WNS Fungus: Mystery Syndrome Is Wiping Out America's Bats

Dec 9, 2015· 6 MIN READ

batsThe scenario sounds like a science fiction plot. A deadly disease appears mysteriously in the New York countryside in 2006 and spreads, infecting thousands, then hundreds of thousands, making a white fungus grow on the body of whatever gets it… before killing it.

It creeps into neighboring states. Vermont. New Hampshire. Massachusetts. More areas report cases; after infecting much of New England, the disease crawls south. Over the next three years it spreads, then picks up speed. Virginia reports infections. West Virginia. Maryland. Delaware. Tennessee. Other states and two Canadian provinces find it. In a final disturbing development, the disease makes a geographical jump all the way into Missouri.

“We don’t see any end in sight,” says Diana Weaver, spokeswoman for the Northeast Region of the U.S. Fish and Wildlife Service, when asked how far the epidemic could go. Even for those who aren't lovers of small, winged creatures, the implications are clear: they remove millions of insects from the environment yearly, and without them, bug populations are likely to rise.

Meanwhile, more than one species could face extinction.

“We don’t know of anything that has been such a wildlife crisis in memory,” Weaver said.

Photo: Marvin Moriarty/U.S. Fish and Wildlife Service

The creatures in the crosshairs: bats. Afflicted by a mysterious disease called "white nose syndrome," (WNS) they are being wiped out in stunning numbers and could be removed from the Eastern U.S. in a short few years.

One of the most ominous elements: scientists are not precisely sure what, exactly, is killing them.

The broad name of the disease says a lot about how little it is understood. Once contracted by a bat, the affliction leads to erratic behavior, early waking from hibernation and, in more than 90 percent of cases, death. The name comes from a white fungus that grows on the muzzles, wings, and limbs of the bats.

Is it the fungus that's killing them? It’s suspected, but not yet conclusively proven, says Alan Hicks, a bat specialist from the New York Department of Environmental Conservation who has studied the outbreak since its beginning.

Though shrouded in unknowns, the basics are these: WNS has killed 90 percent or more of the bats in much of the Northeast in less than five years, and continues to kill nearly every bat it infects. And the disease is quickly spreading in several directions.

In essence, most bats in the Eastern United States are at risk right now.

“Serious risk,” Weaver says. “Especially since we have no way of stopping it.”

Deadly Disease

The origins of white nose syndrome can be traced to upstate New York, where it was first found in 2006, and where bats first started dying off. It’s unknown just how the malady began. Some suspect the fungus was somehow imported from Europe, where it also infects bats, though to what degree has not been fully studied, Hicks says.

Photo: Greg Turner/Pennsylvania Game Commission

The fungus lives independently of the bats in the caves where they hibernate (i.e. it can survive without them) and has a couple of insidious qualities: it is quickly and easily spread bat-to-bat, but can also be moved in dirt—say, if a caver traps spores in his boots and tramps them into a new cave.

The fungus loves the cold and damp, thriving in places where bats are vulnerable—their winter hibernation caves, also called “hibernacula.” It also appears to infect bats indiscriminately of their subspecies.

Once a bat is infected, the effects are well documented but not fully understood.

“It appears that the fungus causes some kind of skin irritation, and they will wake up and groom themselves more frequently [during hibernation],” Weaver says. Bats with WNS will also do “erratic things,” such as flying around the cave when they should be sleeping, and stationing themselves near the mouth of a cave, exposed to the cold, instead of in more sheltered areas.

Though a combination of such factors is thought to be what kills the bat, Hicks says more and more evidence points to the conclusion that the fungus itself is lethal.

“It’s a brand new thing,” Hicks says. “If it is the fungus, it’s the first time we’ve ever had a fungus that’s actually killing mammals in any substantial numbers.”

The syndrome's lethality is beyond any doubt. Hicks says comprehensive surveys of caves in his area, the epicenter of the disease, show that by last year 93 percent of the bats in his region had been killed since 2006—and he expects the 2009-2010 figures to push the toll even higher.


“I think if there’s anything that shakes my confidence a bit, it’s the speed at which this is moving,” Hicks says. 

Photo: Map Courtesy Bat Conservation International

A look at the map of confirmed WNS sites shows a sweeping path of transmission from the epicenter in New York to areas as far north as Canada and as far west as Missouri. Generally following a southwestern line down the spine of the Appalachian Mountains, the syndrome now has Ohio, Arkansas, Illinois and Indiana directly in its path. In April, Iowa preemptively closed some of its caves to public foot traffic to help prevent the spread there.

