Can tech save a dying bat species?

From CNET Magazine: Scientists turn to technology to restore an endangered bat species to the world's longest cave system.

Megan Wollerton Former Senior Writer/Editor
6 min read

There's a bat!" geologist Rachel Bosch, one of the three guides leading me through the bowels of Kentucky's Mammoth Cave National Park, shouted excitedly.

It's always a good day when you spot a bat in Mammoth Cave.

The Indiana bat, a medium-sized variety that used to be plentiful here, has been on the endangered species list since 1967. And more recently, Mammoth Cave bats have been afflicted with white-nose syndrome (WNS), a deadly fungus that has killed over a million bats throughout eastern North America and is now spreading west. Seeing a bat without the tell-tale white fungus covering its face and wings, like the one perched in front of us on a low rock wall, is extremely lucky.

"You better shoot [a picture] fast, because he's awake, or she's awake. And it won't be here long," park ecologist Rick Olson chimed in. "Hopefully nobody comes into contact with it." WNS isn't known to pose a risk to humans, but bats can transmit a variety of illnesses, including rabies.

A little uneasy in this unfamiliar underground world, I wondered whether the 6 inches that briefly separated me and the bat counted as close contact.

Bosch, Olson and engineer Aaron Bird are all members and volunteers of the Cave Research Foundation (CRF), a private, nonprofit organization dedicated to cave exploration and conservation.

Today, they're showing me a section of the cave called Vespertilio Hall. Once a gathering place for thousands of hibernating Indiana bats, Vespertilio is now empty.

And that's just why CRF is here. They're trying to restore the once-thriving Indiana bat population -- with technology.

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Warnings inside Mammoth Cave remind visitors not to touch the bats.

Tyler Lizenby/CNET

Why Indiana bats left

The Cave Research Foundation believes Mammoth Cave's history (see section below) holds the keys to understanding the fate of its Indiana bat population.

After the War of 1812, when the potassium nitrate mines were abandoned and guides started leading tour groups through the cave, Bird estimated that the temperature in Vespertilio Hall was about 43 degrees Fahrenheit.

That was perfect for Indiana bats, which like to hibernate in large clusters in temperatures ranging from 41 to 46 degrees.

Today, the temperature is closer to 51 degrees Fahrenheit. CRF researchers can't say definitively what caused this increase in temperature, but they believe it was due to a cave entrance near Vespertilio Hall being closed off during a particularly competitive tourism period known as the "Kentucky Cave Wars."

In the 1920s and '30s tourism to Mammoth Cave boomed. Though there are 27 natural and man-made entrances to the cave today, competing guides back then would create their own illegal entrances to lead tours or to search for places to drill for oil. When they were done, they'd close off the entrance to keep anyone else from finding the same route.

"There's no historical account of an entrance there, but we have geological evidence and we have the data," Olson explained.

The calcite formations on the walls, which are the result of water droplets evaporating, strongly suggest the presence of airflow at one time, he said. In addition, you can clearly see dark staining where bats once clung to sections of the cave ceiling.

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More than 400 miles of Mammoth Cave have been explored.

Tyler Lizenby/CNET

Some history

Mammoth Cave is the longest known cave system in the world. It is located in southern Kentucky, roughly equidistant between Louisville, Kentucky, and Nashville, Tennessee. More than 400 miles of Mammoth Cave have been explored, and there is a lot more that has yet to be mapped.

In addition to their bat project, this CRF team keeps busy traversing new sections of the cave. Bird told me he'd gone on a 17-hour expedition through a cave river the day before. Each time he walked a step forward, he was setting a record.

The cave owes its existence to the nearby Green River and limestone -- a sedimentary rock that easily breaks apart. Rain water, turned acidic by the carbon dioxide in the topsoil of the Kentucky countryside, makes its way into cracks in the limestone and creates cave passageways. The water then drains into the Green River.

According to the National Park Service, Native Americans discovered the cave roughly 4,000 years ago and continued to have a presence there for 2,000 years. Archeologists have found evidence that these groups ventured far inside Mammoth Cave in search of natural minerals, such as gypsum, for ceremonial, medicinal or trading purposes. After Europeans arrived on the continent, settlers used the cave to mine potassium nitrate, or saltpeter, for gunpowder during the War of 1812. We passed remains of one such mine on our walk to Vespertilio.

Beginning in 1816, people began to see the potential for Mammoth Cave as a tourist destination, and a prospecting site for natural resources like oil. After a century or so of private ownership and intense exploration, competition and surveying, Congress approved the creation of a national park at Mammoth Cave. It wasn't until 1941 that the 52,830-acre cave and surrounding recreational area was officially recognized as Mammoth Cave National Park, though.

Since then, Mammoth Cave has been designated a World Heritage Site, as well as the center of an International Biosphere Reserve, but the bat population has continued to decline.

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Aaron Bird demonstrates the software program used to run hypothetical scenarios on lowering the cave temperature.

Tyler Lizenby/CNET

Bringing the bats home (with tech)

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This weather station is planted under an area of dark staining where hundreds of bats likely congregated in the past.

Tyler Lizenby/CNET

How then to cool the cave? Bird started by repurposing computational fluid dynamics (CFD) software from his day job researching the external airflow for rocket ships at Siemens PLM Software. The same software his company used to help SpaceX land on a floating platform in the ocean he now uses to run hypothetical scenarios on lowering Vespertilio's temperature.

The software allows the team to experiment with a variety of scenarios via computer software that could return Indiana bats to Vespertilio Hall -- pressure, temperature over time and space and airflow velocity. It also tries to account for any potential negative outcomes that could arise from reintroducing airflow to the area.

The Cave Research Foundation also relies on meteorological data from weather stations throughout the cave, some of which we passed on our way to Vespertilio. Held together with duct tape, these seemingly makeshift devices provide all sorts of data on air temperature, air pressure and wind speed -- critical information for understanding the current conditions in the area CRF hopes to restore.

Finally, the team used light detection and ranging, also known as lidar, to create a 3D visual representation of the inside of the cave.

Back at CRF's Mammoth Cave research center, Bird showed me the technology in action on a computer screen. The variables they calculated suggested a specific solution to the uninhabited Vespertilio -- a pipe. The theory? Installing a pipe with a diameter of roughly 2.5 feet (0.75 meters) and a length of about 6 feet (1.8 meters) from above ground into an area near Vespertilio Hall should reintroduce the right airflow to reduce the cave temperature for Indiana bats to return.

Why this matters

Bats are what's called a keystone species in the Mammoth Cave ecosystem, meaning other species rely on them heavily for survival. Bat excrement, or guano, contributes important nutrients to invertebrates and other cave organisms, which then feed larger animal species.

Even if the National Park Service administration agrees to install the pipe and it's successful, some outstanding questions remain as to whether increased temperatures in Kentucky over the past 100 years could keep Indiana bats from returning. CRF plans to continue testing scenarios to see if the data and the software reveal anything new.

Either way, Bosch, Olson and Bird will likely be returning to the cave soon to chart new sections and find additional projects for future exploration.

This story appears in the spring 2017 edition of CNET Magazine. For other magazine stories, click here.

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