Dormouse Surveys
Hazel Dormouse
There is one native dormouse species in the UK: the Hazel Dormouse, Muscardinus avellanarius.
The Edible Dormouse, Glis gliswas introduced to the UK in 1902 and is now established primarily in the Chilterns, with smaller populations reported in parts of the New Forest, Hampshire, Essex, and Oxfordshire.
The Hazel Dormouse is a European Protected Species, protected under Annex IV of the Habitats Directive and the Wildlife and Countryside Act 1981.
As a result, it is an offence to:
- Deliberately capture, injure, or kill a dormouse
- Deliberately disturb dormice in a way that affects their ability to survive, breed, or reproduce
- Damage or destroy a breeding site or resting place
Dormice can be affected by development activities, including:
- Loss or degradation of woodland, scrub, or plantation habitats
- Removal of hedgerows, tree lines, or scrub, leading to fragmentation and reduced connectivity between habitats
- Impacts to rural or suburban gardens, which can provide important habitat and movement corridors
The optimal timing for surveys can be found in our Ecology calendar.
If your Preliminary Ecological Appraisal identifies potential constraints relating to dormice, further surveys may be required.
Adonis Blue can support you with all necessary surveys and, where required, help secure a dormouse mitigation licence.
Dormouse Surveys
If hazel dormice are known to be present within 3 km of the site, and suitable habitat is present or connected, their presence should be assumed unless proven otherwise.
Prior to survey work, a habitat assessment should be undertaken. This evaluates factors such as vegetation structure and species diversity and classifies habitat into one of four categories: Excellent, Good, Fair and Poor.
The main survey techniques used in development contexts include:
Nest Tubes
- Purpose: To determine the presence or likely absence of hazel dormice
- Method: Tubes should be in place at least one month before the first check begins
- Good / Excellent habitat: At least 50 tubes should be installed along transects or grids, spaced 15–20 m apart, and covering a large proportion of the available habitat. The timing will depend on the start date of the first check. April, May, June, and July start dates are likely to finish in September, while August start dates will typically finish in October
- Fair / Poor habitat: At least 100 tubes should be deployed for a full season (April–November), and at least 30 footprint tunnels should be deployed between May and October
- Number of surveys: Tubes should be checked once per month
Footprint Tunnels
- Purpose: To determine the presence or likely absence of hazel dormice
- Method: A minimum of 50 footprint tunnels should be placed 15–20 m apart
- Timing: Surveys may be carried out between April and November, but only data collected from May to October can be used when assessing survey effort
- Number of Surveys: Two visits per month are required to replace the ink
Opened hazel nuts
- Purpose: To determine the potential presence of dormice on site through the identification of characteristic feeding signs on hazel nuts. This method is only suitable where mature hazel scrub is present
- Method: Conduct a ground search beneath mature hazel shrubs and collect a minimum of 100 hazel nuts that have been opened by small rodents (excluding those opened by squirrels). Dormice typically create a distinctive, neat circular hole with smooth, beveled edges around the opening. Collected nuts should be carefully examined to confirm the presence or absence of dormouse feeding signs
- Timing: Surveys should be carried out in between September and February, when opened hazel nuts are most likely to be found
- Number of Surveys: A minimum of one thorough survey is required. However, additional visits may be necessary on larger or more complex sites to ensure adequate coverage and to meet the minimum nut sample size
Protected Species Licensing
Due to the strict legal protection afforded to hazel dormouse, a European Protected Species Mitigation (EPSM) licence is legally required if your development will deliberately disturb dormice in a way that could affect their ability to survive, breed, rear young, or hibernate, damage or destroy a breeding site or resting place (e.g. nests), whether or not dormice are present at the time and result in the capture, injury, or killing of a dormice.
An EPSM licence needs to be obtained from the statutory government body, Natural England.
An EPSM licence application can only be made once planning permission has been granted with all relevant conditions formally discharged.
Our team can help you secure a dormouse migration licence and ensure all necessary mitigation is done.