The mysterious disease is obliterating bat colonies as it spreads across North America, and scientists say time is running out to save them.
Conservation, Endangered Species, Viruses & Diseases, Wild Animals Bats are flying ambassadors of Halloween, adding spooky ambience to countless forests, caves, graveyards and haunted houses. Lately, however, the tables have turned on them — Halloween and the winter it foreshadows are now an increasingly scary time to be a bat in America.
That's because a deadly, cave-dwelling disease known as white-nose syndrome is sweeping the country, with a 100 percent mortality rate in many bat colonies. Seven years after it first appeared in a single New York cave, the fungus has now invaded 22 U.S. states and five Canadian provinces, killing roughly 6 million bats along the way. Scientists still aren't sure where it came from, where it will go next or even how exactly it kills.
"We can't directly link the fungus to organ failure or anything like that," says U.S. Fish and Wildlife Service biologist Susi von Oettingen. "It certainly is ultimately responsible for the death, but we're not sure how."
Scientists are sure, however, that it's bad news for millions of American bats, which recover slowly from population loss since many have just one offspring per year. Bat experts also worry that white-nose syndrome may already be hopping through vast cave networks underneath the U.S. Midwest and Southeast, potentially wiping out endangered species like the gray bat and the Indiana bat.
And what's bad for bats is often bad for people, too. As a top predator of flying insects, bats regulate populations of mosquitoes and other biting bugs that spread disease to humans, as well as agricultural pests like beetles and moths. Every 1 million bats can eat about 700 tons of insects per year, and insect-eating bats overall save the U.S. agriculture industry an estimated $3 billion annually — making a batless Halloween even scarier than one swarming with them.
A long winter's nap
Bats are one of the most successful and diverse mammals on Earth, ranging from 4-inch, sub-Arctic furballs with sonar to tropical "macrobats" with 6-foot wingspans and primate-like vision. (Bats are not rodents, despite appearances, and are actually more closely related to primates than they are to squirrels or mice.)
Many North American bats pay a price for living in colder climates, though. Their frequent flapping uses a lot of energy, and freezing temperatures virtually eliminate the protein-rich insects they eat. Some species migrate south, but the majority of U.S. bats tough it out by hibernating in caves or mines until the bugs come back in spring.
Surviving a frigid New England winter with no food isn't easy, and bats undergo extreme physiological changes so they can conserve enough energy. They slow down their heart rates, suppress their immune systems and drop their body temperatures to within one degree of the ambient air. They enter this low-power, near-death state for up to two months at a time, waking up periodically to stretch, preen, relieve themselves and sometimes mate. These hibernation breaks use up about 90 percent of the energy bats have stored for winter, so it's critical they only wake up at the right times.
Despite its high stakes and risks, hibernation has worked for millennia. It wasn't until the early 20th century that it began to fail for some bats, and only then because of cavers and scientists who disturbed their hibernation without understanding the consequences. Combined with increased pesticide use, habitat loss and bats' naturally slow reproduction rate, this decimated several U.S. bat species over the decades —Indiana bats, for example, fell by 50 percent from 1967 to 2005, and now half of the species' worldwide population spends winters in just two caves.
But today, all 25 U.S. species of hibernating bats face perhaps...