Scientists pin down cause of bat disease

Researchers analyze the air near a hibernating bat in the Adirondacks. Photo by Carl Heilman II.

A study published in the journal Nature confirms that the disease decimating bat colonies in New York and many other states is caused by a fungus known as Geomyces destructans.

Known as white-nose syndrome, the disease causes lesions on the bats’ skin and a white growth on their muzzles. Since its discovery in a cave near Albany in 2006, it has spread to sixteen states and four Canadian provinces.

The disease has so devastated bat populations that some species are in danger of extinction.

Earlier this year, Winnie Yu reported in the Explorer that the number of little brown bats in the Adirondacks—once the most common bat in the region—has plummeted 90 percent. Northern bats are down 98 percent. Indiana bats, an endangered species, are down 60 percent.

Biologist Jeremy Coleman of the U.S. Fish and Wildlife Service, one of the five authors of the study, said today that the disease is continuing to spread, though there is some evidence that it has stabilized in some colonies.

Scientists had suspected that Geomyces destructans was the cause of white-nose syndrome, but the new study confirms it. Researchers at the National Wildlife Health Center in Wisconsin found that healthy bats exposed to the fungus developed lesions and other symptoms associated with the disease. Before the study, some experts speculated that the fungus was itself a symptom, not a cause, of illness.

The researchers say little can be done to control the spread of white-nose syndrome. One possibility is manipulating the habitats of caves to make them less hospitable to the fungus.

The same fungus exists in Europe, but it has not decimated bat populations there. It’s thought that the fungus may have been inadvertently carried to the United States by a human and introduced to a commercial cave in Schoharie County, whence it spread to bat hibernacula.

Coleman’s co-authors included three scientists from the U.S. Geological Survey: microbiologist David Blehert, wildlife pathologist Carol Meteyer, and wildlife disease specialist Anne Ballmann. The fifth researcher was Justin Boyles of the University of Tennessee.

For more information about white-nose syndrome and its impact on the Adirondacks, we encourage you to read Winnie’s story.

Bat die-off continues

White-nose syndrome, the disease decimating bat populations in the Northeast and beyond, is believed to have spread to all known bat caves in New York, according to the state Department of Environmental Conservation.

The fungal disease has reduced the populations of some bat species in the state by 90 percent since it was first documented in 2008.

Bat with white-nose syndrome. Photo by Larry Master.

The Graphite Mine in Hague, once the largest hibernaculum in the state, has been especially hard hit. The number of little brown bats has fallen from 185,000 to 2,000, DEC says. Two other species, the northern bat and the endangered Indiana bat, have disappeared from the mine entirely. Another, the tri-colored bat, has been reduced to a lone specimen.

DEC surveyed hibernacula early this year. “Caves and mines that avoided infection in the early years of the disease, perhaps by chance, are now infected,” acting DEC Commissioner Peter Iwanowicz said in a news release. “This year’s survey included hibernation sites that had not been visited by DEC in decades. What we found was disturbing. We now have sampled sites that represent the full range of environmental conditions across the state—and none have been spared. It is likely the sites not yet inspected are infected as well.”

But the populations held steady in two caves in the Capital Region, albeit at at roughly 10 percent of their pre-disease count. “Infected animals were present at these two sites, so it’s too early to say the decline here has halted,” said DEC bat biologist Carl Herzog, “but these two caves represent the most hopeful results in an otherwise negative report.”

DEC is working with the U.S. Fish and Wildlife Service to find ways to treat the disease and check its spread.

Click here to learn more about white-nose syndrome.

Our vanishing bats

Over the past four years, the number of endangered Indiana bats in New York State has plummeted about 50 percent. And that’s the good news.

The populations of other bat species in the state have fallen as much as 90 percent.

State biologist Al Hicks told the Adirondack Park Agency on Thursday that three species—the little brown, northern, and eastern pipistrelle bats—could be extirpated in the Northeast within a few decades.

A little brown bat with white-nose syndrome. Photo by Larry Master.

“Extinctions are not out of the question here,” Hicks said.

The bats are dying from white-nose syndrome. The disease’s name comes from the white fungus that appears on the animals’ snouts and wings. Infected bats often use up their fat reserves during hibernation and die of starvation. Many will leave caves in winter in a desperate search for food, but the insects they depend on for survival cannot be found at that time of year.

White-nose syndrome was first documented in 2008, when state scientists found thousands of dead bats in a cave south of Albany. They now think the disease originated in Howe Caverns, a commercial cave in Schoharie County. Photos taken at the cave in 2006 showed bats with the white fungus. In recent years, the disease has spread throughout New England, as far south as Kentucky, and as far west as Missouri.

Before the onslaught of white-nose syndrome, New York boasted the country’s third-largest population of Indiana bats, which are on the federal list of endangered species. Hicks put the population at 54,000. This paled in comparison to the number of little brown bats, the most common of the state’s bat species. One cave in the Adirondacks once harbored 200,000 little browns each winter. The Indiana bat, however, seems to be more resistant to the disease.

“There is a chance that the Indiana bat will be the most common bat in New York State, not because it’s doing well, but because it’s not dying out as much,” Hicks said.

When white-nose syndrome was first discovered, Hicks sent out pictures of infected animals to bat scientists around the country. None had ever seen anything like it. However, European scientists had. Apparently, bats in Europe have been living with white-nose syndrome for years, but for some reason it is not as lethal there.

Hicks said it’s possible that European bats have developed a resistance to the disease. Over time, he said, the same could happen here. If not, the die-offs will likely continue.