Bats Disappearing As Fungus Spreads Throughout Known Hibernation Spots In Tennessee

A researcher holds an endangered gray bat – the same species The Nature Conservancy hopes to shelter with its new artificial cave. “We don’t know yet how White Nose Syndrome will affect gray bats,” Cory Holliday says, “But because they’re so susceptible and hibernate in so few caves, White-Nose Syndrome could potentially wipe out those caves and large percentages of the entire population in really no time.” Credit USFWS / Ann Froschauer

A disease that has wiped out millions of bats in the northeast has now spread to every major Tennessee cave where bats are known to hibernate.  White-Nose Syndrome first arrived in 2010 in East Tennessee, where bats are now disappearing.

The disease causes white fungus to grow on the faces of hibernating bats.  It typically takes three winters at a cave before many die off.  Biologist Cory Holliday with The Nature Conservancy says across the state, that lag time is running out.

“So we only have a handful of sites that have had the disease for three years.  But in those sites, especially our East Tennessee sites, the bats have disappeared.”

This past year the number of counties with the disease jumped from 12 to 32.  Tennessee has thousands of caves, but only a small fraction are what are called ‘cold-air traps,’ cool enough to attract lots of bats to roost.
Update at TNC’s artificial bat cave

Bats near Clarksville have been checking out a huge man-made cave The Nature Conservancy built last year, next to the home of a couple hundred thousand endangered gray bats.  The idea is unlike a natural cave, one that’s artificial can be cleaned every summer to keep the fungus from taking hold.

Holliday says a crucial first step has been getting the temperature and humidity to resemble an authentic cave inside the underground chamber, and that effort has proven largely successful.  Less successful, so far, has been thermal video and infrared technology meant to let researchers monitor bats inside the cave.  This past winter, Holliday says they had to rely mostly on audio.

“The best evidence we had was our acoustic data—recording bats as they entered and exited the cave, which gives us a much more limited amount of data… We know there was bat activity there, and we can tell the species,” including tricolor and brown bats, as well as gray.

It’s not clear how many actually stayed this past winter, but Holliday says at the end of 2012 they weren’t expecting many at all.

“When we finished construction and walked away from it, we were well into the hibernation season.  Bats had already arrived at the neighboring cave, and any bat that we saw in there we would’ve taken as a great sign and we did have evidence of at least a handful of bats using the cave over winter, and definitely they were in and out, checking it out as they were flying on the landscape in and out of the natural cave.”

While gray bats are relatively tiny—each weighs just a few grams—Holliday says he’s not worried they’ll be bullied out of the cave by other species.

“It’s not a size issue, it’s the number of bats, and gray bats in fact can really push other species out of a site.  Although they’re small, they hibernate in very large numbers.  All of the gray bats on the planet hibernate in about nine caves.  Those hibernation sites can be over a million bats per site.”

“Time is not on our side on this project.”

As the spread of white-nose grinds on, Holliday says he doesn’t have a specific number of bats he’s hoping will stay this winter.  “If we get a few hundred to a thousand bats in year one, I’d say we’ll be ecstatic.”

The time-crunch stems in part from the discovery two years ago of White-Nose Syndrome at Bellamy Cave, next door.  Time may be running out, and quickly.

“So it has been there for two years now, and we have seen some mortality at the site.  We don’t know yet how White Nose Syndrome will affect gray bats.  But because they’re so susceptible and hibernate in so few caves, White-Nose Syndrome could potentially wipe out those caves and large percentages of the entire population in really no time.  So we’re very cautious and optimistic about saving numbers of bats in the artificial cave.”

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Tennessee received about $50 thousand last month in grants from the Endangered Species Recovery program.  The U.S. Fish and Wildlife Service says such funds, which totaled almost a million dollars to 28 states, will help state agencies support research, monitor bat populations and detect and respond to WNS.