For many of Pennsylvania's bats, White-Nose Syndrome is a fatal alarm clock.

It does not affect humans, but this fungus has been reaping the lives of bats by the thousands.

Dustin Drew, park manager for Moraine State Park, said the bat population at the park has been down for a number of years.

Drew said rangers check on the six bat houses in the park, all of which could sustain anywhere from 50 to 100 bats. None of them is occupied now.

“They were all used at one point in the past,” Drew said.

White-Nose Syndrome, first documented in New York in 2006, is a fungal infection that forms on the muzzles and wing membranes of hibernating bats.

Once infected, the bats — which survive the winter by using their fat stores — wake too early from hibernation. It often proves to be a fatal wake-up call. Restarting their systems takes a lot of energy, and eats into a bat's fat stores at a time when there are no bugs to replenish their reserves.

Drew said the fungus is especially harmful to bats that live in caves.

“It could wipe out all or most of the bats in the cave, and that can be thousands, so it can really take an effect,” he said.

That effect can be a cascading one, because fewer bats means more bugs too.

“You take away one thousand bats, and that's hundreds of thousands of insects that aren't being eaten,” Drew said. “Any time you have a shift or a gap created in the food web, then it throws things off for a while.”

For some bat species the fungus has been devastating. In all six species that hibernate in Pennsylvania, biologists have seen a 99 percent decline in their numbers, according a 2012 report published by the Pennsylvania State Game Commission.

The other three species found in the state are migratory and have not shown signs of contracting the fungal infection, according to state officials.

Last month, Game Commission officials moved to begin the process of declaring three bat species — the Northern long-eared, tricolored and little brown bat — endangered.

Charlie Eichelberger, a terrestrial zoology coordinator for the Western Pennsylvania Conservancy's Natural Heritage Program, started working around bats in 2006, shortly after the fungus outbreak started in the state.

“We do a couple different things for bats,” Eichelberger said. “(Mainly) we help provide assistance where the game commission doesn't have the capacity or needs more bodies for hibernacular surveys in caves in mines.”

Eichelberger said the Game Commission monitors about 30 sites where bats hibernate every other year.

“There's long term data there,” Eichelberger said.

Eichelberger said he watched as the disease entered and swept through the state.

“For the first few years as it was spreading, we were documenting that spread,” Eichelberger said. “We were doing full decontamination of our gear, so we wouldn't spread that disease.”

But, it didn't matter. The disease moved quickly and little was, and still is, known about the fungus.

“You would see a majority of those hibernating with White-Nose Syndrome,” Eichelberger said.

White-Nose Syndrome may not be a new threat, but it is one that continues to be a problem for bats that hibernate in the state.

“To see in just a couple of years, that something as simple as a fungus devastated the bats, it's really disheartening,” Eichelberger said.

The Little Brown bat was once known as the most common in Pennsylvania, but their hibernation tendencies made them extremely susceptible to the fungus, according to Eichelberger.

Eichelberger said the last reports he saw from the Game Commission showed a 99.8 percent decline of the species statewide, and he has witnessed their change from common to rare in his own interactions of helping the commission collect data through catch-and-release methods.

“(Before the outbreak,) in a normal night, you could catch dozens of Little Brown bats,” Eichelberger said. “Now they are one if not the rarest bats in the state. We could go a whole season without catching one anymore.”

Aside from the migratory bats, there are still some species continuing their struggle for life.

Drew said the park has seen bat population in one spot, but it's not on the park's land. He said the park checks on a bat condo near the cemetery of Mount Zion Baptist Church in Prospect.

Drew said in the past, the condo has housed between 500 and 600 bats at one time.

“That (reduced) population has held. It's also down, but still there,” Drew said.

Eichelberger said species like the Big Brown bat have done better at resisting the effects of awakening early because of their bigger size, and others like the Eastern Small-Footed bat have a natural tendency for hibernating in temperatures even too cold for the fungus. He said to see such resiliency in the latter, which was already a rare species in the state, was funny, but made sense.

“They tend to enter the caves last during hibernation and leave them first,” Eichelberger said. “They also tend to hibernate in the coldest parts of the caves.”

Eichelberger said researchers also have noticed bats fattening themselves a little more too. He said some have been weighing about 10 grams, when they used to weigh about 8 grams, a small but significant increase.

