Hanging out at K+S for a winter

The bat bunker is only six months old. You can't see it from the outside: On the site of the former Niedersachsen-Riedel potash plant in Uetze-Hänigsen, east of Hanover, nature has quickly overgrown it since this spring. Bernd Rose looks around: “The surroundings are generally good for bats,” he says. His eyes fall on the shaft's old pile. “There are lots of flowers there, which means lots of insects and that in turn means lots of food for bats.”

Bernd Rose is on the Board of Executive Directors of the Burgdorf, Lehrte, Uetze e.V. Nature and Biodiversity Conservation Union (NABU) and is also the bat representative for the Hanover region. He is holding a large bunch of keys in his hand, dozens of keys jingling. One of them is for the new bunker on the factory premises in Riedel, secured with a massive padlock from old Bundeswehr stocks. So that nobody can disturb the bats during their hibernation. It is the 65th winter roost for bats that Bernd Rose will be helping to look after.

K+S has had an old water tower demolished on the grounds of the Riedel site. Thomas Müller from K+S's Inactive Plants unit explains: “A secondary condition of the demolition was that we had to create replacement roosts for bats for the summer.” This was achieved with several wooden crates under a gutter on an existing building. “These are nursery roosts in which hundreds of pipistrelle bats can give birth to their young,” says bat expert Bernd Rose. The young then fly out after four weeks. The roosts also serve as summer quarters for the animals, as well as mating quarters in the fall.

"As the protection of bats is important to K+S, we have created a winter roost in addition to the ancillary provision,” says Mine Management Engineer Thomas Müller. An excavator was used to dig a pit, 3x3-meter-long concrete pipes were pushed into each other, then earthed over and planted. Bernd Rose then took over the interior work, bricked up the entrance and installed a small door. The animals themselves find their way inside through an opening that is only the width of a hand.

The conditions in the bunker are ideal, says Bernd Rose: high humidity and a constant 2 to 6 degrees in winter. He has hung up perforated bricks, sealed on one side with a little cement, so that the animals feel comfortable. The bats instinctively crawl into the holes and hang upside down to protect themselves from predators. The floor of the bunker is under water, fed by an old satellite dish. It catches some of the rain and channels the water into the bunker via a pipe. Moisture is important to prevent the bats' wings from drying out during hibernation. “I guarantee you: There will be a bat hibernating here in the winter of 2025/26 and then there will be more every year,” says Bernd Rose optimistically.

Why is bat conservation important? Bat expert Bernd Rose also has an answer to this question: “Bats regulate the insect population.” If there were too many insects, this would be detrimental to agriculture, for example, also because more pesticides would have to be used.

Did you know that...

• a common pipistrelle eats 3000 midges per night? That corresponds to a third of its body weight.
• there are 25 species of bat in Germany? 22 of them are threatened with extinction.
• bats are long-lived? In the wild they usually live for several years, in captivity even up to 30 years. Their immune system reliably fends off viruses and cancer cells.
• there are a total of 1460 bat species?
• three quarters of all bat species feed on insects?
• bats spread around the world during the Eocene 50 million years ago?
• bats use their own echolocation to orient themselves at night? Nevertheless, they also have good eyesight.

Some of our native bat species are threatened with extinction. One of the causes is the lack of suitable winter roosts. Bats are dependent on frost-free roosts such as caves, mine tunnels, rock cellars or old bunkers. The Higher Nature Conservation Authority at the Kassel Regional Council is also working closely with local nature conservation associations to open up such roosts for bat protection and, if not available, to create hanging places. On the initiative of K+S employees, K+S converted two former air-raid shelters at the Wintershall site into bat roosts in November 2020. The bunker is an example of successful species protection by K+S, authorities, and environmental protection organizations. 

A new bat bunker was also built at the Friedrichshall spoil tip in 2020. An old bunker that had served as a winter roost for bats and small animals for around 40 years had to be removed as part of the process of covering the slag heap there. The replacement roost was created together with the NABU local group Burgdorf, Lehrte, Uetze and fitted with perforated bricks and species-appropriate entry slots.