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5 December 2013 11:26 am ,
Vol. 342 ,
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Bats Push the Limits of Sonar
19 October 1998 7:30 pm
Researchers have long known that most bats use the echoes from high-pitched sounds they emit to pinpoint moths and other objects. But a report in the 13 October Proceedings of the National Academy of Sciences shows their talents are even more finely tuned than scientists had suspected.
James Simmons, a neuroscientist at Brown University in Providence, Rhode Island, and his colleagues have demonstrated that the big brown insectivore, Eptesicus fuscus, can process overlapping echoes arriving just 2 millionths of a second apart and distinguish between objects that are just 0.3 millimeters apart. "That's something which seems intuitively impossible," comments Alan Grinnell, a neuroscientist at the University of California, Los Angeles. Grinnell was among those who were skeptical of earlier research by Simmons showing that bats could distinguish objects 1.7 mm apart. But the new evidence is "pretty good," he says.
Simmons's team revealed the bat's amazing discriminatory ability by putting a bat on a platform and electronically manipulating the echoes from the sounds it made so that they came back in different patterns. The creature was rewarded with a mealworm whenever it moved toward the variable echoes rather than to the side that produced regularly spaced echoes. The researchers tested the limits of the bat's discriminatory powers by playing the echoes back closer and closer together until the animal could no longer differentiate between them.
Simmons's group has re-created the bat's echo processing prowess in a computer that was able to chart its way through a virtual obstacle course almost as well as the bat itself. The U.S. Navy has given him a grant to see if he can apply bat sonar, which is three times as sharp as humanmade sonar, to defense technology.