Thursday, February 10, 2011

Something Wicked This Way Comes

Tri-colored bat w/ white-nose syndrome fungus (NCWRC photo)
Unless you're tuned in to the environmental news beat, the startling fact that eastern North America's cave bat populations are facing immediate collapse may have slipped under your radar.

For many, the story of white-nose syndrome's emergence and its affect on hibernating bats didn't begin until popular periodicals like "National Geographic"  and "Science" magazines ran articles announcing its discovery and potentially catastrophic consequences.

In truth, WNS was first discovered back in February, 2006 outside Albany, N.Y. A caver there photographed hibernating bats with a mysterious white fungus growing around their muzzles. He also observed several dead bats. The following winter, as bats began returning to their ancestral wintering sites in natural caves and retired mines, the insidious fungus was documented in other locations and the body count rose into the hundreds. Since then, WNS has spread throughout the New England states, south to Tennessee and west to Indiana. More than 1 million bats have perished in five years. Mortality rates in some hibernacula (a big word for caves and mines where bats spend the winter) have been 90 to 100 percent.

Last week, biologists from the North Carolina Wildlife Resources Commission found the state's first WNS cases in a retired mine in Avery County. It was not a surprise, but nevertheless, a dark shadow has descended upon us here in the Old North State.

Marking the spread of white-nose syndrome in North America. (Pennsylvania Game Commission)
The evidence strongly suggests WNS is spread from bat to bat, but many are concerned that human cave visitors may inadvertently spread the highly-contagious disease across large geographic distances.
A USFWS biologist prepares to enter a bat hibernacula in western NC. (USFWS photo)

Infected bats typically display non-typical behavior that includes high levels of activity during a period in their life cycle when they should be hibernating, or more accurately, in a state of torpor. For whatever reason, bats with WNS fidget and fly around to the point that energy stores which were supposed to get them through the winter are exhausted and they subsequently die of starvation, exposure, dehydration and/or the damage the fungus does to their thin wing membranes.

The why here and why now are still open to speculation. Since the fungus suspected of causing WNS - an unusual type that prefers cold, high-humidity environment, specifically bat caves - has been preliminarily identified, the same species has also been found in western Europe, where it seems to have a zero-mortality rate on the bats there. The fungus could have been introduced from Europe inadvertently. Another possibility is the fungus could have been here all along but only recently mutated into the deadly pathogen it is today.

Tri-colored bat in Avery County w/ WNS. (NCWRC photo)
Scientists still haven't come up with a way to stop the spread of WNS or treat bats that have become infected. Efforts to protect uninfected caves and retired mines have been ineffective. Killing the fungal spores inside the caves is a possibility, though not in the minds of many biologists because cave ecosystems are notoriously delicate. The effects anti-fungal agents might have could be worse than the disease itself.

WNS has already caused serious declines in six types of cave bats. Several species already threatened or endangered are susceptible and other populations, once considered to be healthy, could, in the next few years, potentially fall close to the edge of regional extinction (or worse).

What's all this got to do with you and me? Aside from the very real possibility that this disease could spark a major extinction event in North America bat species already at risk, there are tangible consequences to a world without bats. The bats that are affected are insectivores of the highest order. Some studies suggest bats eat as many as 1,000 mosquitoes an hour. If you enjoy the outdoors (and I suspect you do), fewer bats mean more insect pests - both those that bite and those that destroy crops. The question is, when you're sitting on your porch on a beautiful evening this summer, will you notice you're using more mosquito repellent? As you tend your backyard gardens, will you be tempted to break out the insecticide that you haven't thought of using since you went "organic" so many years ago? Will you look into the night sky and wonder, "What happened to all the bats we used to see?" Or will you notice anything at all?

For more information, click here for U.S. Fish and Wildlife Service's compilation of research and recommendations. To support bat research and conservation, check out Bat Conservation International.


  1. I've got two questions that you may know the answers to, since you're up on this stuff:

    Quote - "More than 1 million bats have perished in five years. Mortality rates in some hibernacula (a big word for caves and mines where bats spend the winter) have been 90 to 100 percent."

    1 million bats in 5 years, right? What's the normal mortality rate on the same size sample over 5 years prior to the discovery of this stuff?

    Also, without specific information about the samples you're talking about that had near ( or actual) 1005 mortality, it's hard to make the assumption that those facts are a significant reason for alarm. A cave with 100 bats in it that all die might be less dramatic than a cave of 30,000 with 90% mortality, IMHO.

    I'm not trying to discount your numbers or the importance of protecting bats(I hate bugs, just so you know - and don't mind bats.) but I think we should always be careful when relaying a story about some environmental "catastrophe" looming in the distance. As we've surely learned with Killer Bees, West Nile, Swine Flu ( all killers to be sure, but none turned out to be the epidemic or pandemic predicted by the media and/or CDC )and other dangers the media can sometimes inflate our sense of fear to get the ratings up.

  2. Good points Owl and I will be unable to discount them because, quite honestly, I don't have those numbers you're looking for and I cannot argue that the other "pandemic" examples you cite were overblown.
    What I do know is, bats, despite their tiny size and fragile appearance are remarkably long-lived. Many of the species being affected by WNS live 5-15 years and only rear one baby annually, so populations grow very slowly. From baseline surveys, done every year in NC by NCWRC and USFWS and I assume other states, the populations in specific hibernacula are fairly constant. Once the bats make it through the summer and get to the hibernacula, there is very low mortality that happens in the caves - until now. Bat researchers have never before collected thousands of dead bats from winter colonies and most of the known sites in New England have suffered the 90-100% declines I wrote about. These places aren't hard to find if you know where to look, so the possibility of a significant number of bats in unknown hibernacula is small.
    I just learned today that the state of Massachusetts has listed several once-common cave bat species as endangered (a state, not federal listing). That's a long way from how those populations were perceived five years ago.
    Again, I know I haven't addressed your specific concern over the data and how it's been collected and interpreted, but the biologist in me is quite certain that this is a significant and potentially catastrophic event.
    I do appreciate your comment and the grain of salt you bring to the discussion.