For years, as dusk settled over James Roby's organic farm in Connecticut, bats feasted on the insects hovering near his crops. Counting the dark shapes swooping against the evening sky from his picnic table, Roby said he would lose track of their quick movements as the number passed a dozen.
But last year, the counting was too easy -- he normally saw no more than two bats on a given night.
A single little brown bat, one of the most common species in the United States, can eat up to 4,500 insects per night during their active season. That adds up to about 1 million insects per year for just one bat. Multiply that by the millions of insect-chowing bats in the United States, and it comes out to a whopping $22.9 billion in free pest control for farmers like Roby.
But that agricultural and economic benefit is at risk from a disease creeping from cave to cave and darkening entire colonies at a go.
White-nose syndrome, so named for the fuzzy fungus that grows on the bats' nose, mouth and wings as they hibernate, first appeared in New York in 2006 and has since spread to 16 states and four Canadian provinces. The latest estimates by the U.S. Fish and Wildlife Service pegs the fuzz's toll at between 5.7 million and 6.7 million bats.
While much is still unknown about the fungus, it appears to target a variety of hibernating species that live primarily on insects. "We're not looking at the extirpation or extinction of a single species," said Greg Turner, an endangered mammal specialist for the Pennsylvania Game Commission. "We're looking at a whole guild of species."
Roby said the loss of bats is already noticeable on his farm. He's found new types of caterpillars on his cabbage that he hasn't seen before. Roby said he hasn't started using new pest control measures yet, but that it's only a matter of time before insects take advantage of the lack of predators and explode in population, forcing farmers like him to fill the gap some other way.
"It's ridiculous the level of [pest] control that they have," Roby said. "Less bats means more pesticides, period."
Slowing the spread
The fungus believed to cause white-nose syndrome, Geomyces destructans, has spread throughout the East, from Maine to North Carolina, and is thought to have traveled as far west as Oklahoma. It's expected to continue on its destructive path across the country, though no one knows how quickly it will move, where it will show up next or how bat species in the West will fare, according to Jeremy Coleman, the Fish and Wildlife Service's national white-nose syndrome coordinator.
"We are dealing with the spread of a virulent pathogen, and we don't yet have a lot of tools to control the spread," Coleman said.
The loss of bats to date has already caused a fright, but the disease could hit the Midwest and West much harder than the Northeast. The value of insectivorous bats to agriculture in states like Iowa and North Dakota tops $70 million per year in some counties, according to estimates published in Science last year.
Once a wildlife disease is established in the wild, it's practically impossible to eradicate it, the Pennsylvania Game Commission's Turner said. "It's all about prevention," he added.
Slowing the spread of the disease is a major focus of the national effort, and some of Coleman's key strategies include closing to visitors the caves and mines where bats hibernate and implementing decontamination protocols for spelunkers as they leave caves to prevent the possibility of a stray fungus spore being transported from one end of the country to the other.
"The biggest fear we have is a human-mediated big jump," Coleman said. While it remains open to debate whether that's possible, the leading theory for the disease's origination is that the fungus somehow hitched a ride to the United States from Europe. The European strain appears not to have the same deadly effect on bats, though researchers don't know if it is innocuous, or if bats have built up an immunity to it over time.
Either way, Coleman and his colleagues are doing their utmost to keep the disease in check until researchers can untangle a knot of questions around how it takes out its prey.
Scientists suspect the fungus irritates the bats so they wake early from their winter hibernation, leading to excess energy use and starvation or freezing to death, but they still don't know what cues that process. Some are focused on determing if the spores have another mechanism of directly killing the mammals, as well, according to Kevin Castle, a wildlife veterinarian for the National Park Service and agency lead on white-nose syndrome.
Researchers are also trying to learn how and when bats are exposed to the fungus. Bats have been shown to infect other bats, but researchers don't know if a bat that flies into an infected cave during the summer, when the fungus might not be growing, could still become infected or spread the fungus elsewhere, Castle said.
"We need to find out more about the fungus itself, where it can grow," Castle said. "That will help get a better handle on the places it is most likely to turn up, and we can think about actions to protect those populations."
Geneticists are analyzing the fungus to see how closely related it is to the strain found in Europe, and if it is mutating in the wild, potentially making it a more potent threat to North American bats. They are also interested in learning if there is a gene common to survivors that could help species outlast the fungus.
Beyond a core group of dedicated researchers, it has been a struggle to get the public and agencies outside of the "hot zone" for white-nose syndrome involved, Coleman said. Last year, that changed, he added, when it became clear the disease was not just a Northeastern problem but one that will spread from coast to coast. Now, FWS has a truly national response plan in place, he said.
"People in California don't live and breathe white-nose syndrome like people in the East, but it's on their radar and they are engaged in response planning," Coleman said.
The issue has also gained the attention of Congress, which directed FWS to allocate $4 million for white-nose syndrome research and management next year. While this is the most funding the disease will have received to date, it's still far from what advocates say is needed to be effective. The advocacy group Bat Conservation International has recommended $11 million across all agencies dealing with the disease, said Nina Fascione, the nonprofit's executive director.
Fish and Wildlife has been criticized by conservationists for being too slow to respond, and by recreational cavers for being too aggressive with cave closures. But Coleman defended how his teams have responded to the crisis and said he was pleased with the progress that has been made. "It's challenging sometimes, but we're working to improve connections [with critics] as much as we can," he said.
FWS will release implementation measures for the national plan, which will include a budget outline, in the coming month. The agency is also reviewing the evidence for listing three affected bat species under the Endangered Species Act. Even though listing won't help stop the primary threat, Coleman said it could provide protection from other threats that would help bats' chances of survival, especially if scientists can make the disease breakthroughs that would move bats into a recovery phase.
The agency is investigating the potential for captive breeding programs to help recover the hardest-hit species. But recovery will be slow-going; much like elephants, bats are long-lived and have low reproduction rates, often one offspring per year.
"If bats can recover, it's going to take hundreds of years," Turner said.
While the situation is dire, bat advocates are clinging to a few positive signs. Some bats seem to survive infection, though it is still unclear if they are able to survive multiple years of disease. And while the fungus has bats pouring out of caves by the thousands at unseasonably early dates, they may have gotten lucky this year, as the mild winter could keep them from freezing and lead to an early insect buffet, too.
Coleman said hard data on those hunches will come in via systematic bat surveys to be conducted over the next two months. "You've got to be hopeful," Coleman said.