Merlin D. Tuttle, Bat Conservation International photo
Vampires? Unfortunately for bats, most people associate them with dark and nefarious tales. Women flailing their arms around their heads to keep from getting bitten. Or perhaps it’s Bela Lugosi, cape drawn across his mouth, declaring, “I vant to bite your neck.”
On a recent evening, my wife, my seven-year-old daughter, and I were trying to find some bats, but our search was turning out to be in vain.
“Daddy, you promised we would see bats,” my daughter protested.
“Somebody told me this was a good place to see bats,” I said.
The sun had fallen into the Little Tennessee River. Cave swallows had returned to roost in their round jug-like nests under the bridge. The sky grew darker and darker, but still no bats. We reluctantly climbed back into the car to leave, but I didn’t have the keys. As I got out to retrieve them from underneath the seat, I glanced up. I thought I saw a high-flying bat along the ridgeline.
“Look, there’s one way up there,” I announced.
“Daddy, one just flew over the car!” my daughter shouted.
Everyone scrambled back out of the car. Bats! There weren’t a million, as there are beneath the Congress Avenue Bridge in Austin, Texas. But there were dozens flying around. My wife involuntarily flinched when a big brown bat glided out of the darkness and swooshed past her.
We finally got our encounter with these amazing, nocturnal creatures.
Batty About Bugs
Mylea Bayless, a conservation biologist at Bat Conservation International based in Austin, Texas, gets all sorts of questions when it comes to bats.
“People call me all the time and ask, ‘Why do the bats come out every time I turn on my swimming pool lights?’” she says. “I have to explain that the bats are already there. They come for a drink of water. People just don’t see them unless they turn the lights on.”
People might also ask Bayless, “Why do bats attack me when I’m walking in my field in the evening?”
“When they’re walking through the grass in the evening,” she says, “they’re kicking up a bat buffet of insects. I think the erratic looking flight of bats is frightening to some, but it’s actually a very controlled flight as they hunt down insects.”
And boy, do they like their bugs.
“A little brown bat can eat a thousand mosquitoes in an hour,” says Bayless.
In fact, bats eat about half their body weight in bugs every night. That means that the 1.5 million Mexican free-tail bats that roost under the Congress Avenue Bridge in Austin, Texas, fly out every evening and consume nearly 20 tons of insects. Now multiply this by the hundreds of millions of bats across the United States.
“There’s no doubt that bats provide significant ecosystem services,” says Gary McCracken, head of the University of Tennessee’s ecology and evolutionary biology department.
McCracken has been studying bats since 1976. He says that bats consume large quantities of pests like moths and beetles that would otherwise destroy crops and forests. McCracken’s studies in Texas with Mexican free-tailed bats show that these bats can cue in on and intercept hatches of pests like corn earworm moths as they migrate at high altitudes northward from Mexico to agricultural centers across the U.S. According to the National Science Foundation, those Mexican free-tailed bats save farmers more than a million dollars a year in reduced crop damage.
Bats use a very sophisticated sonar system called echolocation to navigate and capture insects in the night. They emit sound waves from their mouths and/or noses. When these waves come into contact with an object, they bounce back or echo, and the bat hears them. Insect-eating bats have an echolocation that is so sophisticated the bat can tell how large a bug is and in what direction it’s moving.
These aerial predators are adapted to fill different niches as they hunt for insects. McCracken says little brown and big brown bats that hunt close to branches and bushes have short, broad wings that provide lift and maneuverability. Hoary bats, on the other hand, have longer, narrower wings and cruise faster above the treetops. Fast, high-flying bats also echolocate at lower frequencies, which allow the sound to carry farther so they can detect prey at greater distances.
To the Bat Cave...
The Appalachian Mountain region of North Carolina and Tennessee is home to at least 12 species of bats. The big brown bat, little brown bat, eastern red bat, and tri colored bat are probably the most commonly seen bats in the region. Other bats like hoary bats and northern long-eared bats are not seen as commonly but appear to be doing fine in proper habitats.
According to Chris McGrath, wildlife diversity program coordinator with the North Carolina Wildlife Resources Commission, better and more regular surveying of bat populations has led to some good news.
“Back in the 1980s and 1990s, northern long-eared bats were listed as special concern in North Carolina,” McGrath says. “But because of more recent survey work, the northern long-eared bat was de-listed in 2007.”
