Underground sites with suitable conditions for bat hibernation are uncommon and increasingly under threat. But without them some bat species cannot survive. In 2015 David Dodds Associates worked with NWH Group to use a new and unusual approach to preserve one at Middleton Upper Quarry, near Gorebridge, which would otherwise have been lost.
We used acoustic monitoring to work out which tunnels were favoured by bats entering and leaving the disused mine workings at the base of the quarry. Working under a Scottish Natural Heritage (Now NatureScot) license we built up gabion baskets to create a safe route for bats to continue accessing the mine after the quarry was filled in with over 600,000 tonnes of spoil from the Borders Railway. Although the appearance of the site has changed considerably, a section of cliff face above the favoured entrance has been retained and stabilised, acting as a sign-post towards the entrance favoured by the bats.
The position of this entrance within the mine allows warm air to vent naturally, but an additional ventilation pipe has also been installed to ensure that temperature conditions remain suitable should that change.
We're happy to say that the first underground survey, during January 2015 showed that the mine continued to be used by Natterer’s, Daubenton’s and Brown Long-eared Bats. Since then we have continued to monitor the site and it has continued to be used by good numbers of hibernating bats every winter. We're grateful to NWH Group and NatureScot for their support in achieving this.