Until recently, Texas was thought to be a potential bulwark against the spread of a disease that has killed more than six million bats nationwide. First appearing on the East Coast in 2006, white-nose syndrome has decimated several species of the winged mammal across the Southeast and Midwest. National media has referred to the outbreak as a “bat apocalypse,” but experts in Texas believe how the state responds could help turn the tide.
Early on, wildlife biologists hoped that Texas’s ecological diversity, preponderance of migratory species, and mild winters would hinder the spread of Pseudogymnoascus destructans (“Pd” for short), the fungus that causes white-nose syndrome in bats.
Unfortunately, that wasn’t the case.
In 2017, scientists first found evidence that Pd had arrived in Texas. Then, this spring, they discovered that the fungus had rapidly spread across the state. So far there have been no documented instances of white-nose syndrome, but Pd has been found in at least sixteen counties, including parts of the Panhandle, South and East Texas, and the Hill Country. It can take up to four years before the fungus leads to a lethal outbreak of white-nose syndrome—if at all—but conservationists are bracing for the worst.
“There’s a lot of guesswork surrounding what comes next,” says Jonah Evans, chief non-game mammologist with the Texas Parks and Wildlife Department. “Nobody can really say if we are about to face a bat apocalypse.”
Bats provide significant benefits to Texas, including an estimated $1.4 billion in annual free pest control thanks to their insect diet. The state’s best-known species, the Mexican free-tailed, also draws visitors to the nightly spectacle of their emergence to feed at sites like Bracken Cave Preserve near San Antonio and Ann Richards Congress Avenue Bridge in downtown Austin. The first appearance of Pd earlier this year at Bracken, home to the largest known bat colony in the world, amplified the concerns of biologists and captured national headlines. More than 15 million Mexican free-tailed bats roost at the site, the largest concentration of mammals on Earth. Other species also use the Bracken roost.
Yet not every case of fungal contact leads to white-nose syndrome; the mere presence of Pd doesn’t guarantee an outbreak. The disease primarily kills hibernating bats, species that roost in caves and other structures. During winter, bats rely on fat reserves and enter a state of torpor that lasts weeks. White-nose syndrome causes a skin rash and the growth of white fuzz on the animals’ noses, disturbing their hibernation. The resulting discomfort causes the bats to burn energy more rapidly, forcing them to seek food in dangerously cold weather, when the insects they eat are relatively scarce. These negative effects are compounded by the low breeding rates of most bat species, which generally produce only one or two offspring a year. “You could have major die-offs in a single season,” Evans says. “And it could be hundreds of years before you can regrow the population.”
Fortunately, migratory bats like the Mexican-free tailed, which relocate to warmer climes each winter, are less vulnerable to contracting the disease. Conservationists and biologists are far more concerned about eight of the thirty or so other species that reside in Texas, including the fringed myotis, the long-legged bat, and the tri-colored bat. The deaths of 90 percent of tri-colored bats in Alabama and nearly 95 percent of assorted cave-hibernating bats across the Appalachian region since Pd arrived doesn’t bode well for their Texas counterparts. Especially in East Texas, where 70 percent of the state’s tri-colored bats live—they are among the first bat species to hibernate each fall, roosting September through April—white-nose syndrome could result in a biological catastrophe.
Texas bats face threats other than white-nose syndrome. Climate change, for example, is shifting bats’ food sources and reproductive strategies. Depending on how bats respond to climate change, the threat of white-nose syndrome could be amplified in Texas and beyond. A 2016 federal study of national parks, including Big Bend and its 21 bat species, showed warming temperatures and shifting weather patterns have shortened hibernation periods among some bats and altered the migratory behaviors of others.
The tri-colored bat is already in sharp decline across Texas, thanks in part to pesticide use. The proliferation in Texas of wind farms also poses a quite literal flight risk. Bat Conservation International reports turbines endanger 24 species of bats across the country, and offers a “conservative” estimate that turbines have killed hundreds of thousands of bats in the past decade. The nonprofit hopes tracking technologies will reduce fatalities.
These are serious issues, says Winnifred Frick, chief scientist of the Austin-based nonprofit Bat Conservation International, but she cautions that white-nose syndrome requires more immediate action. The disease’s rapid spread across the United States is not entirely understood. It’s thought that cavers or other recreationists brought the fungus with them from Europe, but once in the U.S. it appears to have spread from bat to bat. Evans notes that white-nose syndrome poses no threats to humans.
Meanwhile, wildlife experts are eager to learn whether a Texas Parks and Wildlife plan released in February 2017, just before the state’s first detection of Pd, will pay dividends in bat preservation and disease prevention. The state offers a rich environment for experimentation, due to its diversity of bat species and the presence of manmade roosts where treatment trials can be run with a lower risk of broader ecological side effects.
As called for in the plan, Texas Parks and Wildlife is hiring a bat specialist to help Evans with site monitoring. The agency is also attempting to disinfect manmade roosts in East Texas where Pd has recently been detected. It’s a three-step process that begins with high-pressure steam-washing ahead of the bats’ winter return for the winter, followed by an application of a chemical compound to slow the spread of Pd. Once the bats have arrived for their months-long hibernation, trained technicians will gently swab the animals with a fungicide. “We would not do this in a natural cave system,” Evans says. “There are just too many biological variables, but we can look at whether this disturbs the bats.”
Jonathan Reichard, who assists the national white-nose syndrome response team for U.S. Fish and Wildlife, did his graduate research on bat caves in the Hill Country. He expresses cautious optimism about the feared emergence of the disease in Texas, noting that although Alabama has been hit hard, Mississippi hasn’t seen any cases of white-nose syndrome, despite the presence of Pd since 2014. “Those [Mississippi] bats are active much more of the winter and may be shaking it off or cleaning themselves,” Reichard says, adding that scientists are still trying to determine the switch that turns the fungus into a killer disease. Cave temperature is thought to be one factor. In addition to Texas and Mississippi, North Dakota, California, and Wyoming have Pd but not white-nose syndrome.
If the combination of early detection and experimental remedies proves effective in fighting the spread of white-nose syndrome, it could be a game-changer nationally. “Texas is different,” says Mylea Bayless, a spokesperson for Bat Conservation International. “Texas has the biggest bat colonies and the greatest bat species diversity in the United States, so these potential treatments were designed to address white-nose syndrome on a local level, but they could prove a model for conservation elsewhere.