Preserving a bat hibernation site
Middleton Quarry in 1945.
In 2015, David Dodds Associates undertook an project to preserve a crucial bat hibernation site at Middleton Upper Quarry, near Gorebridge. This project highlights the importance of protecting underground sites suitable for bat hibernation, which are increasingly rare and under threat.
The Challenge
The disused mine workings at the base of Middleton Upper Quarry were set to be filled with over 600,000 tonnes of spoil from the Borders Railway project. This posed a significant threat to the bats using the site for hibernation. We needed to balance the needs to the Border Railway Project, while protecting the bats who return to this site year after year.
Our Approach
While this project took many months, it can be broken down into four areas of work:
Middleton Quarry before filling.
#1 Identifying Key Entrances
We used acoustic monitoring techniques to identify the tunnels favoured by bats for entering and leaving the mine. From here we could prioritise the entrance that was most significant for the local bat populations.
#2 Keeping a Signpost for the Bats
A section of cliff face above the favoured entrance was retained and stabilised, serving as a natural sign post for bats returning to the site after it was filled in.
#3 Protecting the Entrance
Working under a NatureScot license, we constructed gabion baskets to create a safe route for bats to continue accessing the mine after the quarry was filled.
#4 Maintaining the Conditions
We installed an additional ventilation pipe to ensure suitable temperature conditions within the mine, complementing the natural warm air venting. This was vital for ensuring the mine continued meeting the conditions needed for hibernating bats - it needed to stay cool, humid, and stable throughout the winter months.
The protected entrance to the hibernaculum.
Results and Ongoing Monitoring
The first underground survey in January 2015 confirmed that Natterer's, Daubenton's, and Brown Long-eared Bats continued to use the mine for hibernation. Subsequent annual monitoring has shown consistent use by good numbers of hibernating bats each winter!
Why This Matters
Hibernation sites are crucial for bat survival. They require specific conditions:
Stable, cool temperatures (typically 2-8°C)
High humidity levels (usually over 80%)
Protection from disturbance
By preserving this site, we've ensured the continued survival of multiple bat species in the area.
This project's success was made possible through collaboration with NWH Group and support from NatureScot. It demonstrates how industry, conservation experts, and government agencies can work together to protect vital wildlife habitats.
For more information on bat surveys and conservation efforts, explore our other blog posts or contact our team of ecologists below: