Bacon Hole, on the Gower Peninsula, is one of most remarkable sites in Wales.
It’s a cave of national significance both for its archaeology – including Upper Palaeolithic cave art and historic inscriptions, and its ecology – it’s an established hibernation roost of several protected bat species.
In 2024, the National Trust appointed Ecology Group business, Wildwood Ecology to support the installation of a security grille by providing bat licensing support. The grille installation was critical to prevent unauthorised access, conserve prehistoric artifacts, and protect the cave’s bat population.
Although planning permission was not required, the site’s location within an Area of Outstanding Natural Beauty and its importance for bats – including greater and lesser horseshoe bats, brown long-eared bats, Myotis species, and pipistrelle species – meant that a European Protected Species licence from Natural Resources Wales (NRW) was required. Wildwood Ecology provided specialist ecological support from summer 2024 through to the successful installation of the grille in autumn 2025.
The solution
The project presented significant practical challenges. Standard bat survey methods couldn’t be used due to the risk of static bat detector damage from unrestricted public access, and emergence surveys were ruled out on health and safety grounds, given the cave entrance’s position on steep, unstable cliffs above the sea, preventing night-time working.
Rather than allowing these constraints to stall progress, Wildwood Ecology worked closely with NRW to develop a pragmatic, evidence-led licensing strategy built on robust historic monitoring data collected by the local bat group volunteers since 1991. It’s this data that established the cave’s long-term importance as a bat roost and informed a precautionary approach to bat presence during the summer months.
The design of the grille itself was carefully considered. Wildwood Ecology provided detailed input on bar spacing, positioning, and materials to ensure bats could continue to access the cave freely, while preventing unauthorised human entry. Given the physical constraints of the entrance, the grille was installed at the beginning of the rear chamber to protect the most archaeologically and ecologically sensitive areas – requiring close coordination between ecologists, archaeologists, and specialist access contractors.
All works were conducted under ecological supervision. Works were timed to avoid the winter period to prevent disturbance of hibernating bats. Grille components were fabricated off-site and brought into position by rope access to minimise disturbance, and a pre-start briefing (‘toolbox talk’) and full cave inspection were carried out before works began. When a greater horseshoe bat was observed roosting in the main chamber during installation, works were carefully managed around it, with continuous monitoring by an Ecological Clerk of Works to ensure the bat was not disturbed. A lockable access point was incorporated into the final grille design to allow ongoing monitoring by licensed bat group volunteers.
The impact
The security grille has successfully reconciled two important objectives: protecting nationally significant archaeological features while preserving a well-established bat hibernation roost. By securing the most sensitive areas of the cave, the works have meaningfully reduced disturbance to hibernating bats without restricting their access to the wider cave system.
Early monitoring results are encouraging. In the first winter following installation, 30 greater horseshoe bats were recorded – including individuals using the newly protected rear chamber. To avoid additional disturbance, ongoing monitoring will not be done by ecologists but will continue to be carried out by local bat group volunteers, under agreement with NRW, ensuring that any changes in bat usage can be identified and responded to promptly.
Wildwood Ecology remains engaged with the project, providing advice as needed to ensure the long-term preservation of the cave’s archaeology, the bats, and value for the client.