Habitat improvement efforts for bats are giving the Pennsylvania Game Commission (PGC) hope for the future of these flying mammals.
Members of the agency have been working for more than a decade on finding ways to help bats survive a fungus that causes White-Nose Syndrome (WNS).
At one time, Pennsylvania attracted roughly 10 million bats across 600-700 locations. However, after WNS was discovered in late 2008, the population is believed by a leading researcher to now be in just the thousands.
However, there have been efforts underway that are starting to stabilize, and possibly grow, the population.
“We’re seeing the total bats we count in winter going up slightly, and we’re seeing the total amount of little browns in our summer maternity counts going up slightly as well,” said Greg Turner, state mammalogist and protected mammal section supervisor for the PGC.
Tuner has had some success in Blair County and is looking to expand his work in other parts of the state, including in Fayette, Butler, Armstrong and Luzerne counties.
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Bats in Pennsylvania can eat thousands of insects over a 24-hour period. The Pennsylvania Game Commission is working on improving habitat areas to help bats survive white nose syndrome.
Why bats are important
If people don’t like bats, they probably should. Turner said the average female bat is eating between 4,500 and 5,000 mosquito-sized insects per night. When you factor in that they’re active on the landscape at least six months a year, he estimates a bat can eat close to a 1 million insects each year.
“If you had a colony of 300 bats in your barn and you’re a farmer, that’s 300 million insects being consumed,” he said. Many of the insect species, like moths, cause crop damage.
To combat the insects, the farmers are paying for insecticides and fueling their tractors to spray the fields. Those insecticides can impact the food supply and health of humans.
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For those who like seeing or hunting grouse, Tuner said West Nile Virus, which is carried by mosquitoes, has reduced the population of Pennsylvania’s state bird.
Heartworm disease that impacts pets is also spread by mosquitoes.
“Now that we have millions less bats eating hundreds of millions of less bugs, like mosquitoes, diseases like that can likely spread faster than they did before,” he said.
In other parts of the world, bats eat and spread seeds that help forests regenerate and they pollinate different foods.
“Without bats, we wouldn’t have bananas, plantains, avocados, almonds and agave plants for those people who like a margarita. Agave and a lot of cacti are only pollinated by bats,” he said.
Bats are also helpful in research for radar and anti-coagulant drugs that treat blood clots and strokes.
“All of those blood thinner drugs came out of understanding and researching bat saliva from vampire bats,” he said.
Now, Turner is aware of people who are studying why bats don’t get cancer and are able to survive viruses like Ebola. “If we can understand that, we can really derive some important medical questions,” he said about improving human survival.
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Greg Turner, state mammalogist and protected mammal section supervisor for the Pennsylvania Game Commission, stands April 14, 2022, at the entrance to a former limestone mine where bats hibernate.
Modifying climates to save bats
Work is being performed in different parts of the Keystone State to lower the temperature in several abandoned mines and caves where bats spend the winter.
Turner said a White Nose Syndrome Response Team, led by Dr. Michelle Verant, determined about 14 years ago the fungus for WNS, Pseudogymnoascus destructans (Pd), grew slowly or not at all at temperatures that were close to the freezing point.
The fungus grew faster in warmer temperatures. However, if the temperature rose above 55, the fungus would stop growing and higher temperatures killed it.
“The fact that it grows at a colder temperature, makes it ideal for growing in a cave,” he said.
“What we noticed is that the bats, when this pathogen came in and started contaminating sites in Pennsylvania, that the bats were actually selecting roosting winter hibernation sites with internal temperatures that were in the 44 to about 49 degrees Fahrenheit range,” he said.
What that means is that they were selecting sites that were about 75% of the maximum growth rate of the fungi.
The fungus would cause wounds on the faces of the bats. “It was eating them alive, if you will, digesting live skin,” Turner said.
When that was happening, the bats would come out of hibernation more often, causing them to deplete the energy reserves they had for the full winter. “That’s a very energy consumptive process to come out of hibernation,” he said.
The bats were dying because they were running out of energy.
“When we started looking for survivors, we didn’t see them in the vast majority of sites. If we did, we only saw one or two or four, like small numbers. So, sites that had sometimes 10,000, 30,000, 40,000 bats, had just a few individuals left,” he said.
In some of the colder hibernation sites, they started to see a growing population of bats again. Most of the hibernation sites were too warm but the bats that were finding rare colder sites were able to survive. “There’s only a half dozen of these types of sites that we know of in the state that have temperatures in this range in the wintertime,” he said.
They noticed the little brown bats that had more fat in the fall and selected colder temperatures to roost, had a better chance of survival.
With that finding in mind, they found an abandoned limestone mine in Blair County where they could open the airflow to create a colder winter environment.
With the help of the U.S. Fish and Wildlife Service, the agency was able to secure about $30,000 in funding in 2015 to dig open an old opening to the mine.
The team opened the entrance and worked with the airshaft left by the mining operation to create better air flow through the mine shaft. As the cold air moved in, the hot air moved out like a chimney.
“The entire site went from 52 degrees Fahrenheit year round to now all of a sudden we’re at about 38 to 40 degrees in the winter,” he said.
In 2014, a year before the work started, he said there were 10 little browns and one tricolored bat left. At one time there were more than 100 bats wintering there, including northern long-eared bats. The site had three of six species of bats found in Pennsylvania.
After the work was completed, in February of 2016, “We had four big brown bats move in, which had never been documented in the site. And we had a total of seven bats. The very next year, in 2017, we jumped from seven total bats to 28 bats,” he said.
The numbers continued to grow.
“After five years, we were up well over 100 bats at this site, and we were pretty pleased with that. We theorized, not only were the bats selecting these colder temperatures in order to save their energy, they were likely getting less disease because the fungus grows slower at colder temperatures,” Turner explained.
