New Disease Threatens Bat Conservation

Photo By Marilyn E. Kitchell/USFWS

An Indian bat submits to measurement and inspection by a gloved researcher.

By Susan Morse

When it comes to Northeastern bats, there are many things researchers still don’t know, including, most critically, what causes the fungus that scientists suspect is killing these creatures and how to stop it.

And then there are the things the rest of us think we know:

Bats are blinder than your Aunt Nellie.

Bats often have rabies.

Bats are pests.

Wrong.

Wrong.

And dead wrong.

Bats actually have excellent vision. At night, they supplement it with a kind of sonar. Sounds they emit, inaudible to the human ear, bounce off objects and help them find their prey.

The incidence of rabies in bats is small; an estimated one-half of one percent − or one bat out of 200 − has rabies. The great majority (70 percent) of bats feed on insects; most of the rest eat fruit and pollen.

Far from being pests, these underappreciated creatures promote human health and comfort by pollinating fruits and flowers, and providing a potent natural control for mosquitoes and other night-flying insects. Some 80 medicines we use come from plants that need bats to survive.

But bats need help. The endangered Indiana bat (Myotis sodalis) is a case in point. Despite its Hoosier handle, the bat is found throughout the Ohio River Valley and as far east as Vermont. Increasingly, though, it’s being found sick or dead. Earlier this year, concerned that disturbance of hibernacula − bat hibernation areas − was making bats sick, the Fish and Wildlife Service closed caves in 17 states to the public. But bats have continued to decline. And now, a deadly disease known as white-nose syndrome has spread beyond the Northeast into Virginia and West Virginia.

Changing Habits in New Jersey

On the Great Swamp National Wildlife Refuge near Morristown, New Jersey − just 25 miles from Manhattan’s Times Square − biologists and volunteers are racing to study the ecology of some recently discovered Indiana bat colonies before disease wipes them out.

Leading the effort is Great Swamp park ranger Marilyn Kitchell, who devoted her master’s thesis to the roosting habits of Indiana bats after scientists confirmed the species was on the refuge in summer 2005. The refuge’s 7,700 forested, stream-crossed acres (3,335 hectares) seemed like suitable habitat. But the bat’s presence was unproven until deputy refuge manager Sharon Marino scraped together the funding to conduct a four-night search.

How could the creatures have eluded previous notice? Easily. They’re tiny; each weighs just one-quarter of an ounce (seven grams) and span maybe seven inches (17 centimeters) with wings spread. They’re also nocturnal. And even trained researchers have a hard time distinguishing them from another species, the little brown bat (Myotis lucifugus).

You also have to know when and where to look. The Indiana bats that inhabit Great Swamp are summer residents only; in the winter, they hibernate in mines and caves outside the refuge. In summer, females roost in tightly packed colonies under the peeling bark of dead and dying trees or healthy trees like the shagbark hickory (Carya ovata).

For refuge staff, the awareness of the bats’ presence has meant rethinking conservation activities. The effect on nesting songbirds is no longer the only consideration when it comes to habitat management on the refuge.

“For instance,” says Kitchell, “if we need to take down trees, now we think: ‘What time of year is that happening and will it have any impact on the Indiana bats?’ ” Ditto for plans to tear down an old barn. “Now we’re not going to take the barn down in the summertime because the bats are using it,” Kitchell says.

The refuge is just beginning its work on a Comprehensive Conservation Plan that will help set priorities and guide conservation efforts over the next 10 to 15 years.

Volunteer nature interpreter Judy Schmidt has incorporated the Indiana bat in her talks to refuge visitors. “I ask them if they know that bats are mammals,” she says. “And then I ask them, ‘How many night-flying insects do you think one bat would eat in one night?’ ” The answer she’s after: about 500. “And then I say, ‘That mosquito the bat eats isn’t there to bite you, and that’s why they’re so important.’ They love it.”

What does it take to study Indiana bats? Stamina − and lots of help.

Tagging is a key step. Researchers put up tall, fine-mesh nets called mist nets across streams and trails. They open the nets between 9 p.m. and 2 a.m. and check them every 5 to 10 minutes. When they find a bat, they carefully pick it out and weigh it. Then they determine its species, maturity, sex, and reproductive status, and band it. If it’s a reproductively active female, they also attach a radio transmitter so it can lead researchers to daytime roost trees and to streams over which bats forage at night.

But where to put the nets? That’s where help comes in. Volunteers, many of them members of the nonprofit Friends of Great Swamp, conduct echo-location surveys, using a device to detect and record the number of bats calls emitted in 15-minute intervals. Researchers use the results to tell if a site is good to net. Volunteers also conduct “emergence counts,” sitting beneath a roost tree at night and counting every bat that comes out − the only way to estimate a summer bat population.

The refuge’s Friends are critical to data collection, says Kitchell.

The work, she says, is “very labor intensive. It’s also very, very rewarding.” Bats, she says, “are such amazing creatures. The public just doesn’t understand how neat they are and how important a role they play in the ecosystem.”

White-nose Syndrome

Lately, Kitchell is helping state biologists study how white nose syndrome is affecting New Jersey bats hibernating off the refuge in abandoned mines. The work isn’t encouraging. “Mortality is upwards of 90 percent in an affected site,” she says.

Worse, she says: “We know our bats are now affected. We found a dead bat in the mine with one of our bands on it. We put the band on in July.”

Scientists have confirmed the presence of a fungus, Geomyces sp., in the bats, but don’t know for sure if the fungus is what’s making them sick, or, if so, how it’s transmitted. Affected bats cluster abnormally, fly around when they’re supposed to be in a deep torpor, lose adipose (fat) tissue, and basically starve to death before they emerge from hibernation, she says. Their muzzles are covered with a growth of white fungus.

This year will be the first season in which the refuge will be able to see the effects on the summer Indiana bat population. “We don’t know what we’re going to find,” Kitchell says.

“We all want to know how to treat it, how to stop it,” she continues. “I just don’t think an answer is that close, unfortunately. The disease is moving, spreading. If we don’t figure out some- thing soon, we’re going to be looking at very significant losses, including poten- tially the loss of some species. It’s just a terrible thing. It’s huge.”