Pillbox used in D-Day preparations is given new lease of life as a home for bats

Today, Dunwich Heath and Beach is a peaceful wildlife haven but during the Second World War, it was a militarised zone that provided a vital training area for the British army.

In 1943, the heath featured trenches, minefields, barbed wire and anti-tank measures designed to mimic German defences. It was known as Exercise Kruschen and was one of the most significant military exercises of the time, helping British armed forces to test the ways that German defences could be breached in preparation for D-Day, when Allied troops successfully ‘landed’ in occupied Europe.

80 years on, only a small percentage of these structures still remain on the heath, which was acquired by the National Trust in 1968.

Dunwich Heath is now a place of tranquility and peace and a highly designated habitat, home to many special and protected species including the Dartford warbler, nightjar, woodlark and antlion.

In 2011, bat surveys carried out at Dunwich Heath recorded nine different species of bat - half of the 18 species found in the UK – and some are now roosting in part of its remaining military heritage: a converted German-style pillbox.

Regular monitoring and surveys have recorded healthy populations of a number of different bat species, including Pipistrelle (Common, Soprano and Nathusius), Brown Long-eared, Noctule, Serotine, Daubentons, Natterer’s Bat and the Barbastelle, which is considered one of the UK’s most vulnerable species.

In 2012, Sue Morgan, a qualified ecologist and licensed bat worker for Natural England, teamed up with the Dunwich’s Property Operations Manager, Richard Gilbert, who was then Area Ranger, to assess whether one of the few remaining German-style pillboxes, located at the southern end of the heathland, could be used as a potential roosting site.

Permission was granted to modify the pillbox to create a hibernaculum – an underground chamber that provides a stable temperature and moist humidity for bats to roost in, creating shelter and reducing the risk of interference from other mammals.

To do this, Richard and a team of conservation volunteers repaired and sealed the existing apertures to help stabilise the environment, before creating a few new slits for the bats to use as access. They also installed specially designed bat bricks for the bats to crawl into.

Since then, Brown Long-eared and Natterer’s bats have been found to roost inside, with regular checks carried out. The most recent survey, conducted in February 2024, revealed that the former pillbox is currently home to several Brown Long-eared bats.

This year, the team at Dunwich Heath are planning further improvements to the hibernaculum, including installing a monitor to better gauge the moisture and temperature levels inside.

The team will also be hosting bat walks on Saturday 13 July and Saturday 17 August, which will include an evening walk around the heath and a chance for visitors to learn more about the different species that live there.

Richard Gilbert, Property Operations Manager at Dunwich Heath and Beach, says: “Dunwich is not just heathland – it's scrub, woodland, wetland, margins and coast, which makes it the ideal habitat for an incredible and diverse range of species, including the nine species of bat we've been able to identify over the past 10 years.

“Converting the pillbox into a hibernaculum has been a fantastic way to honour Dunwich’s lasting heritage. Lots of visitors are surprised by the significant contribution the heath made to the D-Day landings, and 80 years on, the pillbox is one of the very few remaining Second World War structures we have here.

“By repurposing it into a bat hibernaculum we’ve been able to not only extend its legacy but also encourage nature to thrive and support the wider biodiversity of the heath and woodlands.”

Angus Wainwright, Regional Archaeologist for the National Trust, said: “It was great to work with Richard and his team to bring together the preservation of an important historic structure with the conservation of some threatened species. It is a really good example of the National Trust’s holistic approach to managing its sites.”