A deadly disease is destroying Northeast bat populations so rapidly that one of New England’s most common species is likely to disappear within 20 years, Boston University and other scientists conclude in a study published today.
The regional extinction of the little brown bat, which has the phenomenal ability to eat its body weight in insects every night, would wipe out a predator of many garden and agricultural pests, as well as of some mosquitoes.
"We don’t pretend to be fortune tellers ... but we're very worried," said Winifred F. Frick, a Boston University and University of California, Santa Cruz postdoctoral researcher who is the lead author of the paper in the journal Science. "The loss of so many bats is basically a terrible experiment in how much these animals matter for insect control."
Scientists knew that the illness, discovered in a cave outside Albany, NY, in 2006 and now called white nose syndrome, was so virulent it was killing more than 90 percent of bats in some caves in just a few years. But the findings of the new study are even more alarming.
The researchers ran 1,000 computer simulations of bat populations stricken by the syndrome, and determined there is a 99 percent chance the little brown bat will not sustain a regional population for more than 16 years, unless death rates significantly slow. Little brown bats are found throughout the United States, but the study did not look at populations outside the Northeast.
White nose syndrome is named for a fungus that appears on hibernating bats’ noses, wings, and other body parts. Scientists believe the fungus irritates bats so greatly they wake up during hibernation, expending precious body fat in the process. Many of the flying mammals then leave caves and mines only to die as they search for food on barren winter landscapes.
No one knows where the fungus, called Geomyces destructans, came from, although it may have been inadvertently introduced into the New York cave by humans, who are not harmed by it. Now endemic in New England, the fungus has been found in seven hibernating bat species as far north as Ontario in Canada, south to Tennessee, and west to Oklahoma -- and continues to rapidly spread.
Bats are believed to transmit the fungus when they huddle together during hibernation in caves and mines, but could also be spreading it when they fly as far as 250 miles away during the summer to roost with bats from other caves and mines.
“This is scary -- and interesting," Michael Reed, a Tufts University professor who studies population biology and conservation, said of the study. He said the research, which he was not involved in, was well done. Extinction predictions often are made for species that have few numbers of individuals or are restricted by geography to a small area. What makes this unusual, Reed said, is “this is a species viewed as common, and you don’t usually worry about them. The behavior of bats (hibernating communally) is allowing it to spread so quickly.”
Other species across the world also are experiencing extraordinary declines from infectious disease, including Latin American frogs being wiped out by another type of fungus, and Tasmanian devils disappearing because of cancerous facial tumors. Some frog populations have already collapsed, and scientists fear other amphibians -- and Tasmanian devils -- could become extinct.
Because of concerns that humans can spread white nose syndrome, authorities have closed an enormous number of the nation’s caves and mines to tourists and “cavers”, who explore the crevices and tunnels deep in the earth. Campers and hikers have also noticed the end of the nightly ritual of bats emerging from summer roosts to feed on insects.
Three years ago, "we had enough bats it looked like a swarm … 200 bats maybe," said Monica Matthews, who works at Silver Lake State Park in Barnard, Vt. Bats used too roost each summer in the eaves of a nature and concession center overlooking a lake at the park.
“Last year we probably had 40 and this year maybe 10," she said. "It’s sad to see, to lose part of what has always been here.”
Frick, along with Boston University bat researcher Tom Kunz, former BU doctoral student D. Scott Reynolds and other researchers, used bat population data for 22 caves and mines over the last 30 years in Massachusetts, Vermont, Pennsylvania, Connecticut, and New York to determine that populations were stable or increasing before white nose syndrome hit.
Then, they fed that information into a computer along with data about infected and uninfected bats, rates of decline of bat populations, and other environmental conditions. They included evidence that bat mortality lessens over time in some caves, possibly because bats develop a resistance or the fungus spreads more slowly when the animals are not as closely packed.
The conclusion: A 99 percent chance of regional extinction of little brown bats within the next 16 years. If mortality rates continue to slow over time, that timeline could stretch out, with a greater than 90 percent chance of regional extinction within 65 years.
Frick cautioned there is still great uncertainty about what nature has in store for bats, but said, “This is one of the worse wildlife crises we’ve faced in North America.”
Now, Kunz says, researchers expect white nose syndrome “will adversely affect bat species that form some of the largest hibernating bat colonies in the U.S., including two federally-listed endangered species.”
Contrary to popular belief that bats eat vast amounts of mosquitoes, Kunz says they tend to go for other bugs first -- and many of them are pests that like to attack vegetables, flowers, and agricultural crops.
“(Insect-eating) bats are of considerable value to forests, fields, and to agriculture by suppressing insect populations, but they also sustain cave ecosystems," said Kunz. “Bat guano is often the only organic input to caves” and helps support salamanders, fish, and other species in them.
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