GRAY BATS NEED THEIR CAVES

by Whit Gibbons

September 18, 2005


During a recent visit to Guntersville, Ala., my sister Anne Gibbons and her husband, Bill Fitts, watched thousands of gray bats emerge from a bat cave on Lake Guntersville. This is an account of their adventure, dubbed "Batwatch" by Bill.

Leigh and Paul had told us on previous visits that we really needed to visit the bat cave. "It's an awesome sight," they said. "Thousands of bats fly from the cave. You can get in the water if you want to and be really close to them." But for one reason or another we had not yet made it to the bat cave. This time, we were determined to make it happen.

Since the bats emerge at sunset, the first thing to determine was exactly when the sun would set on September 4. A visit to the U.S. Naval Observatory Web site revealed that sunset would be at 7:07 p.m. and civil twilight would end at 7:32. Sunset we understood. But what was "civil twilight"? According to the naval observatory, civil twilight ends in the evening when the center of the sun is geometrically six degrees below the horizon. What this means for the average person is that when civil twilight ends, artificial illumination is needed to carry on ordinary outdoor activities.

So sometime between 7:07 and 7:32, the bats would venture forth from their cave. Nine of us, seven adults and two preteen girls, were eager to participate in "Batwatch." We packed a cooler of ice with beer, colas, and bottled water; gathered up jackets and long pants (for the trip back after civil twilight ended), snacks, beach towels, and cameras; loaded up the cars; and headed out to the marina. We were soon aboard Leigh and Paul's pontoon boat, ready for the 30-minute boat ride.

The bat cave is a popular destination on Labor Day weekend. More than 20 other lake-going vessels eventually gathered at the site, everything from two-person jet skis to medium-size houseboats. But Paul is a skillful navigator and he maneuvered our craft within several yards of the chain-link fence that blocks off the lower portion of the cave. (The fence keeps people out but allows the bats easy access to and from the cave.)

At 7:22 a collective "aah" and cries of "here they come" could be heard as the first bats emerged. Soon there were far too many gray bats to count, and more continued to flow from the cave. As we'd been promised, they swooped low to the water. The two of us who ventured into the water and swam a little ways from the boat had a ringside view of the graceful creatures. Knowing that these tiny mammals (they weigh from .25 to .50 ounces and have a wingspread of about 10 to 12 inches) were consuming night-flying aquatic insects, including mosquitoes, increased our enjoyment of the show. A colony of bats can consume tons of insects in a single night. Go, bats!

Cave exploration, opening caves to the public, and flooding of caves due to dams caused a serious decline in population numbers of gray bats. One of the few bat species that live in caves year-round, the gray bat (Myotis grisescens) has been listed as an endangered species since 1976. Eight caves (or nine, depending on the source you check) house approximately 95% of all the hibernating gray bats in the United States.

The Bat Conservation International (BCI) Web site (www.batcon.org) has a wealth of information about bats of every ilk, including the gray bat. During the Civil War, according to an article by Merlin D. Tuttle, a leading expert on bats, guano, which was used for gunpowder, was extracted from gray bat caves throughout the South. "Large guano accumulations in these caves undoubtedly prolonged the war by providing a reliable source of saltpeter long after importation had been cut off." Tuttle says that gray bat colonies no doubt suffered severe losses during the Civil War.

Today, thanks to joint efforts by organizations such as the Nature Conservancy, BCI, the U.S. Fish and Wildlife Service, and TVA, indications are that some populations of the gray bat are stable and may even be increasing. Speaking for those of us who enjoyed the 2005 Labor Day "Batwatch" at Lake Guntersville, we wish the gray bat well.



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