Bats on the brink 

A century ago, Neda was an iron town. Hardy miners worked deep beneath the earth’s surface, digging out precious iron ore with picks and shovels. Now the miners are just a memory, and the tunnels are dark and damp – but far from empty. Each fall, the fluttering of wings breaks the still silence of the mine as thousands of bats migrate hundreds of miles to hibernate in the old mineshafts. Today, the old iron mine, located just south of Iron Ridge in Dodge County, is one of North America’s largest bat hibernacula.

“Most people don’t realize that Wisconsin is such an important area for hibernating bats,” says Dave Redell, a bat ecologist with the Bureau of Endangered Resources. More than 140,000 bats, including little brown bats, northern long-eared bats, eastern pipistrelle bats and big brown bats, hibernate at Neda each winter.

Why Neda? “The old mine is big enough to host a large number of bats,” Redell says, “and the four miles of underground tunnels provide perfect hibernating conditions.” Hibernating bats require stable temperatures (41 degrees Fahrenheit is ideal), high humidity, good airflow and a private, undisturbed place. Any disturbances can awaken hibernating bats, causing them to prematurely deplete the fat stores they need to make it through the winter.

But while Neda has provided a safe haven for bats for many years, ecologists such as Redell are worried about the bats’ survival. Three wind farms – Butler Ridge Wind Farm in the town of Herman, Cedar Ridge Wind Farm in Fond du Lac County and another near Byron – have gone up within miles of the hibernaculum, and preliminary data suggest the wind towers may be responsible for the deaths of migrating bats. “We’re seeing some of the highest fatality numbers in the U.S.,” Redell says.

A new and deadly disease also has begun attacking hibernating bats, mainly in the northeastern United States. White-nose syndrome, a disease unprecedented in its ability to kill, was first identified in New York State in 2006 and has already killed more than 1 million bats. “Scientists are seeing anywhere from 90 to 100% mortality at affected hibernacula,” Redell says. While the fungal disease has not yet arrived in Wisconsin, experts believe it’s just a matter of time. “White-nose syndrome spread over 500 miles this year,” Redell says. “It’s now about 250 miles from Wisconsin.”

Scientists such as Redell are working feverishly to learn as much as possible about the disease and the state’s bats in the little time they have left. “We know that bat-to-bat transmission occurs, and now we’re trying to see if the environment remains infected,” Redell says.

Nestled deep within the earth, the mines at Neda are a world apart. For years, bats have wintered in their depths, undisturbed. Now experts can only hope that the bats don’t go the way of the miners before them.

Jennifer L.W. Fink grew up hearing stories about the bats at Neda but didn’t visit the mines until 2000. She currently lives in Mayville.

At right: Studying Neda’s bats
Bat ecologists are working to learn as much as they can about Neda’s bats and the threats posed by white-nose syndrome. If the disease arrives in Wisconsin, it could mean widespread loss of the state’s bat population. Fewer bats would mean an increase in some unwanted insect populations that can destroy farmers’ crops and spread illnesses like West Nile Virus.

From the top: Bats are captured using a harp trap at the mine’s exit. Then, they are carefully removed from the nets that hold them. Next, they are placed in paper bags for safe transportation to a field station. At the field station, the bats are inspected, measured and weighed, their gender is noted, and researchers take samples of hair, blood and DNA. Ecologists hope they can get an accurate count of the number of bats in the mine and their current health while keeping an eye out for signs that white-nose syndrome has arrived.

Want to help the bats?
Visit wisconservation.org or send a donation to the Wisconsin Bat Conservation Endowment Fund at:
Natural Resources Foundation of Wisconsin
Attn: Wisconsin Bat Conservation
Endowment Fund
PO Box 2317
Madison, WI 53701