The North Carolina Wildlife Resources Commission has also worked with partners to help protect federally endangered Virginia big-eared bats on Grandfather Mountain in Avery County—the only known site in the state where the bats hibernate—by installing bat gates to exclude humans. Virginia big-eared bats are especially sensitive to disturbances during hibernation. Since bats don’t eat during hibernation, arousing them at this time causes them to use up their fat reserves and they can starve to death before there are any insects available for food in the spring.
“We’ve been monitoring Virginia big-eared bats on Grandfather [Mountain] since the mid-1980s,” McGrath says. “We survey those caves every two years, and the last survey revealed nearly 400 bats.”
The region is also a stronghold for the federally endangered Indiana bat. According to McCracken, the Great Smoky Mountains National Park is home to one of the largest caves of Indiana bats in the Southeast. While numbers fluctuate from year to year, approximately 8,500 Indiana bats were noted at one cave in the Smokies in 1992. When you consider the total population of these endangered animals is only about 360,000, it’s easy to see how important this cave is.
The Great Smokies Park is also home to a unique type of bat— Rafinesque’s big-eared bat, an icon of southern bottomland hardwoods that lives in old growth forests. In this half a million acres of protected forest, there’s an enormous biodiversity and enough bottomland to make the Rafinesque’s big-eared bat one of the most common species in the park at elevations between 1,500 and 2,500 feet.
The World of Bats
There are more than 1,000 different bat species across the world. Bats make up about 20 percent of all mammals. They belong to the order Chiroptera, which means “hand-wing.”
“If you looked at an outstretched bat wing,” Bayless says, “the wing bones would be analogous to the human hand. The wing looks as if it is made up of elongated fingers.”
One type of bat, known as Megachiroptera, is commonly referred to as “the flying fox” because of its long, fox-like face. Megachiroptera occur in the tropical forests of India, Asia, Africa and Australia. They feed on fruit and pollen. Another type of bat, the Microchiroptera, primarily consumes insects and preys on frogs, fish, small rodents, and even other bats.
Yes, there are also vampire bats.
But they don’t walk in human form around dark, old castles. To be accurate, they don’t suck blood either. They actually make small incisions and lap the blood up with their tongues.
There are three species of vampire bats—the common, the hairy-legged, and the white-winged. They live primarily in Central and South America but likely reach the U.S. along the northern edge of the Chihuahuan Desert in Texas, Arizona and New Mexico. The hairy-legged and white-winged vampire bats feed mostly on the blood of wild birds and occasionally domestic fowl. The common vampire bat feeds on mammalian blood.
“The medical community is doing a lot of research with vampire bats,” Bayless explains.
Apparently, the antiseptic and anticoagulant properties of bats could have significant medical applications. The anticoagulant, which is a substance that stops the blood from properly clotting, has been used to treat stroke patients.
This large, diverse group of mammals has been around for quite some time. Fossil records date back some 50 million years ago to the Eocene epoch and show skeletal remains very similar to modern-day bats.
Bats also come in a variety of sizes. The giant golden-crowned flying fox of the Philippines has a wingspan of six feet and is nearly the size of a bald eagle. With a weight of three-and-a-half pounds, it is thought to be the largest bat in the world. By contrast, Thailand’s bumblebee bat, with a wingspan of around five inches and a weight of two grams (less than a penny), is the world’s smallest bat.
According to Bayless, if you’ve ever had a margarita with your fajitas, you can thank a bat. Mexican long-nosed bats and lesser long-nosed bats are principal pollinators of Agave tequilana, the plant from which we get tequila.
Tequila drinkers aren’t the only ones who benefit from bats. Bats help control the spread of insect pests and disperse seeds in rain forests. Perhaps the more people watch them and learn to appreciate all they do, the less misunderstood they will become.
Take a Bat Walk
There are plenty of opportunities to see and learn more about bats in the Southern Appalachian region. Bats appear almost anywhere across the region by getting out at dusk. Rural areas adjacent to woods and bridges across open water provide good habitats for bats.
Gary McCracken, head of the University of Tennessee’s ecology and evolutionary biology department, leads popular “bat walks” every year in association with the Annual Wildflower Pilgrimage in the Great Smoky Mountains National Park.
“Twin Creeks is a great location [in the park],” McCracken says. “It’s isolated, and there is water and a streetlight that attracts insects.”
