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Bats Face Extinction From Emerging Fungal Disease

August 6, 2010

One of North America’s most common bat species faces extinction in the northeastern U.S. within the next two decades due to a rapidly spreading disease known as White-Nose Syndrome (WNS), according to a new study led by researchers at the Boston University College of Arts & Sciences.

The threatened bats, known as little brown myotis, are critical in controlling insects that spread disease to humans and animals.  The bats have been known to consume their own weight in insects in a single night.

The study, conducted by BU post-doctoral researcher, Winifred F. Frick, BU biology Professor Thomas H. Kunz, and former BU Ph.D. student D. Scott Reynolds, documents a rapid decline of little brown myotis populations due to WSN.

The syndrome was first discovered in 2006 near Albany, New York.  Since then, bat populations have declined 30 to 99 percent in various areas.
 
The illness has now been confirmed in 115 bat-hibernating locations in the U.S. and Canada, and now affects at least seven species of bats, the researchers said.
  
“This is one of the worst wildlife crises we’ve faced in North America,” said Frick.

“The severity of the mortality and the rapidity of the spread of this disease make it very challenging and distressing. Researchers have been working very hard since it was first discovered four years ago to try to better understand the disease and find potential solutions to the problem.”

The researchers analyzed data from the past 30 years to confirm that regional populations of little brown myotis were healthy and thriving prior to the discovery of WNS in 2006.
They then combined the data with current figures on winter mortality of little brown myotis populations to determine the harmful effects of WNS on the millions of bats perishing from the disease.

The research revealed that within 20 years, the regional population of little brown myotis is expected to collapse to less than 1% of its population size prior to WNS — even if mortality slows through time.
 
The loss of so many bats could cause unpredictable changes to the structure and function of the ecosystem, and will likely become a national problem as the disease proliferates further west and south, the researchers concluded.

“Each of the bat species affected by WNS are obligate insectivores — many of which feed on insect pests of agriculture, garden crops, forests, and at times on insects that annoy or pose risks to human health,” said Kunz.
 
“The little brown myotis is known to consume up to 100% of its body weight in insects each night. This level of insect consumption provides an important ecosystem service to human kind, and to the balance of natural and human-altered ecosystems, which in turn can reduce the use of pesticides often used by humans to kill insect pests.”

Geomyces destructans, the newly described fungal species associated with WNS, thrives in cold temperatures.  It grows on the nose, wing membranes and ears of bats as they hibernate in caves and mines during the winter, causing the bats to awaken frequently, thus starving to death before spring.

The fungus has spread rapidly since 2006, and has been reported on bats in eastern Canada as far south as Tennessee and as far west as Oklahoma by the end of the hibernation season in 2010.

“Given the rapid geographic spread of this fungus over the past four years, we can expect that WNS will adversely affect bat species that form some of largest hibernating bat colonies in the U.S, including two federally-listed endangered species that occur mostly in the mid-western states,” said Kunz.

These hibernating colonies contain up to hundreds of thousands of bats of several species in a given cave or mine.  The bats leave these winter roosts in late spring, and females form maternity colonies in the summer to raise their young.

Although the researchers are unclear about many aspects of how the fungus spreads, they suspect that normal movements of bats during different seasons may play a role.
“There are many pressing questions we still need to answer about WNS,” said Frick.

“Our research demonstrates the seriousness of the impact that this disease is having on bat populations, but we need more research on how and why the disease is killing so many bats and, most importantly, what we can do to stop it.”

Research about the potential origin of the fungus in North America is ongoing, with recent evidence suggesting the same species of fungus occurs on hibernating bat species in Europe, hinting that humans may have inadvertently brought the fungus to New York.

The study was published in Friday’s edition of the journal Science. 

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