Save the bats!

Fighting a bat-killing fungus

Crystal Young

Intermountain Region Office of Strategic Communication

October 23, 2023

Two images. On the left, an eye-shaped hole with bright trees in the far distance surrounded by darkness that is actually the rock interior of the mouth of the cave. Light reflects off the metal railings that line the stairs that lead to the door of the cave. On the right, a man wearing a headlamp shines light that reflects off thin nylon string pulled tight around a metal pole like a harp, components of the trap set up in the doorway of the cave to help capture bats. — LEFT: The harp trap is set at the door of the cave just a few cold, wet steps inside the mouth of the Minnetonka Cave. The cave provides a consistently cool habitat for bat hibernation in winter. RIGHT: Jason Beck, biologist with Idaho Fish and Game, tightens a nylon filament on the harp trap the team set up in the door of the cave. The trap is designed to catch the bats and minimize the stress the bats experience when they are captured. (*USDA Forest Service photos by Crystal Young*)

The generator that runs the sodium lights in Minnetonka Cave just outside of St. Charles, Idaho, on the Caribou-Targhee National Forest has been winterized and the lights are off for the season. But just before 6 p.m. on the sixth day of fall, five people wearing headlamps carefully descended about 25 of the cave’s 444 wet, rock steps to the gate.

There they set up a harp trap designed to catch bats as they leave one of the largest hibernacula in the state at dusk.

Two images - on the left, a photo of Tonie Rocke facing slightly away from the camera. On the right, people wearing personal protective clothing and equipment, standing on both sides of a table working on scientific data gathering tasks. — LEFT: Tonie Rocke represents the National Wildlife Health Center which is the part of the U.S. Geological Survey researching solutions to diseases in wildlife populations. She began her career in biology studying waterfowl and wild turkeys and is now working to solve white-nose syndrome in bats. RIGHT: Rita Dixon, state wildlife action plan coordinator for the Idaho Department of Fish and Game, will determine the weight of the bat by subtracting the weight of the paper bag the bat makes his way through the process in from the weight of the bat and the bag to determine whether this bat is a healthy weight for his age. (*USDA Forest Service photos by Crystal Young*)

Tonie Rocke, Ph.D., research scientist for the U.S. Geological Survey’s (USGS) National Wildlife Health Center, and an energetic interagency team of biologists dressed head to toe in protective suits and worked feverishly on a cold September night under a full moon. Wearing the protective suit was part of the protocol of the mission when working in bat roosts.

Just outside the mouth of the popular summer tourist attraction, the team tested the efficacy of a potentially lifesaving treatment for the animals. The treatment is a vaccine that helps protect bats from white-nose syndrome, which is caused by a fungal infection. It is one of the most devastating wildlife diseases and has killed millions of bats across North America since its emergence in 2007.

“Vaccinating bats was one of the alternative management strategies identified during our structured decision-making workshop,” said Rita Dixon, Ph.D., state wildlife action plan coordinator for the Idaho Department of Fish and Game. “Because Tonie Rocke had started her vaccine trial, we had the opportunity to work with her to vaccinate bats at Minnetonka Cave as a preventive measure in advance of the disease.”

Two images. On the left, two women in white protective suits, purple gloves, N-95 facemasks, protective eyewear are shining headlamps on the bat they are holding and taking a picture with a smart phone. On the right, purple gloved hands holding a small brown bat with long ears and an open mouth. — Tonie Rocke, biologist with the U.S. Geological Survey National Wildlife Health Center, and Randi Connel, biologist with the U.S. Fish and Wildlife Service, take a picture of a particularly cute long eared myotis. There are more than seven species of bats in Minnetonka Cave. Most of them are variations of microbats related to Little Brown Myotis that are especially susceptible to Pseudogymnoascus destructans, the fungus that causes white-nose syndrome. (*USDA Forest Service images by Crystal Young*)

Up until last year, there were no signs of Pseudogymnoascus destructans, or Pd, which is the fungus that causes white-nose syndrome, among the winter residents of the cave. This is the seventh location, including bat colonies and maternity roosts, Rocke’s team has visited this year to administer an experimental vaccine authorized for field trials by the USDA.

Minnetonka Cave serves as a winter roost for at least seven bat species and is one of the largest and most species-rich bat habitats in the state. In June 2022, Idaho Fish and Game found that six bats in this cave tested positive for Pd. These included three species, Little Brown Myotis, Long-legged Myotis, and Yuma Myotis – all of which are susceptible to white-nose syndrome.

