When we talk about “clear felling” we mean the removal of all, or most, trees from an area, either through large scale group felling or felling of a whole coupe.
When we talk about “thinning” we mean the selective removal of a proportion of trees from an area, usually to reduce density and make space for the remaining trees, but without completely clearing any significant area of trees.
We do not consider that there are any mitigations that could satisfactorily reduce the risk of clear felling or thinning in dormouse habitat during the core breeding season.
These measures are required if you are working in favourable habitat. In areas of unfavourable habitat, you do not need to follow these measures. However, you should still look for ways to improve its favourability.
If you unexpectedly find evidence of the species during work, you should consider whether you are able to apply the measures in this guide, or seek advice from a competent ecologist.
If you are already operating under an EPS licence, you must continue to follow its terms and conditions.
When working in favourable habitat within woodlands where dormice are likely to be present, the following must be adhered to:
1. Avoid the breeding season when clear felling or thinning
· No clear felling or thinning may be undertaken in the core breeding season, between the 1st of June and 31st of August. Where possible, also avoid the 1st to the 15th of September.
2. Limit the impact of clear felling and thinning
· Clear felling must not exceed the maximum coupe sizes in Table 1 below.
· The total proportion of favourable habitat subjected to clear felling or thinning must not exceed the thresholds in Table 1 below.
· Coupes[1] containing favourable habitat adjacent to worked areas must remain undisturbed for at least 5 years
3. Limit the impact of timber extraction
· Where possible, limit extraction routes to existing tracks and areas of unfavourable habitat and avoid extraction through areas of favourable habitat
· Timber must not be extracted through unworked areas of favourable habitat (areas that have not been counted in your clear felling or thinning thresholds)
4. Avoid timber stacking in sensitive areas
· Ideally, stack timber on hardstanding and away from areas of favourable habitat.
· If you must stack timber near favourable habitat, stacks should be on sparsely vegetated ground and removed between 1 April and 30 September or in the same winter/spring as when stacked.
· Timber must not be stacked in unworked areas of favourable habitat (areas that have not been counted in your clear felling or thinning thresholds)
5. Other woodland operations
· For all other woodland operations, including, removal of brash, mowing, scrub clearance, chemical weeding and ground preparation, follow the prescriptions in the EPS and Woodlands Dormouse Method Statement.
Table 1: Clear felling and thinning thresholds
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Top 5 actions to improve habitat for dormice
Managing your woodland in line with the UKFS can deliver significant benefits for wildlife. The actions below would be particularly valuable for dormice, and will also support many other species:
1. Maintain and Enhance a Well-Connected Shrub and Scrub Understorey
Ensure a diverse understorey with species like hazel, honeysuckle, and bramble. Avoid excessive shading and manage browsing pressure from deer or livestock. Thicket stage growth following clearfell operations can also provide good habitat for dormice; in conifer woodland aim to retain areas of thicket stage growth; retaining self seeded broadleaves during thinning will also increase the potential for dormice.
2. Promote Habitat Connectivity Beyond the Woodland
Maintain or create well-connected hedgerows and scrub corridors linking woodlands. Connectivity is critical for Dormouse movement and genetic diversity.
3. Retain and Encourage Fruiting Trees and Shrubs
Species such as hazel, rowan, yew, sweet chestnut, and oak provide essential food resources. Ideally, manage hazel as long-rotation coppice.
4. Manage Woodland Structure for Diversity
Encourage a mix of age classes and structural diversity (e.g., coppice, glades, rides). Include shrubby glades and species-rich ride edges.
5. Protect and Promote Bramble and Honeysuckle
These provide both food and nesting material. Avoid clearing all bramble during ride or edge management