Tuesday, April 26, 2011

Bats’ survival at stake

Researcher Kate Langwig measures the humidity near a bat in an old mine in Hague in January.Researcher Kate Langwig measures the humidity near a bat in an old mine in Hague in January. Photo by Carl Heilman II

Scientists find few signs of hope as white-nose syndrome continues to ravage hibernating species in the Adirondacks, the rest of the state, and much of the East.

By Winnie Yu

In the five years since scientists first diagnosed white-nose syndrome, the population of bats in the Adirondack Park has plunged so dramatically that their very survival is in question.

Little brown bats, once the most common bat species in the Adirondacks, have plummeted 90 percent. The already endangered Indiana bat is down 60 percent. Northern bats—the species that’s been hardest hit—are down 98 percent.

“Losing northern bats altogether from New York in the foreseeable future is a very real possibility,” says Carl Herzog, a wildlife biologist in charge of bat conservation and management for the state Department of Environmental Conservation.

“It seems likely that it will spread across North America.” –Carl Herzog, state biologist. Photo by Carl Heilman II

“It seems likely that it will spread across North America.” –Carl Herzog, state biologist. Photo by Carl Heilman II

Bats in the eastern United States and Canada are under siege, victims of a mysterious fungus called Geomyces destructans that has destroyed as much as 90 percent of the total bat population. The fungus causes geomycosis, or white-nose syndrome (WNS), a disease named for the white growth that occurs on the muzzles, wings, and ears of infected bats. Once established, the fungal spores invade and destroy the skin. White-nose syndrome causes bats to use up their stored fat reserves, awaken from hibernation prematurely, and leave their winter home in search of food. In the process, most bats die.

A great deal of what we know about WNS has been uncovered in only the last three years, and new information continues to emerge. Just this March, for instance, WNS was confirmed for the first time in a mine in Ohio and in the Canadian province of New Brunswick. Surveys by DEC this past winter found that the numbers of Indiana bats are down again at most, if not all, sites in New York State. DEC also looked at the five original white-nose sites in Albany and Schoharie counties, which are inhabited primarily by little brown bats. Based on the preliminary results, the decline in little brown bats may have stabilized, but it will take years to know for certain, Herzog says.

The U.S. Fish and Wildlife Service calls WNS a wildlife health crisis and is considering extending endangered-species protection to little brown, northern, and eastern small-footed bats, Herzog says.  “Even if they don’t take action, several states, including Pennsylvania, Vermont, Massachusetts, and Wisconsin, have already begun similar action on their own, and others, including New York, New Hampshire, and Connecticut, are contemplating doing it,” he says.

Scientists wear gloves while handling bats to prevent spreading white-nose syndrome. Photo by Carl Heilman II

Scientists wear gloves while handling bats to prevent spreading white-nose syndrome. Photo by Carl Heilman II

Labeling bats “endangered,” however, could have significant ramifications for commerce as well as private-property owners. For example, homeowners would no longer be allowed to kill bats that invade their homes, even if the owners suspected the bats had rabies. Wind farms would be more tightly regulated to minimize the killing of bats by turbine blades. “The potential negative impact on society of regulatory action can be serious,” Herzog says. “And endangered-species protection is not going to give us much in the way of tools to address the biggest threat to these bats, that being the disease itself.”

In the meantime, scientists are working feverishly to understand the disease, where it came from, and why it is spreading at such an alarming rate. “It’s a mystery, it really is,” Herzog says.

Bats in the wild

With approximately 1,100 different kinds, bats account for a fifth of the world’s species of mammals. In North America, there are forty-five species of bats; twenty-six of those are hibernating bats, and the rest are migrating bats that travel south for the winter.

Bats play an important role in our ecosystem. As the only mammals that fly, they are voracious consumers of insects, devouring as many as 1,200 mosquito-size insects in an hour. They also feast on moths, beetles, and other large night-flying insects. “They naturally eliminate forest and crop pests,” says Ann Froschauer, a spokeswoman for the U.S. Fish and Wildlife Service.  “Without them, there’s a greater potential need for pesticide use.” In fact, a 2006 study in south-central Texas found that Brazilian free-tailed bats provided $741,000 worth of free pest control for cotton production.

