A Sad Tale's Best for Winter
~
White-Nose Syndrome Casts an Icy Shroud over the East's
Bat Populations
First published in the January/February 2014 issue of
Virginia Wildlife magazine
~
White-Nose Syndrome Casts an Icy Shroud over the East's
Bat Populations
First published in the January/February 2014 issue of
Virginia Wildlife magazine
A twitch, a twitter, an elastic shudder in flight
And serrated wings against the sky,
Like a glove, a black glove thrown up at the light,
And falling back.
~ D.H. Lawrence, “Bat”
Horror in Hailes Cave
In the winter of 2006-2007, in upstate New York, an endangered species mammalogist named Al Hicks was working at his desk when he received an alarming call from a colleague who had been investigating reports of bats in flight, something inconceivable during the harsh, insect-free winter months. Hicks is an expert on the Northeast’s bat species, many of which are declining due to habitat loss, pesticide poisoning, and the disturbance of their caves during winter hibernation. He has participated in nearly every winter survey of bat caves (“hibernacula”) for the past 30 years and has a profound respect and empathy for the furry little flyers that many people shrink away from. Hicks loves bats: their graceful flight, their incredible echolocation abilities, their habit of cozily bundling together among the pallid stalactites of the caverns Hicks knew so well to spend the winter in a deep, dreamy torpor.
Something in his colleague’s voice that day jerked Hicks away from his computer screen and made him clench the receiver in his fist. The team had been surveying Indiana bats tiny mouse-eared insectivores weighing about as much as three pennies. It was always mildly worrying to survey for Indiana bats, which have been federally listed as endangered since 1967. The local populations were lucky if they remained stable year to year, never mind increasing in numbers. And now the nightmare of every dedicated conservation biologist had come true, in hideous detail.
Hicks listened in dismayed astonishment as the survey team reported what they were looking at: thousands upon thousands of dead bats, Indianas among them, littering the floor of Hailes Cave, one of the East’s most populated hibernacula with over 15,000 colonial bats of multiple species. Forming a ragged leathery carpet spiked with tiny bones and teeth, the dead bats stretched far down into the cave’s darkened throat. A shallow subterranean stream ran down into that underworld, and every single stone that jutted from the water was layered with dead and dying bats, most of whose faces or wings seemed to be swathed in a ghostly white substance. The clusters of bats still hanging overhead were not swaddled in frost and deep slumber as they should be in wintertime; instead the ceiling was undergoing a terrible convulsive writhing, seemingly alive and in agony.
Appalled, the survey team quickly withdrew from Hailes Cave. As they watched in amazement bats continued to fly out after them into the 20°F air, circling randomly over the three feet of fresh snow on the ground before being driven by the biting wind back into the cave. Around them, hundreds of bats had simply expired in midair and fallen silently into the snow, as the tracks of dozens of foxes, coyotes, raccoons and fishers attested. Crows and ravens crowded the brooding trees, waiting for their feast to resume. As the crew began their dismal trek back to the trailhead they saw seven red-tailed hawks slowly circling the cave entrance, picking off weakened bats one after another. If a short dive failed to result in a capture the hawks would decline to pursue; they understood that they wouldn’t have long to wait for fresh victims to emerge.
This wholly unnatural behavior seemed to involve the eerie white dusting on the naked faces and wing membranes of Hailes Cave’s traumatized bats, a feature never encountered before. In the weeks ahead it became apparent to Al Hicks that bats hosting this strange fungal growth were afflicted with an extremely high rate of mortality: 80 to 97 percent of bats in local caves were missing from their customary hibernacula and, given the extreme cold and nonexistence of nourishing insects, were presumed dead. Al Hicks labeled the new disease white-nose syndrome (WNS henceforth) for the sallow mold covering furless areas of the victims’ bodies, and he realized at once that he was dealing with an almost inconceivably bad situation. “The poor little things, they couldn’t fly out and they couldn’t stay in,” Hicks recalls in sorrow. “They didn’t have a chance in the world.”
The Dead of Winter
The gruesome vista first glimpsed eight years ago in upstate New York has now repeated itself with numbing familiarity throughout the East and Midwest: WNS is thought to have killed more than 5.7 to 6.7 million bats in eastern North America, spreading its ghastly pall over 19 states and four Canadian provinces. A previously unknown pathogenic fungus, Pseudogymnoascus destructans, was eventually demonstrated to be the cause of WNS. A “psychrophilic” organism – meaning it is particularly suited to cold temperatures – the P. destructans fungus disrupts the deep torpor of hibernation and seems to create a persistent epidermal and possibly metabolic disturbance, causing infected bats to consume critical energy reserves at inopportune times during the winter in a desperate attempt to rid themselves of the irritation. Evidence of WNS can be seen in bats clustered near entrances of hibernacula and flying aimlessly about during the day. Later phases of the disease reveal dead and dying bats on the ground or hanging like tattered rags from buildings and trees.
