Building A Better Bat Cave
To save the bats of Pennsylvania, Greg Turner wants to build a better bat cave. Turner is a biologist with the Pennsylvania Game Commission. His latest renovation project is a cave under a hillside in Central Pennsylvania. Indian Caverns used to be commercial cave, and there’s still an abandoned gift shop with fake display plants. It closed last year, and now the state is in the process of acquiring it as a way to preserve bats.
Inside the cave is what you’d expect — lots of stalactites hang from above. In between the stalactites are cavities about the size of a fist. These are perfect resting spots for hibernating bats.
“They’ll put their whole body up against that rock because they like it to be really stable temperatures,” explains Turner. “It you’re surrounded by that rock, that rock is going to stay the same temperature pretty much all winter long.”
Those stable temperatures are important for the bats’ hibernation. In contrast to popular belief, bats aren’t really sleeping when they hibernate, but rather their body temperature drops, along with the rest of its systems. And, Turner says, that’s what makes them susceptible to the fungus that causes white-nose syndrome.
“They shut down their immune system,” Turner says. “They shut down their metabolism. Their breathing comes down.”
White-nose syndrome is so destructive because it’s not like other fungi, which eat dead and decaying matter. Instead, this fungus feasts on living cells. A hibernating bat is an easy target.
“The fungus starts eating on them while they’re in this state, and then they come out of that state and are like, ‘whoa, what’s going on?’” says Turner.
The fungus creates whitish infections on the bat’s face, clustered around its nose, hence the name. The bat expends energy fighting off the infection during hibernation. In their weakened state, they can be easily preyed upon by other species when they leave the cave.
The disease has annihilated bat populations, particularly in the northeast, since it was first discovered about 12 years ago in upstate New York. Turner says he saw sites that had 50,000 bats go down to single digits in just one year. But in some places, bat populations have remained steady. That made Turner and his colleagues ask why. And what they found is that caves that were colder had more bats.
The ground temperature in Pennsylvania is around 53 degrees Fahrenheit. But depending on air flow, some caves can get down to 40 degrees or lower, making it harder for the fungus to spread. But how do you get a cave to cool down? Turner says, think about a lake.
“The way to cool off a site like this is looking at the physics of air,” explains Turner. “Water would be the same. In a lake the coldest spot of a lake is down low.”
And the same is true of a cave –cool air sinks to the lowest spot. But cold air can’t build up in Indian Caverns because its former owners sealed it off in some parts to keep tourists from wandering off. Turner says that will change as part of the state’s renovations.
The Game Commission’s plan is to remove a big concrete wall that blocked off the original opening to the cave. That will create a vent that will allow more cold air to come into the gave and accumulate in its lower reaches.
Deeper into the cave is a series of passageways that wind downward, about 100 feet below ground. An underground stream runs alongside the path and there are rocks where Turner hopes bats can roost this winter.
It’s unclear whether bats can recover from white-nose syndrome, but Turner says he’d be satisfied just seeing the population stabilize and maybe some slight increases.
“I’m looking towards the future generations,” he says. “For them to be able to see these species would be a great achievement I think.”
The Game Commission will begin work on the cave this summer. With any luck, bats will be hibernating in a cooled off Indian Caverns by this winter.
This story is part of our series, Wild Pennsylvania, which is funded by the Richard King Mellon Foundation. To check out the other stories in the series, click here.