Why Millions of Bats Are Dying—and How Scientists Are Trying to Save Them
Did you know that North American bats save the agricultural industry $3.7 billion per year? The current threats to the species have huge implications for the environment—and the human population.
A Deadly Disease Closes In
Martin Davis is looking for bats. He turns onto a logging road, his Pathfinder jostling, and heads up toward the cave. It’s an overcast day in June 2017, and the mountaintops surrounding his home of Tahsis, B.C., are hidden among misty rain clouds. He has to ascend 650 metres above sea level, plus another 200 on foot. As the truck jerks, a little rubber bat—black wings extended, mouth open in a shout—falls off the dashboard.
British Columbia is home to Canada’s most diverse collection of bats, but surprisingly little is known about its 16 species, including exactly where many of them spend their time. Most hibernate for the winter, tucking away inside mines or caves like the one we’re visiting today. Seven months earlier, Davis left equipment there to check for the presence of bats.
A mangled sign, chewed by black bears, announces Weymer Creek Provincial Park. Davis helped create the park in 1996 to protect a rare species of bat from commercial logging. Cavers maintain the trails, purposely keeping some of the way hidden to stop visitors from doing damage to sensitive grottoes.
Davis trudges over mounds of late-spring snow and, more than an hour later, arrives at the cave. When he first started exploring it over two decades ago, he thought the entrance, tucked at the base of an old-growth tree and ringed by unstable-looking boulders, would quickly collapse and disappear. But it’s still here, exactly the same.
The bats of Western Canada might not have that kind of longevity. A disease called white-nose syndrome, named for the white fungal spores that grow on the snouts and wings of infected individuals as they sleep through the winter, has decimated populations in the eastern parts of Canada and the United States. And it’s closing in.
Why Bats Are So Important
Bats are critical to the ecosystem because they feed on insects. A little brown bat, of which there were several million in Canada before the disease arrived, can eat between four and eight grams of bugs each night. Collectively, a million little browns consume up to 1,300 metric tons each year. Many of those insects are pests that would otherwise destroy farmers’ crops—losing all of North America’s bats would cost the agriculture industry more than $3.7 billion each year. Others are mosquitoes that could pass diseases to humans.
Researchers estimate that the northeastern American little browns, which make up the majority of the U.S. population, will be extirpated—extinct within the region—in less than 10 years. In Canada, white-nose syndrome has already infected multiple species in Ontario, Quebec and the Maritimes, killing more than 90 per cent of known little brown populations. As the disease spreads, observers in Western Canada are rushing to gather what data they can about their bat populations. They’re facing mountainous odds, and sometimes great physical challenges, to give the bats a sliver of a chance at survival.
“Everybody Was Shocked”
In March 2005, biologists in New York surveyed the population of mouse-eared Myotis sodalis bats in Hailes Cave, near Albany. The species has been officially endangered since 1967, and the most recent survey had counted 685 of them hibernating among the more than 15,000 bats that wintered in the cave. Almost immediately, it was clear that a dramatic change had occurred.
The cave floor was covered in bones, bits of wings, entire bat bodies. Fewer than 7,000 living bats remained, none of them Myotis sodalis. About half had a fuzzy white substance on their faces, the only clue to what had happened. Three other caves in the state also had signs of the mysterious sickness, which scientists called white-nose syndrome.
That August, Cori Lausen, a recent PhD graduate from the University of Calgary, attended a bat research conference in Mexico where American biologists shared their alarm. “Everybody was just shocked,” she says. Lausen had first studied bats for an undergraduate research project and later left a job teaching high school to dedicate her life to learning more about them. A game-changing new threat gave her another reason to continue that work. She moved to British Columbia and dug in.
By the next year, it was clear that white-nose syndrome was not going away. The situation at Hailes Cave had worsened: an additional 5,300 bats were dead, a 91 per cent decline. Other sites emptied out completely. Almost every cave checked within 130 kilometres of the original four was infected.
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Tracking a Killer
Here’s what we know now: a European bat, carrying the spores of a white fungus called Pseudogymnoascus destructans, likely hitched a ride on a container ship bound for New York. (Another common theory is that the fungus arrived in the United States on the clothes of a caver.) In Europe and Asia, hibernating bats developed resistance to the fungus after evolving alongside it for generations. But the North American bats had no built-in defence. The fungus invaded their skin tissue, disrupting their water balance as they hibernated for the winter. The thirsty bats roused to search for water, forced to draw on the fat stores they needed to survive until spring. Once their fat depleted, they needed food—fast. Since there weren’t any insects for them to eat during the cold winter, the bats starved.