The more scientists learn about WNS the more appalling it becomes. The fungus attacks bats by boring hyphae, tough thin filaments sprouting from the fungal body, into and through the bare facial skin and wing membranes as it infiltrates the host body. Infected bats resist this affront with their immune systems, and that’s where WNS kicks in. A new hypothesis postulates that infected bats may suffer from Immune Reconstitution Inflammatory Syndrome, an affliction previously known only in HIV-positive humans, wherein the bats’ bodily defenses wreck havoc on their own thin skin, creating bloody chancres around the hyphae intrusions that eventually eat entirely through the dermis. Biologists recount harrowing encounters with dying bats creeping along the cavern floor using their bared elongated wing bones as spectral fingers to pull their bodies forward. In time the animals literally fall apart, like victims of advanced scurvy, and those colonial outliers who don’t succumb to dermal rot soon starve to death wrapped in the remnants of their flightless wings.
One of the greatest obstacles to countering the WNS plague has been the fact that the disease is caused by a species of fungus previously unknown in the Western Hemisphere. P. destructans is native to Eurasia, and the molecular process that triggers WNS in North American bats is the same as that which occurs in Eurasian bats, but the latter have evidently evolved defenses that make them largely immune to WNS. If these evolved defenses can be understood then perhaps vaccines or biological treatments may be developed that mimic this natural immunity.
But how long will that take? With each winter’s thaw revealing heaps of dead bats littering cave entrances from Minnesota to Georgia, Arkansas to Prince Edward Island, time is very much of the essence. Any genetic treatment of WNS, however, “is likely a long ways off,” says Katie Gillies of Bat Conservation International, the country’s foremost advocate for flying mammals. “We are just at the point of placing this fungus [P. destructans] in the correct genus,” she says. “Now, we have to sequence the genome of several closely related fungi, identify which genes create virulence, then determine a way to turn that off and churn out the ‘silenced,’ altered fungus. This is a really, really, long process, and the end result is years out.”
Is a Cure Even Possible?
In the spring of 2013 a federal assessment of bat survival rates published in in the scientific journal PLoS | One presented a grim outlook if WNS continues its deadly rampage. Among the findings was that the federally endangered Indiana bat had declined 30 percent since the introduction of WNS; given this animal's scattered colonies and low numbers before the plague, this represents a potentially fatal decline in genetic diversity.
The disease’s distressingly rapid transmission is thought to be due to both humans and bats. “Voluntary decontamination significantly reduces the fungal load on (caving) gear,” says Katie Gillies. “We know that people can easily transmit fungal spores. So cleaning our gear according to effective decontamination protocols reduces the fungal load and our capability to transmit those spores.” Federal and state-owned caves are typically closed to all but permitted researchers during the wintry hibernation months, but the great preponderance of accessible caves in the US lie on private land, and these landowners could play a critical role in protecting their stricken colonies from outside contamination.
Contamination from humans, that is. Bats can fly hundreds of miles, carrying spores and fungi with them from cave to cave. Add to that the fact that P. destructans can remain dormant for years in abandoned caves because the fungus is not an “obligate” of bats (meaning it can live elsewhere, like in the soil), and so like starlings, influenza, and the creeping kudzu vine, it will apparently remain an unwelcome but permanent component of the North American ecological landscape. Working under this assumption, some are calling for the wholesale chemical treatment of remaining hibernacula while there are still bats to save.
Craig Stihler is a wildlife biologist with the West Virginia Division of Natural Resources. “It’s been very, very frustrating, but we’ve got to consider the entire cave ecosystem before we act,” he cautions. “We can’t just go into caves and start spraying fungicides around because we’d be killing beneficial fungi along with P. destructans, plus that would poison the groundwater and negatively affect cave invertebrates that are even rarer than bats.” The best we can hope for, Stihler says, is to buy time for the onslaught to somehow bypass remnant bat populations from which future colonies can be grown once a cure is discovered … or more likely, once the epidemic has simply run its course. “There’s not much on the horizon that will lead to treatment,” Stihler says with resignation.
