Deadly bat disease found in Crawford County

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By Ted Pennekamp


The deadly bat disease white nose syndrome is now in Crawford County. Winter surveillance in 2014-15 for white-nose syndrome has been completed, with 75 bat hibernacula visited for disease surveillance throughout Wisconsin.

In total, 14 sites in eight counties have been confirmed with either the disease-causing fungus or white-nose syndrome. Bats at sites in Grant, Crawford, Richland, Door and Dane county have tested positive for white-nose syndrome, while the fungus known to cause the disease has been confirmed at sites in Iowa, Dodge and Lafayette counties.

White-nose syndrome has spread to four additional counties from 2014 to 2015.

The original point of infection in Grant County has experienced an overall population reduction of 70 percent from pre-whitenose syndrome estimates. At this time, this is the only affected location with a noticeable difference in population resulting from white-nose syndrome. Owen Boyle, Wisconsin DNR species management section chief, said that with the past year, white-nose syndrome killed an estimated 700 of the 1,000 bats hibernating in an abandoned lead mine in Grant County. In 2014, the mine became the first place in the state where the disease was detected. Boyle said that the reason that “only” 70 percent of the bats at the site have died of the disease is probably because it is relatively new at the site. 

“It will probably be two or three years when we will see larger mortality events,” said Boyle, who noted that 95 percent of bats with white-nose syndrome have died as the disease has spread from the eastern part of the United States and worked its way west. “Wisconsin was kind of like an island for awhile,” said Boyle who noted that Michigan, Canada, Illinois and Iowa had cases of white-nose syndrome before Wisconsin did. Boyle said that the white-nose syndrome in Door County shows that the disease there likely came from the Upper Peninsula of Michigan.

Boyle said that losing large portions of the bat population would be losing native species and part of our natural heritage. DNR wildlife biologist Dave Matheys agreed, saying, “It would be part of our eco-system that is no longer present.” There are four species of bats listed as threatened in Wisconsin; little brown bats, big brown bats, the eastern pipistrelle and the northern long-eared bat. The northern long-eared bat is also on the federal threatened species list, said Boyle.

In addition to having responsibility for stewardship to help keep native species, losing the bat population has other consequences as well, namely huge increases in insects. “They provide free pest control, essentially,” said Boyle. With fewer bats to eat insects, Wisconsin and Crawford County can expect more damage to crops and forests. Also, there may be an increased threat to humans through insect borne disease such as West Nile Virus which is spread by mosquitoes. 

Wisconsin has one of the largest cave-dwelling bat populations in the Upper Midwest with an estimated 350,000-500,000 hibernating here in the winter. Each bat can eat 500 to 1,000 mosquito-sized insects in an hour. The economic impact could be devastating. According to a study by the National Wildlife Health Center, insect suppression because of bats is worth between $4 billion and $50 billion each year to agriculture in the United States.

Dave Matheys said that scientists have been making some progress in fighting white-nose syndrome by finding ways to break down the fungus that causes it. “Progress is being made. There is a glimmer of hope on the horizon,” he said.  

Although winter hibernation is over, the Wisconsin Department of Natural Resources will continue to review public reports and respond to wildlife mortality events in order to monitor the health of Wisconsin’s bat population.

White-nose syndrome is a deadly bat disease that, among other things, can cause bats to frequently wake from hibernation - this can deplete energy reserves and lead to starvation and dehydration, or death due to exposure before the end of winter. The syndrome was first detected in Wisconsin in Grant County in March 2014, and does not affect people or other animal groups.

Next steps in ongoing 

efforts to save bats

Efforts to control the human-assisted transmission of the fungus remain in place, including strict decontamination requirements for researchers and cavers, and efforts to educate commercial cave and mine visitors to help ensure they do not transport the fungus to other caves or mines. Every hibernaculum owner who allows visitors to their site has a white-nose syndrome plan in place.

The department has been actively exploring effective management strategies and continues to monitor bat populations and conduct research to fill information gaps. Through two Wisconsin Bat Program citizen-based monitoring projects, volunteers are helping to gather crucial data on bat population trends.

How citizens can help, including reporting sick or dead bats

Wisconsin citizens can help by continuing to avoid disturbing bats, especially during hibernation. It is important to remember that visitors to caves and mines could potentially transfer the fungus between sites, regardless of whether bats use the site for hibernation. If you are planning to visit a cave or mine, be sure to check with cave owners and follow white-nose syndrome procedures in place at any specific site.

People who observe sick or dead bats, especially between October and March, are encouraged to report them to DNR. A reporting form and instructions for how to safely collect carcasses of dead bats can be found on the department’s Wisconsin Bat Program website.

For more information regarding bats in Wisconsin, interested persons can visit and search keyword “bats.”

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