White-Nose Syndrome Devastates Bat Colonies

by Nina Fascione, Executive Director of Bat Conservation International and Mylea Bayless, BCI White-Nose Syndrome Response Coordinator

Bat conservationists throughout North America are holding their breath this winter, waiting nervously for the grim news of spring: how much farther has white-nose syndrome (WNS) spread and how many more bat hibernation caves will be littered with the bodies of bats killed by this tragic disease?

WNS has killed at least one million bats—and probably far more than that—as it has raced across the eastern United States since appearing in a single New York cave in the winter of 2006. Since then, each winter’s end has brought word of new species and new states facing the devastation of WNS. Last spring, its front lines expanded an astonishing 980 miles. Despite tireless efforts in biology labs and in the field, scientists are still unable to cure this infectious wildlife disease or slow its relentless spread.

The disease and/or the fungus that’s linked to it (and is the likely cause) has so far hit nine bat species in 14 states and two Canadian provinces. The endangered Indiana bat has been hammered by WNS, and the fungus was recently confirmed on endangered gray bats. Two endangered subspecies, the Virginia and Ozark big-eared bats, are also at imminent risk. Recent research predicts that WNS will likely drive even the once-common little brown bat into regional extinctions. We are struggling against the most precipitous decline of North American wildlife species in a century. The future for hibernating bats looks grim.

The fungus was found last winter on a bat in the Oklahoma panhandle. If the pattern of infection continues, WNS is poised to move into the American West and expose a whole new community of bat species to mortality rates that approach 100 percent at some sites.

To appreciate what that mortality rate means, consider Vermont’s Aeolus Cave. Long considered the most important hibernation site in New England, this cave sheltered tens, perhaps hundreds, of thousands of bats each winter. Then WNS arrived. Boston University graduate student Jonathan Reichard visited Aeolus Cave in January 2009:

“As we approached, the snow was packed with scavenger tracks. Bat wings were scattered on the landscape,” he said. “There was a clearing with tracks of a crawling bat terminating in wing and talon prints of a bird. Bats circling by the cave would crash to the ground and tumble head over heels into the pile of dead bats right in front of the cave. A tufted titmouse scavenged dead bats, eviscerating carcasses just outside the cave. Bats were frozen to ice stalagmites, seemingly having attempted to climb to high ground and to take flight after crashing to the ground.”

A survey last March counted 112 living bats in Aeolus Cave. The impact of such devastation will be felt for decades to come. Bats are long-lived for their size, often with lifespans of 20 years or more. But they reproduce very slowly. Females of most species give birth to a single pup each year. Decimated bat populations are unlikely to recover to pre-WNS levels in our lifetimes—if ever.

The ecological and economic impacts are uncertain but could be immense. Bats are primary predators of night-flying insects, including many that carry disease, damage forests, and attack farm crops. One of the most damaging is the corn earworm moth, blamed for $1 billion in damages to various crops worldwide. Recent research in south-central Texas found that Mexican free-tailed bats consume so many of these pests that they save farmers up to $1.7 million a year in pesticide costs for a crop valued at about $6 million.

White-nose syndrome takes its name from Geomyces destructans, the cold-loving fungus that typically appears on the faces and wings of infected bats. This previously unknown fungus is believed to be transmitted primarily from bat to bat—an enormous problem for animals that often migrate hundreds of miles each year. Circumstantial evidence suggests humans may inadvertently carry Geomyces destructans into previously uninfected sites, which has led some federal agencies to restrict non-essential visits to bat hibernation caves in many states. Extensive decontamination protocols to clean clothing and equipment meticulously between visits are required or strongly recommended for everyone entering caves used by bats.

Twenty-five of the 46 bat species in North America get through the cold winter months, when their insect prey are not available, by hibernating. They gorge on insects to build fat reserves in the fall, then gather at “hibernacula”—mostly cold caves or abandoned mines—to wait out the winter. Their metabolism slows dramatically and body temperature plummets so their fat stores will last through the winter. They briefly arouse from hibernation a few times each winter, and these natural arousals can burn through most of their stored energy.

Bats afflicted with WNS arouse much more frequently than normal through the winter. Anything that increases these arousals, such as disturbances by humans or WNS, can deplete their stockpile of fat before the winter ends and the insects return. This causes bats at WNS-infected caves to exhibit very unbat-like behavior. They are often seen flying around in daytime in midwinter, apparently searching for insects that are not around. They freeze or starve, leaving their emaciated bodies in or near their hibernation caves.

Urgent research by scientists around the country has revealed a great deal about white-nose syndrome, but solutions are elusive. Some fungicides are able to kill Geomyces destructans, but caves are remarkable ecosystems that are rich with diverse, often rare organisms. Treating bat caves with toxins would almost certainly destroy those cave ecosystems. The Nature Conservancy hopes to build an artificial cave in Tennessee to serve as a safe haven for hibernating bats and a test bed for research. Other treatment or isolation options are being pursued by biologists around the continent, but much work remains.

Scientists, meanwhile, will likely discover in coming months whether the WNS fungus, which thrives in cold temperatures, can also work its damage in the warmer climates of southern states. WNS has so far been found only in the cold caves and abandoned mines used for hibernation. Some southern species, however, hibernate in hollow trees, bridges, buildings and cisterns. Will the disease hit these sites? Many questions remain unanswered.

Bat Conservation International (BCI), through its white-nose syndrome grants program, has provided initial funding that allowed a range of urgent research projects to get under way quickly. We were key organizers and funders of a series of annual WNS Science Strategy Meetings that brought together scientists and wildlife managers to share research results and set priorities.

Our funding efforts are focused now on carefully targeted priorities and on the emerging WNS national strategy. We are working to identify critical research gaps in which our funding can make a difference. BCI is also working closely with federal, state and private groups to set and implement standardized guidelines and priorities for WNS surveillance, monitoring and mitigation.

BCI and AWI, as part of a collaborative group of non-governmental organizations, are working to secure significant federal support for WNS research and mitigation. In May, we submitted testimony, endorsed by 60 conservation organizations, to congressional committees requesting urgent funding to deal with WNS. Working closely with AWI, we recently visited Washington, DC, to strategize with other leading nonprofits and to make the case for additional funding with key congressional aides.

Convincing much of the public—and public officials—that they should care about the bats disappearing from their night skies is a challenge that BCI has been meeting for almost three decades. Few animals are as misunderstood and needlessly feared as bats, the victims of countless myths in folklore, books and movies. More than 1,100 bat species fill vital roles in maintaining the health of ecosystems and human economies around the world. Their loss would have catastrophic impacts.

We must find a way to end this unprecedented threat to bats, and that requires real funding from Congress and from private foundations and donors. An incredibly dedicated group of scientists and conservationists are working valiantly to solve this heartbreaking puzzle. The cost of failure is disastrously high.

To learn more about bats and white-nose syndrome, visit www.batcon.org.

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