White-nose syndrome sweeps state
MANITOWOC - It’s a population most of us don’t think much about, but the number of bats in Wisconsin is taking a nose dive.
Environmentalists attribute the sudden loss to white-nose syndrome, a fatal disease that’s passed from bat to bat.
The deadly disease traveled east to Wisconsin in about 2014, and some counties have lost an estimated 90 percent of their bat population.
Manitowoc County also has seen a drop, and officials at the Woodland Dunes Nature Center are helping state wildlife experts track the number of bats in the area.
The Two Rivers nature center is among 30 sites throughout Wisconsin voluntarily monitoring bats for the state Department of Natural Resources. Jessica Johnsrud, assistant director and education coordinator for the center, tracks bats five times throughout the summer for the DNR and the federal government. She also hosts information meetings and bat walks for the public, the next in early October.
Four hibernating bats in Wisconsin are affected by white-nose, including little brown, big brown, tricolor and Northern long-eared.
“We mainly have little brown and big brown bats in Manitowoc,” Johnsrud said. “The numbers are pretty low.”
White-nose syndrome was first detected in the state of New York in the winter of 2006-07 and has since spread to 31 states and five Canadian provinces, according to J. Paul White, conservation biologist with the DNR.
The disease is named for the white fungus that infects the muzzle, ears and wings of hibernating bats.
Scientists with the U.S. Geological Survey’s National Wildlife Health Center discovered and named the fungus that causes the disease and pioneered lab techniques for studying the effects of fungus on hibernating bats.
No known cure exists for the disease, but experts are working on a vaccine that may protect bats.
Humans may also unknowingly spread the fatal fungus, White said.
But while New York first was hit with the disease, which invaded from Europe, a decade ago, Wisconsin officials were first bringing bat counts into the 21st century as part of an overall wildlife plan. The state is home to eight bat species overall, White said, and before this, the state relied on anecdotal sittings and museum records to keep track.
The DNR began training people to use equipment that tracks acoustical sounds that humans can’t hear; bat calls, like bird calls, have distinct nuances that allow scientists to detect different bat species. This allows citizen volunteers to track bats non-intrusively. They spend about an hour at twilight, when bats are most likely to move, tracking the animals.
“We aren’t going to teach hundreds of people in the public to capture bats with a net,” White said. “And physical tracking can take four to six hours a night. This is definitely a way for wider bat tracking.”
Wisconsin, with the help of the U.S. Fish and Wildlife Service, has one of the most active monitoring programs in the country, he said.
Johnsrud said the Woodland Dunes Nature Preserve is a great place to track bats.
"We try to plant native plants, things that will attract insects, which attract bats,” she said. “And we do have bat boxes. I’m trying to educate people about bats and why they’re important. We want to see what’s on the preserve. Bats have an important role in pest control, especially moths and mosquitos.”
Little brown bats can eat 600 to 1,000 bugs in an hour and eat their body weight in a night, she said. “What happens if they’re not here?" she wondered.
She submits a sound file to the DNR to help determine the different sounds from the survey, which helps scientists estimate the number and types of bats in an area and ways numbers change over time.
“We monitor in June, July and August when bats tend to be the most active,” Johnsrud said. Although Manitowoc County doesn’t have a huge bat population, she believes numbers are going down.
Maribel Caves in Manitowoc has been another bat survey site. Sheboygan, New London and the University of Wisconsin-Green Bay have also served as tracking sites.
In northeastern Wisconsin, sites in Door County have noticed the biggest decline in bats, possibly up to 90 percent, White said, although those numbers are difficult to determine since tracking equipment has become more sophisticated over the years.
Three areas in Wisconsin with the biggest bat populations have seen significant loss — one in Dodge County and two in Pierce County, he said.
Since Wisconsin only recently began tracking bats, it’s difficult to pinpoint the impact of white-nose, but the loss of a population that eats insects is bound to affect the state’s $88 billion agriculture industry.
“What happens if you remove the top predator from the landscape?” White said. “We don’t quite know.”
Environmentalists are studying places where bats thrive and where they struggle and working to keep unaffected sites clean. Some bats seem to be immune to white-nose, he said.
White encourages people to report sick or dead bats to the DNR. And he said if they do a survey and don’t get any sounds, that’s important, too.
“If there had been bats in an old barn or cave and now they aren’t detecting any, that’s valuable information,” he said.
He encourages people to participate in programs such as the Woodland Dunes’, saying “For an hour survey, you can get a great idea of what the bat population is like.”
If you go
The Woodland Dunes Nature Center and Preserve, 3000 Hawthorne Ave., Two Rivers, is hosting a bat monitoring demonstration from 6:45 to 7:45 p.m. Oct 2. Johnsrud will host a walk and use equipment that detects echolocation calls that immediately identifies the species of bats. Rain date is Oct. 3, and registration is required by Sept. 29. Visit http://www.woodlanddunes.org for details.
DNR bat information: http://wiatri.net/Inventory/Bats/
Bat surveys in Wisconsin: http://wiatri.net/Inventory/Bats/Volunteer/Results/
An example of an acoustic bat survey completed by Jess Johnsrud and others in Two Rivers (2015): http://wiatri.net/Inventory/Bats/Volunteer/Results/2015/RT3383_21Jul15.pdf
Donation information: http://wiatri.net/inventory/Bats/donate.cfm
White-nose syndrome information: https://www.whitenosesyndrome.org/
Map showing the origin and spread of WNS throughout North America: https://www.sciencebase.gov/gisviewer/wns/