As with other Eastern states that enjoy cold winters, in Virginia the toll of WNS has been devastating. According to DGIF wildlife biologist Rick Reynolds, the little brown, Northern long-eared, and the lovely Eastern pipistrelle or tricolored bat (the latter species is also a regular victim of wind turbines along the Appalachian spine) have declined up to 98 percent from population estimates before the epidemic. Reynolds adheres to his West Virginia colleague’s fatalistic view of ever finding a cure: “The best we can hope for is that there will be survivors out there that can build up immunity before it’s too late.” Before, that is, the black lid of extinction closes over them.
Bat biologists today clearly don’t have a lot to smile about, but among the few pleasant discoveries of late is the realization that WNS is not universally fatal to all of our native bat species. Hibernating bats that overwinter in more northern or high elevation hibernacula are much more susceptible than the migratory species that fill the night skies in the fall en route to warmer climes. The federally endangered Virginia big-eared bat is thought to be holding relatively steady, as even when the presence of P. destructans is confirmed for some reason WNS has failed to develop in this species. As this is a larger bat it’s been thought that perhaps size matters in fending off WNS, but this is simply speculation. It may be something else entirely, some series of biochemical or genetic codes waiting to be recognized and deciphered, cryptic notes from the underground that hold out the promise of an eventual cure. As is typically the case with introduced maladies like WNS, there’s simply too much we don’t know. As Katie Gillies says, “This is the problem with a brand new disease: more questions than answers, and not enough money to answer those questions.”
From winter, plague and pestilence, good lord deliver us!
~ Thomas Nash, Summer’s Last Will and Testament
“If I thought it would have prevented this disaster when we first discovered WNS at Hailes Cave, I would have happily killed every bat in the state of New York,” says Al Hicks. “But by the time a virulent outbreak like this is discovered and confronted it’s too late.” Hicks hopes that with time some factor or combination of factors – microbial? genetic? chemical? – might be unearthed that will mimic the apparent immunity of those few bat species still sleeping soundly through the winter. For those susceptible to WNS time is running very short indeed, and a sense of frustrated hopelessness, almost parental in its intensity, permeates the sensibilities of even the most dedicated of bat advocates. “Looking for bats underground used to be the best part of my job,” sighs Hicks. “Now I don’t want to go into a cave at all, because I know what I’ll see down there.”
SIDEBAR
Learn more about white-nose syndrome and what you can do to help America’s bats at www.batcon.org.
And serrated wings against the sky,
Like a glove, a black glove thrown up at the light,
And falling back.
~ D.H. Lawrence, “Bat”
Horror in Hailes Cave
In the winter of 2006-2007, in upstate New York, an endangered species mammalogist named Al Hicks was working at his desk when he received an alarming call from a colleague who had been investigating reports of bats in flight, something inconceivable during the harsh, insect-free winter months. Hicks is an expert on the Northeast’s bat species, many of which are declining due to habitat loss, pesticide poisoning, and the disturbance of their caves during winter hibernation. He has participated in nearly every winter survey of bat caves (“hibernacula”) for the past 30 years and has a profound respect and empathy for the furry little flyers that many people shrink away from. Hicks loves bats: their graceful flight, their incredible echolocation abilities, their habit of cozily bundling together among the pallid stalactites of the caverns Hicks knew so well to spend the winter in a deep, dreamy torpor.
Something in his colleague’s voice that day jerked Hicks away from his computer screen and made him clench the receiver in his fist. The team had been surveying Indiana bats tiny mouse-eared insectivores weighing about as much as three pennies. It was always mildly worrying to survey for Indiana bats, which have been federally listed as endangered since 1967. The local populations were lucky if they remained stable year to year, never mind increasing in numbers. And now the nightmare of every dedicated conservation biologist had come true, in hideous detail.
Hicks listened in dismayed astonishment as the survey team reported what they were looking at: thousands upon thousands of dead bats, Indianas among them, littering the floor of Hailes Cave, one of the East’s most populated hibernacula with over 15,000 colonial bats of multiple species. Forming a ragged leathery carpet spiked with tiny bones and teeth, the dead bats stretched far down into the cave’s darkened throat. A shallow subterranean stream ran down into that underworld, and every single stone that jutted from the water was layered with dead and dying bats, most of whose faces or wings seemed to be swathed in a ghostly white substance. The clusters of bats still hanging overhead were not swaddled in frost and deep slumber as they should be in wintertime; instead the ceiling was undergoing a terrible convulsive writhing, seemingly alive and in agony.
