Brown bat

A little brown bat with white nose syndrome. Bats in the Osceola region do not appear to have been infected with white-nose syndrome, but DNR biologists won’t know for sure until test results are back from the lab in late spring.


Nearly a century and a half after Veit Geiger sold his last batch of brew, researchers at the Department of Natural Resources have taken an interest in the beer-aging caves he carved into an Osceola bluff, which now serve as a winter home for bats.

Biologists with the Wisconsin DNR’s Bat Program believe the man-made caves could eventually help them learn to manage white-nose syndrome (WNS), a relatively new disease facing America’s bat population.

Hibernating bats infected with WNS burn through their fat reserves before winter is over. Some die of starvation, others freeze when they fly from their winter quarters to look for food.  

For now, local bat populations appear to be free of the disease, according to Jennifer Redell, a conservation biologist and specialist in caves and mines with the Bat Program. Redell and other researchers examined bats at the site in January as part of their annual field surveys. They won’t know for sure whether bats at the Geiger site have avoided WNS until they get results back from lab tests, usually in May.

“I’ll be really curious to see what happens in Osceola because it’s one of the last regions in the state to be infected,” said Redell. “Lab results are pending and we’ll know more in late spring.”

Redell and others at the Wisconsin DNR are part of a national effort to mitigate white-nose syndrome that began in 2009 and includes trials for treating and managing the disease. 

The Geiger caves could one day serve as a trial site for WNS treatments. 

Redell explained, “A man-made site could potentially be decontaminated or altered in some other way due to fewer concerns about effects of treatment on a sensitive established cave ecosystem.” 

Caves, in general, are critical to bats’ winter survival.

“During summer days they roost in bat houses, trees, barns and occasionally attics,” Redell said. “However, from October through May each year their insect diet is no longer available and the onset of cool fall weather drives bats to use an amazing survival strategy — hibernation.”

But unbeknownst to bats, many caves have become hazardous in recent years, infested with a fungus that colonizes on them as they hibernate, turning their muzzles and wings white. The fungus, Pseudogymnoascus destructans, thrives in cool caves and mines. Redell noted that P. destructans is an invasive species, likely from Europe or Asia. Scientists have not yet figured out how to treat it or prevent transmission.

The spores are likely spread in the fall, as bats fly from cave to cave.

“We call it the fall swarm,” said Redell. “They’re visiting multiple caves, mating, and increasing their social activity. … So it’s spread right before they go into hibernation.”

Wisconsin is home to seven bat species, four of which hibernate through the winter, lowering their body temperature to around 50 degrees, slowing their heart rate to four beats per minute, and taking a single breath every 12 minutes, according to Redell.  

Three of the four hibernating species — little brown, eastern pipis-

trelles and northern long-eared bats — can be found at the Geiger site. These and the big brown bat, which also hibernates, are all threatened by white-nose syndrome. 

WNS was first detected in New York in 2006, and spread quickly across the eastern United States, bringing death to more than 6 million bats. The disease was first detected in Wisconsin during the winter of 2014. 

In August 2015 an iron gate was installed over the small remaining entrance to the Geiger caves. Bats can still come and go, but humans can no longer get in – unless they have a key. 

The gate ensures the bats are left alone as they hibernate, but biologists with the DNR’s Wisconsin Bat Program creep inside each winter to survey the population and monitor for white-nose syndrome.

“We look for the fungus or unusual behavior,” said Redell. “We also do a swab test where we test for the genetic signature for the fungus.”

She said they consider the Geiger site fairly important, and encouraged locals to install bat houses by May, when the furry, winged creatures typically emerge from hibernation. 

And just in case anyone is considering opening a local brewery under the Geiger moniker, Redell offered a suggestion for the name of the first batch: Brews Wayne.

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