Populations of bat species are disappearing as a silent killer called white-nose syndrome emerges in caves and other winter refuges across the country.
Scientists at the University of Maryland Center for Environmental Science's Appalachian Laboratory have been trekking to three Maryland caves and a limestone mine to monitor bat populations before and after the disease first arrived here in 2010. The numbers, they found, totally changed.
“After white-nose came around the bat numbers were dropping by the hundreds. It’s really drastic,” said Beth Stevenson, a research assistant working under J. Edward Gates at the Appalachian Laboratory. “It wasn’t surprising; it’s what we were seeing everywhere, just total decimation of populations.
White-nose syndrome is a fungal disease that first appeared in this country near Albany, New York in 2007, potentially coming to the United States from European caves.
Spreading primarily from bat-to-bat contact, it now occurs throughout the eastern U.S. and Canada, and as far west as eastern Oklahoma. In March 2016, a case of white-nose syndrome was even detected in Washington state, about 1,300 miles from the previous westernmost detection of the fungus.
“It’s a cold-loving fungus that lives in caves, so bats pick it up when they’re in caves during the winter,” Stevenson said.
It grows on bats’ wings, muzzles, and other membrane areas while they hibernate. The growth stirs them awake as they feel a need to groom themselves, “which is really, really energetically costly for them,” Stevenson said. They basically burn off their fat reserves before winter ends. The mortality rate for the disease is so high that many species that contract it will die, she said.
Not all species of bats are as susceptible to the fungal disease. The big brown bat, for example, is a species that can fight off the infection, and as a result has been captured more often in scientists’ traps, Stevenson said.
UMCES scientists, under contract with Maryland Department of Natural Resources, are focusing their study on the northern long-eared bat, which is vulnerable to the disease and was federally listed as a threatened species in 2015, she said.
They use traps in the fall and spring to collect data, such as sex, age, and forearm length, and look for signs of the fungus that causes white-nose syndrome. Using data Gates and his students and assistants collected before white-nose syndrome came here, they can understand the decline of the species.
Gates, who has been researching bats since the 1980s, has witnessed both the successful recovery of bats following early conservation efforts, such as gating important places where bats overwinter to prevent disturbance, to the current dire situation with white-nose syndrome.
Although many susceptible bat populations, including the northern long-eared bats, have experienced steep declines since the appearance of white-nose syndrome, Gates said his team is still capturing small numbers of these species.
“We hope that these individuals may have some resistance to the disease that will allow them to recover over time,” he said.
Become a bat expert with this field guide to bats from the Maryland Department of Natural Resources.