When was the last time you saw bats flying over the skies of New Jersey?

If it's been a few years that's because ever since New Jersey was hit by a fungus in 2009, the bat population has dwindled, according to MacKenzie Hall, a biologist with the state  Department of Environmental Protection's Endangered and Non-game Species Program.

Little brown bat rests in a Hibernia mine. (Photo courtesy of the Conserve Wildlife Foundation of New Jersey)

"White-nose syndrome (WNS) has wiped out about 98 percent of some of our cave-hibernating species, most notably the little brown bat and the northern long-eared bat, as well as a few others," said Hall.

WNS has been traced back to a number of European countries and Asia, according to Hall.

"It's another one of these non-native, invasive-type species that has arrived here to bat populations that have never encountered it before and to whom it's novel to, and so these bats have no natural resistance or mechanism for fighting it off," Hall said.

While it's unclear how long WNS has been around in Europe and Asia, it is novel to North America. This year marks the 10th anniversary it has been in the United States and Canada.

Bats hibernating in caves and mines during the winter in New Jersey are very vulnerable to WNS. Hall explained the fungus makes its way into the wing tissue while bats' bodies are nearly shut down to conserve energy during the colder months. Bugs, their primary food source, aren't around, so they've adapted by hibernating.

"So everything goes into a state of nearly suspended animation, including the bats' immune defenses," said Hall.

As the fungus moves into the bats' wing tissues they're unable to fight it off, and the fungus eats at and erodes their wing membranes. It also causes dehydration and forces the bats to awaken too frequently and burn through their energy reserves, which Hall said causes them to starve before the winter is over.

The majority of the New Jersey's bat population during winters usually are located in North Jersey, where caves and mines are located, according to Hall.

"If the bats survive the dehydration and the starvation, then they're basically left with wings that look like Swiss cheese. They're eaten up with holes in them. The unluckiest of the bats, their wings are no longer able to carry them through the air and they collapse and eventually die on the ground," Hall said.

When White-nose Syndrome hits a hibernaculum, Hall pointed out the fungus spreads so fast that it can kill 95 percent of the bats there in a single year.

"It's really tough to get ahead of it, although now the way that the fungus is progressing is mainly from the East Coast toward the West Coast, and so it's fairly predictable about where it's going to hit next," said Hall.

There have been several years of researching how the fungus is killing the bats and what its mechanism is for doing so much damage, as well as what other things occur in natural cave environments and on bats that might also be damaged by potential treatments, according to Hall. She noted steps being taken by researchers are showing some promise, including natural bacteria and yeasts that occur, either on the bats own bodies or in natural cave environments, that could be accentuated and distributed to the right bats at the right time of year, where they can impart some anti-fungal property for the bat and some defense against this fungus.

"One of the things that's really interesting that gained a lot of media attention over the last year is a bacterium that was being researched for the banana industry. It's an anti-fungal that improves bananas shelf-life, and some really clever person from Georgia State University had the question of: Would the same thing work on bats?"

White nose syndrome has killed over 6 million bats, according to Hall.

"In New Jersey alone, it's in the tens of thousands of bats that we've lost," she said. New Jersey has three different bat species that are not impacted by the fungus, because they're forest bats that migrate south for the winter. Hall noted another species, the big brown bat, regularly overwinter in caves and mines underground where it could come in contact with WNS, but it's also a much more flexible bat, and researchers are finding it's common for this species to overwinter in buildings as well.

"Big brown bats are the most commonly found around human settlements because of that adaptability. There the ones that you're normally finding in your attic, or behind your shutters, or in that patio umbrella when you open up in the evening and find a startled little guy inside," said Hall.

A far as ecological consequences, bats aren't necessarily food for other things, but Hall pointed out they are part of the food web. The biggest contribution of bats to the environment is "definitely an insect control," said Hall.

"They are the primary night time consumers of insects. So night flying insects like moths, lots of beetles, even stink bugs, gypsy moths, lots of pests, as well as those mosquitoes that everybody despises, and that also are getting a lot of attention lately with Zika," said Hall.

"[Bats] give us billions and billions of dollars worth of benefits each year. So the loss of those insect predators is a big deal to our community and is a big deal to the ecosystem, even though it can be difficult to measure those balances," she said.

New Jersey is part of a North American grid system that Hall said will be doing a more widespread, uniform bat monitoring program using acoustic detectors.

"Which pick up on the echo location pulses that bats give out as they fly and navigate around at night. That will give us a lot more information about how different bats and different bat species are distributed across the state," said Hall.

Morris, Sussex and Warren Counties, where there are networks of underground cave systems and mines, have larger concentrations of bats. Hall said bats can migrate 5 miles to as far as 300 miles from their hibernation site to the places where they summer.

Homeowners who find unwanted bats should be aware that it's almost certainly a colony of mother bats raising their young for their summer. Guidelines for how to properly and humanely remove the bats can be found here: http://www.state.nj.us/dep/fgw/ensp/bat.htm

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