Dormouse Survey

Dormice are legally protected under the Conservation of Habitats and Species Regulations 2010 (the Habitats Regulations), as well as the Natural Environment and Rural Communities Act 2006 (Section 41) and the Wildlife and Countryside Act 1981.

Survey methodology for dormice reflects the life-cycle of this species and usually requires the installation of artificial nest boxes or tubes in woodland or hedgerows, which are checked on a monthly basis by an appropriately licensed ecologist. Different survey methods must be carried out at specific times: nest tubes and nest boxes can be used between March and November, whilst nut searches can be carried out all year (where hazel is present) to confirm presence only.

All of our dormice surveys follow guidance within The Dormouse Conservation Handbook. Searching for gnawed hazel nuts is the most efficient method of assessing dormouse presence, This is generally not recommended to demonstrate likely absence in relation to any development site. Nest tubes are used where hazel is absent as Dormice use the tubes for shelter and sometimes breeding, and they can be easily checked for occupants.

Deploying a minimum of fifty tubes per site is considered an adequate sample size to robustly determine if dormice are present or likely absent. Nest boxes are best suited to long-term monitoring, particularly within woodland sites. They are more robust and generally last a number of years before replacement is required.

The hazel, or common, dormouse is a small member of the dormouse family, with adults reaching a body length of six to nine centimetres and a tail that is usually around six centimetres long. In the spring and summer, they typically build nests using honeysuckle bark and grass a metre or so above the ground and they may also use nest boxes and tubes deployed for the purposes of surveying.

Dormice emerge and forage in the canopy after dark. They have bright golden fur with a pale underside and are most easily distinguishable from other small British mammals by their long fluffy tails. The UK population of hazel dormice has declined significantly over the last fifty years or so, mainly due to accelerating habitat loss, a decline in quality of the habitats that remain, inappropriate habitat management and habitat fragmentation.

Hedgerow removal has resulted in the reduction of wildlife corridors between woodland areas and dormice are generally reluctant to cross open ground to colonise other areas, thus are vulnerable to local extinctions when suitable habitat disappears. Dormice also have a specialised diet not usually found in young, isolated or small areas of woodland.

The hazel dormouse spends up to three-quarters of its life asleep, either in hibernation (between October and April) or, if spring or summer weather is poor, in torpor (a sleep like state used by animals to survive colder temperatures by saving energy). In the spring and summer, dormice build nests in trees, shrubs and other habitats, whilst in the winter they hibernate in leaf litter and root systems below the woodland or hedgerow floor. Dormice breed between May and September and usually produce one litter (sometimes two) with an average of four young.