Deep beneath the bustling city of Frankfurt (Oder), a hidden world thrives within the Fledermausquartier Brauereikeller. This isn’t your typical brewery tour. This is a journey into the heart of one of Germany’s largest and most important bat wintering grounds. The Fledermausquartier Brauereikeller, housed in the ruins of the 19th-century Ostquell Brewery, isn’t just a historical relic. It’s a sanctuary. In the dimly lit caverns, where the air hangs heavy with the scent of damp earth, thousands of bats cling to the crumbling walls and ceilings.
The Ostquell Brewery, abandoned in 1950, might have been demolished if not for the bats and the dedicated citizens who rallied to protect them. In 1989, a citizen’s initiative formed to preserve the brewery ruins, recognizing their importance as a bat habitat. This grassroots effort resulted in the site’s initial protection as a bat sanctuary by the Frankfurt (Oder) district council in 1989 and 1990. The ruins of the Fledermausquartier Brauereikeller whisper tales of brewing history intertwined with the fluttering wings of these nocturnal creatures. The upper floors, once used as storage for adhesives, paints, and varnishes, now offer additional nooks and crannies for the bats to explore.
The true heart of the Fledermausquartier Brauereikeller lies in its extensive cellar. Spanning over 1,150 square meters, this subterranean labyrinth consists of seven large, vaulted chambers, some reaching heights of up to 8 meters. The temperature within the cellars hovers around a cool 5 degrees Celsius with near 100% humidity. These conditions, coupled with the brewery’s proximity to the Oder River and its location on the Oder slope, create an ideal microclimate for bats. The first bat count in 1987 recorded a modest 250 individuals. By the late 1990s, after conservationists secured the ruins, the numbers soared to around 2,500. Today, the Fledermausquartier Brauereikeller typically hosts between 1,500 and 2,000 bats each winter.
Among the more than 30 bat species documented at the Fledermausquartier Brauereikeller, the Greater Mouse-eared bat holds a prominent position. In fact, the brewery ruins represent the largest known wintering ground for this species in all of Germany. Interestingly, researchers believe the majority of these Greater Mouse-eared bats originate from western Poland. Four bat species are consistently present throughout every winter: the Greater Mouse-eared bat, the Natterer’s bat, the Daubenton’s bat, and the Brown Long-eared bat. Their numbers vary, with the Greater Mouse-eared bat always appearing in the greatest abundance. Conservation efforts have been ongoing since 1988. From installing protective fences and repairing locks to negotiating with developers and establishing buffer zones, these efforts demonstrate a commitment to safeguarding this vital bat haven. Even the construction of a nearby parking garage was modified to minimize disturbance to the bats’ flight paths and hunting grounds.
The Fledermausquartier Brauereikeller stands as a testament to the power of community action and the importance of preserving urban wildlife habitats. Today, thanks to ongoing restoration work, the roof is secure, supporting beams reinforce the structure, and some cellar walls have been insulated against frost to ensure the bats’ comfort. The exterior now boasts nesting boxes for swifts and additional niches for bats, demonstrating the ongoing commitment to the creatures that call this place home.