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National Geographic : 2002 Apr
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"Hot-air balloons are the safest mode of aviation," our pilot assured us as we prepared to ascend in the predawn August darkness near Uvalde. Launching and flying at night isn't a problem-but landing can be. In the dark, power lines and barbed wire fences create invisible hazards during descent. So it would be a quick two-to-three-hour flight, then hopefully a safe landing soon after dawn. It was still pitch-black when we rose from Ray King's farm near Frio Cave. We drifted silently, save for occasional blasts from the propane burners, which kept us aloft. To the bats we must have looked like a giant lightbulb. As the sun began to rise, we could see deer scattering below us in the dim light and the faint outline of a hawk in a tree. When we rose to several thousand feet, we began to hear bats. Our pilot pointed to a group close to the balloon, apparently investi gating the large object that had invaded their airspace. They were Mexican freetails. As we approached 5,000 feet-the limit of our flight plan-we saw and heard more freetails and recorded their feeding buzzes with bat detec tors. But we saw only a few moths, mostly in the distance. Already it was daylight. Shortly after dawn we bumped down, exhilarated but a bit disappointed. Where was the feeding frenzy? We had flown in August, well after the June moth migrations from Mexico, so a subsequent generation of moths was already leaving en masse from the patchwork of crops far below us. Billions of these insects should have been flying at our altitude. Why had we seen so few? Simple math eased our disappointment. Although Doppler radar shows billions of moths as a huge cloud, we later calculated that the density-from our vantage point in the balloon-translated to perhaps one moth per 30,000 cubic feet of airspace. With 20/20 hindsight we realized that we shouldn't have expected to see swarms of moths. Later DNA analysis of the insect remains in bat feces by Sunitha Vege, a graduate student at the University of Tennessee, finally con firmed our suspicion: The insects in the free tails' droppings are in fact corn earworms and tobacco budworms. Our project now involves more than a dozen scientists in the U.S. and Mexico. Together we are trying to determine the dollar value of the bats. How much crop damage would there be without the freetails? How many more tons of insecticides would farmers need to spray if it weren't for the bats? Even before these questions are answered, how ever, it's clear that we need to safeguard our free-tailed bats, which cost us little to protect but could cost us a great deal if we lose them. O ON OUR WEBSITE Watch video footage of more than a million bats flooding the skies over Austin, and get tips from Bat Conservation Inter national on how to help save bats worldwide at national geographic.com/ngm/0204. AOL Keyword: NatGeoMag BAT PATROL
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