State scientists explore one of the corridors in the abandoned mine. Photo by Carl Heilman II

State scientists explore one of the corridors in the abandoned mine. Photo by Carl Heilman II

New York State is home to nine species of bats, six of which hibernate. All six of the hibernating species (WNS hasn’t affected migrating bats) have been severely impacted by WNS, with little brown bats and northern bats being the hardest hit, says Al Hicks, a retired bat specialist for the state Department of Environmental Conservation, who still works on bat research. “What we’re seeing isn’t consistent from site to site,” Hicks says. “Some sites do better than others, meaning there’s a lower percentage of animals dying in some sites. All of them are pretty much dying at rates that we’d consider horrendous.”

Not long ago, it was common to find the ceiling of an Adirondack cave covered with bats in the wintertime. These days, such a find would be considered nothing short of a miracle.

We recently went with a team of DEC scientists to an old graphite mine in Hague that once housed the largest population of hibernating bats in New York State. Back in 2000, scientists estimated that 185,000 bats lived in the mine. By the winter of 2010, scientists counted 2,049. This winter, they did not do a thorough count, but judging from appearances, the numbers are down again. When we scanned the ceilings, we found only small clusters of two or three bats here and there—a far cry from the days when hundreds, even thousands, huddled together.

“It’s pretty doom and gloom in the Northeast,” Froschauer says. “Our mortality numbers are astounding. I recently went into Aeolus Cave in Vermont, where historically there were three hundred thousand bats. There were thirty-six bats left. They were wiped out in just two years’ time.”

A mysterious killer

The rapid spread of G. destructans is only one of the many mysteries surrounding the insidious fungus, which was first documented in 2006 in Howe Cave in Schoharie County, forty miles west of Albany near the popular tourist destination, Howe Caverns. A recreational caver noticed a white growth on the muzzles of hibernating brown bats inside the cave and hundreds of dead bats on the floor.

The remains of a diseased bat on a rock wall. Photo by Carl Heilman II

The remains of a diseased bat on a rock wall. Photo by Carl Heilman II

According to a 2010 study in the journal Science, WNS has been confirmed in at least 115 bat hibernacula in the United States and Canada and has spread at least 745 miles from Howe Cave. The fungus has been suspected in states as far west as Oklahoma and confirmed as far south as Tennessee. It’s also been found in the Canadian provinces of Quebec and Ontario. “It seems likely that it will spread across North America, although the bats of the far west are different enough that things may look somewhat different,” Herzog says.

The spread has been deadly, causing a 30-99 percent decrease in hibernating bats every year.  “The bat population is clearly crashing,” Hicks says.

No one knows exactly how the fungus got into Howe Cave. Experts believe it was introduced by a human visitor, most likely someone from Europe. A study in the journal Emerging Infectious Diseases said the fungus has been found on bats in Germany, Switzerland, and Hungary.  Oddly enough, none of the bats in those countries died from the infection. “It’s possible that the fungus coevolved with the bats in Europe, so there may be a symbiotic relationship,” Froschauer says. “Our bats here don’t have any defenses.”

Hibernating bats have provided a perfect environment for the fungus to grow and spread, in part because of the bats’ physiology, but also because of their behavior. During hibernation, bats go into a state of deep sleep that allows them to conserve body fat over long periods of time. Body temperature drops and becomes the same as their surroundings, often falling to somewhere between 33 and 55 degrees Fahrenheit, which happens to be the optimal temperature range for the growth of G. destructans. At the same time, the immune system shuts down, so the bat is unable to mount an effective defense against the invading fungus.

Moreover, hibernating bats usually cluster together and seek out humid areas like those found in caves and abandoned mines. The moist environment and close quarters only encourage the growth of the fungus.

