First Butterflies and Bees Disappear, Now Bats
Investigating Scientists Blame a Hitherto Unknown White Nose Fungus
Nov 1, 2009
Man hasn’t yet solved the riddle of the disappearance of the bees, the tiny creatures responsible for pollinating most plants. Butterflies do some pollinating, but many of those are disappearing as well. And suddenly, science is faced with another die-off of an equally serious nature; little brown bats have been getting covered with a strange white mold during hibernation – and many of them never wake up.
In fact, hundreds of thousands of several bat species have died annually during hibernation in the Northeast U.S. from late October through April or May, covered in the fungus.The phenomenon was first noted by field biologists in the Howes Cave near Albany, N.Y. during the winter of 2006. Alan Hicks, a bat specialist with the New York State Department of Environmental Conservation sounded the alert in early 2007 after receiving reports of dead bats in caves near Albany.
The Spread of White-Nose Fungus in Bats Was Rampant
About that time, according to David Blehert of the U.S. Geological Survey in an interview with LiveScience.com, (a branch of the technology news organization TopTenREVIEWS whose scientific sources include the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA)), bats were found dying in five caves, within 10 miles of Howes Cave. "And by last winter,” he said, “it was present at 33 sites..."
The ceilings of caves being examined were in the past typically covered with hibernating bats at that time of year, but instead had large vacant areas. In one instance, scientists found the floor of a cave littered with dead bats covered with this mysterious white mold. Blehert's lab got involved after Hicks had taken ailing bats to an animal disease specialist at the NY State Department of Health, who couldn’t identify the problem. The white fungus was so fragile it disappeared at the slightest touch making identification virtually impossible, until lab operations moved right into the hibernation caves (hibernacula).
Multiple Species Found to Be Affected
After an investigation, Blehert and four colleagues (Andrea Gargas, Marie Trest, Martha Christensen, Thomas J. Volk) published their findings in the journal Mycotaxon ("Geomyces destructans sp.nov. associated with bat white-nose syndrome", Volume 108, pp. 147–154 April–June 2009). The fungus genus was identified as Geomyces, but its shape was unlike anything described, so it was considered a new species and named Geomyces destructans. Bats infected with this fungus present with white powdery muzzles, thus the description of the disease as white-nose syndrome, considered to be their killer.
Blehert found the DNA on the affected bats resembled other psychrophilic (cold-loving) fungi. His team performed necropsies on over 100 bats from the affected regions, including little brown bats (Myotis lucifugus), northern long-eared bats (Myotis septentrionalis), big brown bats (Eptesicus fuscus) and tricolored bats (Perimyotis subflavus).
Bats Reside in Northeastern U.S. States
Since 2006, drastic declines in cave-hibernating bat populations in the Northeast have occurred, with more than 75 percent of the bats having perished. As of March 2009, white-nose syndrome has been confirmed by gross and histologic examination of bats at caves and mines in Massachusetts, New Jersey, Vermont, West Virginia, New Hampshire, Connecticut, Virginia, and Pennsylvania. (Blehert et al. 2009).
Blehert and his team question if the fungus is the sole killer, since most of the fungus-affected bats are also emaciated. The hallmark of the infestation is that the bats come out of hibernation too early, using up their fat reserves before spring. The emaciation might be caused by the fungus, or the fungus might depress their immune systems resulting in death before the bats wake naturally.
"The bats have … hibernated in these same caves,” says Blehert, “using the same physiological mechanism, not eating, dropping their heart rates and core body temperature down, and they didn't used to get moldy."
Investigators Remain Puzzled
Scientists continue to speculate on the equation: have the bats’ immune systems become weakened so they are suddenly more susceptible to the fungus? Or is infection happening to otherwise healthy bats as a result of the intrusion of this new species of mold? With variables including weather, habitat, food sources, species, and locations and regions of the world affected, what set of conditions suddenly make this a scientific possibility?
Hicks went looking for evidence of the plague again in late 2008 in an abandoned iron mine near Port Henry, a village in northeastern New York. Hicks’ specimens showed no signs of the white fuzz, but bats were getting wiped out completely in some nearby caves. In two closely monitored sites, up to 97 percent of the bats had died. He feared some sites might be empty when visited again.
There is still no proof that Geomyces destructans is the actual cause of death, but Hicks and Blehert’s team feel that its identification is a major step in solving this latest ecological threat.
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