May 3, 2011
MADISON - A recently completed statewide survey of known bat wintering sites in Wisconsin showed no sign of white-nose syndrome, a fungus that kills bats by invading their skin and depleting their energy reserves during winter hibernation.
The invasive fungus currently exists in 18 states and four Canadian provinces and has been linked to the death of more than one million bats since 2007. White-nose syndrome (WNS; scientific name Geomyces destructans) has been confirmed within 190 miles of Wisconsin, well within the dispersal range of Wisconsin's most common bat species, the little brown bat.
"It is a relief to not find any signs of the disease in Wisconsin this winter, but it is likely only a matter of time before it does appear," said David Redell, a bat ecologist with the Department of Natural Resources. "Since it is a near certainty WNS will show up, possibly as soon as next winter, we are moving rapidly to survey our known bat colonies, seek out and document new colonies and develop plans aimed at minimizing the spread and effects of white-nose syndrome in Wisconsin."
Bats congregate in large numbers during winter weather in Wisconsin hibernacula (caves and mines). As many as 300,000 bats winter in the state with up to 143,000 in a single hibernaculum in east central Wisconsin. Redell says the arrival of white-nose syndrome in a large colony like this could easily kill many thousands of bats and spread the fungus to other bat populations as surviving bats emerge in spring to carry the fungus to other locations.
Survey crews monitored more than 100 possible hibernacula in the state representing more than 90 percent of the known underground locations over the winter of 2010-11. Redell says this effort represents one of the most extensive and thorough surveillance efforts in North America. The DNR has been aided in this endeavor by private landowners protecting sites, commercial cave operators educating their visitors, and recreational cavers practicing decontamination of their gear.
DNR staff and partners also are working to establish volunteer agreements with hibernacula owners, hold stakeholder meetings and increase the number of outreach and education programs. Scientists and others working on the problem will concentrate on coming up with workable and effective solutions for the disease when it arrives, hopefully saving as many bats as possible for recovery efforts.
Protecting hibernation sites in Wisconsin is important because of the state's high concentration of bats.
"Wisconsin has one of the highest concentrations of hibernating bats in the Midwest," said Redell. "Bats from our neighbor states Illinois, Indiana, Minnesota, Iowa and Michigan spend winters here so anything that happens to our hibernacula has far reaching impacts on the summer landscape."
A recent study, published in the journal Science, summed up the potential impacts that loss of our bat populations might produce. The cooperative study, authored by scientists from the University of Pretoria (South Africa), U.S. Geological Survey, University of Tennessee and Boston University, estimate that pest-control services provided by insect-eating bats in the United States range from a low of $3.7 billion to a high of $53 billion a year. Bats also eat mosquitoes, which are not only pests but can carry deadly diseases like the West Nile Virus, and harmful invasive species such as gypsy moths.
Wisconsin currently is home to four species of at-risk cave bats. The little brown bat, the northern long-eared bat, the eastern pipestrelle and the big brown bat all have suffered drastic declines in states where bats have become infected with WNS, with losses approaching 100 percent of cave bat populations. A mortality rate this severe means that these cave bat species face a very real threat of extinction.
A single little brown bat, which has a body no bigger than an adult's thumb, can eat 4 to 8 grams (the weight of about a grape or two) of insects each night according to the Science researchers. This amount represents the entire body weight of each individual bat, which is equivalent to a 100 pound human eating about 400 quarter-pound cheeseburgers every night. In terms of the number of insects eaten it adds up--the loss of the one million bats in the Northeast has probably resulted in between 660 and 1320 metric tons of insects no longer being eaten each year by bats in the region, say the Science authors.
"The lost consumption of this amount of insects could have many effects to the economy and ecosystem services these animals provide," adds Redell. "In addition to agriculture, insects impact forest and human health. More than two-thirds of all bat species in the world are insect-eaters which includes all 8 species of insectivorous bats found in Wisconsin."
People can learn more about how to help Wisconsin bats by visiting the Saving Wisconsin Bats page on the DNR website.
FOR MORE INFORMATION CONTACT: David Redell - (608) 261-8450 or (608) 212-8719