Bats snuggle in a bore hole in the mine. Photo by Carl Heilman II

Bats snuggle in a bore hole in the mine. Photo by Carl Heilman II

Once on the bats, the fungus invades the dermal layer of the skin and erodes the tissue, wiping out hair follicles and sweat glands involved in regulating the bat’s body temperature, respiration, and hydration. Wing tissues die as oxygen supplies are choked off and dehydration sets in. Many dead bats are found emaciated. “We thought the fungus was just waking them up,” Froschauer says. “We’re now learning that it’s disrupting them physiologically.”

If they’re awakened and hungry, the infected bats often emerge prematurely from hibernation and go searching for food. They may be seen flying around in midwinter or clustering near the entrances of hibernacula. These bats usually freeze or starve to death.

Slowing the slaughter

Taking action against WNS has proven to be a challenge, and a race against time, with the future of bats at stake and many unanswered questions still lingering. But some things are slowly becoming clear. For instance, scientists are fairly certain that the fungus was brought here from Europe, most likely by a caver visiting Howe Cave. DNA investigations are expected to reveal exactly where the fungus came from, Herzog says.

Scientists are also fairly certain that the disease is spreading primarily bat to bat, though other modes of transmission have not been ruled out. “[Bats] are very social animals, and with 75 percent of the counted hibernating bats in New York found in just five caves and mines, the potential for swift and devastating results is obvious,” Herzog says.

What’s less clear is the extent to which people are contributing to the spread. But most experts don’t want to take any chances. “Human transmission has not been definitively proven, but it certainly has not been disproven either,” says Jeremy Coleman, national white-nose syndrome coordinator of the U.S. Fish & Wildlife Service.

To that end, the agency has closed all caves and mines on National Wildlife Refuges across the country, and the U.S. Forest Service has closed caves in regions where WNS has been documented. Closing the caves to the public is designed to prevent the possible spread of the fungus by humans.

“It is unlikely that we will ever be able to prove that people unwittingly transporting Geomyces destructans have added to the spread of WNS,” Coleman says.  “However, scientific evidence and logical deduction supports the position that human transmission is a very real concern. Our approach has been to assume that people are capable of transmitting all kinds of things. To me, the people who demand definitive proof are not willing to accept the potential for human responsibility.”

Meanwhile, in labs, scientists are looking for treatments. Tests of 1,900 different compounds showed that most did nothing to kill the fungus, Herzog says. Some even promoted the growth of G. destructans, though a few did inhibit its growth and even killed it. Applying the treatments, however, is another matter. Any antifungal drug could seriously disturb the natural environment of the cave and hurt other species. “My personal feeling is it’s not a viable option for widespread use,” Coleman says. “It is unlikely that a chemical treatment could ever be applied in a natural cave for fear it could impact a non-target species.”

Other options include captive propagation, as was done for California condors and black-footed ferrets. Large numbers of bats would be bred, kept in captivity, and eventually released into the wild. Another option is to capture bats as they enter their hibernacula for the winter, clean them off, and transport them to an artificial site for hibernation. They could also be removed by hand from caves or mines once they’ve gone into hibernation and taken to an artificial site. The bats would be released in spring. Yet another option is cryopreservation: freezing eggs, sperm, or tissues to enable in-vitro reproduction of bats.

One thing for certain is that the losses are rapidly altering the state’s hibernating bat population. Tri-colored bats may be at risk of disappearing, much like the northern bats, Herzog says. “Little browns have the benefit of having previously been the most common species by far, but if the bottoming-out of the decline doesn’t materialize they will also follow,” he says

Meanwhile, the loss of Indiana bats has been slow but steady, with no end in sight to their decline, Herzog says. Data results on small-footed bats are unclear, though these bats will remain rare. “Of the six [in New York], big browns are clearly doing the best,” Herzog says. “They are now the most abundant species in the state, and it’s even possible they will benefit from the reduced competition.”

What you can do

Coleman says people can help by spreading awareness of the disease. “Be aware and report bats [to DEC] if you see them in bad condition or behaving unusually,” he says. It’s also helpful to donate money to nonprofit organizations that do bat conservation or speleological groups concerned about caves. Most important, he recommends staying out of caves and mines to reduce human contact with the fungus and the possibility of spreading it.

