It has been two full years since the last group of visitors toured Indian Caverns in Franklin Township in late 2016 and in that time period, extensive work has been completed to transition the once commercial cave into a restored bat habitat designed to combat the ravages of White Nose Syndrome (WNS).
Game commission biologists visited the site Monday as part of a state-wide bat population count to track the number and species of the bats hibernating in the cavern.
“There were three openings to the cave prior to it being commercialized and all three of those were sealed. One was the sinkhole opening which was sealed with a concrete wall and two had a building built in front of them to control access,” said Greg Turner, state mammalogist for the Game Commission. “We dug open the sinkhole and placed a four foot diameter pipe in there and gated the outside portion of that. The building was razed and openings that were there were opened back up to the natural size and bat-friendly gates were placed on there.”
The location is unique in that it is the first commercial cave in the state to be returned to its “wild” state. The cave had been actively explored by Native Americans and early colonists, and opened as a part of a roadside attraction in the late 1920s.
“We are already seeing bats starting to use it, which is good. When we purchased the cave, we went in and did a survey and put the data loggers in,” Turner said. “There were two bats in there at that time — one tricolor and one little brown.”
Indian Caverns joined other locations in Pennsylvania as a “cold site” where bats can hibernate in lower temperatures to help them combat the affects of WNS, a fungal disease.
“The fungus, even thought it is a cold-loving fungus, has its maximum growth rate at 50-55 degrees. So, when we get down to about 40 degrees, it is about 25 percent of its maximum growth. As it gets to freezing, the growth is close to zero. The colder it is, the slower the fungus grows and, theoretically, the lower the infection load the bats will have,” he said. “We know White Nose Syndrome causes bats to come out of hibernation about twice as often as they should and that causes them to burn through their fat supply in the middle of winter instead of the end of winter. Now, if they have less infection, they should be saving energy because they are at a colder temperature and coming out of hibernation less. They will be saving energy. Hopefully, that will give them a leg up on surviving.”
By reopening the natural entrances to the cavern, while adding gates to prevent unwanted disturbances, the temperature within Indian Caverns dropped with the onset of cold weather.
“The temperature in the cavern had been the ground temperature of Pennsylvania because it was all closed up, so it was 53 degrees,” said Turner. “Today, it was 36 degrees in the upper room and 41 in the second level down, so that probably happened as soon as the cold weather happened. Now, we just need to get the cold air to slowly settle into the bottom. Because this site slopes downhill from the entrance, it will continually cool for the next several years.”
Biologists quietly walked through the underground passages, using flashlights to search the ceilings, walls and crevices for hibernating bats. When one was discovered, the location and species were documented, as was the temperature of the hibernation site.
“We’ve gone from two bats to 10 and from two species to four species. We counted big brown bats, one small-footed bat, which is on the state’s threatened species list, a tricolor bat and some little brown bats,” he said. “Considering that we didn’t open the cave up and do the work until most of the bats were already hibernating, that’s a big jump. Some of them may have come in late in November.”
The increasing numbers look promising and hopes are for even better population counts in the future.
“Any little step forward is a good step forward for the bats. We hope others will start to find the site and the numbers will grow. That doesn’t necessarily mean we’ve increased the number of bats, it may just mean that the bats that have survived White Nose Syndrome have found the site,” Turner said. “Recovery would mean juveniles moving in and surviving at the site. That would mean the population is recovering and going up. That’s my hope — that once the adults find the site, they’ll show the juveniles and eventually we’ll see stabilization and recovery of the population with a few of these cold sites spread across the state.”