Bat biologists like Dan Feller get excited every year for the summer field work season, a time to get out of the office and into the forest in search of their quarry—in this case, the 10 species that range throughout Maryland’s mountains and woodlands. Bats are most active in the summer, because it’s their breeding season, and its when their insect prey are most abundant.
But this summer is a bit different. Instead of capturing bats with ultrathin nets or special traps (don’t worry, they don’t get hurt), Feller and many of his colleagues across the country are counting them remotely with acoustic devices that record their sonar calls. That’s because of the risk of humans transmitting the coronavirus to bats.
It may sound strange, but bats now need protection from humans. Yes, it’s true that the SARS-CoV-2 virus that encircled the globe likely emerged from bats in China before jumping to another animal and then to people, a process called spillover. But people can also transmit viruses back to animals; that’s called spillback.
In Maryland, researchers like Feller are taking precautions to prevent viral transmission in either direction. “We’re taking a conservative approach and we’re no longer handling them,” says Feller, who has been conducting annual bat surveys in Maryland since 1990. “We have reevaluated some of the research projects we had lined up. We’ve changed techniques for the year until we have additional information.”
Feller and others will count bats this summer with devices that record the acoustic signals the animals use to navigate while flying, but they won’t check them directly for signs of white-nose syndrome, a devastating disease that decimated bat populations by more than 90 percent since it first arose in four caves near Albany, New York, where it killed more than 10,000 bats in 2007 alone.
Officials from the US Geological Survey and US Fish and Wildlife Service recently issued new guidelines for biologists like Feller, recommending that they wear protective gear such as masks and respirators to reduce the risk of spreading the virus when they come into close contact with bats or do research in the caves where many of the animals hibernate during the winter.
“We are treating bats the way we are treating the human community,” says Kristina Smucker, nongame bureau chief with Montana Fish, Wildlife, and Parks, where she oversees permits for researchers who study animals that are not hunted. “We are going to use personal protective equipment to keep bats safe. That means wear an N95 mask, gloves, take your temperature, and don’t do the work if you have tested positive or if you are not feeling well.”
The federal agencies issued the guidelines after consulting with wildlife health and virology experts over the past year. The guidelines also included data from two earlier experiments in which researchers exposed bats to the coronavirus. In the first study, published in December, a team of scientists from the USGS, the University of Wisconsin, and Louisiana State University found that the big brown bat (Epstesicus fuscus), one of the most common in the United States, was resistant to infection by the virus. A separate study done by German researchers in 2020 found that Egyptian fruit bats (Rousettus aegyptiacus), which are common in the Mediterranean, Europe, and North Africa, were somewhat susceptible to the virus.
The USGS study assessed the likelihood of US scientists and wildlife managers transmitting coronavirus to bats, and it found that fewer than 2 in 1,000 bats would likely become infected if no protective measures were taken. The 32-page study was posted in May on the bioRxiv preprint server and has not yet received peer review or been accepted for publication in a journal.
While that figure is small, researchers are still concerned enough that they are suggesting protective equipment, according to Evan Grant, a research biologist at the USGS Eastern Ecological Science Center in Patuxent, Maryland, and an author on the new guidelines. “Folks were worried about the effect that SARS-CoV-2 might have on North American bat species. They thought it might have detrimental effects on bat health here. They were also worried that if it could be introduced in the bat population, that might serve as a reservoir for an introduction later,” he says. Grant says that the new guidelines will help protect both humans and bats until more is known about how the coronavirus evolves in animal populations.
The USGS preprint found that researchers can reduce that risk of transmitting the virus to bats by approximately 66 percent if they test negative for Covid-19 three days prior to conducting research, and by approximately 95 percent when properly wearing N95 respirators, 89 percent with surgical masks, 54 percent with cloth masks, and 23 percent with face shields.
While Feller’s team in Maryland is not handling bats at all, in Ohio researchers are allowed to handle them if needed, according to Joseph Johnson, a bat researcher and assistant professor of biology at Ohio University. “I am able to handle bats in some places, yes,” Johnson wrote to WIRED in an email. “In Ohio we have been approved by the state DNR [Department of Natural Resources] to conduct some of our studies, and we exercise an abundance of caution while in the field. (We wear masks, change nitrile gloves between each animal handled, and decontaminate everything that bats come in contact with.)”
For now, the scientific evidence points to a limited risk of humans spreading this particular virus to bats in the US. But North American bats have been under siege for the past two decades by white-nose syndrome, a disease caused by the fungal pathogen (Pseudogymnoascus destructans) that began infecting hibernating bat populations as early as 2006. It may have been brought to the US by a backpacker from Europe, where the microbe that causes the disease is endemic. The disease has killed millions of bats, affected at least 12 species, and has already spread across half of the US and Canada. While white-nose appeared in Maryland in 2010, it just arrived in Montana this year.
The coronavirus “feels like one more potential risk for a group of species that already has a lot of strikes against it,” says Montana biologist Smucker. She also noted that bats are threatened by the spinning turbine blades of wind farms, a loss of habitat, and a decline in some insect species that are their source of food. “Here we have this whole taxa that has a lot of conservation threats, then you add this potential risk of SARS CoV-2 on top of that. It makes you pay attention to the work you are doing and how you are handling species,” she says.
Smucker says that wildlife biologists are used to protecting themselves from wildlife diseases that can infect humans, such as rabies or hantavirus. But the Covid-19 pandemic has proven that humans are part of the viral transmission ecosystem as well. “We will continue to have emerging diseases that go both directions,” Smucker says, “and we need to be more cognizant of how we may impact wildlife species when we handle them.”