The Fast Bat Gets the Worm

National Wildlife, Feb-March, 1999

Bats' sonar abilities are three times sharper than scientists had thought. That's what neuroscientist James Simmons at Brown University School of Medicine found recently when he recorded sonar sounds from big brown bats and then played back the echoes to the creatures in various patterns. Bats normally send out their own high-frequency sound waves and then "see" by interpreting the echoes, which vary according to the size of the object reflecting the waves. The creatures are able both to measure distance to an object and discern a three-dimensional image of it.

In Simmons' lab, the flying mammals, which were collected from New England homes, quickly learned that there was a reward in the form of a mealworm (left) when they approached the sources of variable echoes rather than evenly spaced ones.

That allowed the researchers to determine that the bats were able to perceive and process separate but overlapping echoes arriving as little as two microseconds (a mere two millionths of a second) apart. "Using the same sounds as the bat, the best man-made sonar equipment can only process echo delays arriving 5 to 10 microseconds apart," points out Simmons.