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Hazel Dormouse Survey

The common or hazel dormouse  measures around 6cm as an adult. It has golden fur and is pale underneath, and unlike other small British mammals its tail is long and furry. Clear features of its head are its fine whiskers and prominent black eyes.The dormouse is a threatened species with population numbers falling dramatically due to habitat loss, it’s also a protected species.

Dormice are protected under UK and European law: the Conservation of Habitats and Species Regulations 2010, Natural Environment and Rural Communities Act 2006 and the Wildlife and Countryside Act 1981. It's an offence to kill them, capture or disturb them, or damage their habitat.

The dormouse is also a species of principal importance and has a UK Biodiversity Action Plan in place to curb its decline in numbers.

Dormice live in woodland (generally deciduous but can be found in all woodland types), species-rich hedgerows and scrub land. It can also be found in gardens and conifer forests. The creatures are active from late April to late October, spending the rest of the year instate of hibernation. They're mostly found in southern England and Wales, not Scotland, Northern Ireland or the Republic of Ireland.

If you are commissioning development on land and the proposed work may impact on hazel dormice or their habitats, a licence may be required.

3 types of dormouse survey

There are three types of dormouse survey:

  • Nest boxes
  • Nest tubes
  • Nut searches

Nest box and nest tube surveys involve placing boxes and tubes in suitable habitats like hedgerows and woodland over several months. Nut searches look for nuts gnawed by hazel dormice, which are easy to spot because the pattern they make is distinct from other nut-eating mammals, like squirrels. 

Searching for gnawed hazel nuts is the most efficient method, but this only works when there is fruiting hazel on site. However, a lack of hazel does not mean there are no hazel dormice on site. 

  • Nest tube surveys are the most commonly used survey method. The nest tubes are made from a light wooden tray housed in plastic. Dormice use these to makes nests from leaves and torn honeysuckle bark for shelter and sometimes for breeding purposes.
  • Nest boxes are best for longer term monitoring, particularly in woods, simply because they're more robust than the tubes and last for several years.

We can only use nest tubes and boxes between March and November when dormice are active, during periods of cool or wet weather they can spend time in a state of 'torpor'. Nut searches can be carried out all year round, but only to confirm the presence not absence of the hazel dormice, although these surveys are best conducted around November when fresh nuts have not deteriorated to much.

A survey usually begins with a desktop search examining all biological records available and aerial imagery to identify blocks of woodland and connections through the wider landscape such as hedgerows. This helps us assess the likelihood of the animals being on your site. 

If there is the potential for the site to support hazel dormice a nest tube survey will be recommended. This usually involves placing at least 50 nest tubes on the site, which we hang from horizontal branches in dense vegetation and check monthly for the dormouse nests.

Arrange a Dormouse survey

Dormouse surveys can be time consuming simply because it takes so long to adequately sample an area. Survey’s can take up to six months, and are carried out between March and October. We can carry out a thorough nut search in a single visit, but these are best undertaken in November.

Mitigation for hazel dormice can be difficult and it is therefore always best to try and avoid impacting their habitats. However, if disturbance cannot be avoided, we have a great deal of experience resolving hazel dormouse issues. Our experts have both personal survey licences and have vast experience with mitigation.

If you'd like to go ahead or have any questions, call us on 07487 700305 or: