More than a decade after a devastating, bat-killing fungus was first discovered at a State Parks cave in the Capital Region before sweeping across half of the U.S., that same cave now offers a glimmer of hope for some survivors.
Hailes Cave stretches for nearly a mile beneath the 100 million-year-old limestone escarpment at Thacher State Park in the rural western portion of Albany County. It was in this cave, long an important winter hibernation site for thousands of bats, that state wildlife biologists in 2007 observed the first cases of what was later known as White Nose Syndrome (WNS).
This fungal disorder kills bats by infecting their skin, disturbing their hibernation, exhausting critical fat reserves needed for winter survival, and rousting them early from caves to starve without insects to eat. WNS has swept out since in all directions, killing millions of bats in 32 states and seven Canadian provinces
“White nose” refers to a ring of white fungus seen on the nose of affected bats, and which can spread to the rest of its body. The fungus originates in Europe and Asia, where native bats have developed a resistance to it.
With bat populations exposed to WNS in the U.S. plummeting by 90 percent or more, the outlook has been uniformly bleak for more than a decade, since there are no known methods of treating infected bats or eliminating the cave-dwelling fungus, identified as Pseudogyymnoascus destructans.
Some Bats Fending Off White Nose Syndrome
But now, it appears that a certain species of bat – the little brown bat, or Myotis lucifugus – is evolving its own natural resistance to better survive the fungal infections, according to a December 2019 study of hibernating bats in a former cement mine in Ulster County in the Hudson Valley. (The location of this mine is not revealed to reduce the risk of human intrusion, which can reduce the bats’ potential for survival.)
The recent study is co-authored by Carl Herzog, a wildlife biologist with the state Department of Environmental Conservation (DEC); Craig L. Frank, with the Department of Biological Sciences at Fordham University, and April D. Davis, with the Griffin Laboratory at the state Health Department’s Wadsworth Center in Albany.
Historically, Hailes Cave has been a critical statewide cave for hibernating bats. Caves provide a constant temperature above freezing all winter long that allows bats to hibernate until spring, and as such, is called a hibernaculum. During this period, bats are in a state called torpor, in which their bodily functions slow dramatically, allowing them to slowly draw down a reserve of body fat needed to survive until spring, when insects return as a food supply.
Hailes Cave Shows Rebound in Bat Population
Researchers have found that the numbers of bats hibernating at Hailes Cave, which plummeted after the onset of WNS to a low of about 1,200 bats by 2010, have been steadily rebounding, and by 2019 totaled about 7,200 animals. Before the fungus arrived, however, bat populations at Hailes were at least double this level. Bat populations at the Ulster County hibernaculum also increased significantly during that same period.
Most importantly, the recent study found that little brown bats at the Ulster County site are somehow developing a natural resistance to the fungal infection, so that an increasing number of bats get only a moderate infection, or perhaps no infection at all, even though the fungus is present in the cave. And this resistance appears to be behind the increased population at Hailes Cave.
“Clearly, Hailes Cave provides what little brown bats need, but exactly what those factors are is a subject of some speculation… there is some research suggesting that caves draw bats from a geographically larger summer range than mines, because caves have been available for thousands of years, whereas most mines only became available in the 20th century.”
DEC Wildlife Biologist Carl Herzog
Normally, bats wake from torpor during hibernation about once every three weeks. Bats infected with WNS were waking up every week and using up precious calories in the winter months, causing them to leave caves early and die of starvation. Now, little brown bats are waking up an average of once every two weeks, the study found.
This allows these bats remain in hibernation longer and retain sufficient fat reserves needed to survive until spring. Exactly how the little brown bats are developing this resistance to WNS is still unknown.
However, this encouraging evolutionary adaptation applies only to little brown bats, meaning that other bat species found at Hailes Cave, including the endangered Indiana bat (Myotis sodalis), the Northern long-eared bat (Myotis septentrionalis), and the tricolored bat (Perimyotis subflavus) are so far demonstrating no such defense, and their numbers are not rebounding.
The resurgence in the little brown bat at Hailes is also tempered by the fact that this species has not rebounded at other bat caves surveyed by state wildlife officials in Albany and Schoharie counties. This implies that surviving WNS-resistant bats from around the region might be congregating in Hailes for reasons as yet unknown. Brown bats can travel many miles from their summer ranges to ar hibernaculum, with the record for a little brown bat being a journey of 300 miles.
But for now, the study is a small bit of hope in a story that so far has been very grim.
State Parks, DEC and Cave Explorers Group Work Together To Protect Hailes Cave
In 2013, to protect the remaining beleaguered bats at Hailes from being disturbed by human intruders, crews from Thacher State Park, DEC and the Schoharie-based, not-for-profit Northeastern Cave Conservancy installed a two-ton steel “bat gate” near the Hailes entrance. The gate has bars that allow bats to come and go, but blocks human entry.
Read this 2014 account in the New York State Parks blog about the gate project…
State Parks crews at Thacher keep an eye on the cave to ensure the gate remains in place to deter trespassers. When crews last spring noticed that some emerging bats died after becoming trapped in burdock patches near the mouth of the cave, those plants were cut away.
Every entry by people into a hibernaculum while the bats are present is likely to cause harm to the bats. It is illegal to enter most active bat hibernation sites in New York. To help the bats, people must stay away to prevent spread of WNS and to not disturb the bats.
Hailes Cave is among the largest bat hibernation caves in New York, and plays an important role in supporting our remaining bats. This cave, along with the Ulster County mine site, is now also giving us insight into how this tiny mammal appears capable of a rapid evolutionary response to a fungal attacker, which may help it to survive as a species.
Post by Brian Nearing, State Parks Deputy Public Information Officer
Cover Shot: Little brown bats cling to the ceiling at Hailes Cave (Photo Credit- Department of Environmental Conservation)
What Can You Do To Help Bats?
- Build a bat house for their use during the summer season.
- Reduce your use of pesticides and more, based on these tips from the U.S. Fish and Wildlife Service.
For More Information
Read the Bats of New York brochure; some of these bats are rarer than they were when brochure was created.
New York Natural Heritage Program Conservation Guides, which cover seven of the nine species of bats found in NY.
New York State Parks and Historic Sites Blog 