At the moment, the best hope is that bats will develop a way of dealing with the disease on their own, whether that comes from an immune-system response, behavioral changes, or a combination of the two. Survivors that are immune may produce offspring that are resistant, and the population may eventually rebound.

“There are some very early hints that this might be taking place for little brown bats, but it will take years to tell if that’s happening and it’s way too early to say,” Herzog says.“Barring that, the prognosis for most of the state’s hibernating bat species is not good.”

……………..

Bad news from an old mine

The graphite mine has been abandoned for years. The timbers propping up the roof are rotting, and the iron rails that once ferried carts of valuable stone are rusting. Old buckets and tools are strewn about the damp floors.

At one time, these desolate corridors and caverns in the hills of Hague harbored the largest population of wintering bats in the Adirondack Park. The mine used to contain two hundred thousand bats, nearly all of them little brown bats (Myotis lucifugus).

That was before white-nose syndrome.

Last year, state scientists counted only 2,049 little browns. During a follow-up visit this past January, state scientists saw even fewer. Usually, the bats were alone or in small groups of two or three.

“Before white-nose, these ceilings would be full of little brown bats—clusters of forty or fifty,” said Scott Crocoll, a biologist with the state Department of Environmental Conservation. After we left one chamber, he remarked: “We’re lucky if there were fifty to sixty bats in there, and there used to be thousands.”

But the main object of the scientists’ search was the Indiana bat (Myotis sodalis), which is on the federal list of endangered species. Several years ago, before white-nose, they found more than a hundred Indiana bats here. Last year they found none. On this visit they would find one.

“It’s hard to get excited about one, but it’s better than nothing,” said Carl Herzog, DEC’s main bat expert.

Another slender ray of hope: Herzog believes the number of small-footed bats (Myotis leibii) stayed the same as last year. One theory is that small-footeds are more cold-hardy and thus better able to withstand the side effects of the disease.

The bad news—not unexpected—is that many of the bats in the mine showed signs of white-nose syndrome. The ill ones would be lucky if they survived the winter.

Joe Racette, another DEC biologist, said one study suggests that bats are picking up toxic chemicals from insects. The toxics may make bats more vulnerable to white-nose syndrome, but the correlation, if any, is not understood.

Whatever the cause, scientists have been unable to stop the disease.

“What can we do about it other than continuing to research?” Racette asked.

—Phil Brown

8 Responses

  1. [...] feature-length article from the Adirondack Explorer dives deeply into the problem of white-nose fungus that’s [...]

  2. Scientists pin down cause of bat disease | says:

    [...] this year, Winnie Yu reported in the Explorer that the number of little brown bats in the Adirondacks—once the most common bat [...]

  3. [...] hope of observing a single bat. Unfortunately, no bats ever appear as the white-nose syndrome has decimiated many bat species in the Adirondacks. With the mosquitoes swarming around my head, I can wait no longer and I retreat to my tarp for the [...]

  4. [...] Some of the bats are killed more quickly as oxygen supplies are choked off, wing tissues die, and dehydration sets in. Many dead bats are found emaciated (Adirondack Explorer). [...]

  5. [...] 60 percent. Northern bats—the species that’s been hardest hit—are down 98 percent” (Adirondack Explorer). It would not be surprising for the Northern Bat to become completely extinct in the Adirondack [...]

  6. Adirondack Bats: Endangered Bats - Lake Champlain Life says:

    [...] percent. Northern bats—the species that’s been hardest hit—are down 98 percent” (Adirondack Explorer). It would not be surprising for the Northern Bat to become completely extinct in the [...]

  7. Adirondack Bats: White-nose Syndrome - Lake Champlain Life says:

    [...] Some of the bats are killed more quickly as oxygen supplies are choked off, wing tissues die, and dehydration sets in. Many dead bats are found emaciated (Adirondack Explorer). [...]

  8. Adirondack Bats: Endangered Bats says:

    [...] down 60 percent. Northern bats—the species that’s been hardest hit—are down 98 percent” (Adirondack Explorer). It would not be surprising for the Northern Bat to become completely extinct in [...]

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