Bardney Limewoods Dormouse Project
The Bardney Limewoods National Nature Reserve in central Lincolnshire, declared under Section 35 of the Wildlife and Countryside Act in 1997, is owned and managed by the Forestry Commission with advice on (particularly local) conservation matters provided by a Management Advisory Group. In 2002, the MAG was offered the opportunity to take part in Natural England’s (then English Nature’s) ‘Species Recovery Programme’ for dormice by receiving a number of pairs, providing that sufficient volunteers were available to undertake the initial release and subsequent monitoring. ESL has provided volunteers for specialist surveys and habitat design and management since declaration, and already having licensed personnel, therefore undertook to manage the dormouse project.
The dormice arrived in July 2002; they came from three different licensed breeders and were selected so that none of them were related to any other, thus maximising the gene pool among the founders. Each animal arrived in its own personal nest box and a male and a female – who had not previously met! –were settled into each release cage.
The release cages were set up, about 100m apart, in ancient coppiced woodland. Every evening for two weeks food and water were provided to the mice by a rota of volunteers. The standard fare was peanuts, sunflower seeds, a slice of apple and half a rich tea biscuit, but most volunteers supplemented this: grapes became popular with some mice but tomatoes were not and the favourite treat was found to be an occasional early blackberry. After two weeks the cages were opened so that the mice could move out, but feeding continued for another week.
Towards the end of the feeding period, 180 nesting boxes were erected in the adjacent woodland. The boxes were numbered and set up in a grid, 20m apart. Once they were free to explore their new home, some of the mice moved out immediately, but others returned to the release cages for several days. All dormice were ‘chipped’ so that they could be recognised as individuals when caught again.
Since 2002 the boxes have been checked by licensed volunteers monthly between May and October. Dormice found are sexed and weighed, litters are counted and their age is estimated. For the first three years each adult dormouse was also examined with a chip-reader, but no chipped dormice were found after 2004.
These surveys show that the population is healthy and a record litter of 6 young was found in 2007. All release cage and nesting box locations are stored on a GIS so that movement and habitat preferences (eg age since last coppice cut) can be examined. At the end of 2006, with the help of Lincoln University students from Riseholme campus, transects and quadrats were set out for use in hazel-nut-hunting: dormice have a unique way of gnawing these nuts open, so providing signs of their presence outside the boxes.
To check the suspicion that the mice had moved out of the release woodland, a further 80 boxes were erected in adjacent areas in 2006 and from 2008 up to 40 tubes have been deployed annually in boundary scrub and along hedges leading out of the release woodland.
In 2002, all mice were found in the release area, but their chips showed that they didn’t stay near their own cages; moves of 100m+, involving ride-crossings (both at that time believed not to happen) were not uncommon. By 2003/04 a southward spread, both down the wood edges and the central ride, was being recorded and by 2005/06 movement along the western boundary had become very pronounced, with a litter born nearly 0.5km from the nearest release point. By this time the mice had also moved out of ancient woodland into conifer plantation. In 2007/08 came proof that the mice have crossed the main hard-surfaced extraction road, and the exciting find of a ‘wild’ nest in brambles, again among conifers, out to the east. At the same time they are also shown to have moved north, out of the woodland completely into an area of adjacent bramble scrub.
Monitoring within the NNR woods will continue, but the focus has now turned to assisting the animals to spread naturally out into the surrounding country, via hedgerow creation and enhancement schemes, and eventually into other woods. A further introduction into a second suitable ancient woodland, also within the NNR but some kilometres from the first release site, is now under discussion. With global warming making winters too warm for hibernation in the south, this spread may give dormice their best chance of survival, and will mean that the project has succeeded.