Researchers go caving to tackle bat sickness
By TOM MITCHELL
Correspondent | April 14,2013
Tom Mitchell Photo
Above, wildlife researcher Joel Flewelling looks at a dew-covered bat in the Aeolus cave in East Dorset. Below, little brown bats roost in crevices in the hibernation cave.
EAST DORSET — White nose syndrome has left some bats in East Dorset with so much tissue damage they likely won’t live through the spring, state wildlife officials report.
And others among the 173 bats recently counted in the first section of the giant Aeolus mountain cave appear to be so scrawny and dehydrated they may not survive, either, according to wildlife specialists who have been studying them.
The affected bats have exhibited odd behavior since the white nose, or geomyces destructans, fungus first struck Vermont bats in 2008.
At that time, many bats devastated by the disease were coming out of the cave in mid-winter to die en masse in trees, or do other odd things like fly over ponds at the foot of the snow-covered mountain, based on firsthand reports. Eventually they crashed to earth.
Hiking to the East Dorset cave in late winter this year, state animal specialist Alyssa Bennett and state wildlife technician Joel Flewelling stepped swiftly through light snow and up the steep southeast slope of the Aeolus limestone mountain.
Once they climbed through an iron gate and into the cave, they stepped carefully over very slippery, uneven rock at the bottom.
“We are only seeing a fraction of the bats” that live in the entire cave in winter, Flewelling said of his tally.
The first 100 feet of the cave, known as Guano Hall, represents a small part of the 3,077-foot-long cave, Flewelling said. In a quick survey (more than 45 minutes), they count as many bats as they can find in all the nooks and crannies.
This year the final tally at Aeolus is 161 little browns, nine Northern long-eared and three tri-colored for a total of 173 bats.
Before the white nose epidemic hit, as many as 3,000 bats hung from the ceiling in Guano Hall.
Another 20,000 bats likely remain throughout the entire huge hibernaculum, wildlife officials say in a rough estimate.
“There is no way for us to tell how many are deeper in the cave,” Flewelling said.
Whatever the exact number, it’s a small fraction of the 250,000-plus bats that biologists documented there in the 1960s.
To work inside Aeolus and keep from spreading the fungus, Bennett and Flewelling put on bright white Tyvek suits plus uninsulated black boots. They also use decontamination equipment.
Helmet lights pointed down, the researchers scour through as much of the front part of the cave as far as they can, shining potent flashlights in all crevices, snapping pictures of sleeping bats.
Not only is the cave dark, but it’s also cold enough that the cold air seeps through their boots to nip at the researchers’ feet.
They speak in whispers to avoid disturbing the creatures. They don’t want them to spread the fungus.
Bennett was able to see up close a little brown bat with a white nose. This one was awake and grooming itself, a sign of a potentially sick bat.
The current mission is to document declining bat numbers and try to learn how to combat the white nose fungus.
“We’re in recovery mode,” said Scott Darling, a state wildlife biologist who has overseen management of the white nose crisis in the state.
For 10,000 years, various bat species have been coming to Aeolus, the largest natural cave and hibernaculum in the Northeast, he said.
“Those bats in Aeolus probably feed on most of New England,” flying to other states at this time of year as the air warms up, Darling said.
He continues to survey caves and mines other than Aeolus.
Researchers say they hope the bats that survive can pass on survival traits to their young. A sustaining population is needed to keep the bats from being wiped out, Darling said.
The bottom of Aeolus cave is strewn with bat skeleton fragments from years past. “That’s all skulls and bones,” Bennett said of the cave floor, a graveyard that bats must cross to hibernate for the winter.
Researchers are particularly concerned this year about northern long-eared bats found dying in crevices near the entrance of Aeolus.
“Sick bats tend to move to the front of the hibernaculum and even roost outside the entrance in the cold,” Bennett said.
The long-eared species has become so scarce at all sites that it was added to the state endangered list last fall, along with the tri-colored bat.
One of the newer discoveries has been what appears to be “immune reconstitution inflammatory syndrome” or IRIS, in infected bats. The immune system goes into overdrive as it perceives infection. In turn, IRIS can cause severe inflammation and tissue damage, hampering a bat’s ability to survive after hibernation.
For this survey crew, going deeper than Guano Hall is not in the cards because their helmets could dislodge bats hanging from the low ceiling, Flewelllng said. The top priority is to avoid hurting the bats, he said.
It is also dangerous to go deeper into the cave, he said.
To exit the cave, researchers slide their legs and then their torsos and heads through a small opening in a massive iron gate. This slotted barrier allows bats to come and go while shielding them from the outside world.
A bright sun blinds the dark-acclimated eyes of the researchers for a few seconds, and they reach for their sunglasses.
About 20 feet from the cave it’s safe to talk normally again.