The dormouse, one of the UK’s most charismatic species, has suffered from significant decline over the past 50 years. This arboreal mouse lives in woodlands, hedgerows and scrub habitats, forming nests in the trees and foraging on insects, berries and nuts. They rarely come to ground except when they hibernate, forming nests at the bases of trees in amongst the leaf litter. Dormice receive protection under UK legislation and appropriate licences are required to work with dormice.
Habitat loss and fragmentation have contributed to the severe decline of dormice, which now only occupy small population ranges restricted to southern England and Wales. Clarkson & Woods have considerable expertise and experience in the survey, assessment and protection of dormice. In 2009 we hosted the International Dormouse Conference using a flagship dormouse monitoring project set up by Michael and his father Doug as the focal point.
Dormice can use a wide range of habitats such as woodland, hedgerows and even habitats such as gorse and scrub. Our surveyors can assess the potential for habitat to be used by dormice, generally based upon an evaluation of the suitability of habitat and the connectivity of that habitat to other suitable areas.
Surveys for dormice are conducted using dormouse tubes erected throughout suitable habitat between April and November. This technique was pioneered by Mike Woods some 20 years ago.
Alternatively where fruiting hazel is available it is possible to search for evidence of characteristically gnawed hazelnuts. This technique is rarely reliable to confirm the likely absence of species but if the presence of dormice is considered likely then findings a ‘dormouse nut’ will provide instant confirmation of the presence of the species and is a much quicker and cheaper alternative to traditional surveys.
Other techniques such as the use of footprint tubes and camera traps are also currently in development. We have trialled both with mixed success but we will continue to be early adopters of pioneering techniques in dormouse survey.
Where dormice are encountered on site we provide appropriate advice to protect the species and avoid committing offences.
The clearance of habitat supporting dormouse may need a licence from Natural England, particularly where the extent of habitat is considered ‘significant’ – i.e. likely to affect more than one animal. Obtaining a licence will allow habitat to be cleared and any dormice to be caught and moved into suitable retained habitat. The translocation of populations of small mammals such as dormice is however considered a last result. The translocation process can be extremely stressful and so translocation is typically only considered as a last resort.
Instead we find it is typically better to rely upon the displacement of dormice from suitable habitat into adjacent retained habitat through the use of phased vegetation clearance.
One of the key tools in dormouse mitigation is the creation of new habitat, such as species-rich hedgerows, woodland and scrub land habitats. New areas of planting and connecting up existing, otherwise fragmented habitats can help to ensure the long-term survival of dormice at a site.
Dormouse surveys can require regular site inspections between April and November to confirm presence and/or absence. Due to the long period of time required to complete surveys the requirement can often lead to delays in planning so we advise that these surveys are considered as early as possible within a project.
Nut searches, where feasible, can be completed at any time of year.
Dormouse mitigation work is generally completed during the spring or autumn, generally avoiding the periods when there may be dependent young. Some of the vegetation clearance techniques might also require vegetation clearance over the winter whilst dormice are in hibernation.
After being approached to provide advice to development of a new care home in Somerset Clarkson and Woods were provided with a PEA completed by another consultancy who recommended completing dormouse nest tube surveys. This was problematic as the surveys would have taken approximately 6 months to complete and a planning application submission was planned in 3. We agreed with the local authority ecologist that a nut search at this site would represent a suitable alternative technique given an abundance of fruiting hazel and the limited potential for impacts upon dormouse resultant from the development.
We decided to do a thorough in-depth nut search within the adjacent woodland and in one afternoon were able to confirm the presence of dormice. This allowed the application to be prepared on time and for appropriate mitigation measures to be designed to allow the progression of the project.
Clarkson & Woods were appointed by the Eden Project, Cornwall to undertake baseline species surveys and provide advice and ultimately deliver a licensed mitigation strategy with regards to a proposed geothermal power plant. Surveys identified presence of dormice within the wet woodland and scrub habitats, part of which required clearance to enable construction of the power plant. A licensed sensitive habitat removal approach was used, using two-stage winter and summer clearance.
Construction of a multi-phased commercial estate within Wellington, Somerset required licensed mitigation and habitat creation to compensate for removal of hedgerow supporting hazel dormice. This involved the successful translocation of hedgerow as well as planting of wide, native woodland and scrub margins. Monitoring of this habitat has since recorded numerous dormice successfully using the nest boxes installed across the site, with the population maintained at its favourable conservation status.