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White-nose syndrome: Questions and Answers

Why are bats dying in North America?
An estimated 6.7 million bats have died since 2006 because of an outbreak of white-nose syndrome, a fast-moving disease that has wiped out entire colonies and left caves littered with the bones of dead bats. The epidemic is considered the worst wildlife disease outbreak in North American history and shows no signs of slowing down. It threatens to drive some bats extinct and could do real harm to the pest-killing services that bats provide, worth billions of dollars each year, in the United States.

What is white-nose syndrome, and how does it kill bats?
White-nose syndrome is the result of a fungus called Pseudogymnoascus destructans that invades and ingests the skin of hibernating bats, including the wings. It causes bats to wake up more frequently during the winter, using up their limited fat reserves very rapidly. Massive destruction of wing tissue may lead to disruption of bats' water and electrolyte balance, and it could be the actual cause of death. Some bats may survive a winter with white-nose syndrome only to subsequently succumb in the spring, when their immune systems kick into overdrive, attacking the fungal invader and their own tissues at the same time. Dead or dying bats are frequently observed with a white fuzz around their muzzles, hence the name “white-nose syndrome.”

How deadly is it?
Typically, the disease kills 70 percent to 90 percent of bats in an affected hibernaculum (the area where bats gather to hibernate for the winter). In some cases, the mortality rate has been 100 percent, wiping out entire colonies. Some caves that once hosted hundreds of thousands of bats are now virtually empty.

Where did the fungus come from?
The fungus appears to have been introduced to North America from Europe. It has been found on cave bats in 12 countries in Europe, where bats appear to be adapted to, and unaffected by, the fungus. Because bats do not travel between the continents, this strongly suggests the fungus was newly introduced to North America by people — likely cave visitors who transported it on their gear or clothing. This pattern is reminiscent of the spread of diseases that ravaged American Indian people when Europeans first colonized. White-nose syndrome was first discovered in North America in upstate New York in February 2006, in a cave adjoining a commercial cave visited by 200,000 people per year.

Does it affect all bats in North America?
So far, white-nose syndrome appears to affect only bats that hibernate, which make up about half of the 45 bat species in the United States. Pollinating bats and long-distance migrants that don’t hibernate don’t seem to be affected.

How many bat species have been affected, and which ones are they?
Eleven species (including four endangered species) have been affected by the disease or are immediately threatened by it. The disease has affected: the big brown bat, eastern small-footed bat, Indiana bat (endangered), gray bat (endangered), little brown bat, northern long-eared bat and tricolored bat. The fungus has also been found on the cave bat, southeastern bat and Virginia big-eared bat (endangered). Other endangered bats living in areas where the fungus is present are Ozark big-eared bats.

Where has white-nose syndrome been found?
The disease has been confirmed in 25 U.S. states and five Canadian provinces: Alabama, Connecticut, Delaware, Georgia, Illinois, Indiana, Kentucky, Maine, Maryland, Massachusetts, Missouri, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Vermont, Virginia, West Virginia, Arkansas, Wisconsin and Michigan in the United States and New Brunswick, Nova Scotia, Ontario, Prince Edward Island, and Quebec in Canada. The fungus causing the disease has also been found in Iowa, Oklahoma, Minnesota and Nebraska. See an animation of the disease’s spread 20062011.

How many bats have died?
An estimated 6.7 million bats have died in North America.

How does this disease spread?
It is passed from one bat to another, or from the cave environment to bats, but it also likely spreads when people inadvertently carry it from one cave to another on their shoes, clothes or equipment.

Are there ways to stem its spread?
Yes. One of the most important is to close caves and abandoned mines to all but essential human travel. The Center for Biological Diversity filed a petition in January 2010 to close all caves and abandoned mines on federally controlled lands in the lower 48 states. . Keeping all but essential human activity out of caves also reduces disturbance of vulnerable hibernating or roosting bats. If people must go into caves for research, monitoring or safety reasons, they should always follow the latest decontamination procedures, which are developed by the U.S. Fish and Wildlife Service.

Have enough caves been closed?
No. Although there have been widespread cave closures in the eastern United States, where the disease is most prevalent, land managers in the West — where the disease is expected to arrive soon — have yet to take the threat of this wildlife crisis seriously. Although some caves in the West have been closed, it’s not nearly enough to slow the spread of this deadly disease.

Is there a cure?
No, but researchers are learning more about how the disease kills bats, which is an important step toward developing an effective treatment. Also, European bats appear to be immune to the fungus, and finding out why could provide vital clues to a cure for North American bats.

Is the federal government doing enough about this wildlife crisis?
No. The response to white-nose syndrome has been slow, and the resources for research and management have been scarce.  While important scientific study is happening, much more is needed. Meanwhile, most federal land agencies in the western United States have still not implemented widespread emergency cave closures or decontamination requirements, and some are even back-tracking on earlier measures to reduce the risk of human transport of the deadly fungus.

Why are bats important?
Bats account for about one-fifth of all mammals on Earth and provide enormous ecosystem services. One of the most important is controlling insects. A single bat can eat thousands of insects in a single night.

Do bats have an economic value in the United States?
Yes. Bats consume millions of pounds of night-flying insects each year and help keep in check bugs that are problematic for agriculture and forestry. A recent study found that the value of bats’ pest-control services in the United States ranges from $3.7 billion to $53 billion per year.

Could some bat species go extinct?
Yes. Of particular concern are those bats already on the endangered species list, including the Indiana bat, gray bat, Virginia big-eared bat and Ozark big-eared bat. A 2013 study by federal scientists found that Indiana bats are likely to disappear from the majority of their range within a decade. Even the little brown bat, one of the most common bats in North America, is in trouble. A leading bat scientist said in 2010 that the little brown bat is “in imminent danger of extinction” in the Northeast by 2016, because of white-nose syndrome. The Center and others have requested that the government review the little brown bats’ status in light of the disease. The Center has also petitioned for the endangered species listing of the eastern small-footed bat and northern long-eared bats.

What can I do?
Become a Bat Advocate. We need your help to save America’s bats from this deadly disease. By lending your voice to this effort, you’re letting Congress, the president and other decision-makers around the country know something must be done now to address this unprecedented wildlife crisis. You can start today by writing a letter to the editor of your local newspaper, liking our Facebook page and sharing it with friends and family.

Photo courtesy of New York Department of Environmental Conservation