Appalled, the survey team quickly withdrew from Hailes Cave. As they watched in amazement bats continued to fly out after them into the 20°F air, circling randomly over the three feet of fresh snow on the ground before being driven by the biting wind back into the cave. Around them, hundreds of bats had simply expired in midair and fallen silently into the snow, as the tracks of dozens of foxes, coyotes, raccoons and fishers attested. Crows and ravens crowded the brooding trees, waiting for their feast to resume. As the crew began their dismal trek back to the trailhead they saw seven red-tailed hawks slowly circling the cave entrance, picking off weakened bats one after another. If a short dive failed to result in a capture the hawks would decline to pursue; they understood that they wouldn’t have long to wait for fresh victims to emerge.
This wholly unnatural behavior seemed to involve the eerie white dusting on the naked faces and wing membranes of Hailes Cave’s traumatized bats, a feature never encountered before. In the weeks ahead it became apparent to Al Hicks that bats hosting this strange fungal growth were afflicted with an extremely high rate of mortality: 80 to 97 percent of bats in local caves were missing from their customary hibernacula and, given the extreme cold and nonexistence of nourishing insects, were presumed dead. Al Hicks labeled the new disease white-nose syndrome (WNS henceforth) for the sallow mold covering furless areas of the victims’ bodies, and he realized at once that he was dealing with an almost inconceivably bad situation. “The poor little things, they couldn’t fly out and they couldn’t stay in,” Hicks recalls in sorrow. “They didn’t have a chance in the world.”
The Dead of Winter
The gruesome vista first glimpsed eight years ago in upstate New York has now repeated itself with numbing familiarity throughout the East and Midwest: WNS is thought to have killed more than 5.7 to 6.7 million bats in eastern North America, spreading its ghastly pall over 19 states and four Canadian provinces. A previously unknown pathogenic fungus, Pseudogymnoascus destructans, was eventually demonstrated to be the cause of WNS. A “psychrophilic” organism – meaning it is particularly suited to cold temperatures – the P. destructans fungus disrupts the deep torpor of hibernation and seems to create a persistent epidermal and possibly metabolic disturbance, causing infected bats to consume critical energy reserves at inopportune times during the winter in a desperate attempt to rid themselves of the irritation. Evidence of WNS can be seen in bats clustered near entrances of hibernacula and flying aimlessly about during the day. Later phases of the disease reveal dead and dying bats on the ground or hanging like tattered rags from buildings and trees.
The more scientists learn about WNS the more appalling it becomes. The fungus attacks bats by boring hyphae, tough thin filaments sprouting from the fungal body, into and through the bare facial skin and wing membranes as it infiltrates the host body. Infected bats resist this affront with their immune systems, and that’s where WNS kicks in. A new hypothesis postulates that infected bats may suffer from Immune Reconstitution Inflammatory Syndrome, an affliction previously known only in HIV-positive humans, wherein the bats’ bodily defenses wreck havoc on their own thin skin, creating bloody chancres around the hyphae intrusions that eventually eat entirely through the dermis. Biologists recount harrowing encounters with dying bats creeping along the cavern floor using their bared elongated wing bones as spectral fingers to pull their bodies forward. In time the animals literally fall apart, like victims of advanced scurvy, and those colonial outliers who don’t succumb to dermal rot soon starve to death wrapped in the remnants of their flightless wings.
One of the greatest obstacles to countering the WNS plague has been the fact that the disease is caused by a species of fungus previously unknown in the Western Hemisphere. P. destructans is native to Eurasia, and the molecular process that triggers WNS in North American bats is the same as that which occurs in Eurasian bats, but the latter have evidently evolved defenses that make them largely immune to WNS. If these evolved defenses can be understood then perhaps vaccines or biological treatments may be developed that mimic this natural immunity.
But how long will that take? With each winter’s thaw revealing heaps of dead bats littering cave entrances from Minnesota to Georgia, Arkansas to Prince Edward Island, time is very much of the essence. Any genetic treatment of WNS, however, “is likely a long ways off,” says Katie Gillies of Bat Conservation International, the country’s foremost advocate for flying mammals. “We are just at the point of placing this fungus [P. destructans] in the correct genus,” she says. “Now, we have to sequence the genome of several closely related fungi, identify which genes create virulence, then determine a way to turn that off and churn out the ‘silenced,’ altered fungus. This is a really, really, long process, and the end result is years out.”
Is a Cure Even Possible?
