Millions of bats have died from white-nose syndrome, but scientists are striving to slow the fungus down
A tri-colored bat soars along the Conasauga River in Georgia. Among North America’s smallest bats, tri-coloreds have been hit hard by the deadly white-nose syndrome.
BLACK DIAMOND TUNNEL, a relic from a Civil War–era railroad, slices deep into the side of a solid granite mountain in northeastern Georgia. Up until 2013, it was a winter home for more than 5,500 tri-colored bats, beautiful animals with reddish-brown fur, pink noses and pink forearms. But during a survey last spring, biologists could find only 220 tri-coloreds hibernating in the abandoned tunnel. The rest have all died, victims of white-nose syndrome (WNS), a devastating fungal disease that has wiped out more than 6 million bats in 29 states and five Canadian provinces during the past decade.
“It is the most severe wildlife disease in recorded history,” says Chris Cornelison, a microbiologist with Georgia State University and the U.S. Forest Service (USFS). “The only thing that comes close is chestnut blight,” an introduced Asian fungus that between 1905 and 1940 virtually eliminated the American chestnut, formerly a dominant tree of eastern deciduous forests.
First found in the United States during the winter of 2005–2006 in caves near Albany, New York, the WNS fungus was likely brought into this country accidentally from Europe or Asia. Because the disease has been on those continents for centuries, European and Asian bats seem to have evolved immunity. But North American bats have little or no resistance, and the deadly fungus has been on a relentless march across the continent, steadily moving north to Canada, south to Georgia and west to Nebraska and Oklahoma. Last March, a WNS-infected bat was even found in the state of Washington, an unexpected—and worrisome—1,300-mile leap across the Great Plains and Rocky Mountains.
Named for fuzzy white spots that appear on the muzzles, ears and wings of infected bats, white-nose syndrome is caused by the cold-loving, and aptly named, Pseudogymnoascus destructans. “It occurs during hibernation,” says Craig Frank, a mammalian ecologist at Fordham University. “The fungal spores are spread from one bat to another in the confined space where they overwinter,” he explains. Infected bats wake up more frequently, leading to early depletion of fat reserves. Without their fat stores, which the animals need to survive the winter, “they starve to death,” Frank says.
“It’s heartbreaking,” says Leslie Sturges, a bat rehabilitator who runs The Save Lucy Campaign, an educational effort to raise awareness of white-nose syndrome. “Whole colonies are just disappearing.” About eight years ago, Sturges worked with two Boy Scout troops that had put up bat boxes in Fairfax County, Virginia. “There were more than a thousand bats raising their young in those boxes,” she says. But after 2010, the year the syndrome was first detected in the state, the colony began to crash. Last year, only two bats nested.
“I think people forget that WNS is affecting all of us, whether we see fungus-covered bats or not,” says Sturges. Bats are critical players in both natural and agricultural ecosystems. In one night, a single pregnant bat can eat almost her weight in insects, including many major crop pests.
According to Katie Gillies, director of the Imperiled Species Program for Bat Conservation International, little brown bats, northern long-eared bats and tri-colored bats have been hit hardest by the disease. “We’re very concerned about these three species,” she says. The U.S. Fish and Wildlife Service recently listed northern long-eared bats as threatened and is reviewing petitions to list tri-coloreds and little browns. In some places such as Pennsylvania, little brown bats—once the continent’s most common bat—have declined by as much as 99 percent. “We saw no signs of trouble for these species prior to white-nose syndrome,” Gillies says.
Despite staggering bat declines, a few positive signs are emerging. In Vermont, where 90 percent of little brown bats have been lost to WNS, state biologist Alyssa Bennett says mortality rates seem to have dropped to 10 percent for individuals that have survived. “It’s hopeful,” says Bennett of the Vermont Fish and Wildlife Department. “Most of the little brown bats are infected with the fungus, but they are not succumbing to the disease. We’re not sure why. They may be resistant. For some reason, they are able to fight it off.”
Vermont is one of many states enlisting public support to save bats. To help scientists track the progression of WNS, officials are asking citizens to report sick and dying bats. In addition, Bennett has launched a “Got Bats?” project to monitor the summer maternity roosts of Vermont’s big brown and little brown bats, which raise their pups in attics, old barns and bat houses. With the help of volunteers, she is pinpointing the locations of these colonies and recruiting people to census bats as they fly out in the evening.
