COLUMBIA — The cool breezes of fall accompany the changing color of the leaves — a sign that winter is on its way. The fall migration has begun, and soon, all over Missouri, bats will be settling in for their annual winter hibernation.
The schedule for each species varies, but October to April is the prime time for the bats to hibernate. As they retreat into Missouri's caves for a long winter's nap, they face a threat more dangerous than any predator.
HOW WHITE-NOSE KILLS
The fungus geomyces destructans, thrives in moist cool environments, the same sort of environment bats seek out for hibernation.
“It’s kind of a perfect storm,” Mylea Bayless, head of Bat Conservation International's white-nose syndrome program, said. “You’ve got this fungus that can cause disease in the very same environments that bats seek out in order to suppress their immune systems.”
The first signs of the disease are white spots on the nose, muzzle and wings of the bat. From there the fungus makes it way into deep tissue.
“The fungus actually invades through the first layer of skin and down into the living skin tissue and destroys it,” Bayless said.
When this happens, it causes the bat to wake up out of hibernation more frequently than it normally would.
“Every time a bat wakes up, it burns through the same amount of fat that would keep it alive for a month of hibernation,” Bayless said.
This cause bats to go out in search of food to replenish their fat reserves. During winter, however, the bats cannot find food and starve to death, Paul McKenzie, biologist with the U.S. Fish and Wildlife Services field office in Columbia, said.
“People in New England have seen bats flying in the middle of the day, in the middle of the winter, and that’s extremely unusual,” McKenzie said. “In fact it had not been heard of prior to this outbreak.”
Kathryn Womack, a graduate research assistant in the MU Department of Fisheries and Wildlife, said even if a bat gets the disease late enough in the winter to survive hibernation, the disease often spreads to the wings and eats away at the wings, destroying and scarring them.
While the exact reason bats wake up during hibernation is unknown, Bayless said the fungus may be aggravating to the bat, causing it to wake up early and groom itself. Or the bats could be waking up as a way to try rebooting their immune system. The fungus also could upset the balance of gas exchange and lead to dehydration.
Bats are most vulnerable to the disease while hibernating.
“The fungus is persistent on bats in summer months, but it doesn’t cause the disease then,” Bayless said.
That's because although the fungal spores can survive the warmer summer temperatures, the fungus can’t grow in the summer. Also, during the summer months, the bats aren’t hibernating so their immune system is more able to combat the fungus.
A silent killer that is spreading westward has already claimed more than 1 million bats in 17 states. White-nose syndrome is knocking at Missouri's border, and scientists fear it could decimate the bat population.
The disease hits bats during hibernation, when their defenses are down.
"In the areas where the disease has been the longest, it's estimated that 90 percent of little brown bats and northern long-eared bats have been lost, as well as 70 percent of big brown bats," said Columbia research wildlife biologist Sybill Amelon of the U.S. Forest Service.
Missouri is home to 15 different species of bats, two of which, the Indiana and the gray bat, are endangered. Bats are the primary predators of night-flying insects. By helping to control the insect population, bats contribute $961 million to Missouri agriculture.
In mid-April of 2010, one little brown bat with suspicious wing spots was found in northeastern Missouri, in Pike County. It tested positive for the fungus geomyces destructans, which is believed to cause white-nose syndrome.
In early May 2010 along the Current River, bat researchers from Missouri State University were searching for Indiana bats through a project funded by the National Park Service.
Because white-nose syndrome was inching its way closer to the state, the Missouri State research team was also keeping an eye out for it as they looked for the endangered bat species.
Their vigilance turned out to be warranted because outside a cave in the Ozark National Scenic Riverways, in Shannon County, the team netted five gray bats with wing damage characteristic of the disease. Wing samples were sent to the National Wildlife Health Center in Madison, Wis., and came back positive for the fungus.
Within days of the discovery, the Missouri Department of Natural Resources closed or restricted access to most of its 175 caves in 18 state parks and historic sites. The Missouri Department of Conservation closed 80 of its 290 caves because they were known bat caves. The closures were in accordance with the Conservation Department's white-nose action plan, which was approved a day before the first case in Pike County was confirmed.