To further test their findings, they placed male little brown bats in cages in different temperature locations in the mine. “What we indeed saw, was that bats that were at about 40 degrees Fahrenheit in February, had significantly less disease than the bats at 45 to 50 degrees,” he said.
The additional air flow helps in the winter, but it creates a problem in the summer by allowing warm air to enter the mines.
With the help of his PGC colleague, Mike Scafini, an endangered mammal specialist, they placed insulation foam across about 95% of the openings during the summer months. “We left a small opening there for bats to get in and out, but we really wanted to restrict that airflow. The idea was to see if we could minimize that hot air from blowing in and if we could retain that cold temperature a little better,” Turner said.
The insulation worked as the temperature dropped to 45 instead of the usual 53 at the end of August.
The efforts have improved the chances of survival for bats.
“When we counted bats that winter, there were 100s of new bats in that site,” he said.
The improvements have helped stabilize the winter temperatures to the 38 to 42 degree range. With about four seasons of data, the site now has an average of 290 new bats each year compared to about 15 before the project. “The site has now become the third largest hibernation site in Pennsylvania,” he said. “We have over 1,200 bats in there now,” he said.
Pennsylvania Game Commission researchers are studying the temperatures where bats hibernate. The work is designed to save bats from the fungus that causes white-nose syndrome which can be fatal.
More than 1,000 of them are little browns and there are about 83 tricolored bats. He’s also found small footed and big brown bats there.
“Most of the growth has been with tricolored bats and little brown bats, but those are the two species that are being considered for federal listing (endangered) because of the declines from white nose syndrome,” Turner said.
“For us to see the benefit to those two species in particular is very heartening that we’re making a difference,” he said.
He’s hoping the results lead to long-term survival for these bats.
“Theoretically, if the adults can survive better at those colder temperatures and they’re successfully reproducing, which they are, they should be teaching their young on where to hibernate,” he said.
The big question he has with the new population involves what level of mortality or survival these modified places will have with juvenile bats.
“Are we at a point where we are getting more juveniles surviving that first year than we do adults surviving, because that is truly what recovery is, is that your adult population is constantly losing a few individuals due to predation or old age or whatever. But every year they are producing enough juveniles that recruit to that adult class to offset that and grow the population some,” he explained.
It’s a challenge as bats move along the landscape from site to site, making it more challenging to know if there’s true recovery happening.
“We’ve manipulated a number of these sites. We’ve had success with a couple of them and we’re working on a few more of them. It’s a very time-consuming process. It’s a very expensive process. So, we approach it diligently and slowly, tweaking things slowly, a little bit at a time so that we’re constantly moving in the right direction,” he said.
When he looks at these sites that lost bats to WNS and now, they are starting to survive and have an upward trend in numbers and he realizes that change is happening.
“We’re cautiously optimistic that we are indeed having some true recovery of having some juveniles recruiting into the adult population and seeing some growth that way,” Turner said.
Future bat habitat work
The goal is to have a few of these modified hibernation sites in each region of the state. They are looking for sites that were never biologically important habitat areas but are on state lands where the work will be permanently preserved.
“The sites that historically, before white nose, that had a lot of bats and were really good, we’re trying to leave those alone and leave those protected so that as bats evolve resistance, if they want to go back to those same historic temperatures, they have that ability to do so,” Turner said. “And some of that may soon start because we are seeing less disease in our bats based off our examinations of little brown bats specifically.”
They want to create environments that get that cold to slow or stop the fungus but also have different temperature zones in the cave or mine. “The bats will have the ability to select where they want to go at any given time during their hibernation period,” he said.
Looking ahead, he’s looking at sites in Fayette County this summer and he’s examining a new location in the Armstrong County and Butler County border. He’s also interested in projects in Luzerne and Huntingdon counties. “It’s a slow business. We kind of just focus on one and do some things and watch for what the response is,” he said about rotating around and monitoring the results.
He’s also been involved in some private sector partners. He said CNX Gas Co. has been a great partner in helping with the manipulation work. “We’re working on our first artificial hibernation site and hopefully having it come online soon,” he said about Greene County.
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Pennsylvania opened Laurel Caverns in Fayette County as its 125th state park this year. The property with a massive limestone cave was donated by David and Lillian Cale to the state.
Turner said there may be opportunities to improve the habitat for bats there in the future. The underground part of the park already is slated to close over the winter months because bats have been hibernating there.
“There’s a decent opportunity to open up some of the historic openings that were sealed and restricted in order to maintain a commercial operation. And if we do that and provide areas of that site where we don’t have common disturbances of lights and people, it has the potential for some bat recovery for sure,” he said.
“But I want to temper that and say that the education of people seeing these sites and learning about this and learning the value of bats to our ecosystem, to our human health, they’re all interconnected. Having people understand what’s going on is important. Laurel Caverns can play a dual role in educating people as well as helping bats. Finding that compromise would be an ideal situation for Laurel Caverns,” Turner explained.
He personally likes bats for a variety of reasons and is looking forward to future successful projects with them.
“They’re a really diverse mammal group. They are unique in so many different ways from all other mammals, not just the ability of flight, but their echolocation and their evolution to reproduce the ways they do that. There’s just so many different unique things about them and so much more to learn from them,” he said.
Brian Whipkey is the outdoors columnist for USA TODAY Network sites in Pennsylvania. Contact him at bwhipkey@usatodayco.com and sign up for our weekly Go Outdoors PA newsletter email on this website’s homepage under your login name. Follow him on Facebook @whipkeyoutdoors.
This article originally appeared on Erie Times-News: Pennsylvania modifies mines to save bat populations