Tens of thousands of bats now reside in the ruins of what was the largest and arguably the most technologically advanced fortification ever designed by Nazi Germany.
The Ostwall Fortification – A.K.A. the Festungsfront Oder-Warthe-Bogen, or Międzyrzecki Rejon Umocniony, in German and Polish, respectively – was built by the Nazis in the years 1934-38 between the Oder and Warta rivers, near the town of Miedzyrzecz Poland. The Nazi Defense line consisted of approximately 100 concrete “pillboxes” interconnected by a sprawling network of underground tunnels, spanning over 40 kilometers from its northern to southernmost points, and approximately 12 kilometers at its widest points from East to West. The underground system originally held railway stations, engine rooms and barracks to house approximately 24,000 Nazi soldiers.
The Ostwall Fortification was supposed to serve as a bulwark to hold off invading forces from Russia. Had it been fully staffed by the time the Vistula Oder Offensive reached the defense line, perhaps it might have done just that. As it was, there were less than a thousand Nazi soldiers manning the base by January of 1945, and Stavka’s troops tore through the barricade like a pit bull on PCP chewing apart a couch cushion fortress. One of the largest defense perimeters ever constructed by the Nazis took less than 72 hours to fall.
Nowadays, up to 37,000 bats of over a dozen different species call the Międzyrzecki Rejon Umocniony home between the months of October and April, according to Jan Cichocki, zoologist at the nearby University of Zielona Gora.
Cichocki, has spent the last year exploring the labyrinth of black tunnels in an attempt to catalogue and count the legions of teeming bats, said that the former Nazi superbase is an ideal bat habitat, at least in the wintertime.
“The area is perfect because of a steady temperature and humidity,” Cichocki added.
Winter temperature in the underground base sits right around 7 – 10 degrees Celsius (45 – 50 degrees Farenheit) while maintaining almost 90 percent humidity in some spots. For a bat looking for a comfortable place to bed down for the winter, it doesn’t get much better than that.
While the winter weather packs the greatest number of bats into the Ostwall Fortification, thousands remain in the Nazi catacombs all year round. Myotis myotis, or the greater mouse-eared bat, is one of those perennial residents. With an average weight of just over 1 ounce, and slightly larger than a house mouse in size, myotis myotis is one of the largest European bats. They prefer to cluster together in large groups, and in the Ostwall tunnels, some of those clusters number in the thousands.
Waking a bat prematurely from its nocturnal slumber can induce a state of shock, and sometimes even kill it. For this reason, Ostwall now functions as a wildlife preserve.
“You need a permit to enter. It’s our way of protecting the bats against vandals and tourists,” Cichocki said. Tourists may visit, and have been in increasing numbers lately, but most of the cyclopean Nazi base, and its black arterial underground filled with the papery rustling of bats, lie somewhere behind a barrier of padlocked gates.