Bats are making a comeback, and that will mean fewer mosquitoes. Here's how you can help

Carey Friel lowers gloved hands to the ground at Nockamixon State Park in Bucks County as a small, injured baby bat slowly crawls toward her. 

"So sweet, it just curled right up into my glove," said Friel, leader of the Nockamixon Bat Project. "These are wild animals, but the trust is there.”

Bats — nature's only flying mammal — appear to be making a long-awaited comeback in Pennsylvania, and that's good for the environment and public health, scientists say.

The return of bats to Pennsylvania will mean less pest insects and bugs that can damage crops, forcing farmers to use more pesticide.

Bats eat tons of insects — about 25 percent of their body weight with each feeding.

One bat colony of 100 little brown bat eats more than 250,000 mosquitoes per year, according to the Penn State Extension.

Less insects could mean less cases of encephalitis, Zika virus, and fewer cases of heartworm in pets. All are spread by mosquitoes.

White-nose syndrome causes 'mass mortality' 

At the turn of the century, Pennsylvania was home to tens of thousands of bats feasting on flying insects. Then, white-nose syndrome wiped out much of the species.

Pennsylvania Game Commission biologist Greg Turner was among those trying to save the bats, which were, essentially, starving to death. Sadly, white-nose syndrome caused the bats to use up more energy than they could conserve for hibernation.

"It was mass mortality," said Turner. "Once in a while, you would stumble on a site where you would just see thousands of them dead in a small area."

Now, researchers at the University of Michigan are finding bats resistant to the fungal disease. Genetic variations in some bats suggest a "very rapid — though not unprecedented — evolutionary adaptation," researchers said.

In Pennsylvania, bats also seem to be adapting to white-nose syndrome, Turner said. Bats are selecting colder places to ride out the winter. And, they are putting on more weight. 

"The sites where the bat population is growing are colder sites — locations the bats had never used before," said Turner. "The average weight of a Little Brown bat was 7.5 grams. Now, we’re finding an average of 10 grams, and the heaviest bats we’ve weighed are about 14 grams."

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In Pennsylvania, summer bat counts are showing "slight increases," said Shannon Fredebaugh-Siller, of the Heritage Conservancy of Bucks County. The nonprofit protects more than 15,000 acres that provide food and shelter for bats. The organization monitors three sites where mommy bats raise babes.

More than 200 bats were spotted in July in Bucks County, Fredebaugh-Siller said. That's about a quarter of the bats counted on the site before white-nose syndrome swept through the colony. 

Volunteers are working to nurture bat species at Nockamixon State Park and other locations across Pennsylvania. Injured bats are treated and returned to the wild, and the Pennsylvania Game Commission is working provide bats with more spaces to hibernate.

In Luzerne County, a former rail tunnel is being transformed into a bat cave. "We built a huge earthen mound (at the entrance)," Turner explained. "It’s helping with the air flow that gets into the tunnel. We’re drilling holes to draw the heat out of the tunnel."

As the sun sets on Nockamixon, volunteers fan out with bat detectors — audio devices that can pickup on frequencies used by bats. Those bat sounds are on frequencies too high for human ears.

A member of the Nockamixon Bat Project, Friel insists that the bats in the park have come to know her and the other volunteers. The two dozen bats near the park office are friendly, she said.

"They can tell who you are by your voice and by your scent," said Friel. "If we bring someone new on a (bat) count, the bats behave differently." 

How you can help the bat population 

Four bats are on the state’s list of endangered species, and one is considered threatened. Pennsylvanians can help bats come off the endangered species list with a little bit of care and understanding.

First off, leave them alone. Avoid places where bats are known to hibernate, scientists say. Disturbing bats during the winter forces them to use energy when they are struggling to survive.

If a bat is in your house, don't try to kill it. Give it an exit strategy, experts say. 

Bats that accidentally fly into your home will try to escape as quickly as possible through any open doors or windows. 

If a bat lands in your home, you can cover it with a small box and then slip a piece of cardboard under the box to trap it. Wait until nightfall, hold the box high above the ground, and then tilt the container to the side, encouraging the bat to fly out. 

Also, consider hosting a new family.

With less available wilderness, bats sometimes enter into attics and under roof tiles when they are in the process of giving birth and raising babies. Forcing their exit during this period can kill the pups. (Baby bats are called pups because they nurse milk from their mothers.)

Bat Conservation International provides other tips on safe ways to remove bats from buildings as well as instructions on construction of bat "houses" on its website, batcon.org

What bat was that?

Here’s a list of the most frequently spotted bats from the Pennsylvania Game Commission: 

The Big Brown is the most prevalent in the state. It has a brown coat with a black face and ears. The Big Brown likes attics, barns, hollow trees, and has been known to hang out in window shutters. It has a 12-inch wingspan and likes to fly at dusk.

The endangered Little Brown and Northern Long-Eared bats are almost bronze in color with wingspans of between 8 and 10 inches.

The Red Bat can appear almost rust-like with pointy wings that can span 13 inches.  

The endangered Indiana Bat has a purple hue and a 10-inch wingspan.  

The Tri-Colored Bat is teeny-tiny and weighs just 0.25 ounces (as much as a tablespoon of nutmeg).

The Hoary Bat is Pennsylvania’s largest and likes to hang out in trees. It has white and brown fur and a 16-inch wingspan.

Bucks County's 'Bat Cave'

Steeped in legend and now protected from intruders, a network of mines in Durham Township was once one of the largest bat hang outs in the state.

Researchers don't know when the bats first discovered the mines, which date back at least three centuries. Iron ore was drawn from the ground to supply a blast furnace built in 1727. 

During the Revolutionary War, the mill produced cannons, cannon balls and military equipment for American troops, according to the National Register of Historic Places.

In 2010, the Pennsylvania Game Commission first reported cases of white-nose syndrome in the mines and predicted total devastation of the bat population.

Once home to an estimated 15,000 bats, the Durham mines are now nearly empty, according to Fredebaugh-Siller. "The last survey that I'm aware of was conducted in the winter of 2018 and there were eight bats counted."

Monitoring and preserving the Durham mines is important, though the site is no longer the best barometer for assessing bat populations, said Turner. To cope with the white-nose syndrome, bats are choosing colder spots for hibernation. 

"Durham was a really good site before white-nose syndrome," Turner said. "Now, the bats are seeking something that’s colder. Right now, we just don't know where."

"They know that if they move from a warmer area to a colder area that they will stay in hibernation longer," Turner added. "That will save them energy."

If and when the bats truly recover, the Durham mines could once again play a critical role for the environment, he continued. "If that’s truly where healthy bats want to be, then we want sites like that one to remain. We want to give bat populations as many options as possible for them to grow."

Contact reporter James McGinnis at jmcginnis@couriertimes.com