In the year and half since the fungus was discovered on bats in Missouri, no incidents of the disease — where the fungus actually makes its way into the bat’s tissue — have been reported.
During the past winter, a team of bat and cave biologists from the Conservation Department went back to the caves where the fungus was found in the spring of 2010 and found no signs of the disease, surprising researchers who were expecting the worse.
Researchers, however, don't believe the threat of white-nose syndrome to Missouri bats has diminished. Since it was first found in New York in February of 2006, the disease has jumped to 16 other states and three Canadian provinces. Additionally, the fungus has been documented in Oklahoma as well as Missouri.
"Once it hits here, I see it decimating the bats of Missouri," Kirsten Alvey, president of Columbia caving group Chouteau Grotto said. "I see the bats I love being gone."
In the spring of 2011, cases of the disease were confirmed in Kentucky — just 55 miles across the Missouri border.
"We think it’s not a question of if it’s going to get here but when it’s going to get here," said Paul McKenzie, biologist with the U.S. Fish and Wildlife Services field office in Columbia.
How the survey was done
A total of 29 caves, chosen because they either had a large population of bats or diverse populations of bats hibernated there, were surveyed last winter. Biologists used a small battery-powered air sampler to test for spores of the fungus that is believed to cause white-nose and looked for visual signs of the disease on bats.
"The most obvious signs are the white fungal growth around the nose of the bats or on the wings," said Tony Elliott, a forest bat ecologist for the Conservation Department.
Abnormal looking white flecks were found on six bats — one gray, one tri-colored, two northern long-eared and two little browns — and the bats were sampled and sent for testing. They did not have the fungus or white-nose syndrome.
"We avoid killing the bats just out of curiosity because we are here to conserve the bats," said Bill Elliott, (no relation to Tony Elliot), a cave biologist with the Conservation Department. "It really pains us, but there is no other way to truly determine whether they have the disease."
The winter survey included Devil's Icebox, a cave at Rock Bridge Memorial State Park south of Columbia.
"During last winter we had a cave trip into Devil's Icebox," Roxie Campbell, a naturalist at the park, said. "We looked at the bats, photographed them, counted them and did not find any signs of the disease."
The researchers also checked the caves in Shannon and Pike counties and found nothing.
The fate of bats found with the fungus in Shannon County, however, remains unknown, Lynn Robbins, a bat researcher from Missouri State University, said.
"Because we didn’t have a permit to send the whole specimen off to the lab, we just put a numbered arm band on them and released them back into the wild," Robbins said.
None of the bands have been returned. Robbins said that's not uncommon because bats move around a lot and become more aware of efforts to catch them after they have been caught once.
Theories about the survey results
Researchers aren’t sure why they didn’t find the disease in Missouri this past winter.
"Most of the other states around us have it, and we full well expected to find at least a confirmed case," Alvey said. "It was exciting when we didn’t, but it raises many questions."
Bill Elliott said researchers might not have found any cases of the disease because they only were able to survey a small percentage of the more than 6,300 caves in Missouri.
"The chances that it is already here, and we just have not seen or taken a bat that confirms it, is very high," Alvey said.
The survey’s finding suggests that the bats previously found with the fungus in Missouri may have migrated from places in the eastern United States where white-nose syndrome is more prevalent, Bill Elliott said.
That doesn't mean Missouri bats are safe from the fungus, said Anne Ballmann, a wildlife disease specialist from the National Wildlife Health Center.
"Once the disease-causing agent shows up, it’s just a matter of time before the disease shows up," Ballmann said.
The bats with the fungus in Shannon and Pike counties were classified as suspected cases of white-nose syndrome. To be classified as white-nose syndrome, the fungus has to be inside the bat, causing tissue damage.
"It’s kind of like having HIV without having AIDS," Mylea Bayless, the head of Bat Conservation International's white-nose syndrome program, said.
