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June 11, 2005, 10:28PM When these bats feast, crops surviveThe mammals feed on moths whose offspring grow up to devour corn, cotton plantsBy BETSY BLANEYAssociated Press
Every night as the sun sets across Central Texas, an estimated 100 million bats take flight.
Sound scary? Perhaps to anyone but area farmers. These nocturnal mammals aren't seeking anyone's jugular. They're headed to an aerial smorgasbord of agricultural pests whose offspring devour corn and cotton plants. Nationwide, crop damage by pests and chemicals to treat fields cost farmers $1 billion a year, said Gary McCracken, a bat researcher from the University of Tennessee who is studying the bats' impact on insects. "The bats really chow down on these moths in big numbers," McCracken said. That big number equals about 1,000 tons of insects devoured each night in Texas, which claims the nation's largest bat population and the world's largest single bat colony. The bat is the state's official flying mammal. The study, in its second year, will use infrared thermal imaging cameras to get a more accurate count of bats in Central Texas. Computer software will extrapolate population numbers from the images. Other scientists will try to figure out how much of a bat's diet consists of moths. "This is very important work, and we're happy to see it taking place," said Barbara French, science officer with Austin-based Bat Conservation International, a nonprofit group that works to protect bats and their habitats worldwide. Most of the state's bats live within a 100-mile radius of San Antonio, but farmers in other regions feel their influence. The research could help the environment as well. Fewer pests means less use of chemicals to kill them. By eating the moths, bats prevent them from laying thousands of eggs, which grow up to become corn earworms and pink cotton bollworms that chomp through crop fields. "That definitely translates into a dollar savings to the farmers," said Patricia Morton, a spokeswoman for the Texas Parks and Wildlife Department, which is part of the study. "It's much more environmentally friendly in not putting those chemicals into the soil." Female bats, which have only one pup a year, migrate to Texas in March to munch on moths and feed their offspring. Surviving adult moth generations migrate through Texas on their way to Midwest corn fields. "So our bats in Texas are the front line," Morton said. If the bats in Central Texas eat enough moths, there will be fewer of the insects heading north to the world's largest cotton patch, Texas Cooperative Extension cotton entomologist Jim Leser said. That could be good news for South Plains cotton farmers during late July, August and September, he said. It may seem easy for the bats to catch those moths, but it's trickier than it looks. The moths can detect bats' echolocation, or sonar, which the mammals use to see at night. "They will fly erratically to avoid bats chasing after them," French said. The research, funded by a $2.4 million National Science Foundation grant, took shape after mysterious large "clouds" appeared on National Weather Service radar in Central Texas in the early 1990s on otherwise clear days. The clouds turned out to be millions of bats. Not long afterward, a weather service radar station in South Texas picked up more strange clouds intersecting with the bat clouds thousands of feet above ground. Researchers found the unknown clouds to be millions of migrating moths. Bracken Cave north of San Antonio is home to the world's largest bat colony with an estimated 20 million.
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