TWIN FALLS • Chances are you’ve seen them just after sunset — dark winged bodies flitting against a pale sky.
Despite their menacing look, these creatures of the night are a danger only to the tons of flying insects they consume every night. But so far, Idaho’s bats are defenseless against an oncoming threat that has devastated bat populations in the Eastern U.S. and last week was confirmed in Washington state.
In a race against time, wildlife biologists have enlisted the help of professionals and amateurs alike to learn as much about bats and white-nose syndrome as they can as the disease spreads to the West. But such information will be beneficial only if scientists can use it to limit the spread of the disease or to find treatment options to reduce disease mortality.
On board the North American Bat Monitoring Program are the U.S. Fish and Wildlife Service, Bureau of Land Management, National Parks Service and U.S. Forest Service, along with state fish and game agencies and university researchers.
White-nose syndrome is caused by Pseudogymnoascus destructans, a fungus that kills bats while they hibernate. The disease has caused a catastrophic decline in bat populations in the East since the its 2006 discovery in a New York cave.
“WNS is now recognized as one of the most devastating wildlife epidemics in recorded history,” Winifred Frick, Sebastien Puechmaille and Craig Willis, university researchers who work internationally, wrote in a 2016 paper.
A powdery white growth encases the nose and mouth of an infected bat. The fungus also grows on its wings, causing lesions. The bat’s immune system goes into overdrive, mounting a hyper-attack on the fungal spores and causing the bat’s body to burn off its energy reserves before the end of hibernation. The bat wakes to a harsh, cold environment with no food or water.
Since 2006, bats with white-nose syndrome have been confirmed in 28 states and five Canadian provinces; until a hiker's March 11 discovery of an infected little brown bat near North Bend, Wash., the disease had been confirmed only as far west as Oklahoma.
“We are extremely concerned about the confirmation of WNS in Washington state, about 1,300 miles from the previous westernmost detection of the fungus that causes the disease,” U.S. Fish and Wildlife Service Director Dan Ashe said in a release. “... It is important that we stay focused on stopping the spread of this fungus. People can help by following decontamination guidance to reduce the risk of accidentally transporting the fungus.”
Prevention includes rigorous rules about decontaminating caving gear and clothing — anything that’s exposed while inside a cave.
Bat populations are particularly fragile because most species give birth to only one pup per year.
“Bats require high survival to ensure stable or growing populations,” wrote Tom O’Shea, a U.S. Geological Survey emeritus research scientist. A hard-hit population may take years to recover after a single epidemic; it may never recover after a multiple-year epidemic.
“Many of the 1,300 species of bats on Earth are already considered threatened or declining,” O’Shea said.
But the threat of white-nose syndrome is the greatest of all.
Bats are critical to the planet’s health, so critical that when white-nose syndrome was discovered in New York, the first reaction was to lock down human access to caves on public lands. Eventually federal agencies reopened many of the caves to responsible entities in order to monitor the bat population.
The U.S. Fish and Wildlife Service has spent $24 million since 2008 on white-nose syndrome research and response, and nearly $5 million in 2015 alone. Some of that money went to states.
“After the onset of white-nose syndrome, every state with bats wanted to start their own bat data set, so it was like comparing apples and oranges,” said Todd Stefanic, a wildlife biologist for the National Park Service at Craters of the Moon National Monument and Preserve.
Tom Rodhouse, who outlined the North American Bat Monitoring Program, proposed an organized effort with researchers in each state doing the same thing. The national bat inventory began in 2015.
“We each do the same monitoring, so we can compare Idaho numbers with numbers in South Carolina,” said Stefanic, who has been in Idaho since 2011. “There were a couple guys who did some research in the ‘90s, but there has been no consistent effort in winter before now.”
Rita Dixon of the Idaho Department of Fish and Game kicked off the bat count’s Idaho effort last year, dividing the state into grids for acoustic surveys at a sampling of random locations to detect the high-pitched frequencies emitted by bats as they navigate in the dark. Researchers can map out the bats’ ranges using the acoustic surveys in a nonintrusive way.
This year, the National Park Service hired Kathleen Slocum as the bat monitoring program’s coordinator for Washington, Idaho and Oregon.
Enlisting Recreational Cavers
There are 48 species of bats in the U.S. and 14 in Idaho, including several which the state considers species of special concern.
Not much is known about bats in Idaho and their various hibernacula, said Ross Winton, a wildlife biologist with Fish and Game in Jerome. To learn how the disease works — why the fungus infests one cave and not another, and why it infects some species of bats and not others — individual caves must be monitored for temperature and humidity, and bats must be counted.
So Winton in mid-March approached south-central Idaho spelunkers from Silver Sage Grotto about joining the national effort to identify which bat species hibernate where, and to monitor cave conditions.
“Grotto” means “cave,” but in this instance grotto is the term for a local chapter of the National Speleological Society, which has more than 200 grottoes in the U.S. and three in Idaho.
Grotto members are fascinated by the bat and consider it their mascot, said Steve Frye, who coordinates the local grotto’s caving trips.
“This is the animal of the cave,” Frye said. “We are going into their home. We teach people to respect the cave — how not to hurt the cave or hurt the animals or hurt themselves.”
Ordinarily, the cavers wouldn’t enter caves when bats are hibernating, said Chris Anderson, the group’s co-founder. It would be like signing a bat colony’s death warrant. Bats are light hibernators, and a caver’s body heat is enough to wake a bat — which would, with no food source during winter, subject it to starvation.
The spelunkers enlisted to count bats and place temperature and humidity recorders are following scientists’ guidelines for minimizing the effects of their cave visits.
Bringing the grottoes in on the project was a no-brainer, Winton said, because the National Speleological Society has strict ethical requirements for its members. Its creed: Take nothing but pictures. Leave nothing but footprints. Kill nothing but time.
Bat-to-bat transmission is the primary vector for the spread of P. destructans. But the fungus can be carried from cave to cave by humans. The spelunkers committed to decontamination standards upon leaving any cave to prevent the spread of the disease — even if its presence has not been confirmed.
By recording the condition of caves and the types of bats that live in each, biologists will form a baseline for comparison with the survival rate of bats in the East. If a certain species is able to survive white-nose syndrome there, biologists will know where to focus protection efforts in Idaho.
Fish and Game’s cave monitoring with grottoes is separate from Idaho’s acoustic bat monitoring program, Stefanic said, but the “information found will be folded into the national program.”
Winton gave the grotto a list of 20 caves chosen for the study. Club members visited two caves — Pot of Gold and Giant Arch, both north of Shoshone — on their first outing in March. They found only 20 bats in Pot of Gold but 200 in Giant Arch. Eighty percent of those were Townsend’s big-eared bats; the rest were small brown bats.
“Fifteen years ago, there would have been few Townsend’s bats, and more small browns,” Frye said. “Today the populations have flipped.”
By monitoring caves as the disease spreads, biologists are forming ideas about how to protect bats in the West. The fungus shows up in a cave a year or two before the disease infects the bats hibernating there. That gives a little time to block access to the infested cave and possibly reroute the bats to safe caves. Spelunkers could become an early warning system.
“We are the eyes and ears in the caves,” Anderson said.