“Two grams on an animal that normally weighs 4 to 6 grams in the summer season, that's spectacular,” Eichelberger said.

Eichelberger said even the Little Brown bat population has shown some of these adaptations.

“There are some colonies of little brown bats that are hanging on and seem to be doing well,” he said. “In some instances we are seeing modest increases.”

Eichelberger said these adaptations and new signs of life are not guarantees, but they offer hope for a better future for bats and insect-hating humans alike.

“We're hoping their resiliency and their ability to tolerate the disease, that their hearty genes are being passed down to their offspring,” Eichelberger said.

Pennsylvania is home to nine species of bats. Bats are mammals that give birth to live young. Mothers nurse their young. Bats use echolocation to find food, emitting sounds that bounce off objects, like insects.All of Pennsylvania’s bats are insectivorous, consuming moths, grasshoppers, mosquitoes and beetles.Here are brief descriptions of the Pennsylvania bats:<b>Little Brown bat</b>Appearance: Brown body with black wingsHabitat: Found statewide. Summers, buildings near rivers, marshes and lakes; winter hibernation, tunnels, mine shafts or caves.<b>Northern Long-Eared bat</b>Appearance: Brown body with black wings. Looks like Little Brown bat, but has a longer tail and has narrower and longer ears.Habitat: Found statewide, but less common than Little Brown bat. Females form colonies in attics, barns and in the cavities or beneath the bark of trees; winter hibernation, the bats move to caves.<b>Indiana bat</b>Appearance: Similar to the Little Brown bat, but with a pinkish cast to its fur making it look purple-brown.Habitat: Roost in trees in the summer. They rarely roost in buildings. Winter hibernation, in specific caves in Missouri, Kentucky, Indiana, Illinois and small parts of Pennsylvania (Butler County is within its range.)Special notice: It is an endangered species. Following major declines due to white-nose syndrome, there were as few as 25 known left hibernating in the state in late 2015.<b>Big Brown bat</b>Appearance: A large bat that can be as long 5 inches with a one-foot wingspread, these bats have a dark brown fur. The face, ears, and wings are blackish.Habitat: These bats like living in attics, belfries, barns and hollow trees. They can also make homes behind doors and shutters, making them able to roost in cities and rural areas alike; winter hibernation.Special note: It is the most common bat in Pennsylvania, and 150 big brown bats can eat enough cucumber beetles during the summer to protect farmers from 18 million rootworm larvae.<b>Red bat</b>Appearance: A bright rusty color with long, pointed wings.Habitat: Summer, this bat roosts individually in trees on forest edges, in hedgerows and shrubby borders. They prefer American elm trees. They rarely use caves or buildings. Winter, this bat migrates.Special note: Despite being migratory, these bats can withstand body temperatures as low as 23 degrees.<b>Tricolored bat</b>Appearance: Small in size, its fur is yellowish-brown, which is darker on its back. The back hairs also feature three colors: gray at the base, a band of yellowish-brown in the middle and dark brown near the tip.Habitat: Summer, they roost in open woods near water, in rock or cliff crevices, in buildings and caves; winter hibernation, they head deep into caves.Special notes: Formerly known as the Eastern Pipistrelle bat and is also known as the pigmy bat.<b>Hoary bat</b>Appearance: The largest bat in the Eastern U.S., this bat can have a body as large as 6 inches with a 15-inch wingspread. Their fur is dark brown and heavily tinged white. This species can be found anywhere in the state, but is uncommon.Habitat: These bats roost in trees, but they prefer conifers. They roost high in the air, typically between 12 to 40 feet high; winter, these bats migrate to warmer climates.<b>Silver-haired bat</b>Appearance: Soft, long fur that is blackish-brown and tipped with white.Habitat: Summer, this bat roosts in dense foliage, behind loose bark and in hollow trees. They rarely live in caves; winter, they migrate south of the state.<b>Small-Footed bat</b>Appearance: One of the smallest species in North America. Smaller feet. Has black features in its fur that appears like a mask on its head. Also has a golden tint to its brown fur. Black wings.Habitat: Rare in Pennsylvania. In Summer, this bat roosts in rock cliffs, boulder fields, rock-strewn abandoned mine lands and rocky road cuts. They rarely call buildings or trees home; winter hibernation, narrow cracks in the wall, floor or roof of caves.Source: Pennsylvania State Game Commission