For other areas, it appears to be too late. This year in West Virgina, bats were seen flying out of the state’s most populous bat cave, a place called Hellhole, in the middle of winter. Bats that were captured in January and tested were confirmed to have WNS, putting some 200,000 hibernating bats at risk.

Researchers hope the broad plains of the Midwest might halt the westward spread of WNS, but while that's possible, in April, Quebec confirmed cases of WNS, opening a northern route to the Western states, Hicks says.

Major unknowns remain. Will warmer climates stop the fungus? Will different bat species better resist it? Nobody knows, but officials at Bat Conservation International, based in Austin, Texas, where tens of millions of free-tail bats roost, hope so.

Those free-tails, says BCI Director of Publications Robert Locke, right now appear to be relatively safe, because WNS to date has only been killing hibernating bats—though Hicks adds nothing can be ruled out with such a new and fast-moving disease.

“What we know is that the bats that die from it are all hibernating bats,” Locke says.

Free-tails might not die from it, but they can, potentially, carry spores elsewhere. As migrating bats, the fear is that they could transmit the disease hundreds of miles south into Mexico, Locke says, causing outbreaks there.

Greater Implications

So what happens if vast populations of bats continue to die off? The first answer is a rise in insect populations, particularly night-flying insects, which include a number of species known to be pests.

Photo: Ryan von Linden/New York Department of Environmental Conservation

A single bat, Hicks pointed out, can eat almost half its weight in insects every night; a single cave's healthy population can eliminate literal tons of bugs every night in summer months.

“Everyone thinks of mosquitos, and while bats do eat them, a greater proportion of their diet is in beetles and moths,” Weaver says. Many of those insects are agricultural pests, which means crops and forests could see harsher effects from infestations—or a bat demise could lead to a greater use of pesticides.

“Do not underestimate the value of bats as consumers of insects,” Locke says. 

What’s Next

Over and over, when asked about the true scope and potential threat of WNS, officials say it is hard to overstate the peril.

Could an isolated fungus really lead to the extinction of bats in the east or on an even greater scale? Really?

“Well…” says Weaver with a slight hesitation. “Yes, it’s entirely a possibility. Within the short term, we’re looking at that possibility.” She also notes that some of the money her office received from its national headquarters recently was from a “preventing extinction” pot of cash.

Hicks is without pause on whether WNS has the potential to render bats extinct in the East. 

“Yes, I really think it does,” he says. “There are a million things that can happen to prevent it...[but] they haven’t happened yet, or if they have it’s not obvious to us...but yeah, the potential is absolutely there.”

Locke is unequivocal.

“We could have mass extinctions of hibernating bats,” he says.

At last count, about a million bats were estimated to have already died from WNS, a number that has surely gone up by now. The threat is so severe that researchers have already captured and attempted to create a captive breeding program for one endangered bat species in the disease’s path, the Virginia big-eared bat.

Photo: Greg Thompson/U.S. Fish and Wildlife Service

But the experiment was highly problematic: fewer than 10 of the original 40 bats captured in the fall survived past March. The program was so unsuccessful that one watchdog group charged that it was mismanaged. The Fish and Wildlife Service investigated and quickly determined that the handlers, at the Smithsonian’s Conservation and Research Center, had met their “compliance criteria.”

In another effort, researchers are sampling and preserving bats’ DNA to save as a record in case species go extinct, says Weaver. That’s how serious things are.

To combat the problem, experts say their only efforts are to try to contain the disease—because there is no treatment for it. But moves are underway to study and fight the disease: last year Congress appropriated $1.9 million to battle WNS, and last week the Fish and Wildlife Service granted $450,000 of that cash to natural resource agencies in 23 states to coordinate response and monitoring.

Photo: N. Heaslip/New York Dept. of Environmental Conservation

Still, the sheer speed and deadliness of WNS is working against these efforts.

“This disease is moving remarkably fast, and it’s killing a remarkably high percentage of animals, I mean, damn near all,” Hicks says. “This is something new for folks in terms of how serious the problem is and how quickly it’s spreading.”

What You Can Do

Avoid Spreading WNS
Stay out of mines or caves where bats are known to hibernate. Hikers and cavers can spread the white nose fungus. Check out more information here.

Report Unusual Bat Behavior to your natural resources agency. Find a local one here

Some of those state agencies offer conservation classes and activities, such as bat counts.

Help out Bat Conservation International’s Rapid Response Fund.