In the spring of 2013 a federal assessment of bat survival rates published in in the scientific journal PLoS | One presented a grim outlook if WNS continues its deadly rampage. Among the findings was that the federally endangered Indiana bat had declined 30 percent since the introduction of WNS; given this animal's scattered colonies and low numbers before the plague, this represents a potentially fatal decline in genetic diversity.
The disease’s distressingly rapid transmission is thought to be due to both humans and bats. “Voluntary decontamination significantly reduces the fungal load on (caving) gear,” says Katie Gillies. “We know that people can easily transmit fungal spores. So cleaning our gear according to effective decontamination protocols reduces the fungal load and our capability to transmit those spores.” Federal and state-owned caves are typically closed to all but permitted researchers during the wintry hibernation months, but the great preponderance of accessible caves in the US lie on private land, and these landowners could play a critical role in protecting their stricken colonies from outside contamination.
Contamination from humans, that is. Bats can fly hundreds of miles, carrying spores and fungi with them from cave to cave. Add to that the fact that P. destructans can remain dormant for years in abandoned caves because the fungus is not an “obligate” of bats (meaning it can live elsewhere, like in the soil), and so like starlings, influenza, and the creeping kudzu vine, it will apparently remain an unwelcome but permanent component of the North American ecological landscape. Working under this assumption, some are calling for the wholesale chemical treatment of remaining hibernacula while there are still bats to save.
Craig Stihler is a wildlife biologist with the West Virginia Division of Natural Resources. “It’s been very, very frustrating, but we’ve got to consider the entire cave ecosystem before we act,” he cautions. “We can’t just go into caves and start spraying fungicides around because we’d be killing beneficial fungi along with P. destructans, plus that would poison the groundwater and negatively affect cave invertebrates that are even rarer than bats.” The best we can hope for, Stihler says, is to buy time for the onslaught to somehow bypass remnant bat populations from which future colonies can be grown once a cure is discovered … or more likely, once the epidemic has simply run its course. “There’s not much on the horizon that will lead to treatment,” Stihler says with resignation.
As with other Eastern states that enjoy cold winters, in Virginia the toll of WNS has been devastating. According to DGIF wildlife biologist Rick Reynolds, the little brown, Northern long-eared, and the lovely Eastern pipistrelle or tricolored bat (the latter species is also a regular victim of wind turbines along the Appalachian spine) have declined up to 98 percent from population estimates before the epidemic. Reynolds adheres to his West Virginia colleague’s fatalistic view of ever finding a cure: “The best we can hope for is that there will be survivors out there that can build up immunity before it’s too late.” Before, that is, the black lid of extinction closes over them.
Bat biologists today clearly don’t have a lot to smile about, but among the few pleasant discoveries of late is the realization that WNS is not universally fatal to all of our native bat species. Hibernating bats that overwinter in more northern or high elevation hibernacula are much more susceptible than the migratory species that fill the night skies in the fall en route to warmer climes. The federally endangered Virginia big-eared bat is thought to be holding relatively steady, as even when the presence of P. destructans is confirmed for some reason WNS has failed to develop in this species. As this is a larger bat it’s been thought that perhaps size matters in fending off WNS, but this is simply speculation. It may be something else entirely, some series of biochemical or genetic codes waiting to be recognized and deciphered, cryptic notes from the underground that hold out the promise of an eventual cure. As is typically the case with introduced maladies like WNS, there’s simply too much we don’t know. As Katie Gillies says, “This is the problem with a brand new disease: more questions than answers, and not enough money to answer those questions.”
From winter, plague and pestilence, good lord deliver us!
~ Thomas Nash, Summer’s Last Will and Testament
“If I thought it would have prevented this disaster when we first discovered WNS at Hailes Cave, I would have happily killed every bat in the state of New York,” says Al Hicks. “But by the time a virulent outbreak like this is discovered and confronted it’s too late.” Hicks hopes that with time some factor or combination of factors – microbial? genetic? chemical? – might be unearthed that will mimic the apparent immunity of those few bat species still sleeping soundly through the winter. For those susceptible to WNS time is running very short indeed, and a sense of frustrated hopelessness, almost parental in its intensity, permeates the sensibilities of even the most dedicated of bat advocates. “Looking for bats underground used to be the best part of my job,” sighs Hicks. “Now I don’t want to go into a cave at all, because I know what I’ll see down there.”
SIDEBAR
Learn more about white-nose syndrome and what you can do to help America’s bats at www.batcon.org.
