Bat Man vs. White Nose
Thomas Kunz is fighting a killer disease
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Select from the topics below to hear Thomas Kunz offer his impressions of bat surveillance, using a thermal camera.
On a sticky August evening, the woodsy suburbs of Boston fading into darkness, gray clouds threaten rain. As the cicada and mosquito buzz grows louder, attention focuses on a dark, open window of an old barn; it’s a bat stakeout.
A camera is mounted on the barn wall, paired with an infrared light source and wired into a computer. Another video camera sits on a tripod. All this is under the watchful eyes of Thomas Kunz, a College of Arts & Sciences biology professor, director of Boston University’s Center for Ecology and Conservation Biology, and one of the world’s top bat experts. He’s studied these misunderstood mammals for more than four decades, around the country and world, trying to counter their horror-movie image by extolling their critical roles in pollination, controlling insect pests, and sustaining ecosystems.
But in the past couple of years, a mysterious bat-killing disease has spread across the eastern United States, threatening entire species with extinction. The disease, known as white nose syndrome, has transformed Kunz the scientist into Kunz the crisis manager, convening emergency meetings and testifying before Congress to warn of ecological and economic disaster if the bats can’t be saved.
The barn is one of several hundred known sites throughout New England used by migrating female bats and their pups. Kunz reclines outside in a blue folding chair, counting bats as they flutter from their roosts and head out the window on the first of two nightly insect hunts. These are “little brown bats,” one of the most numerous in the United States, capable of eating their own weight of insects in a single night. Last year, there were more than 600 bats in this barn; this year, Kunz has counted 350. It’s worse at another colony in a state park near Worcester, where Kunz says the bat population has dropped about 90 percent in a single year.
Estimates are that since white nose syndrome was first seen in a cave near Albany, N.Y., in 2006, it has killed more than one million bats across several species, spreading throughout the Northeast and as far south as Virginia, wiping out entire caves. It isn’t slowing down, and bats produce only one pup a year, leaving researchers in a race to maintain bat populations in the United States.
The disease gets its name from a fungus that appears on the faces and wings of infected animals while they’re hibernating. And this brings up the first mystery: is the fungus killing bats, or is it a symptom of a compromised immune system caused by something else — perhaps a pathogen, an environmental contaminant, or a sudden change in diet?
This question is at the heart of research being done by one of Kunz’s students, Marianne Moore (GRS’10), a biology doctoral student in the ecology, behavior, and evolution program. Over the past two winters, Moore has traveled to hibernation caves and abandoned mines around the country, known as hibernacula, collecting blood samples. She takes blood from infected and seemingly unaffected bats where white nose syndrome is prevalent, as well as from bats hibernating in sites where the disease is not yet apparent. She is now running immune response tests on the samples and hopes to have some definitive results later this year.
“In addition to being fascinated by bats, I’m also interested in infectious disease ecology and immune function, and so I could not imagine a bigger opportunity than this research,” says Moore. She describes the bats dying off as “really scary.” What began as a few dead bats around caves in the winter of 2007-2008 became thousands of frozen bat carcasses observed last winter. “It’s just devastating,” she says.
European bats have been documented as having a similar fungal infection, but without the die-offs. David Blehert, a microbiologist for the U.S. Geological Survey National Wildlife Health Center, whose lab investigates large-scale mortality among animals, is now analyzing the DNA of the European fungus, to see if it’s the same as what’s killing American bats. If so, it would suggest that European bats developed an immunity long ago, and this fungus was somehow introduced to American bats with no natural defenses.
“This is the most significant disease that I’ve encountered in my six years in this position,” says Blehert. He’s also looking into the mystery of how exactly white nose syndrome kills. Some fungi produce toxins, but cultures of the fungus haven’t yet revealed that, and dead bats don’t exhibit any telltale damage to their livers or other organs.
One thing that is shared by most (although not all) of the dead bats is emaciation — is the fungus causing bats to starve to death? Kunz invokes the “itch and scratch theory”: perhaps the fungus is an irritant, waking bats up from hibernation, burning precious body fat needed to survive the winter and early spring.
Yet the fungus does cause damage to skin and wings, as Kunz and doctoral student Jonathan Reichard (GRS’07,’11) document in yet-to-be-published research. That’s not a cosmetic problem; wing membranes of healthy bats are pliable and flexible, which makes it possible for them to fly and effectively catch more than a thousand insects every hour, says Kunz. But the wings of many bats with white nose are covered in lesions and stiff scar tissue. “Some had such bad damage that we suspect they couldn’t feed,” he says.
A lack of body fat could also disrupt the hormone triggers in females that lead to ovulation, says Kunz, preventing reproduction. “All of this has come together pretty suddenly, and now we have a national crisis.”
Kunz, who became fascinated by bats as a young man exploring caves in the Ozarks of his native Missouri, has taken up the challenge. He’s stepped up efforts to quantify what are known as bats’ “ecosystem services.” They make tons of chemical pesticides unnecessary and help pollinate and protect untold acres of agricultural crops; their 1,116 known species represent about 20 percent of all mammals. In one paper Kunz published in 2006, he and several colleagues, including lead author Cutler Cleveland, a CAS professor of geography and environment, calculated that Brazilian free-tailed bats save Texas cotton farmers about $750,000 in pesticides needed to control cotton bollworm. Kunz also cites a calculation that the one million bats killed by white nose syndrome would have eaten about 1.4 million pounds of insects in a year
Kunz and ecologist Merlin Tuttle, founder of Austin-based Bat Conservation International have organized two Emergency Science Strategy Meetings to combat white nose. This past June, Kunz argued before Congress for millions in additional research money.
“I’m what they call a silver back,” he says, “one of the older guys who, due to my age and tenure, may get a little more traction and a better hearing when I speak up.”
Thus far, Kunz’s efforts have not been successful. “Bats have never had great public relations,” he says. “People think of them as vile, dark, and icky. And people fear the darkness.” He has often been called out to help panicked neighbors deal with a wayward bat that has found its way indoors. His advice: calm down, turn on the lights, and open a window.
During the congressional summer break, Kunz has been in touch with sympathetic legislative staff members, lobbying to obtain more money by spreading research costs across several federal agencies.
In the meantime, he and fellow bat researchers continue with as many investigations as funding allows. This fall and winter, Blehert will try various fungicides as potential treatments; such efforts will have to work bat by bat, rather than spraying whole caves. “Caves are complex ecosystems, with hundreds, sometimes thousands of species, in addition to serving as important filters for groundwater,” says Kunz.
Stretching out of his blue folding chair, feeling the rain around the suburban barn grow heavier, Kunz stops this night’s bat count at 117; no bats will emerge in the downpour, while the ones who left earlier swarm back inside. It’s time to pack up for the evening. In a week or two, the mother bats, along with their pups, will begin flying off to hibernacula, where they’ll mate and store sperm throughout hibernation, before ovulating in the spring. Kunz predicts that researchers will find white nose syndrome in more states this winter, which could mean far fewer bats at the barn when he returns next June.
Edward A. Brown can be reached at email@example.com Comments