The fungus thrives in cold dark environments, grows on a bat’s skin and is easily spread. Pd is normally found within a cave one or two seasons before bats develop white-nose syndrome.

Rocke represents the part of the USGS that conducts research on wildlife diseases. She was onsite with her assistant, Sadie Trombley, and 11 other biologists from the state of Idaho and other federal agencies to vaccinate bats against white-nose syndrome before its arrival in Idaho. This marks the third year of collaboration.

“The partnership is so very important because there are so many moving parts, no one agency could do everything that needs to be done here,” said Mike Larsen, USDA Forest Service wildlife biologist. “The U.S. Geological Survey is leading the research on the vaccine, the U.S. Fish and Wildlife Service is the lead agency for white-nose syndrome, the Idaho Department of Fish and Game manages the wildlife in this state, and the USDA Forest Service manages the cave and the surrounding habitat.”

The biologist team’s experience ranged from a biologist with more than 20 years working with bats to a biologist holding a bat for the first time in her life. The effort at this cave and at a maternity colony in the Oneida Narrows provided rare opportunities to work with many bats in one night. This group set out to capture at least 150 individuals from diverse microbat species. Rocke says the bats are very smart and they rarely catch the same bats twice.

Three images. On the left, two sets of gloved hands are holding a bat and placing a numbered band on the bat’s right wing. In the center, a researcher with an Idaho Department of Fish and Game fleece cap and headlamp wearing a white protective suit and gloves is measuring the forearm of a small bat. On the right, a pair of blue gloved hands is holding a bat and spreading its wing as a third blue gloved hand is swabbing its wing with a cotton swab. — The bats are smart and the team rarely catches the same bat twice. The metal band that is attached to the bat’s arm is numbered so that researchers can identify what is happening with that specific bat if they happen to capture it again. Biologists weigh, measure, and check the health of each bat and record the findings. At this time of year, almost all the bats caught in this cave were adults, and most were male.

At the processing table, the team weighs the bat, measures the forearm, determines their sex and age, swabs their wing to detect the fungus, gives them a numbered band, puts a few drops of vaccine in their mouths, then releases them. Half of the bats received the vaccine; the other half received a placebo. Because of the time of year, almost all the bats were adults, and the majority were male.

At nearly 11:30 p.m., bat number 153 was weighed. The team’s exhaustion showed as the excitement dwindled to the sounds of only the necessary information that needed to be recorded, screeching of the acoustic app that identifies bats by sound, and flutter of wings as bats dodged between the researchers in the light of the full moon.

Bats are vulnerable to the fungus during hibernation when they become inactive and use less energy. Rocke said the vaccine is mixed with a raccoon pox virus vaccine vector, which is a kind of vaccine that only affects the bats for a short time. The research is to learn whether boosting the bats’ immune system for a little longer will help them ward off the effects of the fungus. The treatment is likely to be most effective prior to or immediately after the fungus shows up in a cave where bats hibernate.

Two images. On the left is a close-up shot of a woman in a white protective suit wearing an N-95 mask, glasses, a baseball hat, and a headlamp is looking at what she is holding in her hands. On the right, purple-gloved hands are holding a small brown bat with an open mouth and using a pipette to give the bat liquid from the tube. — The biologists carefully and gently vaccinated the bats. The control group of bats received a placebo, the other half received a vaccine designed to boost the bat’s immune system to help them fight the effects of Pseudogymnoascus destructans, or Pd, the fungus that causes white-nose syndrome. (*USDA Forest Service images by Crystal Young*)

Dixon said they didn’t see any clinical signs of white-nose syndrome or anything else concerning on the bats that took the 10-minute journey through the assembly line. They all seemed to have healthy weights and were well hydrated. But it may be weeks before she learns whether Pd was detected on any of the bats sampled.

“I don’t think things could have gone more smoothly. We had enough experienced people to manage the harp trap, process bats, and get them safely released,” said Dixon. “Everyone had a job and worked as a team, remaining focused on the task. It was a beautiful night, the bats were flying, and we were able to meet our objectives.”

While there is no evidence that the fungus affects humans, pets, livestock, or other wildlife, it has substantially impacted bat populations, including declines of over 90 percent in Northern Myotis, Little Brown Myotis, and Tricolored Bat populations in less than 10 years.

Because most bat species that are affected by white-nose syndrome only produce one to two pups per year, it can take decades or longer for their populations to recover from the devastating mortalities associated with white-nose syndrome.