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October 2005

Release date: October 13, 2005

Professor Goes Underground for Bat Research

For most people, the only time they think of bats is Halloween, but for Angelo State University professor Loren Ammerman, bats are a year-round occupation.

Her most recent research trip took her to Big Bend National Park, where she spent summer evenings perched at the entrance of a cave pursuing a new method to count the Mexican long-nosed bat, whose survival is intertwined with that of the agave plant -- a vital ingredient in tequila.

Of the more than 1,100 bat species in the world, 32 can be found in Texas, and 22 can be found in Big Bend. But the Mexican long-nosed bat's importance to the ecosystem -- it accounts for most of the successful pollination of agave plants and its population density spurred Ammerman to research this species' population.

"If something happens to one cave, a large percentage of the population could be wiped out," Ammerman said.

Ammerman began the project this summer with help from a Bat Conservation International grant and collaborators from Boston University. Using the money from the Austin-based animal-protection organization, she and a group of three researchers made trips to the park in June, July and August to use an infrared thermal camera to record the exit of bats from Emory Cave.

On each two-day trip, Ammerman and her group hiked three hours to their campsite in the Chisos Mountains, then hiked another 30 minutes every afternoon to prepare to record the exit of bats from the cave with the thermal camera.

As dusk approached, Ammerman and her group mounted the camera next to the cave's opening. Less than an hour after sunset, a flurry of the winged mammals flew out of the entrance, a hop hornbeam tree directing their flight paths.

The thermal imaging camera documented their dusk flight in slow motion, capturing the bats' body heat profile against the cool rocks of the cave. The thermal images are an eerie, almost-Halloweenish sight; hundreds of bats fly into the West Texas skies, their quickly fluttering wings a blur flanking their round bodies.

The purpose of the experiment is to more accurately count the number of Mexican long-nosed bats ¯ which have been classified as endangered since 1988 in the cave. Previous methods have involved estimating the number based on density estimates an imprecise method, considering density estimates have ranged from 62 bats per square foot to 150 bats per square foot.

"We're comparing guesstimates with the more accurate thermal imaging technique," Ammerman said.

In addition to counting the bats on the video taken at the cave opening Ammerman must count by hand each bat on the video -- the group also entered the cave to measure the surface area occupied by the bats and extrapolate the population from previous density estimates. They compared this number with the number counted from the video.

One night, density estimates inside proved impossible the bats had moved to other parts of the cave, slinking through crevasses and fluttering through chambers unreachable by humans. The bats could not be seen, but they could be heard, their chatter echoing through the empty main chamber of the cave, emanating from above and below the researchers.

Bats moving to other parts of the cave could have proved problematic for previous researchers, Ammerman said.

"All these years the numbers weren't accurate because they couldn't be sure they were seeing all the bats," she said.

Ammerman has been studying the bats of Big Bend for 10 years. She first became interested in bats when, as an undergraduate student at Texas A&M, she took a field trip to the Guadalupe Mountains. She was amazed at the number of bat species there.

"I saw 10 species in one night and said, 'Wow,'" Ammerman said. "I didn't know there were so many in the sky."

Her bat research has taken her to other parts of the Big Bend region. When she is not participating in field studies, she focuses on genetic research of bats.