Bedded rock layers gave way to water that dripped down the earthy limestone rock, covered in thick green moss, and created a muddy floor below.  The drops echoed in the deep depression of earth, created by the sinkhole that exposed the mouth of the historic entrance of Mammoth Cave in Mammoth Cave National Park.  Brown leaves dangle from rock crevices and concrete steps make up a staircase that leads its visitors into the damp darkness of the underground world.  

Slipping deeper into the cave, traversing through sinuous passageways, bats cling to the rocky walls and nestle in small roosts.  This cave as well as many others in the park provides ideal locations for Kentucky bats to hibernate during winter months.  

Steve Thomas, the monitoring program leader for the Cumberland Piedmont Network, and his crew, outfitted in helmets, headlamps and gloves, worked their way through Bat Avenue – a passage in Mammoth Cave once teeming with bats.

Thomas, left, photographs a bat hibernating on the ceiling of the Historic Entrance section of Mammoth Cave.

“There used to be tens of thousands of bats,” Thomas said.  “This passageway is named for the bats.

“Now there’s no bats,” he added.      

Thomas and his team are part of a network that actively tracks the presence of bats in Mammoth Cave during their winter hibernation.  Every winter, Thomas and several Mammoth Cave National Park employees spend full days underground, taking inventory of each bat species found in Mammoth Cave and other caves in the park.

In addition to counting the bats Thomas will also swab the bat’s muzzles and surrounding cave walls.  These swabs are properly labeled, stored and sent to a lab for testing.  Results will indicate the presence or absence of White-Nose Syndrome spores.

The fungal disease, White-Nose Syndrome, exists as spores that cling to the surfaces of cold and humid places, with caves and mines exhibiting prime locations for the fungus to thrive.  The same places that the fungus favors are also preferred by several bat species in the eastern United States to use as winter hibernating areas called hibernacula.

Mammoth Cave is filled with large columns, draped with flowstone that has been shaped and molded from water that has found its way hundreds of miles underground.  Graffiti, some old and some new, is etched on almost every crack and crevice of the cave walls.  The cave is dark, quiet and damp – a perfect home for the bats that no longer roost there in the massive numbers that they used to.

After a lengthy search, the passageway filled with the screech of an unhappy Indiana bat as Thomas plucks a roosted bat from the cave wall.  After swabbing its nose and examining its wings, the scientists found a small band wrapped around the forearm. These bands have been used by several research groups to track bats for an array of research projects.  This Indiana bat’s arm was wrapped with a red band – confirmation that the bat is positive with White-Nose Syndrome.  

Thomas, while placing the bat back on its roost, wonders aloud which research group is tracking this Indiana bat and for what purpose.    

“Because they’re disappearing,” replied Chris Clark, a National Park Service employee and bat monitoring crew member.

Bat populations are disappearing – many at a rate of 90 percent – since the emergence of White-Nose Syndrome, a fungal disease native to Europe.  After nearly 11 years in the United States the fungal disease continues to kill bats at an alarming rate. With approximately 7 million bats lost to the fungus an important agricultural, ecological and human health component is also vanishing. 

 The fungus Pseudogymnoascus destructans, or White-Nose Syndrome, is native to Europe and China.  Scientists have discovered several reports of the white growth of the fungus on bats from the late 1970s in Estonia, the early 1980s in Germany and since the 1990s in France.  

Named for white fuzz that grows on the bats’ muzzles and skin, once in contact with White-Nose Syndrome spores a bat’s skin is invaded by the fungus that eats away at the flesh and causes dehydration.  

A recently deceased Little Brown Bat displaying symptoms of White-Nose Syndrome

During winter hibernation, a bat’s immune system is mostly shut down – useful in conserving fat reserves – making the bat highly susceptible to fungal infection.  Irritation from the fungus creates unusual behavioral patterns in the bats, such as leaving caves or mines during winter hibernation when there are no bugs to eat.  Without a source of food to replenish energy, the bats will burn through their fat reserves too quickly and die from both starvation and from freezing to death.

In late 2006, wildlife authorities in Albany, New York took notice to the sudden and drastic decline in the population of Little Brown Myotis Bats – one of the most common species in North America.  These dying bats emerged with white fuzz surrounding their noses, which researchers at the Federal Fish and Wildlife Service have now identified as White-Nose Syndrome. 

Since it is not normal for bat species to migrate between continents, it is suspected that humans who traveled to areas where fungus spores already inhabit, introduced the fungus to North America.  Like cave walls, the spores can become easily attached to clothes and shoes and then transported with human movement.      

Research suggests thus far that the White-Nose Syndrome fungus only infects bat species that hibernate in clusters.  According to the White-Nose Syndrome web site, an Internet based database that compiles information about the disease and its spread, more than half of the 47 bat species residing in North America rely on winter hibernation for survival.  Of those 47, seven bat species have been confirmed to suffer from White-Nose Syndrome – two of the species are federally endangered and another is federally threatened.  

