As White Nose Syndrome Spreads, Worries Persist About Potential Impact on Bats, Ag Industry
After a 10 minute climb up a gentle incline just off the main trail at Mammoth Cave National Park, Rick Toomey stands on a wooden platform overlooking Dixon Cave.
“It’s one of our most important hibernation sites,” said Toomey, the park’s research coordinator.
He says during the winter thousands of bats, including several different species hibernate here. But those numbers might be on the verge of a drastic change.
“This is a site that could be vastly altered in five years. In five years we might go in there and find five or ten bats total,” said Toomey. “It’s a very realistic possibility based on what’s been seen elsewhere. And that would be devastating to our ecosystem up here.”
The problem: White Nose Syndrome. It started in the northeast in 2006. It was first noticed at Mammoth Cave in 2013 and has since spread to the caves that welcomed nearly half-a million visitors last year.
Toomey says the fungus that gives White Nose Syndrome its name is just one of the symptoms of the devastating disease.
“This fungus seems to cause them to wake up a lot more often and burn through fat reserves, so they end up looking emaciated and dehydrated,” said Toomey. “It will cause them, instead of sleeping in the middle of February when there’s snow out, they’ll be hungry, flying around at the cave entrances, moving to colder areas, heading out into the snow looking for bugs to eat and looking for things to drink.”
The disease is fatal in some bat species. It’s not harmful to human health, but scientists continue to warn the biggest consequence to humans could be an economic one.
Researchers at Mammoth Cave haven’t seen a mass die off, but they say they may get a better picture of the effects of White Nose Syndrome in a few months from now after the next hibernation season.
The hopes that the warmer climates in the South and Midwest would reduce the number of White Nose Deaths seem to have been dashed by early evidence.
“We were hoping Kentucky was going to be an area, where if the winters were short enough that the bats could make it through without high mortality," said Toomey. "But we’re starting to see mortality in Kentucky this year in a number of places and in a number of species. Unfortunately, we’re less hopeful that the shorter and warmer winters would make a difference.”
In the Northeast, meantime, the mortality rates are staggering. In some populations, like the Little Brown bat or the Northern Long Ear bat, there’s a 98 to 99 percent drop off in populations. In all, it’s estimated at over five million bats have died from White Nose. And that’s where the economic impact comes in. As Toomey points out, bats plays an important role in the ecosystem as a major consumer of night time pests.
A 2011 study published in the journal Science estimated the economic impact of bats for the agriculture industry between $3 billion and $50 billion dollars annually.
As White Nose Syndrome slowly inches south and west, it may begin to threaten areas whose economies depend more heavily on agriculture.
But measuring the effect of the disease on the inspect population remains a challenge says Jonathan Reichard with U.S. Fish & Wildlife Service.
“We’ve got annual changes in weather, and spraying and various other environmental impacts that are going to be influencing the number of pests that are around,” said Reichard.
But Reichard says researchers will continue trying to find ways to parse those numbers.
“We can design some studies that will get at it, through some elaborative, empirical design,” said Reichard. “But farmers most likely would be the first ones to see it through increase pestilence in their crops or decreased yields.”
Stopping The Spread
Scientists believe the most common way the disease is spread is from bat to bat. Some species of bats have prolific migration patterns. Toomey says some Indiana bats, for example spend the winter hibernating in Kentucky before returning to a tree roost in Central Michigan.
“The bats in the eastern part of North America are largely different species than the bats in western North America. There are a few species that cut across, but we don’t really have good information about how much breeding and gene flow goes across east-west. There’s a lot of gene-flow north-south in all of these bats.”
Toomey says he takes part in conference call every two weeks with local, state and federal researchers from around the country. He says when the calls started a few years ago, there were about three dozen people on the call. Now, that number is now doubled and sometimes tripled, according to the U.S. Fish & Wildlife Department.
In addition to bat migration spreading the syndrome, it can also be passed incidentally by cave visitors. That’s why at Mammoth Cave, when visitors emerge from a cave tour, they walk across a black mat – fiberglass cloth and foam soaked in a Woolite solution, which Toomey says has shown effectiveness in killing the spores carrying the fungus.
“What we’re doing here at Mammoth Cave, with people walking over mats so they can’t take it some place, is we are actually trying to defend Colorado, New Mexico, Oregon and California because we don’t want to have people move it into the western bats," said Toomey. "If people move it into the western bats we’re also fairly certain the western bats will be very efficient at moving it amongst themselves and starting a new epidemic there.”
As Mammoth Cave's public information officer Vickie Carson notes, there are hopes a cure can be found soon.
“It’s not in Carlsbad Caverns, it’s not in Oregon’s caves, it’s not in Timpanogos, it’s not in Wind Cave or Jewel Cave – those are National Park Service caves out west," said Carson. "There’s probably no doubt that it will get there at some time. We’re hoping that if we can slow the spread of it, maybe science can catch up in some way and do something about it."