Note: This is the second part in a blog series on The Nature Conservancy’s new artificial bat cave, an experiment to help stop the spread of white-nose syndrome, a fungal disease killing millions of bats. Read the first blog.
Cory Holliday, the cave and karst program director for The Nature Conservancy in Tennessee, was living the field biologist’s dream: a career that involved exploration and discovery, strange new creatures, unknown corners of the earth.
While exploring caves, he documented wildly cool critters like blind salamanders and cave crayfish that lived more than 70 years. Discovering new species was a regular occurrence; Holliday even has a species of millipede named after him. He climbed and crawled through some of the least known habitats on the planet. And he loved every minute of it.
“I saw a lot of places where it was safe to assume nobody had been before,” says Holliday. “Every cave was different. There was a real feeling of exploration.”
That dream work has now been replaced by the grim task of tracking white-nose syndrome in Tennessee caves. It’s work that often involves bad news and dead bats.
It’s not fun, but it’s vitally important: The information gathered is playing a critical role in shaping ways to combat the spread of white-nose syndrome, the fungal disease killing millions of bats in the eastern United States.
It has helped lead to the creation of the artificial bat cave, the first structure ever designed to mitigate the effects of the disease.
Today’s blog examines the information and research that helped lead to this cave experiment.
The Path to the Bat Cave
From December through March, Holliday spends nearly every day checking caves for presence of white-nose syndrome.
“There are caves where you don’t expect to find it, and then you’ll see the bats are already in poor health,” he says. “That’ll ruin your day pretty quick.”
Due to fears of decontamination, Holliday uses twenty completely different sets of caving clothes. Once a set of clothes is worn into a contaminated cave, it can only be worn in other contaminated caves, no matter how much it has been cleaned.
“Decontamination is brutal,” says Holliday. “We often visit three caves a day, so we have to be really careful that we have completely different sets of clothes and equipment for each trip.”
Such surveys provide important information, information that may prove critical in combating the disease. Holliday notes that white-nose syndrome has been documented to have a three-year cycle.
That cycle usually looks like this:
Year 1: The presence of white-nose syndrome is detected. Bats have the infection on their wings but do not appear seriously impaired. They’re able to clean off the infection, and injured areas will heal. Come summer, the bats may have scarring from the infection, but they’re alive and healthy.
Year 2: The bats are sick, likely covered in wispy fungus that is seen not only on their wings, but also around the head. But there is no apparent mortality.
Year 3: The bats have disappeared from the cave. They have all died from the disease.
At first glance, it might appear that white-nose syndrome slowly kills bats over three years. But Holliday doesn’t think that’s the case.
“It seems the fungus builds up over three years, to the point where so much of it exists that it wipes out bats,” he says. “The first year, the fungus is not present at levels where it kills bats.”
There’s a feeling of helplessness once white-nose syndrome is found. The fungus will spread and bats will die, and there’s nothing anyone can do about it.
Or is there?
Some researchers discussed capturing bats and raising them in captivity, a tactic used with varying success for other rare species. But insectivorous bats – the species found in eastern United States caves – fare very poorly in captivity. The one effort at captive breeding resulted in every bat dying within a year.
But if white-nose syndrome does spread over time, only becoming fatal to bats in three years, then perhaps another solution could work. Enter the artificial bat cave. The bat cave could be cleaned each spring, so the fungus would never grow to deadly levels.
“This is a way to mitigate the effects on bats, while allowing them to remain wild and maintain their natural history,” says Holliday.
Race Against Time
Once the decision was made to construct an artificial bat cave, the next decision was location. It had to be located near another cave. But Tennessee has 9600 caves, which hardly narrowed down the location.
But picking a spot was actually quite easy. The first artificial bat cave had to do one thing: Protect gray bats.
Gray bats are a federally-listed endangered species. They hibernate in large colonies that can reach 500,000 individuals, and therein lies the problem.
The entire population hibernates in just nine caves.
That’s right. Nine.
Two of those colonies now have the confirmed presence of white-nose syndrome. These are the first infected gray bat colonies, so no one knows for sure if it will affect them the way it has other bats. But conservationists can’t wait three years.
“There is a definite, serious risk of extinction in a short period of time,” says Holliday. “The risk is immense. If we didn’t build this cave, there would probably be no hope.”
The artificial cave was built just 100 yards from Bellamy Cave, a Conservancy acquisition now owned by the State of Tennessee. It’s home to 270,000 hibernating gray bats each winter, making it an ideal site to test the artificial cave.
But can an artificial cave really compete with a highly desirable natural one?
“We need to make it a more attractive place for bats than the real one,” says Holliday. “This cave is engineered to be the ideal gray bat environment.”
How can scientists improve upon the real thing? Next up, the blog series will look at the engineering designs and other features designed to make bats feel at home this winter. Stay tuned.
Photo: Little brown bats with white-nose syndrome. Credit: Jonathan Mays, Wildlife Biologist, Maine Department of Inland Fisheries and Wildlife.