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The big brown bat is bouncing back after devastating disease, biologist says

Little brown bats' numbers were reduced by 98 percent in New Jersey over the past decade due to white nose syndrome,

ROCKAWAY -- Some bat species are doing better a decade after a deadly disease decimated populations throughout the Garden State, but even with these rebounding numbers, it will likely be decades before other bat species rebuild their numbers, experts say.

Big brown bats are showing some resilience to white-nose syndrome, due in part to their size, their range of hibernation spots and their ability to hunt during warm winter days, said MacKenzie Hall, lead biologist of Fish and Wildlife's endangered and non-game species program.

Their numbers have grown by upwards of 20 percent since white-nose syndrome arrived, "probably due to the idea of 'competitive release' -- fewer bats to compete with for food and space."

However, cave dwelling bat species continue to be devastated by the disease, Hall said, including little brown bats whose numbers were reduced by 98 percent in New Jersey.

"The community of bats that we see in the sky will probably never be the same as what it was before (white-nose syndrome)," she said.

New Jersey supports nine species of bats including migratory, forest dwelling and cave dwelling species, Hall said.

Little brown bats are most susceptible to the fungus that causes white-nose syndrome during hibernation since their immune systems and metabolisms are effectively suppressed during that time, she said.

Unlike big brown bats, which tend to hibernate toward the front of cave systems where temperatures are more variable, little brown bats typically hibernate further inside the cave where temperatures are warmer and more stable -- and more supportive of the fungus responsible for white-nose syndrome.

One of the changes seen recently in little brown bat populations in Pennsylvania and New York, Hall said, is these bats have been hibernating in cooler parts of caves and mines, with temperatures of 38 to 41 degrees Fahrenheit. The fungus responsible for white-nose syndrome grows best at temperatures of 41 to 50 degrees.

The bats, Hall said, "shifted their behavior in order to survive."

A study by Rutgers University indicated survival of little brown bats was improving with each subsequent year since white-nose syndrome hit the Garden State. The annual survival numbers of bats was improving and getting close to "normal levels of survival," she said.

Additionally, studies by researchers at Rutgers University and other institutions have found some commonalities among survivor bats including similar genetic traits and a larger body mass and body fat.

Still, Hall said, even if the number of little brown bats were to return to normal survival levels, it would take decades at the least for these bats to rebuild their numbers. 

"Some of our bats will probably never return to the pre-white nose numbers," Hall said.

Fish and Wildlife officials were taking various steps to help bats in New Jersey bounce back, including monitoring efforts and an outreach program to homeowners "to make sure bat problems are handled in an effective and bat-friendly way."  

"Harming bats is illegal in New Jersey anyway, but a little education has gone a long way toward helping people understand and appreciate these animals," she said. "Every last bat is precious these days."

Fish and Wildlife is also planning to implement its "first project to restore cold air flow into one important bat hibernaculum this year, hoping it'll make things more favorable for the bats," Hall said.

Justin Zaremba may be reached at jzaremba@njadvancemedia.com. Follow him on Twitter @JustinZarembaNJ. Find NJ.com on Facebook.


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