Some bat populations across Kentucky have fallen by up to 90 percent as the full force of the deadly white-nose syndrome settles in, three years after it took hold in the state, according to the latest scientific surveys.
That loss means more mosquitoes and insects that are active at night and are normally on bats’ menus, expert said. Some of them are serious pests, potentially costing agriculture billions of dollars, and help to spread human illnesses like West Nile virus.
“The long term affects could be pretty devastating,” said Brooke Hines, a bat ecologist with the Kentucky Department of Fish and Wildlife Resources.
Mammoth Cave National Park scientists said this week they have completed their winter bat counts in six of the caves they use to track bat numbers, and for three species — little brown, tricolor and Indiana — the preliminary results are grim.
It’s not that researchers are finding hordes of dead bats, said Rickard Toomey, director of the Mammoth Cave International Center for Science and Learning. “They simply are not there.”
Kentucky wildlife officials wrapping up winter surveys of more than 70 caves in 21 counties are seeing the same thing for tricolored and little brown bats, which had been among the most common bats in the commonwealth.
“Our declines are 80 percent for the tricolored, and up to 98 percent for the little brown,” said Hines.
“As it is now, it’s very sad, walking into a hibernaculum, and seeing just a few bats or in some cases just a few species where you had seen many,” she said.
Indiana Department of Natural Resources completed the last of its bat cave surveys on Tuesday.
“We hope to have some preliminary numbers for this season in approximately two weeks,” said Marty Benson, agency spokesman.
It reported an 80 percent decline in little bat populations last year, compared to two years earlier, and a 21 percent decline in total bats counted.
Fungus from Europe
White-nose syndrome is a cold-loving fungus from Europe that affects bats’ muzzles and wings during winter hibernation.
It damages their wings, causes irritation and makes them wake up early and expend energy they cannot afford. Some have been leaving their caves early this winter, then freezing to death with Kentucky’s unusual late-winter polar plunge, Toomey said.
Hines said she’s worried that crazy weather patterns possibly fueled by climate change could be a double-whammy for the troubled bats.
The losses regionally mirror those in other states that were hit first.
Indiana and Kentucky both documented the first cases of white-nose syndrome in 2011, making its way to the Midwest and the South from where it was first detected in New York state in 2006. Named for the white fungus on the muzzles and wings of affected bats, scientists say it is killing millions of bats in North America and has no known cure.
It’s now in 25 states and five Canadian provinces and is likely killing millions of bats, said Catherine Hibbard, a spokeswoman for the U.S. Fish and Wildlife Service, which is coordinating a national response to the problem. The federal government and its state partners spent a combined $40 million from 2007 through 2013 on surveys, research and other responses to the disease.
There are several promising areas of research looking into treatment methods, including using different bacteria for biological control, or chemicals, she said. But she said none are ready yet, and that scientists want to be sure any forms of treatment don’t damage other cave life or animals.
Gray bat populations are still increasing in the park, and that’s good news, Toomey said. And big-eared bats so far don’t seem to get the disease, he added.
Elsewhere in Kentucky, populations of the Indiana bat, already a federally protected endangered species, have not been crashing, Hines said.
Tracking the changes
Toomey said Mammoth Cave National Park has research partners at Eastern Kentucky University and University of Kentucky trying to document how the loss of bats may be altering the park’s ecological systems.
“This may be among the first studies where we are getting pre- and post-white nose results,” he said.
Bats can eat half their weight or more in insects every night, when not hibernating, so fewer bats likely means more insects.
That could mean damage from insects that attack plants in forests and more annoyance to people, Toomey said.
Some bugs eaten by bats are also big farm pests, including cucumber beetles, he said.
There are also species that have evolved to live on guano, or bat waste, and that will go away as the bats die out, altering cave ecology, he added.
State and federal officials in recent years have responded by closing caves to people as a way to slow the potential spread of the fungus. At Mammoth Cave, cave tours continue and visitors walk on special mats to remove spores and dirt before leaving the cave. They are also asked to wash hands, change clothes and footwear before visiting other caves or mines.
White-nose syndrome can cause bats to behave erratically, and last year there were 11 reports of such contact between bats and people in the park. But park officials said the bats represent only a small risk to park visitors.
For now, Hines said, there’s not much state biologists can do, other than document bats populations, and hope research provides some “tools for our tool boxes” to fight back.
I don’t know whether we will ever be able to make it up,” she said. “Most of these bats have just one pup per year. They are not like mice. They are not prolific in their reproduction.”
Mammoth Cave National Park bats*:
Little brown bats: 768 in 2013; 137 in 2015; down 82 percent.
Indiana bats: 2,751 in 2013; 558 in 2015; down 80 percent.
Tricolored bats: 651 in 2013; 203 in 2015; down 69 percent.
*Survey taken this winter by the National Park Service at five key caves where bats hybernate.
By James Bruggers