Bat Bunker

Paul Waterhouse,  Assistant Field Officer Breckland

Those of you who have visited East Wretham Heath will have probably noticed a number of buildings and bunkers dotted around the reserve. These are remnants of East Wretham Heath's former life as an Air Field during the Second World War and are a very important reminder of the reserves and our own history. The buildings themselves are not obtrusive but are in fact very subtle and seem to blend into the landscape of the reserve. Over the years they have turned from harsh military building into valuable habitats of their own, supporting a wide range of flora and fauna. 
There is one bunker in particular that the Brecks team have made some minor alterations to, with the intention of creating bat hibernaculum. Ten of the UK’s fourteen bat species have been recorded in the Brecks and research suggests that artificial or man-made structures are becoming more and more important as hibernation sites for a number of these species.
 

The transformation from air raid shelter to bat bunker only took one day and the materials came in well under £100. The first job was to create artificial bat niches in the bunker including bat bricks and wooden structures, which will provide roosting habitat. 

We then covered the floor of the bunker with sand and gravel which will help to maintain humidity. Both temperature and humidity are important factors in a bat hibernaculum, along with darkness and lack of disturbance. 

There were initially two entrances to the bunker: the one you can see in the photo and also an escape hatch. In order to prevent a draught running through the hibernaculum, which is another unfavourable factor, we had to block off the escape hatch. Finally we covered the main entrance but without forgetting to leave a gap to allow bats to access the bunker. 

I don’t think this renovation project will be making Grand Designs, but these simple changes could provide a valuable habitat for species such as Brown long-eared, Daubenton, Natterer’s and Barbastelle.