NEW SCOTLAND — In 2007, bats started dying due to white-nose syndrome — a disease first verified at Hailes Cave in Thacher Park. Nearly a decade later, the social animals have spread the disease north to Canada and west all the way to Nebraska, according to New York State Department of Environmental Conservation biologist Carl Herzog.

​His associate, wildlife technician Samantha Hoff, spoke at Thacher Nature Center last week. Hoff has worked exclusively studying the bat population for the last two years, “hopefully contributing to the effort to finding out more about the problem, and what we can do about it,” she told The Enterprise.

Six species of bats in New York can get the disease,” Herzog told The Enterprise. Hailes Cave in Thacher Park is a significant bat hibernation site, he said, and, “as the site where white-nose syndrome disease was discovered in America, it’s an important place to monitor white-nose syndrome.”

The disease, caused by a fungus, was likely introduced to the United States from Europe or Asia, where it previously existed, Herzog said.

The disease is actually a collection of related symptoms, which include a fungus, according to DEC materials. The most obvious symptom of the disease is a white fungus that encircles the noses of some of the bats. The majority of the hundreds of thousands of bats that hibernate in New York do so in just five caves and mines, according to the DEC.

“It is not clear how this fungus alone can cause bats to die; however, impacted bats deplete their fat reserves months before their normal springtime emergence from hibernation, and starve to death as a result,” the DEC website states.

Bats eat thousands of mosquitoes and other flying insects in a single night during warm months, and help control insect populations that might otherwise affect forest health or agriculture, according to materials from Penn State Extension.

Herzog and Hoff caution the public to stay out of caves and mines where bats hibernate.

“The mere presence of people in caves causes the bats to arouse and awaken from their hibernation,” Herzog said. “It uses up their energy reserves. If you disturb them too much, you cause them to starve to death.

“The disease causes them to arouse more frequently than normal,” he continued. “That seems to be the primary mechanism of harm that it causes the bats. 

“It resulted in the death of a very large percentage of the bats in New York,” Herzog said. “It’s very severe, for four of the six species.”

Little brown bats “make up the majority of bats at Thacher Park,” he said. Before 2007, bi-annual counts found 16,000 little brown bats hibernating in Hailes Cave, he said. In 2009, the number had dropped to 1,000 bats.

“Since then, the number has built up. Now, there are about 3,500,” he said. “That seems like recovery, but that’s not typical of all the hibernation sites for us. It’s unusual to see that kind of increase.”

Herzog speculated that decreased populations across the state have been coalescing, and regrouping, to account for the higher numbers here.

“They’re very highly social animals,” he said. “They may be moving around to different caves. The loss has disrupted their social structure — they’re redistributing. The decline seems to have halted.” 

Herzog said that the little brown bat population has stabilized, but biologists have not yet seen the population recover.

Other bats also traditionally hibernated in Hailes Cave, including northern long-eared bats, which were recently identified as threatened on federal and state endangered species lists; endangered Indiana bats; and unlisted but severely reduced tri-colored bats.

However, northern long-eared bat populations have dropped by 99 percent, he said. 

“We have a very tiny fraction of what we used to have previously found in most hibernation sites,” Herzog said. 

Indiana bats used to be found hibernating in Thacher Park, he said; a population of about 700 was often recorded in biannual counts before 2007. 

“They seem to be wiped out there, now,” he said. 

The bats can fly long distances during warm weather, and may have flown to forested areas 50 miles from hibernating sites, he said. Biologists knew the Indiana bats wintered in Thacher Park, but did not know where they summered, he said.

“Now, we’ll never know,” Herzog said.

Many bats are compatible with “reasonable” amounts of urban development, he said. 

“They live in close proximity of humans all the time. Large parts of Albany County are suitable,” he said, noting nearby Hailes Cave as a hibernation site for the region’s bats.

“Any site with hibernating bats is now protected,” Herzog said. Disturbing the bats, he said, is now illegal because of the bats’ protected status.

“If you see bats, you should assume that you shouldn’t be in there,” Herzog said. Bats in New York hibernate between Oct. 1 and April 30, he said.

Herzog said that the disease has spread to “virtually all of Eastern North America.

“There is no reason to think it’s going to stop,” he said. “Bats spread it amongst themselves. They are very social animals that cluster together in very close groups. Physical contact is definitely a factor. They’re very good at spreading it.”

“Specifically, there are currently a number of possible treatment approaches being developed,” the DEC shared in an email to The Enterprise. “None can be considered especially promising as potential broad-scale solutions to the disease problem.”

“We’re doing quite a bit,” Herzog told The Enterprise. “We’re working with a number of different researchers.” 

He agreed with other DEC assessments that a long-term solution has not been forthcoming. In the meantime, the DEC has posted state-owned hibernation sites, like the ones at Thacher Park, to keep the public out, he said.

“We may be over the hump, in terms of little brown bats, in which the decline seems to have arrested,” Herzog said. “Unfortunately, it isn’t true for other species. There really is no end in sight, there. We may lose them. We, maybe, already have. They may even become extinct.”

Clarified on Feb. 19, 2016: The original story said bats dying of white-nose syndrome was "discovered" at Hailes Cave in the winter of 2006-07; it was changed to "verified" because subsequently a picture taken the year before of sick bats in Howes Cave emerged.