Experts say the comeback will be good for the environment, even if they may be a pest in homes.
In Exton, Joe Roberts has been dealing with a swarm of about 50 bats in his attic for almost two months. He discovered them while he was eating breakfast.
"Are you kidding me? I've got a bat in my fireplace," Roberts remembers thinking. He says he hasn't exactly slept well since.
"Every time you walk into the bedroom you still think, you're looking around thinking there's going to be a bat," he said.
He called in experts from Montgomery Wildlife to help.
"As more and more trees are cut down, as more and more old barns are cut down, these bats have to go somewhere and they tend to find their way into residential property," said Austin Jahner, who co-owns the company with his brother, Thomas.
They have spent the past week sealing up Roberts's home and will build a one-way exit for the bats next.
"The problem is that bats can get into the smallest of gaps, so if you were just trying to evict them, you're just moving them a few feet over," Jahner explained.
The goal is to release the bats back into the neighborhood.
"I believe in around 2008 they were labeled as one of the most abundant species, one of the lowest priorities from a conservation standpoint. And as of 2018, they're now endangered," he said.
That drop in population was because of White Nose Syndrome, a disease that killed up to 90% of some species of bats, and it was a big blow to the environment.
"The average little brown bat would eat approximately a thousand mosquito-sized bugs per hour," said Jahner.
He says the population is slowly starting to recover, which is good for business and the ecosystem, even though Roberts hopes they're gone soon.
"We hope so too. We really do," he said.
Bats are a protected species so if you do get them in your home, you need to call an expert who can remove them humanely. You want them to stick around your neighborhood too to help control insect populations.