For more than a decade, Bat Conservation International Science Officer Barbara French has shared her Austin, Texas-area home with a colony of up to 75 Mexican free-tailed bats. Her collection is the largest captive insectivorous bat colony in the United States and is proving to be an incredible resource for bat researchers, reports National Geographic News.
Watching and listening to those bats, day and night, the online news service says, has allowed French to decode a basic repertoire of bat calls and decipher the social context in which they are used.
Her role as bat medic arose serendipitously after she found an injured bat near Austin's Congress Avenue Bridge, home to the world's largest urban colony of bats. After inquiring which animal shelter could help the creature, she discovered few people cared for bats, so she began treating them herself, National Geographic News says.
The National Geographic Channel's Bijal P. Trivedi talked to Biologist Gary McCracken of the University of Tennessee and one of BCI's Scientific Advisors. “Barbara is exceptional,” he said. “She is at the extreme end of enthusiast and has done things with bats that no one can do. She has taken bats splattered on trucks, nursed them back to health and performed C-sections and amputations on these animals.”
As her colony grew larger, the online news service said, French gave the bats their own turf. The “Bat Barn” is a small red shed beside French's house. Inside are wooden cages carpeted with specially made denim fabric pouches, which simulate the cozy roosting crevices inside caves that bats prefer.
The consequence of this intensive care, National Geographic News says, is that French has handled individual bats for years and learned a portion of their language that falls within the range of human hearing. “The territorial calls produced by the males are short buzzes, trills, chirps and combinations of clicks,” French told Trivedi.
To date she has identified about 24 distinct calls and the social situations in which they are used within her bat colony.
French has teamed up with George Pollak, a neurophysiologist at the University of Texas at Austin, who is using sophisticated equipment to record the bat calls, much of which are too high-pitched for humans to hear, National Geographic reports.
The bat sounds are complicated, almost like birdsong, Pollak said. French believes the animals are using sounds with syntax. To test the hypothesis, French, Pollak and one of his graduate students are cataloging all the calls and analyzing the acoustic structure of each to study how sounds are manipulated to produce different meanings.
During mating season, for example, males produce a “territorial announcement buzz” to woo females, the news service says. The same sound, albeit at a different intensity and pace, seems to be used to ward off competing males. “It's the difference between saying something sweetly and screaming those same words. They could have very different meanings,” said French.
