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December 2006, Volume 4, Number 12
Bats in the News - Magnetic Bats

Scientists have added another item to “the impressive array” of sensory abilities bats use to get around in the dark, BBC News reports. Bats use the Earth’s magnetic field to keep their bearings as they fly across the night sky, the British radio network said.
 
The researchers, from the United States, Denmark and the United Kingdom, described their discovery in the journal Nature.
 
Over short ranges, and especially when hunting flying insects, bats use a biological sonar system called echolocation, bouncing sound waves from objects and analyzing the returning echo.
 
But, the scientists told BBC, echolocation doesn’t work over very long distances, and researchers have been unsure how bats navigate their way home after a night of hunting.
 
Homing pigeons, migratory birds, newts and turtles and some other animals use magnetic fields for orientation, the BBC said. To determine if that’s how the bats navigate, the researchers captured big brown bats in a barn near Princeton University in New Jersey.
 
Some of the bats were exposed at dusk to an artificial magnetic field that pointed either east or west relative to magnetic North, said reporter Rebecca Morelle. Other captured bats were left unexposed.
 
A tiny radio transmitter was attached to each bat, and they were taken 12 miles (20 kilometers) north of the roost and released. The team tracked them in a small aircraft.
 
“The control bats, relying on their natural magnetic field, headed south, directly towards home,” said Richard Holland, a visiting research fellow at Princeton and a member of the research team.
 
Bats exposed to the artificial fields flew in the wrong direction. “Those exposed to the east field flew east and those exposed to the west field flew west,” Holland told the BBC. “This indicates they were using an internal magnetic compass, calibrated at sunset.”
 
Some of the wayward bats, however, were able to reorient themselves and shift direction back toward the roost, suggesting that they realized their compass was faulty and were able to switch to some other, unknown, mechanism.
 
The network also consulted Bat Conservation International President Merlin Tuttle, who noted that, “Probably 90 percent of the world’s bats have barely been studied other than to give them their names. They rank as one of the least studied mammals.
 
“It does not surprise me that they use magnetic fields, although I am sure further research will disclose additional ways that they can navigate.”
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Robert Locke is BCI's Director of Publications.

 
All articles in this issue:
Bats in the News
Scientists have added another item to “the impressive array” of sensory abilities bats use to get around in the dark, BBC ...

Water for Wildlife
Drought and development are taking an increasing toll on natural water sources in North America’s arid western regions. Bats, ...

Stoats, Rats & Bats
New Zealand has only three native terrestrial mammals, and all three are bats. One, the greater short-tailed bat, hasn’t been ...



Unless otherwise noted, all images are copyright ©Merlin D. Tuttle and/or ©Bat Conservation International