Dormouse Surveys

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  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • © Arbeco Ltd.

Background

The common or hazel dormouse, Muscardinus avellanarius, is a small nocturnal mammal that is found in deciduous woodland, hedgerows and scrub as well as gardens and conifer plantations. Dormice hibernate between late October and late April.

The Common dormouse is protected by laws which make it an offence to intentionally kill, injure or take a dormouse, possess or control live or dead specimens or anything derived from a dormouse, damage, destroy or obstruct a breeding site or resting place of a dormouse, or disturb a dormouse.

Survey

A dormouse survey would typically begin with a desktop search of biological records to evaluate the likelihood of dormouse being present on site. A walkover survey may then be done to search for evidence of dormouse such as characteristically gnawed hazelnut shells and dormouse nests in dense vegetation.

When it is likely that dormouse are present, it will often be necessary to conduct a nest tube/box survey to confirm presence or absence from the site. Typically a minimum of 50 nest tubes/boxes should be suspended along horizontal branches in suitable vegetation and checked thereafter for dormice and their characteristic nests.

Nest tube/box surveys can be conducted any time during the dormouse active season (April to October). Each month is assigned an index of probability value of finding dormice. The thoroughness of a survey (search effort score) is based on a calculation of index of probability values for the months surveyed and the number of nest tube/boxes used. Natural England recommends that dormouse absence should be considered likely if a search effort score of 20 or more has been achieved without finding evidence of dormouse in nest tubes.

Mitigation

The damage, disturbance and removal of dormouse habitat would typically need to be implemented under a license issued by Natural England, the Countryside Council for Wales, Scottish Natural Heritage, the Northern Ireland Environment Agency, or the National Parks and Wildlife Service (RoI), depending on geographic location. This will require appropriate mitigation which minimises the risk of harm to dormice.

Maintaining habitat continuity and connectivity are other factors that need to be taken into account when planning a dormouse mitigation and compensation strategy. Translocation of dormice to suitable off-site habitats is possible, but should be considered a last resort option.

Arbeco can carry out a dormouse assessment that tells you whether your proposed development may be affected by dormice, and how to resolve any issues arising as swiftly and effectively as possible.

  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • © Arbeco Ltd.
  • © Arbeco Ltd.

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