Much remains unknown, both about bats and white-nose syndrome. Recently, researchers from the University of California–Santa Cruz (UCSC) studied bats in China, where the disease is endemic, and in Wisconsin, Illinois and Virginia, where it is emerging. “By comparing Asia to North America, we hope to understand what might play out in the future for our bats,” says UCSC graduate student Joseph Hoyt. “There is a real urgency for some of our species,” he says. “The future for northern long-eared bats is looking very bleak.”
But Hoyt and his colleagues also have seen some changes for the better that echo what Bennett is finding in Vermont: Many little brown bats that have survived the white-nose epidemic are now doing well. According to Hoyt, some of the midwestern little browns they examined had very little fungus growing on them. “If this is because of genetic differences,” he says, “it could eventually lead to the evolution of resistance in that species.”
The Santa Cruz biologists also studied big brown bats, and these findings may be the most encouraging of all. “They are not really affected by white-nose syndrome,” says Hoyt. Other researchers confirm this. Fordham’s Frank has analyzed fatty acids in the wings of several bat species and determined that the skin on wings of big brown bats possesses a biochemical property that retards growth of the fungus. Building on that discovery, Frank and his colleagues are working on a potential preventative treatment for white-nose syndrome.
Other scientists are trying to help bats that already are infected. Cornelison and colleagues at Georgia State, USFS, the Missouri Department of Conservation and the Kentucky Department of Fish and Wildlife Resources announced in spring 2015 that they had successfully treated and released WNS-infected bats. It started with a “wild idea,” says Cornelison, who works in a lab where a native soil bacterium, Rhodococcus rhodochrous, has been enhanced for several commercial applications, including delaying the ripening of fruit. “I began to wonder,” he says, “if it will stop mold from growing on bananas, maybe it will stop mold from growing on the wings of bats.”
To find out, the scientists first exposed healthy bats to the bacterium in the laboratory. “There were no negative effects,” Cornelison says, so the work shifted in the winter of 2014–2015 to hibernation sites in Missouri and Kentucky, where the researchers captured bats with WNS symptoms and placed them in mesh bags hung inside 72-quart coolers. At the bottom of each cooler they placed two Petri dishes containing Rhodococcus rhodochrous. “It does not need to touch the bats,” explains Cornelison, just share the same air space. After 48 hours, the biologists retrieved the bats and put them inside cages in the cave interiors. At the end of winter, they took all the animals into the lab and evaluated them to see if they were free of the WNS fungus and capable of surviving in the wild. Many were. “We had several releases of healthy bats,” says Cornelison. Now researchers plan to move from coolers to entire caves.
More antifungals are also in the works. One being tested by Western Michigan University’s Maarten Vonhof is called chitosan and is derived from the exoskeleton of insects and crustaceans. So far, it has shown promise in laboratory experiments. Other researchers are investigating the use of probiotics, or beneficial bacteria. “We are trying to develop a suite of short-term treatments and deploy them,” says Gillies. “The idea is to buy time until a long-term solution such as a vaccine can be developed.”
New treatment options became even more critical last spring when scientists found white-nose syndrome in a little brown bat 30 miles east of Seattle. At first, says Katherine Haman, a veterinarian for the Washington Department of Fish and Wildlife, “we thought it might have been a bat from another part of the country,” perhaps one that hitchhiked west in a shipping container. But researchers confirmed the dead bat was the western subspecies of little brown bat, not an eastern interloper. Since then, surveys throughout the state have turned up no additional cases. “Every bat has looked great,” Haman says.
Still, the news from the West has been sobering for biologists, who expect the disease will keep spreading. Even under the most optimistic scenarios, Gillies notes that we never will see the recovery in our lifetime of some species because their numbers have fallen so low and bats produce only one pup a year. But the scientists are persevering. “We are attacking the disease from many directions,” Gillies says. “Five or six years ago, it was very depressing. Now we are hopeful.”
To cut back on the fossil fuel emissions that are causing climate change, the nation needs massive amounts of renewable energy from sources such as wind power—but not at the expense of wildlife. As a member of the American Wind Wildlife Institute (AWWI)—a nonprofit alliance of leaders in the wind industry and conservation community—the National Wildlife Federation is helping bring together partners to advance research that promotes wildlife-friendly wind development. One AWWI project focuses specifically on bats. Each year, tens to hundreds of thousands of bats are killed when they collide with wind turbines. In the Midwest, victims include little brown bats, whose numbers are plummeting as a consequence of white-nose syndrome. To learn more, visit awwi.org.
Doreen Cubie wrote about roadside wildlife reserves in the April–May 2016 issue.
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