Post by L Roebuck on Feb 20, 2006 11:40:13 GMT -5
Common Sense: Bats 'See' Like Humans, Study Finds
By JON FOGG
Capital News Service
WASHINGTON - Cynthia Moss is tired of hearing old wives' tales -- especially the one about bats being blind. Now she has the data to dispel that myth.
In fact, bats "see" in much the same way as humans do -- but with their ears, according to a study published earlier this month by a University of Maryland, College Park researcher.
Using their ultrasonic sense of hearing, bats convert sounds they hear into behavior, Moss and doctoral student Kaushik Ghose found. Their results, published Feb. 8 in the Journal of Neuroscience, may offer insight into how other species translate sensory information into behavior.
"We found the bat, using its sonar 'beam,' looks ahead of where it flies, and that there is a relationship between how the bat moves and where the beam is directed," said Moss, a psychology professor and director of the university's Neuroscience and Cognitive Science graduate program.
Armed with a unique array of infrared cameras and high-powered microphones, Moss and Ghose studied how bats move in relation to the sounds they produce. Bats rely on a complex sonar system called echolocation.
Echolocation contrasts starkly with the way humans perceive their surroundings. A human walking down a city street can look side to side while walking in a straight line. When an object in a store window catches her eye, she stops and turns toward it.
Moss found that bats process echolocation into action in much the same way. Bats constantly emit high-frequency sounds inaudible to humans. Due to their frequency, these sounds reflect well off bugs and other small prey.
"When (the bat) gets an echo back, it uses features of the echo to tell how far away the bug is," said Moss, who has been studying bats for the past 20 years.
Moss and Ghose worked with the big brown bat, a species common to North America. "Big" is a misnomer in this case -- no bigger than a mouse, the bat weighs 15-20 grams and has a wingspan of nine to 10 inches.
Moss is the only bat researcher in the world whose lab has high-speed infrared cameras. For this study, Moss and Ghose outfitted the walls of the 20-foot-by-20-foot room with foam and 16 microphones about the width of a dime. The microphones, which use technology found in hearing aids, were designed by Ghose for his doctoral thesis.
After the pair set up the cameras and dimmed the lights to nearly pitch black, they had to get the bats to their targets. To solve this, Ghose fashioned a device triggered by beams of light scattered throughout the room. When the bat struck a beam, a mealworm tied on a string plunged from a trapdoor in the ceiling.
"Beep, beep, beep." Moss mimics the chirping sound the bat makes as it searches for prey. The chirps sound like an air raid siren to insects such as the praying mantis, which have evolved acute auditory systems to perceive the bat's ultrasonic shrieks. When the bat finds prey, the bat turns its head, swoops toward its target and chirps 100 times per second.
All of this takes place in a split-second -- much too fast to perceive with the naked eye, Moss said.
"To actually go from detecting the insect to the capture, our eyes just don't take it," said Moss, who has collected about 70 bats donated by local residents.
Ghose and Moss used the audio and video data to reconstruct a 3-D picture of the bat's movements and the location of its sonar beam. They found the bat's flight paths varied according to what it sensed using its echolocation system.
"This gives us a lot of insights we wouldn't be able to make using static images," Moss said.
The results are not limited to bats, Moss said.
"Sometimes when you study a specialized animal, you may learn generalizations that apply across species," she said.
Although this study was the culmination of four years of work, Moss and Ghose didn't pause long before moving to the next phase of their research. They're now looking at how the bat uses echolocation to track free-flying insects, such as the praying mantis.
Their next study will likely showcase how echolocation works like a "sixth sense." Moss offered a preview: "The bat predicts where the insect is going to go and looks ahead to go for the kill."
www.wtopnews.com/index.php?nid=25&sid=704379
By JON FOGG
Capital News Service
WASHINGTON - Cynthia Moss is tired of hearing old wives' tales -- especially the one about bats being blind. Now she has the data to dispel that myth.
In fact, bats "see" in much the same way as humans do -- but with their ears, according to a study published earlier this month by a University of Maryland, College Park researcher.
Using their ultrasonic sense of hearing, bats convert sounds they hear into behavior, Moss and doctoral student Kaushik Ghose found. Their results, published Feb. 8 in the Journal of Neuroscience, may offer insight into how other species translate sensory information into behavior.
"We found the bat, using its sonar 'beam,' looks ahead of where it flies, and that there is a relationship between how the bat moves and where the beam is directed," said Moss, a psychology professor and director of the university's Neuroscience and Cognitive Science graduate program.
Armed with a unique array of infrared cameras and high-powered microphones, Moss and Ghose studied how bats move in relation to the sounds they produce. Bats rely on a complex sonar system called echolocation.
Echolocation contrasts starkly with the way humans perceive their surroundings. A human walking down a city street can look side to side while walking in a straight line. When an object in a store window catches her eye, she stops and turns toward it.
Moss found that bats process echolocation into action in much the same way. Bats constantly emit high-frequency sounds inaudible to humans. Due to their frequency, these sounds reflect well off bugs and other small prey.
"When (the bat) gets an echo back, it uses features of the echo to tell how far away the bug is," said Moss, who has been studying bats for the past 20 years.
Moss and Ghose worked with the big brown bat, a species common to North America. "Big" is a misnomer in this case -- no bigger than a mouse, the bat weighs 15-20 grams and has a wingspan of nine to 10 inches.
Moss is the only bat researcher in the world whose lab has high-speed infrared cameras. For this study, Moss and Ghose outfitted the walls of the 20-foot-by-20-foot room with foam and 16 microphones about the width of a dime. The microphones, which use technology found in hearing aids, were designed by Ghose for his doctoral thesis.
After the pair set up the cameras and dimmed the lights to nearly pitch black, they had to get the bats to their targets. To solve this, Ghose fashioned a device triggered by beams of light scattered throughout the room. When the bat struck a beam, a mealworm tied on a string plunged from a trapdoor in the ceiling.
"Beep, beep, beep." Moss mimics the chirping sound the bat makes as it searches for prey. The chirps sound like an air raid siren to insects such as the praying mantis, which have evolved acute auditory systems to perceive the bat's ultrasonic shrieks. When the bat finds prey, the bat turns its head, swoops toward its target and chirps 100 times per second.
All of this takes place in a split-second -- much too fast to perceive with the naked eye, Moss said.
"To actually go from detecting the insect to the capture, our eyes just don't take it," said Moss, who has collected about 70 bats donated by local residents.
Ghose and Moss used the audio and video data to reconstruct a 3-D picture of the bat's movements and the location of its sonar beam. They found the bat's flight paths varied according to what it sensed using its echolocation system.
"This gives us a lot of insights we wouldn't be able to make using static images," Moss said.
The results are not limited to bats, Moss said.
"Sometimes when you study a specialized animal, you may learn generalizations that apply across species," she said.
Although this study was the culmination of four years of work, Moss and Ghose didn't pause long before moving to the next phase of their research. They're now looking at how the bat uses echolocation to track free-flying insects, such as the praying mantis.
Their next study will likely showcase how echolocation works like a "sixth sense." Moss offered a preview: "The bat predicts where the insect is going to go and looks ahead to go for the kill."
www.wtopnews.com/index.php?nid=25&sid=704379