The fungus reached Central Canada by 2010. The federal government declared three of the hardest-hit species “endangered” in 2014. At least 5.7 million bats died between 2006 and 2012 in Canada and the U.S. The disease was expected to spread to the West Coast as early as 2025.
Lausen, who now works for Wildlife Conservation Society Canada, wanted to make the most of that time. First, she had to know where the bats were. In the East, bats congregated in groups of hundreds or thousands in giant hibernation sites. No such locations were documented in B.C. or Alberta, and Lausen knew she didn’t have the skill set to scour deep, dangerous cave systems in search of them. Martin Davis, however, did.
When he was eight years old, Davis toured a cave in Virginia with his parents. “I was hooked immediately,” he says. At 13, he convinced the McMaster University caving club in Hamilton, where he grew up, to let him join their expeditions. Caving brought him into contact with bats, and he did some work protecting and researching them in the 1990s. Now 61, he has the skills to get into hard-to-reach places, decades of experience and an extensive network in the caving community.
Lausen approached him with an idea that eventually turned into a program called BatCaver: Davis and a team of volunteers across B.C. and Alberta placed data collectors inside caves over the winter and started to map the West’s bat populations.
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Enter the Bat Action Team
Bat conservationists in Washington state thought they had about 10 years to prepare for the arrival of the disease. Then, in March 2016, a little brown bat found near Seattle tested positive for white-nose syndrome.
At first, Lausen wondered if the news was a false alarm but it wasn’t. White-nose syndrome had jumped to the West Coast. “I was feeling pretty desperate,” she says. “We thought we had so much more time.” She called an emergency meeting of the BC Bat Action Team, a group dedicated to the creature’s conservation. It had never met in person before.
Twenty-two biologists gathered at a hostel near Chase, B.C., in September 2016 and spent two days discussing potential strategies. “It definitely galvanized us as a group,” says Leigh Anne Isaac, the team’s coordinator. They released a plan, stuffed with 83 actions grouped into categories and prioritized into three levels. Lausen says that a few things rose to the top.
Step one: find the bats. Along with BatCaver, the action team decided it was important to strengthen the 2016 North American Bat Monitoring Program, which uses sound detectors to track population numbers in the summer. The hope is to build a database of different bat species over time.
Meanwhile, the province’s community bat programs began recruiting local volunteers to add to that data set. Observers sit outside known colonies in the summer, counting each bat as it flies by. They’ve become vital agents on the front line of white-nose syndrome, taking calls from the public about dead bats that are then tested for the disease.
Step two: figure out some way to help the bats survive. There’s promising research into compounds that could be sprayed on a bat to slow the progression of the disease. But the timeline for getting the remedy field tested and approved is long, to ensure it isn’t harmful for other parts of the ecosystem.
Lausen is exploring other options. With a cave microbiologist, she’s identified some bacteria and fungi that naturally occur on bats’ wings and slow the growth of the white-nose fungus. These could be added in high concentrations to summer colony entrances, which bats would rub against on the way in and out, picking up the helpful microorganisms. The pair has received funding to test the idea.
In New York, 10 years after the disease first appeared, a few colonies have survived, persisting at five to 30 per cent of their original size. They seem to have found some way to fight the fungus. If so, it’s possible a small number of bats could survive across the continent. But they breed slowly, one pup a year. It would take generations to get back to their original levels, at a time when they’re facing other threats from climate change, industry and wind power. Even the most hopeful admit that it’s going to be rough.
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Hoping for the Best
The day after Davis returns from the cave, he pops open the acoustic data logger, puts its memory card into his laptop and checks the graph. The frequencies plotted on his screen, brief bursts of sound repeating every second, look like bat calls. But as he flips through the rest of the data, he starts to second-guess himself. The data points aren’t linear enough, the shapes not cohesive. “I wonder if it’s a drip or something,” he says.
A couple of minutes later, he’s decided they probably aren’t bat calls at all. The local bat populations don’t use Fracture Cave every year, and it seems like they went elsewhere this time.
Data sets like this, empty of bat voices, could become all too common in a year or two if the white-nose fungus hits the West. Until then, all Davis can do is soldier forward. Soon, he’ll embark on another hike, descend into another cave, retrieve another bat logger and share the data with Lausen and her team. Maybe this time they’ll find some bats. “I just have to have hope,” Lausen says, “that we’re going to be able to do something.”
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© 2017, Elena Gritzan. From “Bat Patrol,” The United Church Observer (September 2017). ucobserver.org