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Wednesday, 13 September 2006 00:00

Nighttime navigators

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Usually I sit on the front deck of our house for a while after getting home from work. Then, before dusk, I normally retire to the kitchen area to listen to the radio while eating supper. One evening last week, however, I remained on the deck watching the evening shadows seep down into the valley. Just before dark, I spotted what at first appeared to be a flock of birds circling over the creek and pasture.

Their graceful patterns made me think at first that they might be swallows. But most swallows have returned to the Gulf Coast or South America by mid-August. After a few moments, it dawned on me that I was observing bats that were hawking a recent hatch of insects.

Swallows are, I think, the most graceful of all the birds. The patterns etched in the sky by bats are more halting and fluttering than the serene lines created by swallows, but as I watched those bats at work over the pasture, it occurred to me that bats must surely be among the most graceful of mammals. It is, after all, the only one that can fly.

Unfortunately, more superstition, prejudice, and apprehension exist about bats than any other animal, excepting, of course, snakes. In ancient European lore, vampires (from the Serbian “wampir”) were bloodsucking ghosts, dead men’s souls who siphoned blood from sleeping victims. The name “vampire” was then applied by the French naturalist Buffon to bats that were observed taking blood from other animals in the South American tropics. Before long, the gothic novelists in Europe had depicted bat-like beings that sought out victims (usually beautiful damsels, of course) in their bedchambers at night (where else?).

Bats are, in essence, mammals that can capture insects on the wing or feed on fruit high in trees. By evolving wings, they were able to exploit a niche in the food chain that other mammals couldn’t utilize.

The three bat species ranging from Mexico to Argentina that do feed on the blood of other mammals usually attack large animals like horses and cows. They land near the animal, climb up its leg, and select a sparsely haired spot into which they make superficial bites that allow them to gorge on oozing blood. They can’t do much with dogs, which can also pick up high-frequency sounds and hear them coming.

The real danger to the targeted animal is not the bite or the blood loss, but the fact that bats can transmit rabies. To my knowledge, few cases of rabies in the United States have been accurately attributed to bats. The species here studiously avoid human contact, and their jaws are so weak they could hardly break the skin of someone who attempted to hold one.

According to Mammals of the Carolinas, Virginia, and Maryland (UNC Press, 1985), there are 13 bat species in Western North Carolina. Their days are mostly spent in old buildings, tree cavities and caves.

While a bat’s vision is notoriously poor, it navigates the nighttime skies with exquisite precision. A sophisticated echolocation system allows them to emit ultrasonic sounds through their mouth or nose. These are set at a frequency far beyond the limits of human hearing. The lumps that can be observed on a bat’s nose are thought to aid in the production of these sound pulses.

Returning vibrations (echoes) received in oversized highly sensitive ears from trees, posts, fences, etc., warn them to navigate around or through these obstacles. But they instantly hone in on vibrations emitted by insects. Watch a bat circling your yard and you’ll notice that it sometimes pauses briefly in mid-flight with its hind parts directed groundward. This is the moment at which the bat is capturing an insect by literally enfolding the prey into its mouth with the aid of its wing and tail.

The critters are insect-capturing machines without equal. Dr. Olaf Ryberg, a Swedish scientist, performed tests in which he determined that bats hear “a fly cleaning its wings or rubbing its legs together. Immediately the ears of the bat would be erected and pointed in the direction of the insect. Then the bat would dart in that direction and snap up the fly its ears had first discovered.”

George Ellison wrote the biographical introductions for the reissues of two Appalachian classics: Horace Kephart’s Our Southern Highlanders and James Mooney’s History, Myths, and Sacred Formulas of the Cherokees. In June 2005, a selection of his Back Then columns was published by The History Press in Charleston as Mountain Passages: Natural and Cultural History of Western North Carolina and the Great Smoky Mountains. Readers can contact him at P.O. Box 1262, Bryson City, N.C., 28713, or at This email address is being protected from spambots. You need JavaScript enabled to view it. .

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