McCracken says they’ve captured five different species of bats at Twin Creeks. He also takes live bats with him and participants get to hear bats with the aid of bat detectors, a device that lets you hear the bat as it echolocates. Since different bats echolocate at different frequencies, the detector can help determine which bat one is listening to.
The North Carolina Nature Conservancy also leads hikes in its Bat Cave Preserve in Rutherford County. For more information, contact Debbie Crane either by email at dcrane@tnc.org or by phone at 919.403.8558 ext. 1018.
Bats in peril
As scary as some bats might be to humans, bats in the eastern United States are facing a serious threat to their very existence.
White-nose syndrome, named for the white fungus that appears around the muzzle of infected animals, is killing thousands of bats at an alarming rate. The disease was first documented in Schoharie Cavern, near Albany, N.Y., in 2007. Once word of white-nose syndrome began to spread, photos from February 2006 showed bats with white-nose syndrome from Howe Cave, also in New York. By early 2008, the malady had been documented in caves across the Northeast including New York, Vermont, Massachusetts and Connecticut.
The disease has spread rapidly and is moving south. Pennsylvania, New Jersey, New Hampshire, West Virginia and Virginia have been added to the list of states reporting white-nose syndrome, bringing the total to nine states.
At least 60 caves have been infected, and estimates indicate that more than a million bats— including 25,000 endangered Indiana bats—have succumbed to white-nose syndrome. As many as 97 percent of the bats living in some caves have died. Those infected include the little brown, big brown, tri colored, northern long-eared, small-footed and Indiana bats.
To date, biologists and research scientists remain puzzled by what causes white-nose syndrome. They cannot be sure whether the fungus causing the white muzzles is the pathogen causing the deaths or whether it is simply a symptom of some other disease.
The white-nose syndrome fungus has been isolated. It is a never-before-described psychrophilic fungus that thrives in cold damp habitats—just the kind you would find in a cave where bats hibernate in the winter months. It has, in fact, been collected from bats across a widely dispersed range of caves in the Northeast.
Scientists are developing several theories to explain what may be causing white-nosed syndrome. Excessive pesticide spraying or other toxins could be reducing the bats’ insect populations and thereby causing bats to use up their winter stores of food, making them hunt in cold temperatures when they should be hibernating. Bat flies, tiny parasites that live in a bat’s hair and feed off its blood, could also be the culprit, as it may be transmitting the disease. Others think it may be likened to a similar crisis that has colonies of honeybees disappearing at an alarming rate.
Because white-nose syndrome has suddenly popped up far away from known infected sites, the U.S. Fish & Wildlife Service is concerned that humans may be aiding the spread of this disease. These concerns have led Fish & Wildlife to close caves on property it owns and call for a voluntary moratorium on caving in states with known cases of white-nose syndrome as well as in adjacent states. Agencies like the National Park Service and the Nature Conservancy have followed suit and closed access to caves on their property. The rapid spread southward has scientists worried about the Smokies.
“I wouldn’t be surprised to see white-nose syndrome in Tennessee this winter,” said Gary McCracken, a bat expert and head of the ecology and evolutionary biology department of the University of Tennessee.
According to Mylea Bayless, a conservation biologist with Bat Conservation International, white-nose syndrome has the potential to affect half of the 25 species of bats that hibernate.
“It could be particularly devastating in the Smokies where there are large roosts of endangered and threatened species,” Bayless said.
In an effort to stop the spread of white-nose syndrome, the U.S. Fish & Wildlife Service has issued a list of the following recommendations:
1. A voluntary moratorium on caving in states with confirmed white-nose syndrome and all adjoining states.
2. Cavers/spelunkers in states not affected by white-nose syndrome and not adjoining infected states must use clothing and gear that has never been in caves affected by the syndrome or in caves in adjoining states.
3. State and federal conservation agencies should evaluate scientific activities for their potential to spread white-nose syndrome.
4. Researchers should use clothing and gear that has never been in caves in states affected by white-nose syndrome or adjoining states.
The U.S. Fish & Wildlife Service has closed four caves at Wheeler National Wildlife Refuge, near Decatur, Ala., and may close more on its property in accordance with advisory guidelines. In addition, the U.S. Fish & Wildlife Service recommended other government agencies, organizations or private landowners close its caves to help prevent or slow down the spread of white-nose syndrome.
To learn more about the latest news regarding white-nose syndrome, go to www.batcon.org.
— By Don Hendershot