Into the Earth with TVA

by Staff
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Imagine, for a moment, stepping into the yawning mouth of a cave.

Drips echo as the jagged outline of daylight disappears. Boots slide over mud studded with crunchy gravel like thick cookie dough.

The ground – the whole room – slopes upwards, climbing to a peaked dome. Its plummeting sides bottom out in depths unseen.

Above, a rocky, rippled cathedral ceiling rises 100 feet high.

For Tennessee Valley Authority terrestrial biologists and zoologists, this is just another day at work.

Each winter, the team searches for roosting bats in about two dozen caves. The bats, no bigger than a clenched fist, sleep tucked into a cave’s dark crevices, folds and holes.

The zoologists count the animals, identify them by species and check their health.

Yet their job has gotten harder over the years.

Many bats are dying as a result of white-nose syndrome, a fungus first found in the Valley region in 2009.

The fungus grows on hibernating bats’ noses, ears, feet and webbed wings. The stressed animal can die from starvation, dehydration or its own immune system attacking its body as it fights off the fungus.

As devastating as the disease is, it’s also an opportunity to learn more.

TVA zoologists and land managers work with state and federal agencies and universities to understand bats and their behavior before it’s too late.

“We’re still down at low numbers (of bats) at this point,” TVA biologist Liz Hamrick said. “We’re hoping that as the decades roll on, there will be a slow creep back up.”

A Cave Maze
Hope is what drove the zoologists to the cave on a recent winter day. Outside, trees bent in the wind and a curtain of rain covered the cave’s entrance.

Inside, the zoologists shook off and suited up in protective layers.

They already wore tall rubber boots and coveralls, but they added rubber gloves, face masks and caving helmets topped with headlamps.

Caves can be risky places, not only because of exposure to bats and the guano they leave behind.

“You have to be mindful of rocks that can move,” Hamrick explained. “Waters could rise at any moment. More so, getting stuck, getting pinned in small areas where there are tight squeezes.”

“My concern often is getting lost,” Sara McLaughlin-Johnson, a TVA terrestrial zoologist, said. “Everything looks the same. Some of (the caves) are Swiss-cheesy and a lot of the passages connect.”

Hamrick and her team crowded around the cave map, headlamps illuminating the snaking outline.

“It looks all cute and small, right?” Hamrick said, chuckling. “Total length, 1,270 feet.”

She ran her fingers along the route. “This is the giant, giant dome area. This is the room where if you’re going to feel any sense of vertigo, it’ll hit you.”

Teams of two headed left and right. Headlamp beams scanned the rough walls and hand-held flashlights illuminated dark pockets in rock curlicues.

“Tricolored,” Rob Stinson, TVA terrestrial zoologist, called in a whisper voice.

The tricolored bat could have been a knob or hole on the distant cave wall to anyone but a bat expert.

Stinson held up a cupped hand, fingers tight together as if holding water.

“Their bellies are kind of flat and their backs are kind of C-shaped,” he whispered. “On that one, its forearm bisects the butterscotch-colored fur.”

Hamrick, crunching past, nodded, and the team moved slowly farther into the cave.

White-Nose Syndrome

Laura Vining, another TVA terrestrial zoologist on the team, pointed to a single bat dangling 15-feet overhead.

“There, another tricolored,” she said.

Its body cast a tiny shadow in the headlamp glare. Even from that distance, its brown fur looked impossibly soft.

Zoologists were most likely to find tricolored bats, big brown bats and gray bats in Norris Cave, Hamrick explained.

They can all carry white-nose syndrome, and tracking studies show how it can spread.

“We have cave connections from up in Kentucky down to Alabama,” Hamrick said. “The maps … look like somebody took a bowl of spaghetti and threw it against the wall.”

Yet the Valley region’s bat species have very different fates once infected with white-nose.

Scientists are trying to discover why.

“Of the three (at Norris), the tricolored bats are the most at risk,” Hamrick said. “We’ve had about 95% decline in some of our caves.”

Already, the team had spotted the distinctive white fuzz of white-nose syndrome on some of their muzzles.

Other bats are doing better.

Gray bats, they get the fungus,” Hamrick said. “They can move it around. They can get a minor infection, but they’re not succumbing to the syndrome, even though they were already on the endangered species list.”

Gray bats were listed as endangered in 1976. They’re still at risk because millions roost in just a few caves throughout the Southeast.

Humans bring sounds and smells that scare bats. Gray bats awakened in winter can starve or freeze. In summer, frightened bat mothers may abandon their young, or flightless pups may fall from roosts into the mud and guano piles below and die.

Yet grey bats’ bigger body size or other factors, such as the microbiome on their skin, might protect them from white-nose syndrome.

Bats’ lifestyles – if they roost together in great clusters or hang alone – may also determine if they get sick and to what extent.

“Each species does something a little bit different,” Hamrick said.

Cave Gates
The mystery is both daunting and intriguing for scientists.

As the team members slid one by one down a mud chute, holding fast to knobs of guano-slicked rock to reach the farthest room of the cave, they tallied more bats.

The only sounds were the crunching and snucking of boots across gravel and mud.

Warm, misty air sparkled in headlamp beams.

“It feels like a different planet altogether,” McLaughlin-Johnson said as she searched the dimpled walls. “It feels like you’re not even on Earth.”

Because caves are unique habitats, it’s important to protect them.

“One really cool thing about the Tennessee bat world is the coordination that happens between state and federal (agencies), educational institutions, non-governmental organizations and contractors,” Hamrick said.

In summer, TVA’s Environmental Compliance and Natural Resources team members monitor artificial and tree roosts throughout TVA’s seven-state service area.

Natural Resources staff also install and monitor gates that let bats through but keep people out of cave entrances.

Although it’s prohibited to enter gated caves, zoologists have found litter, fire rings, graffiti and broken stalactites there. They’ve found broken or missing scientific equipment, which can mean entire years of data about cave conditions lost.

“We have gates there for a reason,” Hamrick said. “They protect the bats and sometimes cultural resources as well. And they keep people safe.”

When people break through the gates, not knowing they can spread white-nose spores or cause damage, Heather Hart, TVA’s senior Natural Resources conservation specialist is ready.

“If a gate has been compromised (or damaged) … I’ll work with our Natural Resources staff,” Hart said.

The Natural Resources team works closely with local ironworkers, welders and fence builders to fix and install new gates as quickly as possible to ensure bats aren’t disturbed and cave resources are safe.

“There’s more of a concern for gating many more caves than there was before,” Hamrick said, given the stress of white-nose syndrome and decline in bat numbers.

Media Release/TVA Newsroom

 

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