Finally, hope for bats in grim disease fight
Harrisburg — A glimmer of hope has emerged in what has been a dark and deadly time for bats in Pennsylvania and dozens of other states.
Although white-nose syndrome has wiped out nearly all of Pennsylvania’s bats, some adults infected with the fungal disease now appear to be surviving through their own adaptive strategy, according to Greg Turner, the Pennsylvania Game Commission’s endangered mammal specialist.
“We’re seeing some steps in the right direction,” he said. “The problem is not over by any means, but we’ll take whatever good news we can get.”
In their study of bats in a mine and a cave in Fayette County, Turner and his team are finding some adults alive after at least two years with the disease that once meant certain death, because they have been able to increase their body mass by 25 to 35 percent, Turner said.
White-nose syndrome causes bats to arouse in winter when they should be hibernating, and to burn through fat reserves as they warm up and move around. Besides the tell-tale fungus on their faces and wings, infected bats develop lesions and muscle-wasting.
The Fayette County survivors seem to sense they need to bulk up even more for winter, which appears to be helping them to live with the syndrome, Turner said.
“We know from our study sites that when bats get infected, their arousal rates will double in winter.
The more infection they get, the more the arousal rate increases to the point where it triples before they die,” Turner said. “In my mind, bats have ‘learned’ this disease is causing them to use up their energy reserves too fast, so they’re packing on more fat.”
The Turner team has studied infected bats through increasingly refined means. Dime-size data loggers glued to bats’ backs in one site allows the biologists to monitor arousal rates, while ultra-violet light enables them to measure the amount of infection on a bat’s body.
Whereas scientists once had to destroy some bats to harvest tissue samples, they now can take tiny biopsy “punches” from bats’ wings that are non-fatal, Turner said.
At sites where Turner has found survivors, their degree of infection seems to be decreasing every year, he said. “Every individual gets infected … and the first year we had the highest level, but every year after that, the levels were less and less.”
And while all of Pennsylvania’s six species of hibernating bats have the syndrome, some appear to have a survival edge, Turner noted.
“The little brown bat was our most abundant species and it took the hardest hit. They and northern long-eared bats are down by 99.99 percent.”
By contrast, the big brown bat and the small-footed bat are doing much better, he said.
“White nose likes a specific temperature range, which you typically find at the back of a mine, where there’s also high humidity and no sunlight. The big brown and small-footed bats hang toward the front of caves, where conditions are different. They’re last in and first out.”
Although it is speculative at this point, it may also be that these two species have stronger immune systems, thicker wing tissue, or a type of bacteria on their bodies that fights the fungi, said Turner, who also is looking for clues in hibernacula environments.
It’s possible, he said, that some caves and mines produce a “good” fungi that may be out-competing white-nose spores.
With a lot of unknowns still being explored, the Game Commission is trying to purchase mines and caves where bat survival has been documented. “In order to have the quickest recovery possible, we want to preserve the survivors and let their young survive,” Turner said.
That one young bat banded in Pennsylvania was captured alive and healthy by scientists 130 miles north in New York is an encouraging sign, said Turner, who believes white nose in the United States is moving closer to what’s happening in Europe, where bats began adapting to the disease decades ago. White nose is believed to have originated in Europe.
“The coup de grace is that we’re seeing less and less infection among bats with white nose,” Turner said. “In Europe, juveniles are surviving. The big question for us is whether juveniles are surviving here. Hopefully, we’ll see that soon.”