Hazel Dormouse Surveys
The hazel dormouse or common dormouse (Muscardinus avellanarius) is a small mammal and the only living species in the genus Muscardinus. It is the only dormouse native to the British Isles so is often referred to as simply the Dormouse. They live in woodland and species rich hedgerows and are nocturnal, spending most of their waking hours searching for food amongst the trees and hedges. They prefer to remain off the ground to avoid predators. Dormice are active between late April and late October, spending the remaining months in hibernation. The hazel dormouse is legally protected because its numbers and distribution has declined substantially over recent years. This is primarily due to loss and fragmentation of woodland habitat as a result of forestry, urbanisation and agricultural practices.
The main non-native species of dormouse is the edible dormouse (Glis glis) which has a generally squirrel-like body, with small ears, short legs, and large feet, and is occasionally mistaken for the hazel dormouse.
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Dormouse Legislation
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In England, Wales and Scotland, the hazel dormouse is protected under Schedule 5 of the Wildlife and Countryside Act 1981 (as amended), and under equivalent legislation in Northern Ireland. It is also a European Protected Species and as such it has additional protection in the UK under Regulation 41 of the Conservation of Habitats and Species Regulations 2010. It is an offence to intentionally kill, injure or take a hazel dormouse, possess or control any live or dead specimen or anything derived from a hazel dormouse, intentionally or recklessly damage, destroy or obstruct access to any structure or place used for shelter or protection by a hazel dormouse (in practice this includes its terrestrial habitat). It also an offence to intentionally or recklessly disturb a hazel dormouse while it is occupying a structure or place which it uses for that purpose.
The dormouse is a Priority Species under the UK Biodiversity Action Plan (UK BAP), and has been adopted as a Species of Principal Importance in England under section 41 of the NERC Act 2006 (section 42 in Wales).
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Dormouse Seasonal Constraints
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Initial surveys for dormice can generally be undertaken at any time of year. However surveys between November and March are limited to searching for evidence of dormice such as characteristically gnawed hazelnut shells (only possible where hazel trees are present) and dormouse nests in dense vegetation. The optimum period for surveys, including nest tube and nest box surveys is between April and October. Please click below to view our dormouse survey and mitigation calendar.
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Dormouse Survey Methods
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A dormouse survey normally begins with a desktop search of available biological records to assess the likelihood of dormoice being present on site or in the vicinity. An initial field survey may then be completed to search for evidence of dormice such as gnawed hazelnut shells and dormouse nests in dense vegetation. Should evidence suggest that dormice may be present, a presence/absence survey would then need to be conducted using artificial nest tubes, nest boxes and nut searches. Nest tubes are placed in suitable habitats and inspected for nests and individuals. Nest boxes can be used in conjunction with nest tubes and increase the likelihood of dormice to support the nest tubes survey.
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Dormouse Mitigation
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Ecological mitigation for dormice may be avoided if it is possible to protect the areas of woodland and hedgerow during the development process. However, if damage, disturbance and removal of dormouse habitat is unavoidable it would normally need to be implemented under a European Protected Species (EPS) licence issued by Natural England. This would require appropriate mitigation to be implemented based on timing and undertaking habitat clearance in such a way as to minimise the risk of harm to dormice, their dependent young, and to hibernating individuals. If the dormouse habitat area is small and there is suitable adjoining habitat (or suitable adjoining habitat is created), it may be possible to encourage the dormice to move away from the area by progressively removing the trees and shrubs in the area under licence.
