White-nose syndrome haunts bats

Bats are flying ambassadors of Halloween, adding spooky ambience to countless forests, graveyards, and haunted houses. Lately, however, the tables have turned — Halloween and the winter it foreshadows are an increasingly scary time to be a bat in America.

(Photo: U.S. Fish and
Wildlife Service)

That's because a deadly, cave-dwelling disease is sweeping across the U.S. Eastern Seaboard, killing 90 to 100 percent of bats in some colonies. Hundreds of thousands of bats have died so far, and some estimates put the total at 1 million.

Like Freddy Krueger, this killer waits until its victims are asleep, but it's even more mysterious than the sweater-clad Elm Street villain. Three years after first appearing in a single New York bat cave, the fungus has now infected 81 caves in nine states, and scientists still aren't sure where it came from, where it will go next or even how exactly it kills.

"We can't directly link the fungus to organ failure or anything like that," says U.S. Fish and Wildlife Service biologist Susi von Oettingen. "It certainly is ultimately responsible for the death, but we're not sure how."

Scientists are sure, however, that it's bad news for millions of American bats, which recover slowly from population loss since many have just one offspring a year. Bat experts are also worried the disease, known as "white-nose syndrome," will soon begin hopping through vast cave networks underneath the Midwest and Southeast, potentially wiping out endangered species like the gray bat and the Indiana bat.

And what's bad for bats is often bad for people, too. As a top predator of flying insects, bats regulate the population size of everything from gnats, flies and mosquitoes to costly agricultural pests, and they play key ecological and economic roles throughout the United States — making a batless Halloween even scarier than one swarming with them.

A long winter's nap
Bats are one of the most successful and diverse mammals on Earth, ranging from 4-inch, sub-Arctic furballs with sonar to tropical "macro-bats" with 6-foot wingspans and primate-like vision. (Bats are not rodents, despite appearances, and are actually more closely related to primates than they are to squirrels or mice.)

Many North American bats pay a price for living in colder climates, though. Their frequent flapping uses a lot of energy, and freezing temperatures virtually eliminate the protein-rich insects they eat. Some species migrate south, but the majority of U.S. bats tough it out by hibernating in caves or mines until the bugs come back in spring.

(Photo: Kentucky Department
of Parks)

Surviving a frigid New England winter with no food isn't easy, and bats undergo extreme physiological changes so they can conserve enough energy. They slow down their heart rates, suppress their immune systems and drop their body temperatures to within one degree of the ambient air. They enter this low-power, near-death state for up to two months at a time, waking up periodically to stretch, preen, relieve themselves and sometimes mate. These hibernation breaks use up about 90 percent of the energy bats have stored for the winter, so it's critical that they only wake up at the right times.

Despite its high stakes and risks, hibernation has worked for millennia. It wasn't until the early 20th century that it began to fail for some bats, and only then because of cavers and scientists who disturbed their hibernation without understanding the consequences. Combined with increased pesticide use, habitat loss and bats' naturally slow reproduction rate, this decimated several U.S. bat species over the decades — Indiana bats, for example, fell by 50 percent from 1967 to 2005, and now half of the species' worldwide population spends winters in just two caves.

But today, all 25 U.S. species of hibernating bats face perhaps the greatest threat to their biological business model they've ever seen. The seemingly safe caves and mines where they've always sought refuge are increasingly infected with Geomyces destructans, a previously unknown fungus that's now being implicated in North America's steepest wildlife decline of the past century, and seems to be causing bats to wake up from hibernation too early and then fly outside as if spring arrived.

From cave to grave
White-nose syndrome doesn't directly damage, or even infect, any of bats' internal organs.  But if bats' vital organs are left untouched, what's killing them? And what possesses them to fly outside?

"One of the theories is, because it's invading the skin in winter, it could be an irritant, waking up the bat from hibernation because it itches and causes stress,"  von Oettingen says. "The bat may then leave the cave simply to try to flee the itching."

Although the case against Geomyces destructans is still in its infancy, most affected bats seem to die from starvation, having exhausted themselves by flying around — or even just being awake — when no food is available. Their dead bodies often have little or no fat left on them.

Other theories range from wing infections, which might disrupt bats' temperature-regulating abilities, to disorientation and confusion, which could be what sends them flapping crazily into the outside world.

(Photo: National Park Service)

Lights at the end of the tunnel
Sometimes natural immunity emerges as a ray of hope during disease outbreaks, but von Oettingen says there's no sign of it yet with white-nose syndrome.

Finding a cure, vaccine or treatment won't be easy, either. It would need to be something that can easily be applied to a large number of bats, is safe for bats, is safe for people, and isn't deadly to other, beneficial fungi that also live in the cave.

Scientists are still fighting, though, armed with grant money the Fish and Wildlife Service has allocated to white-nose syndrome research. In March, a pair of researchers proposed putting space heaters in bat caves to help sick animals save enough energy to survive the winter. And in mid-October, a team of biologists set up video cameras in a New York mine where white-nose syndrome has been hitting bats heavily, as well as a cave where it's expected to spread this winter.

The urgency of white-nose syndrome is driving a flurry of similar research this year, and von Oettingen says it could be a pivotal winter for discovering the disease's secrets, and for planning how to save endangered bat species before it's too late.

"This year's going to tell it," she says. "If it spreads even more rapidly than last year, that gives us an indication of how fast this is going to go and how devastating it can be. But if we're able to find at least some short-term treatment, maybe we'll be able to slow the spread, or at least contain it.

"I am hopeful this year that we are able to find a treatment," she adds, "or maybe find out the caves in the Southeast just have a different environment, and it stays confined to the Northeast. But most biologists you talk to think it will keep spreading."

Russell McLendon is an associate editor at the Mother Nature Network, where a version of this post originally appeared.

More from Mother Nature Network

• Which is better? Rice, hemp, cow, soy, almond or goat milk?
• Swedes begin labeling food emissions
• How to roast pumpkin seeds
• How can I make lunch less of a landfill hazard?
• Bacon, cheesecake, and Ho Hos turn rats into junk food addicts

Check out Yahoo! Green on Twitter and Facebook.