Western Pennsylvania Conservancy A little brown bat rests at the Western Pennsylvania Conservancy. White-nose syndrome wiped out 99% of the bat population in Pennsylvania.

White-nose syndrome decimated local bat populations when it showed up in the state in 2008 and began killing cave bats in 2009.

Now, more than a dozen years later, bats are starting to make a comeback, though the population numbers won’t rebound completely for thousands of years.

“It’s going to take tens of thousands of years to see bats come back to pre-white-nose syndrome … because they multiply very slowly,” estimated Ann Dulavy, owner of Lincoln Caverns, Huntingdon.

White-nose syndrome, a fungal disease that awakens bats while they are hibernating, killed almost all the bats in the Lincoln Caverns, she said.

After awakening, the bats lack the fat reserves to survive until insects emerge.

Dunlavy witnessed the cave losing almost all of its bat population in the winters of 2009 and 2010. Sometimes she would see one or two bats outside, crawling on the ground, and other times, she would find dead bats.

The bat population went from 40 to 50 known bats to nearly zero.

Now, walking along the tour route, Dunlavy can track “a few here and there,” calling them “fat bats” because they fed on enough insects to help combat the disease and see them through the winter.

“We get very excited when we see a few bats that are doing well,” Dulavy said.

While the caverns don’t have a bat colony, per se, they are liked by several lone bats who prefer time away from their group. Dunlavy said they usually come back to the same spot every winter.

Colony rebounds

Canoe Creek State Park had one of the largest bat colonies in Pennsylvania, but lost most of its population, too.

Greg Turner, the endangered and nongame mammal biologist with the Pennsylvania Game Commission, said white-nose syndrome decimated the bat population at the park’s mine site — from 30,000 bats to just 71 — and wiped out the 20,000 little brown bat and Indiana bat population at the Frank Felbaum Bat Sanctuary.

Since that low of 71, Turner said the winter site now has a population of about 1,000 bats.

The bat sanctuary — the summer site — has witnessed a similar trend.

White-nose syndrome wiped out 99% of the bat population in Pennsylvania.

Heidi Mullendore, the education specialist at Canoe Creek State Park, said the bat sanctuary was home to about 800 bats last summer.

After the little brown bats were wiped out by white-nose syndrome, big brown bats moved in. Last year, the little brown bats came back, too, she said.

“I believe they are doing quite well,” Mullendorre said. “They reproduce slowly, but they live longer than other mammals their size. So the count is going up, but it goes up slowly each year.”

The state game commission also sees “significant growth” in two sites in Blair County and one site in Centre County — a site Turner can not disclose because he is afraid of drawing attention and causing people to disturb the bats.

Fragile population

Despite the good news at Lincoln Caverns and Canoe Creek, the bat population is very fragile. Out of the nine types of bats in Pennsylvania, two are on the federal endangered list while some others are on the state’s endangered list.

“The intersection between habitat loss and diseases like white-nose syndrome makes it difficult for the population to be sustained,” said Melissa Kreye, assistant professor of forest resource management at Penn State University Park.

Bats face multiple challenges, she said, including pressure from climate change.

Warmer winters and hot, early springtime temperatures are also a problem.

Mullendore said she could see bats emerge from hibernation earlier and fly around on warmer nights.

Industrial farms also pose challenges to bats. Before farming starts, farmers use lage machines and chemicals to treat their land, and insects — the main food source for bats — are greatly affected.

“When we were kids, there weren’t that many industrial farms around,” Mullendore said.

Today, though, farmers use spray to kill weeds before planting crops. That spray affects the insects, which the bats rely on.

“The pesticide works up the food chain into the bat population,” she said.

“From cats to wind turbines to automobiles to pesticides to other pollutants out there. … There are other factors that caused bats to perish, but whether they’re significant factors it’s hard to say,” Turner said.

Cooler sites

Turner said the survivors of white-nose tend to aggregate in cooler sites and the mine at Canoe Creek is one of the coldest in the state.

To protect the species, scientists are purposefully making some sites cold to draw survivors into the cave. A treatment spray that neutralizes the pathogen has also been developed and delays bats’ exposure to the disease.

An unpublished paper scientists are currently working on also found out that bats in cooler temperatures get less disease.

As spring turns to summer, visitors at Canoe Creek State Park often turn out to watch the bats emerge from the Frank Felbaum Bat Sanctuary to feed. While the numbers aren’t as high as the years before white-nose syndrome was discovered, they are getting better and the park is taking extra care so the bats’ habitat is not disturbed.

“We are here to protect and conserve species in our park. We make sure our bat watching is not interfering with the bats,” Mullendorre said.