The number of bat deaths in just the last few years has been estimated at around 6 million and rising. The culprit is something called white nose syndrome (WNS) which is caused by the fungus Geomyces destructans that now infests many caves around the country. It was first identified and reported in New York in 2006-2007 and as of 2013 has been found in hundreds of caves and mines ranging mostly throughout the Northeastern U.S. and as far south as Alabama and west to Missouri as well as in four Canadian provinces. Entire bat colonies have been decimated.
Bat expert Alan Hicks with the New York State Department of Environmental Conservation describes the impact as "unprecedented" and "the gravest threat to bats...ever seen". Mortality rates in some caves have exceeded 90%.
The little brown bat, a once common species, has suffered a major population collapse and may be at risk of extinction in the northeastern U.S. within 20 years due to the syndrome. Nine hibernating bat species are currently confirmed to have infections of Geomyces destructans, and at least five of those species have suffered major mortality. Some of those species are already on the U.S. Endangered Species list, including the Indiana bat, whose primary hibernaculum in New York has been affected.
I can recall as a child seeing many bats zooming around me on summer nights. Now I see none. Why should this matter to gardeners? Bats play an important roll in insect control. A single bat can eat 500-1000 mosquitoes an hour and can devour over 3000 larger insects per night. Illnesses vectored by mosquitoes are already on the increase.
Bat losses could also mean a potentially huge problem for farmers trying to control damage to food crops and may result in the use of even more chemical sprays. The same holds true for the home vegetable, fruit and ornamental garden. Bats are also pollinators for certain crops, among them bananas, mangoes, peaches, figs, avocados and agaves.
It can take as little as two or three years from the time the fungus is found in a cave until the entire hibernating colony of bats is wiped out. A number of agencies, organizations and entities have now joined forces in an attempt to study and address the problem. Just a few miles from me, the first man-made bat cave was recently completed, a joint effort between the Nature Conservancy and the State of Tennessee.
"The concrete box buried in a hillside is almost as long as a basketball court, but only half as wide. It's high-tech inside, with surveillance cameras that detect heat without getting warm or making any noise - even ultrasonic sound could be a deal-breaker to bats moving in. To power the gear, workers screw in electric panels. The idea is to offer bats a safe winter home where every summer humans could go inside and clean out any lurking fungus, keeping white-nose syndrome in check."
The Nature Conservancy has reported that a number of bats did explore the new man-made cave and at least a few of them hibernated in the cave during the winter of 2012-2013.
To see the new man-made bat cave, use this link
On a more positive note, as many species of bats struggle against white nose syndrome and possible extinction, natural adaption as well as micro-climates located within caves appear to be helping some species survive.
Species that hibernate in dense clusters even as their populations get smaller will continue to transmit the disease at a high rate, dooming them to continued decline, according to results of a new study led by biologists at the University of California, Santa Cruz (UCSC).
One gregarious species has surprised biologists, however, by changing its social behavior. The little brown bat, one of the most common bat species in the northeast, appears to be changing its social behavior, going from a species that preferred to roost in dense clusters to one in which most bats now roost apart from other bats ... analysis suggests that the little brown bats are probably not going to go extinct because they are changing their social behavior in a way that will result in their persisting at smaller populations.
Another gregarious species, the Indiana bat, continues to hibernate mostly in dense clusters and will probably continue to decline toward extinction. Since the appearance of white-nose syndrome, both species have become more solitary, but the change is much more dramatic in the little brown bats. Researchers now see up to 75 percent of them roosting singly. For Indiana bats, only 8 to 9 percent are roosting alone, which does not appear to be enough to reduce transmission rates.
Even solitary roosting habits may not be enough to save some species, such as the northern long-eared bat ... some bat populations are stabilizing at lower abundances, while others appear to be headed for extinction.
The results, published in... the journal Ecology Letters, centered around data from bat surveys between 1979 and 2010, covering a long period of population growth followed by dramatic declines caused by white-nose syndrome."
It is the hope of many that new research will provide more answers to this very serious situation and that natural adaption along with solutions like man-made bat caves will be successful in leading to a resurgence in the number of bats able to survive white nose syndrome. Only time will tell. But time is short. Although it may sometimes seem like trying to empty the ocean one cup at a time, some positive and useful steps can be taken by groups and individuals. Here's what you can do to help:
Educate yourself and others
Stay out of caves and mines
Respect all cave closures
Report any suspicious bat behavior or appearance to your state resource agency
If you come upon a pile of dead bats or bones, report it
If you do go into a cave or mine, follow decontamination protocols
Support organizations that are working together for a solution.
Wikipedia, "White Nose Syndrome"
National Public Radio, September 20, 2012
The Nature Conservancy
Phys.orgTM, July 03, 2012
Both images of hibernating bats are courtesy of Wikimedia Commons.The Big Brown Bats in the barn courtesy of Melody Rose