The fungus infecting North American bats has resulted in severe population declines ranging from 30 to 100 percent for infected hibernating roosts.  These devastating mortality rates have led to regional population collapses.  For the little brown bat in which the fungus was first identified, recent studies predict complete extinctions within approximately 10 to 14 years.  

In a 2011 study published in the Cell Press journal, scientists investigated a link between the White-Nose Sydrome fungus present in North America and that present in Europe.  It was reasoned that the fungi were identical.  This discovery indicated the spread of White-Nose Syndrome from Europe to North America.  

The devastating fungus is present in nine of Europe’s bat species, yet the same characteristics in North America – premature loss of fat reserves and unusual winter activity that leads to mass death – have not been documented.

Scientists, including conservation biologist working out of Arizona, Karen Krebbs, have several hypotheses why European bats feel no apparent threat from a fungus that is decimating North American populations.

Krebbs supports the evidence that suggests the fungus has been present in Europe for a long time and has only recently found its way to North America.  Krebbs calls what occurred in Europe to be the survival of the fittest.  After prolonged periods of exposure to the disease, European bat populations drastically declined.  Eventually, with low bat numbers, the disease bottlenecked and bats began to adapt to withstand the effects of the fungus, she said.  

Krebbs credits the larger body masses of European bats and the small population numbers to their historical exposure to White-Nose Syndrome. 

 “I think that’s what’s going to happen in the U.S.,” Krebbs said.  “Many bats already have a 95 percent mortality rate.”

Scientists, including Krebbs, believe that some North American populations will soon bottleneck and certain species will reach extinction.  

“When disease goes through populations, sometimes they bounce back and sometimes they don’t,” Krebbs said.

By 2011 the effects of the fungus were seen across much of the eastern U.S., including for the first time in Kentucky. White-Nose Syndrome first appeared in caves of southwestern Kentucky during the 2011-2012 bat surveying season. 

It wasn’t long before the fungus made its way across the state, traversing from cave to cave. In early January 2013, the fungus was discovered on bats in Mammoth Cave National Park.  The park has several caves where bats roosts, including the longest cave in the world and the park’s namesake, Mammoth Cave.

There are 13 species of bat that inhabit the park, and eight of those regularly hibernate in its caves.  Out of the eight regulars, three of the species are listed as federally endangered.  

Thomas, of the Cumberland Piedmont Network, said it is impossible to know just how many bats inhabit a region, and researchers must guess on approximate numbers.  Bat populations are regularly monitored to determine status and trends in each species in the park.  The numbers deduced from these surveys are used to reveal death rates of individual species of bats, which for some Kentucky bats are upward of 90 percent. 

“We’ve seen a lot of decline in a short amount of time,” Thomas said.  “You can see over a thousand bats and come back two, even one year later and see 75 percent less or fewer bats.”

The fungal disease, once thought to be confined to the northeast, quickly began to spread farther west, leaving only death in its path. 

In March of 2016, to the astonishment of scientists, White-Nose Syndrome was confirmed for the first time in Washington State after evidence from a gray bat was retrieved.  This was also the first case of the merciless fungal disease in the western U.S. 

One year later, in early 2017, a single pile of bats was found outside of the Soudan Underground Mine in Minnesota.  After only two weeks, nearly 3,000 bats had been found outside dead, and many more were believed to have died farther away.  This number was rounded up by the Minnesota Department of Natural Resources who say, since the introduction of White-Nose Syndrome to the state in 2013, more than 70 percent of the mine’s bat population has been lost in just nearly four years.  

The disease continues to plague bat species farther west with new cases discovered in Nebraska, Texas and Oklahoma in 2017. Infected bats now span across 34 United States and six Canadian providences. 

As for Texas, six of its northern counties were confirmed with White-Nose Syndrome by the Texas Parks and Wildlife Department – infecting two new species of bat.  The cave myotis bat and the Townsend’s big-eared bat have newly been confirmed to be susceptible to the fungus.  

Nearly two-thirds of Texas’ 32 bat species do not regularly hibernate, leaving state biologists hopeful for their survival.

“There is still hope for bats in Texas,” Texas Parks and Wildlife Department state mammologist Jonah Evans said in a press release.   “The fungus thrives in colder climates and it remains to be seen if WNS will have the same serious impacts in Texas as it has in northern states. 

“Additionally, 20 of the 32 species of bats in Texas do not regularly hibernate and we are hopeful they will not suffer significant population declines.”

Texas is home to some of the world’s largest bat roosts, including the famous roosts of the Mexican free-tailed bats in Austin and Bracken Cave.  With the massive densities of bat populations in the state and new bat species becoming infected, the spread of the disease is nearly inevitable.   