The persistence rate of the fungus is unknown. Some fungal spores can remain dormant in locations for years, and research is under way at the National Wildlife Health Center to determine whether geomyces destructans is one of these fungi, Ballmann said.
There is also hope that as the fungus spreads west, the warmer, drier climates may not be as conducive for the moist and cold-loving fungus to grow, giving bats a better chance of survival.
This past year, the disease spread to Ohio, Kentucky, Indiana and Maine.
Even with warmer climates, Amelon expects the disease to continue to spread across the country.
"Maybe not spread quite as fast as it makes its way into warmer, dryer areas, but it probably will continue to spread until we find some sort of solution," Amelon said.
Since the initial round of cave closures, all caves on federal or state land in Missouri have been closed or had access restricted, Bill Elliott said. Closed caves are off-limits for everyone except researchers with special permits.
The reason caves are closed, Amelon said, is "to avoid the possibility of humans accelerating the rate of the fungus being spread."
White-nose syndrome is thought to be spread primarily through bat to bat contact; Ballmann and McKenzie said there is only circumstantial evidence and no conclusive proof that humans help spread the disease.
"What we're worried about is that the spores of the fungus can be transferred from bat to bat and then be deposited on the walls or sediments of the cave," Bayless said.
According to a federal Wildlife Health Bulletin, long-distance jumps of white-nose that exceed the known migratory distance of bats suggest that humans helped spread the disease.
"There’s no known bat migration detection patterns that would account for the jumps we saw in Oklahoma," Ballmann said.
Ballmann also said that fungal spores have been detected in the sediments and soils of the caves and there's a possibility humans can carry them to other caves.
"I don’t think that there’s going to be any way to definitely show that humans moved the fungus from Point A to Point B at this point," Ballmann said.
Bill Elliott said closing caves helps "to give the bats quiet time for survival and reduce the stress on bats."
"The benefit is that just like when we are sick, we don’t like to be disturbed," Alvery said.
"By giving bats time to recover from the disease, hopefully there will be some individuals who develop an immunity to pass on to ancestors," McKenzie said.
Of the estimated 6,300 caves in Missouri, about 1,000 are on federal land and 290 are owned by the Missouri Department of Conservation, Bill Elliott said. He estimates that about 80 percent of the caves are on private property, and those are open to those who own them. Private show caves are also still open to the public as well as show caves on public land such as Fantasy World Caverns in Eldon.
Devil’s Icebox is closed except to researchers. The wild cave tours, which brought in $10,000 to $15,000 annually, were canceled in July 2010.
Rocheport Cave Conservation Area along the Missouri River south of Rocheport and Hunter’s Cave in Three Creeks Conservation Area south of Columbia remain closed as well. Endangered gray bats can be found in both of these caves.
Some caves with particularly large populations of bats or with diverse populations have steel gates across that allow bats to come and go but keep people out. Bill Elliott estimated that about 200 Missouri caves have cave gates.
He thinks closing caves is a necessary step until more is learned about the disease.
"We have to go through a lot of things before opening caves again," Bill Elliott said.
Alvey is the president of Columbia’s caving society, Chouteau Grotto and has been caving since she was 5 years old when she went to her first cave in Hannibal. She remembers playing in them and using caves as clubhouses.
"I cave anywhere from one to four days a week depending on my work schedule," Alvey said. "It’s just a way of life."
She is particularly interested in the biology of caves — bats, fish and salamanders — and worries about what white-nose syndrome could do to the bats.
"Every time I go into a cave, period, I always look for bats and signs of white-nose syndrome" Alvey said.
Although the cave closures have pulled a few of the group's favorites out of the mix for spelunking, she said, there are still plenty of private caves to explore. Several members of the caving club participate in a stewards program with the Conservation Department where cavers help with research in caves that have been closed.
Alvey said preliminary steps are being taken to create this sort of programs with the Missouri Department of Natural Resources as well.
"Knowing that a cave that I love, I’m going to walk in one time and find piles and piles of dead bats like they did on the East Coast just breaks my heart," she said.