Eavesdropping on Bat Chat
As the colony grew larger French gave the bats their own turf. The "Bat Barn" is a tiny red shed that sits beside French's house, in the countryside just southeast of Austin. Inside are wooden cages carpeted with specially made denim fabric pouches which simulate the cozy roosting crevices inside caves that bats prefer.
French even installed a baby monitor in the bat barn so that she could listen to the bats chat as she fell asleep—sounds of a mother calling her baby, territorial and courtship calls.
The consequence of this intensive care is that French has handled individual bats for years and learned a portion of their diverse language which falls within the range of human hearing. "The territorial calls produced by the males are short buzzes, trills, chirps and combinations of clicks," said French as she demonstrated.
To date she has identified about 24 distinct calls and the social situations in which they are used within her bat colony.
Captivity provides a rare opportunity for detailed recordings of vocalizations at the roost, which would not be possible in a wild situation—with thousands of animals, unknown social relationships, and a cacophony of calls and bat-to-bat conversations.
"Barbara has animals that she knows intimately," said McCracken. "She knows who's who, who's the mother of whom, who are the siblings, and the history of past matings. She knows the social history of the colony and has the background to interpret the calls."
Same Words, Different Meaning?
French, with her keen powers of observation, 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. The recording equipment is particularly important because only parts of the calls are audible, or sonic; the rest is ultrasonic.
The bat sounds are complicated, almost like birdsong, said Pollak. 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 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.
The Jane Goodall of the Bat World
Bats are incredibly social animals. They live in huge colonies and talk with one another. Pollak is interested in how the brain processes and interprets these communications. Bats are particularly good research subjects for him because they are mammals and their auditory system is enlarged, due to the importance these creatures place on hearing.
"I'm stunned when I watch her [French] in action," said Pollak. "She has knowledge of these bats, and empathy for these creatures like Jane Goodall has for her chimps. These animals are her family—she knows their faces, temperament, age, genealogy, and she recognizes their sounds."
Pollak is just one of the scientists with whom French is collaborating. Her home has become a veritable research hub with graduate students and scientists visiting and working in her barn.
"Barbara has all the talent with the animals, and she teams up with the scientists who have experience and the equipment," said Fenton, co-author of Bats. "There is always a place in science for people like her."
Be the Creature, Sundays at 8 p.m. ET/PT in the United States, is available only on the National Geographic Channel. Click here to learn more about it.
|
SOURCES AND RELATED WEB SITES
|
