White-nose syndrome, the disease that’s killed millions of insect-eating bats, keeps getting worse. It’s made a thumb-sized bat rare in parts of New England and has spread through most of the Eastern U.S., as far west as Missouri. Now another species has it, the endangered gray bat of caves in the Southeast.
The loss of bats is serious because they provide natural pest control. They live throughout the country, and the disease could end up almost everywhere as well. In places where bat populations have been lost, it could be decades before they recover, scientists say.
The fungus that causes white-nose syndrome spreads in cold weather, when bats hibernate. Gray bats might be especially vulnerable because they hibernate in huge numbers in only a few caves. The mortality rate differs among species of bats that have the disease, but in some cases it’s nearly 100 percent.
The gray bat was listed as being in danger of extinction in 1976, but its population had been growing. Although it’s too early tell how hard white-nose syndrome will hit the gray bat, Paul McKenzie, the Fish and Wildlife Service’s endangered species coordinator for Missouri, said the discovery was “devastating news.”
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“Because gray bats hibernate together in colonies that number in the hundreds of thousands, (white-nose syndrome) could expand exponentially across the range of the species,” McKenzie said Tuesday in a news release . A loss of gray bats also could destroy other cave-dwelling species that live off the bats’ guano.
Biologists recently saw the tell-tale white fungus on the muzzles, tails and wings of several gray bats in Hawkins and Montgomery counties in Tennessee. The bat’s main range, besides Tennessee, is Alabama, northern Arkansas, Kentucky and Missouri.
First detected in Albany, N.Y., in 2006, white-nose syndrome spread through the Northeast and down the Appalachians. In the winter of 2010-11, it hit the Midwest. This March it was reported for the first time in Alabama and Missouri, and in Acadia and Great Smoky Mountains national parks. The disease is now found in four Canadian provinces and 19 states.
“Eventually the disease is going to spread across the country,” said Ann Froschauer, a spokeswoman for the Fish and Wildlife Service.
Bats are the main nighttime predators of beetles and moths. Those insects and their larvae damage forests and crops, including cotton, tomatoes, corn, apples and cucumbers. A study last year estimated the loss to farmers at $3 billion a year or more.
“They’re essentially the only nighttime predator of many of our agricultural and forest pests. They save us a lot of money,” said Dave Waldien, a wildlife ecologist and the interim director of Texas-based Bat Conservation International.
Bats also eat mosquitoes, though not as their main source of protein, Froschauer said. “Mosquitoes are potato chips to bats.”
No cure or way to stop white-nose syndrome has been found. Earlier this year, biologists estimated that 5.5 million to 6.7 million bats have died.
Waldien said the disease had been spreading to new states and filling in more areas of states it had reached in recent years.
In Maryland, for example, white-nose syndrome was found on some state property last year, and this year it was detected for the first time nearby in an abandoned mine in the C&O Canal National Historical Park, about 90 miles from Washington.
“We do suspect that it will slowly move to the West,” Waldien said. “Right now it’s hit the most obvious migration paths, and so further westward expansion should be a little slower unless humans inadvertently carry it.”
The fungus was brought to the United States from Europe, where for some unknown reason it doesn’t kill great numbers of bats. A cave visitor probably introduced it inadvertently.
It’s named for the way the fungus grows around bats’ noses, but it also grows and causes lesions on other parts of their bodies, including the wings. Dead bats appear to have starved. Bats with the fungus wake up from hibernation in winter – when there are no insects – and quickly use up the fat stores in their small bodies.
The United States has 46 bat species. Most already have been declining in numbers because of habitat loss, wind turbine collisions, pesticides and pollution. The disease previously had been found in six species, including the endangered Indiana bat.
The Fish and Wildlife Service is leading efforts to study the disease and try to stop it. It announced $1.4 million in research grants last month. The agency also has recommended closing caves so that people don’t track in the fungus.
White-nose syndrome has been particularly devastating for the little brown bat, a species that makes up a huge chunk of the overall bat population and has a range throughout Canada and the United States except for the desert Southwest. Where its population has been measured, the death rate from white-nose syndrome is more than 90 percent.
Two years ago, a team of researchers made news when they reported in Science magazine that the little brown bat could become regionally extinct in 16 years.
Winifred Frick, the report’s lead author, said she’s now studying how the disease is transmitted. New findings could change the extinction estimate, she said. “We desperately hope we’re wrong.”
So far, however, extinction in a short time remains possible.
“The mortality rates have been catastrophic,” she said.
Most North American bats hibernate. They swarm and mate in the fall, hibernate in caves or abandoned mines all winter, emerge in April and disperse for the summer. Females bunch up in maternity colonies, where they nurse their young and care for them until they’re ready to fly.
Bats use the same hibernation and maternity colonies year after year. Scientists still have many questions about how far they travel, Frick said. Radio transmitters that are small enough for bats don’t last long enough or work very well.
“In the Rockies and the West, we don’t know where our bats go to hibernate,” Frick said. “A lot of our species we never see in winter.”
In the West, bats haven’t been known to hibernate in clumps of hundreds of thousands, as in the East, she said. It may be that there are big gatherings and scientists just don’t know where they are. But if bats are more dispersed in the West, the disease might pan out differently there, Frick said.
Bats are unusually long-lived for such small mammals. The little brown bat, for example, can live for more than 30 years. Unlike mice and rabbits, they’re not speedy reproducers. Females generally have only one pup per year.
Froschauer and Waldien say they hear people talk about how they don’t see bats anymore in places where white-nose syndrome has killed so many of them.
“People who used to sit on their porches with their children, watching the bats in the evening after a long day of work, say there are no bats here,” Waldien said. “And it is very hard to recognize that they will never see them in their lifetime again.”