“The scary thing with the Texas discovery is that the two species that came down with it are two prominent bats in the west,” Krebbs said. “The cave myotis travels all the way to Honduras.”

Krebbs, who has been working with bats since the 1980s, believes that the spread of White-Nose Syndrome across the western states of the U.S. is imminent.  

“I think it’s going to move all over the west,” Krebbs said.  “We have no control over it all.”

Krebbs said the fungus is often spread between bats, but a lack of following preventative protocols has resulted in even greater issues in the spread of the disease.  There is a strict decontamination protocol that Krebbs said is evidently being ignored by cavers and researchers who enter caves.  

“Even if you disinfect, you shouldn’t bring your things out west,” she said.

Some scientists fear the expansion of the infectious disease to most cave bearing counties in the U.S. by the winter of 2105-2106.  

As more and more bats disappear, scientists are left baffled and fearful of the impact their absence will have on the U.S. economy, the environment and even human health.  

Bat Conservation International reports that a single ounce of bat waste, known as guano, contains enough useful bacteria to detoxify industrial waste, produce natural insecticides, improve detergents and convert waste byproducts into alcohol.

More remarkably, bats save the agricultural industry billions each year in the reduced use of pesticides, including chemical fertilizers, and the pollination of plants, proving bats to be a vital economic resource. According to a 2011 report in Science Magazine, the value of bats to the agricultural industry is estimated between $3.7 billion to $53 billion per year.     

Bat guano has made an economic mark in the U.S., with guano extraction becoming largely popular in U.S. industry and has recently risen to the top as Texas’ largest mineral export before oil.  According to the Bat Conservation International report, railroad officials estimate the annual transport of 65 carloads, each containing approximately 30,000 pounds of guano, from Texas.  

Bat guano can also be used as a natural fertilizer, and according to the Bat Conservation International report, 100,000 tons of bat guano, predominantly from the Mexican free-tailed bat, were removed from Carlsbad Caverns in New Mexico and sold to fruit growers in California.

Bats also act as natural pollinators, with the lesser long-nosed bat, which is federally endangered, pollinating and dispensing seeds for some 60 species of the agave plant and cacti that are used by several different animal species for food and shelter, according to a Bat Conservation International report.

Bats’ pollination also aids in the production of Tequila, a multi-million-dollar industry, which is reliant on the pollination of the agave plant by bats.  Scientists estimate that with the absence of bats, agave propagation can be expected to fall to 1/3000th of normal.  

Most notably, as natural pest eaters, bats are crucial in reducing insect populations that are harmful to crops, spread disease and are active in tree-top removal in forests.

A Crane Fly, a bug eaten by the Little Brown Bat

Beetles, corn-earworm, cotton-bollworm, grain moths, leafhoppers and mosquitoes are all insects consumed by several different bat species and a single bat may eat more than 50 percent – around 3,000 bugs – of its body weight in these insects each night, according to the Tennessee Wildlife Resources Agency.  

Bat Conservation International has reported that between 77 to 85 percent of little brown bats living in the northern U.S. and Canada eat mosquitoes, with a single little brown bat catching more than 1,200 mosquitoes and other mosquito-sized insects each hour.  For the little brown bat, this equates to 4,800 mosquitoes per night or approximately 873,600 per year. 

Without this large feasting from bats, the report estimates farmers could incur costs anywhere from $12 to $173 per acre to spray chemical pesticides to suppress pests from their crops. 

Dr. Chris Groves, distinguished professor of hydrogeology and Western Kentucky University and director of the Crawford Hydrology Lab, proposes the issue of a higher prevalence of insect borne diseases because of the loss of 7 million bats.  

He said the issue will be exacerbated as we continue the battle with climate change.  Not only will a loss of bats possibly increase the presence of mosquitoes, but climate change is impacting the migration of these insects, Groves said. 

The presence of mosquito borne diseases is now emerging in areas where bat populations are declining. 

“Because of climate change, bugs are moving,” Groves said.  “They didn’t use to have West Nile in Florida, but now they do.

“If climate changes and the range for malaria changes, more people will be exposed to it.”    

Along highway 31-W in southcentral Kentucky, a breeze blows just enough to allow the bright yellow, pollinated buds that tip green stalks of a field to find motion against the blue, cloudy sky.  In the next field, green stalks sway in an ocean of juvenile wheat, which will grow into the mid-summer before it is harvested.  

Amid the welcoming colors of spring, merely a few fields away, sits brown, barren earth.  Every spring chemical pesticides are used to rid these agricultural fields of weeds and insects in which genetically modified corn will soon be planted.  

