Die-off of bats could hurt area crops

Mystery illness hits caves in Vt., N.Y.

These little brown bats in a New York cave were suffering from a disease scientists have dubbed "white nose syndrome." (NANCY HEASLIP/NEW YORK DEPARTMENT OF ENVIRONMENTAL CONSERVATION)

A mysterious illness is sickening and killing thousands of hibernating bats in New York and Vermont, baffling scientists who fear that tens of thousands more may be dying in abandoned mines and dark caves throughout the Northeast.

Humans are not believed to be at risk from the disease, but the death of large numbers of bats could indirectly affect New Englanders: Bats devour crop pests, midges, and mosquitoes.

"I've studied bats for 40-something years, and I've never seen anything like this; it's alarming," said Thomas Kunz, a preeminent bat researcher at Boston University. "It's frustrating and perplexing, because we don't know what it is and we don't know how to control it."

The US Fish and Wildlife Service warned the public in the last week to keep out of caves and mines in New York and Vermont because humans might be inadvertently spreading the unknown pathogen. The National Speleological Society has closed all caves it owns in New York and Pennsylvania, and other caving organizations have urged people to avoid places where bats may hibernate in the Northeast.

No dead or diseased bats have yet been found in Massachusetts, but state officials are organizing an expedition in coming weeks to look for sick bats in four long-closed Western Massachusetts mines. Those mines are off-limits to the public, and bats hibernate in only a few tiny caves in the state, mostly on private land.

The disease was first discovered in a cave near Albany, N.Y., in January 2007 and was soon found in three more within 7 miles. In March, officials at the New York Department of Environmental Conservation determined that as many as 11,000 bats had died from the disease, dubbed "white nose syndrome" because of a flaky white fungus on the nose of many of the sick and dead bats.

Scientists do not yet know if the fungus is a cause of the illness or an effect. Some of the sick bats behaved oddly, clustering near the entrance of New York caves, flying in winter when they should have been sleeping and crashing into snow banks.

Scientists hoped that last year's outbreak was an anomaly. But in the last two weeks, it has become clear that the disease has returned and is spreading. Sick bats have now been found in caves 135 miles apart. Sick bats have been seen again in the original four caves, plus four others in New York, including one discovered yesterday. Bats in a western Vermont cave are also sick.

Researchers have found a small number of dead bats this year. But based on last year's experience, they expect many more to succumb around March.

Scientists say they are extraordinarily concerned because the disease is already affecting four species - including the Indiana bat, recognized by the federal government as an endangered species - and mortality has reached as high as 97 percent in some caves. In one New York cave, the population crashed from 1,300 bats several years ago to 38 this year.

"If we assume only 50 percent decline at the new sites, we are talking hundreds of thousands of bats that could die," said Alan Hicks, a bat specialist with the New York Department of Environmental Conservation.

Bats hold great ecological importance worldwide. In addition to feeding on insects, they pollinate plants in many places and disperse seeds, though not in New England. The animals can live longer than 30 years and generally have only one offspring a year, meaning that it would take many years for the population to rebound if it crashed.

While overall bat numbers in New England are hard to estimate, scientists say the nine bat species here probably number in the hundreds of thousands. Three of the species are migratory and leave in the winter, while others hibernate in old mines or in a line of limestone caves stretching north from the Berkshires through western Vermont and into adjacent New York. Some big brown bats, as many homeowners know, find a warm winter home in buildings.

Vermont officials examined four bat caves last week and did not see diseased animals, but will investigate more caves in the next two weeks. Similarly, in New Hampshire, which has smaller groups of bats, officials investigated four mines in recent weeks and found no evidence of disease.

More than a dozen government and university labs across the country are trying to determine the cause of the problem. So far, scientists have just a few tantalizing clues: They know that affected bats are using up fat reserves far earlier in the winter than normal, possibly because they are responding to the disease. Some of the bats also appear to be exhibiting symptoms similar to pneumonia.

"But really we have no idea what is causing it yet," Hicks said.

He said scientists don't even know whether the disease is spread by bats or by humans who visit the caves and mines. If bats are transmitting the disease, hibernating groups are particularly vulnerable, because they are in such close quarters. Often 300 animals are packed per square foot.

Researchers want to find out whether other colonies will become infected once bats of all species come out of hibernation this spring and disperse to their maternity roosts. Bats also travel great distances, wintering in Vermont, for example, but summering in Rhode Island, increasing the transmission risk.

Bolstering the theory that humans are spreading the disease is the fact that most of the infected populations have been found in caves or mines popular with cavers, with the exception of infected bats in the cave discovered yesterday.

Cavers say they will avoid caves until more is known about the disease. "Our goal is to find out any way cavers, through action or inaction, can help to prevent any further problems or assist in protecting the bats in the region." said Emily Davis, office manager of the New York-based Northeastern Cave Conservancy Inc., a nonprofit cave land trust that is holding an emergency meeting Sunday about the issue. Members "are willing to curtail the caving if it will help the bat populations," she said.

Bat specialists say they do not believe the request to stay out of caves should be extended to tourist attractions, because so few hibernating bats are in places where people visit.

Kunz and other scientists will be entering New York caves next week, using respirators and dressed in plastic suits that will be decontaminated afterward to make sure they don't spread the disease. They will draw bat blood to analyze the animals' immune systems.

They will also use thermal cameras: Because bats use so little energy when they are hibernating, if their bodies give off more heat than expected, it may indicate they are using up energy reserves and are afflicted with the disease.

"There is a lot we don't know," said Scott Darling, a wildlife biologist with the Vermont Fish and Wildlife Department. "There is a real threat."

Beth Daley can be reached at bdaley@globe.com.