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 their 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, as well as in China. The European and Chinese bats appear to be adapted to, and unaffected by, the fungus. Because bats do not migrate between North America and Europe or Asia, 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?
Thirteen species (including three on the federal endangered species list ) have been affected by the disease. The following species have been infected by white-nose syndrome: little brown bat (once the most common bat in the eastern United States), northern long-eared bat (threatened), tricolored bat, Indiana bat (endangered), the big brown bat, eastern small-footed bat, and gray bat (endangered).  The fungus has also been found on, but has not yet infected, a number of other species, including the cave bat, southeastern bat, Virginia big-eared bat, and silver-haired bat.

Where has white-nose syndrome been found?
The disease has been confirmed in 34 U.S. states and seven Canadian provinces, from coast to coast.  In March 2016, white-nose syndrome was found on a dying bat in Washington state —a jump of 1,300 miles from the closest known location of the disease. 

How many bats have died?
In 2012, the U.S. Fish and Wildlife Service estimated 6.7 million bats had died in North America. Many more bats have died since that estimate was made.

How does this disease spread?
It is passed primarily from one bat to another, or from the cave environment to bats, but it also likely spreads when people inadvertently carry it from one bat roost to another on their shoes, clothes or equipment. The jump of the disease from the Midwest to the West Coast in spring 2016 was almost certainly due to human-caused transmission.

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, and to mandate decontamination procedures for anyone who may come into contact with bats or bat roosting sites. 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 on federal lands in the eastern United States, where the disease has been most prevalent, land managers in the West — where the disease was first documented in spring of 2016  — have yet to take the threat of the spread of this disease seriously. Although some caves in the West have been closed, there are still no rules mandating decontamination on most public lands, and it's not nearly enough to slow the spread of this deadly disease.

Is there a cure?
Not yet. Some promising interventions are being researched, such as naturally occurring bacteria that seem to limit the growth of the white-nose fungus. However, these treatments need to be carefully tested before widespread release in the environment, to make sure they'll actually be helpful, and not cause more stress to either bats or the ecosystems in which they live.

Is the federal government doing enough about this wildlife crisis?
No. While important scientific study has happened, containment strategies for the disease have fallen far short of what they could and should be. Despite scientific evidence that the white-nose fungus is capable of persisting on gear, in caves, and in other environments for years, and can readily be transmitted by people from one bat roosting site to another, most state and federal land agencies have still not implemented widespread cave closures on public lands, or required decontamination procedures for recreational cavers, commercial caves, or others who may come into regular contact with bats and their roosting and hibernating sites.

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 bugs in check that are problematic for agriculture and forestry. A 2010 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. The northern long-eared bat is perhaps the hardest hit of all bat species affected thus far. It has declined at rates of 99 percent or greater in several eastern states, and its entire 37-state range in the United States is now almost entirely encompassed within the zone of white-nose syndrome. The Center petitioned for the northern long-eared bat and the eastern small-footed bat to be listed on the federal endangered species list in 2010. The U.S. Fish and Wildlife Service listed the northern long-eared bat as threatened in 2015, but unfortunately, the agency backpedaled from its original recommendation that the species be listed as endangered, due to political pressure from industry and conservative politicians.

A 2013 study by federal scientists found that Indiana bats are likely to disappear from the majority of their range within a decade. The little brown bat, once one of the most common bats in North America, is now extremely rare in the Northeast, and continues to die in the Midwest. The Center sought its listing in 2010. The first bat discovered to have white-nose syndrome on the West Coast was also a little brown bat.

What can I do?
Become a Bat Advocate by joining our e-network. 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.

Bat photo by Marvin Moriarty, USFWS