With drastic decreases in bat populations, scientists predict an increase use in pesticides, resulting in greater exposure to both humans and the environment.

In 2007, the United States Geological Survey conducted a study of U.S. streams and groundwater that concluded that pesticide compounds, inclusive for insecticides, herbicides and chemical fertilizers, were found in significant amounts in both stream water and groundwater across the U.S. 

The study also identified pesticides in water wells that tap major aquifers used for water supply. 

This is a major issue for many parts of Kentucky where pesticides can easily contaminate the groundwater where the aquifer system is in karst terrain.  This type of landscape gives the chemical pollution direct access to much of the state’s water supply.      

Data from water samples retrieved by the Kentucky Geological Survey and evaluated by the Environmental Protection Agency, showed high levels of several pesticides located in numerous water sources across Kentucky.  

According to the EPA even the least-toxic pesticides, including those that are classified as natural or organic, can cause health problems with great amounts of exposure.

There is a small sinkhole, a good mile hike away from the main road, in which mossy green limestone blocks dip into the earth.  Rocky steps and a seemingly unreliable hand rail leads to the base of the sink where visitors are met with a rusty, barred gate.  This gate protects the contents of Colossal Cave, a cave passage in Mammoth Cave National Park. 

Three weeks after Thomas’ bat count, researchers, including Toomey, Dr. Brooke Maslo, a biology professor at Rutgers University, and their team slip through the small square opening into the dark, underground cavity.  Adorned in puffy coats, knit hats and backpacks stuffed with equipment, they braced themselves against the fierce wind as they traversed down rock rubble and patches of ice to reach the cave floor.  

Reaching level ground, they were met with a high roof, carved out by water many years ago, and large broken down blocks that separated the open room into two halves.  Water droplets descended into a pool of water that had collected in a cove.  The splash of drops was the only sound filling the room.  

Maslo and her team whispered and worked quietly setting up their equipment as to not disturb and wake the cave bats.  Maslo works as a wildlife specialist at Rutgers University and one of her concentrations is on bat conservation.  In her current study, Maslo is testing the microbiome and genome in different bat species in hopes of identifying the qualities that make some bats more resistant to contracting White-Nose Syndrome.

To do so, Maslo has traveled from New Jersey to obtain 70 different bat samples from Kentucky’s indigenous species.  In collaboration with the Mammoth Cave International Center for Science and Learning, led by Toomey, bats in Colossal Cave will have their wings swabbed for microbes and a tiny speck of wing will be punched from the bat for further testing. 

Bat samples will be tested in hopes of finding microbial and genetic links that allow some bats to survive the fungal disease.  

Bats are placed in the cloth bags while waiting to be evaluated.

A bungee cord-like line dangled in between two limestone outcrops covered in small bubbly sprouts from the cave wall – known as cave popcorn.  Attached to the line were carabiners in an array of colors, and from these carabiners, beige cheese cloth bags were suspended.  Each bag contained a single, sleepy bat that awaited inspection from Maslo.

Detaching a bat from a cloth bag, Maslo’s assistant extends the brown, thin wing of the now screeching female bat.  After measuring the bat’s foreman and weight, Maslo is ready to perform the procedure known as wing punching.  

“A feisty female,” Maslo said, as she heated the end of a small metal prod and a pair of tweezers.

The prod is used to extract a piece of skin from the bat, which is quickly placed into a vial to be sent off for further testing.  

Deeper into Colossal Cave, Toomey and the rest of the team have been busy collecting clusters of bats and swabbing their wings.  An old tourist trail, once used to guide tours in the 1800s, is now used to guide researchers in search of bats.  

Equipped with an extendable metal pole with a Play-Doh cup duct-taped to the end, Clark reaches it to the cave ceiling to capture a roosting bat for examination.  The group had been in search of the Little Brown Myotis species, specifically for a female.  With a stroke of luck, they had nabbed their first girl.  

“It’s the only girl,” Clark said, turning the Little Brown over in his hand.  “That’s a sign that their species is going extinct.”

Bats with tattered and torn wings had been seen throughout the group’s search, but it was a little brown bat, the species most heavily impacted, that showed the most obvious sign of White-Nose Syndrome.  Visible white fluff clung to the nose of the bat – a positive confirmation of White-Nose Syndrome and the imminent death of this bat.  After swabbing, the bat was placed back on a rocky ledge. 

“We should put that in the notes,” Clark said as he tossed his blue latex gloves to the cave floor.  The gloves would need to be properly disposed of for the group to avoid contact with the fungus. 

A fellow team member sighed in response.  

“Write down the white death,” bat ecologist Brooke Hines said.  “After all, that’s what it is.

Chris Clark, a Mammoth Cave National Park employee, continues through Bat Cave, named for the hundreds of years of bat bones found here, a sign that it was once a large hibernaculum.