Silent Night

Scientists around the state are scrambling to save Maine’s bat population from a deadly fungus.

By Virgina M. Wright

Photo: Jason Edwards/National Geographic/Aurora Photos

On a warm June evening in the central Maine town of Corinna, Elizabeth Vigue sat down in a lawn chair alongside her daughter and a friend in anticipation of an aerial show. They had been told to expect hundreds of hungry mother bats to come soaring out of a nearby barn at dusk — bats that the Maine Audubon Society volunteers would dutifully count for a statewide census.

Instead, they counted fewer than fifty of the tiny winged mammals. A month later, when the colony’s population should have doubled with the addition of fledgling pups, they counted fewer than a dozen. That likely meant, Vigue says, that three-quarters of the adults had died, leaving their nursing babies to starve. “It was very saddening,” she says.

Over the past two years, Maine’s night sky has undergone a silent but devastating transformation: tens of thousands of bats that once swooped and darted through the summer darkness have all but disappeared, victims of white-nose syndrome, a disease that weakens their immune systems and eats at their wing tissue, turning it as holey as Swiss cheese.

“The speed with which it has spread is shocking,” says Steve Agius, assistant manager of the Aroostook National Wildlife Refuge in Limestone, where Cold War–era bunkers have been converted into artificial caves to serve as laboratories for researchers studying the disease. “The die-off we’ve experienced with cave-hibernating bats is unprecedented. It is the most precipitous decline of a species that we have seen in our lifetime. It’s frightening, and it’s disturbing.”

With only three known hibernacula — caves and mines where bats overwinter — Maine’s bat population has been particularly hard hit by white-nose syndrome, but the situation is dire throughout the Northeast. The U.S. Fish & Wildlife Service estimates that more than five million little brown bats — the most common bat species in North America — have succumbed since 2006, when biologists discovered a large number of dead bats on the floor of a cave near Albany, New York. All of the animals had a white fungus, recently reclassified as Pseudogymnoascus destructans, growing around their noses and mouths.

“It’s an exotic fungus, not native to North America,” says John DePue, a biologist with Maine Inland Fisheries & Wildlife. “It is very similar to strains in Europe. One hypothesis is that the spores were carried to the cave in New York on some caving equipment that was used in Europe. The spores sloughed off and were dispersed into ideal growing conditions, which is the same environment in which bats hibernate in winter.”
Five of Maine’s eight bat species hibernate in mines or caves, making them susceptible to white-nose syndrome, which was first identified here in the spring of 2011, in a mine in Oxford County. “We had been monitoring these hibernacula sites for a number of years, and we increased our monitoring when we started hearing about the disease,” DePue says. “We knew it was coming, and we were looking for it. The species being affected that humans are most likely to notice are little brown bats, which in summer often roost in attics, barns, and other manmade structures. We still have little brown bats showing up in attics and barns, but those likely don’t winter in Maine. Our wintering population has been hit hard — we’ve lost 90 to 100 percent of the bats in our hibernacula.”

Chiroptophobes might welcome the news, but Annie Kassler of Camden, a self-described bat enthusiast and speaker for Conservation International and the Bat World Sanctuary, is on a mission to change their minds. Bats, she says, are among nature’s most fascinating and beneficial animals. They also are among the most misunderstood.

“Bats don’t get caught in your hair,” says Kassler, as she begins refuting the myths one by one, “not on purpose, because they don’t care about you or your hair, and not by accident, because they’re much too clever for that.”

Moreover, Kassler continues, bats are no more prone to rabies than any other wild animal (fewer than one-half of 1 percent are rabid), and they don’t want to feast on your blood (vampire bats live only in Latin America, where they take blood harmlessly from livestock).

Bats are not winged mice. They are not, for that matter, rodents. They belong to an order all their own, Chiroptera, and, Kassler says, have more in common with primates than with mice, rats, and squirrels. They do not, for example, have litters; females generally have just one pup a year. A healthy bat will live eighteen to forty years, depending on the species. “Usually in biology there is a distinct ratio between body size and longevity,” Kassler says. “Small creatures tend to live fast and die young. Bats are the longest-lived creature for their size. Irish bat scientist Emma Teeling believes bats hold the key to human longevity because they are able to live so long without a lot of wear and tear on their bodies. Flight is not only difficult, but also metabolically costly, yet the bats just don’t wear out.”

And — surprise, surprise — bats are not blind. That misconception, Kessler says, probably arises from observations of bats’ erratic flight patterns, as the critters use echolocation to find insects in the dark.

Which leads us to why even chiroptophobes should care about the danger that white-nose syndrome is posing to bats. “Bats eat a lot of insects at night — one little brown bat can eat one thousand mosquitoes an hour, and not just mosquitoes, but moths and other insects,” John DePue says. “Now those insects are not being consumed. Some of those mosquitoes and flies carry diseases that impact humans, like eastern equine encephalitis. There’s research showing that bats provide American farmers at least $3.7 billion worth of pest control a year. It’s a big deal. The fear is not just crop damage but an increase in pesticide use on crops, which then leaches into water sources.”

As the species die-off is unprecedented, so, too, is the response. “The collaboration and partnership among federal and state agencies, nonprofit organizations, and academics is quite profound,” says Steve Agius, who worked with state biologists in New York and Vermont to bring thirty hibernating little brown bats to a climate-controlled bunker at the Aroostook National Wildlife Refuge last December. The Limestone bunkers were among several in the Northeast considered for a study into whether artificial caves might be used as part of a mitigation strategy against white-nose syndrome and the only ones found to mimic the temperature and humidity conditions of bat hibernacula. The idea is to provide a sterilized structure for hibernation that might give infected bats “a fighting chance” when they are most vulnerable, Aguis says. “In summer, when bats are actively feeding and foraging, their immune system is active and robust. They are able to groom themselves and keep the fungus down. But when they are hibernating, their immune system is suppressed so they can’t invest their energy into fighting it and the fungal load on them is able to ramp up.”

All of the thirty bats brought to the refuge were infected with the fungus; nine survived the winter, which Agius says is better odds than what is being seen in many caves. This winter, researchers will bring not bats but Petri dishes of the fungus to the bunkers and experiment with biological controls such as bacteria. In the future, they will attempt to attract native bats to the artificial caves.

John DePue, meanwhile, is now analyzing data from acoustic transect surveys conducted over the summer. The surveys, which involve placing a bat-call detector on the top of a truck and driving about twenty miles per hour over a thirty-mile area, is expected to yield information on population trends.

At Maine Audubon, biologist Susan Gallo is working with homeowners who have summer colonies roosting in their attics and barns. Some are looking for ways keep the colonies productive. Those who want to exclude the creatures are encouraged to wait until after the pups have fledged; otherwise, the mothers cannot get inside to feed their young.

Enthusiasts like Annie Kassler and Elizabeth Vigue are also doing their part. “When I hear people say they have a bat in their house and they want to kill it, I step up to the plate and say, ‘Let me help you remove it,” Vigue says. “‘I will be more than happy come over there with my net and catch this guy and release him.’ There’s a certain beauty to bats when they are flying out of a building. I’ve become quite fond of them.”

Virginia M. Wright

Virginia M. Wright is the senior editor at Down East.