Bats have fair night vision ? they are not blind, contrary to popular belief. But nature's best flying insect control primarily relies on sound to track and catch its prey. As they fly through the night, insect-hunting bats emit a pulsating stream of high-frequency squeaks and clicks through either their nose or mouth, depending on the species. When the sound waves strike an obstacle ? a tree limb or a mosquito ? they bounce back to the bat as echoes. The bat instantly processes the data and responds accordingly; swerving in the case of the branch, attacking in the case of the mosquito, and often doing both at the same time. This sonarlike system, called echolocation, is amazingly sophisticated and precise: An echolocating bat can detect objects as small as a human hair; it can use riverbanks, vegetation and other terrain features as acoustic landmarks; and it can determine not only a target's speed and direction, but also its size and surface texture. Researchers have found that bats can perceive an object's position and its 3-D form. The echo from a deciduous tree is different from the echo of an evergreen. The echo from an unappetizing hard-shelled beetle is different than that from a tender gnat.

As a bat searches for prey, it sends out a relatively low number of sound pulses; typically about 10 per second. When it detects prey and flies closer, it speeds up its clicks and shortens their duration. Just before the bat strikes, the pulses may be only a fraction of a millisecond long and may number as many as 200 per second; scientists call this a 'feeding buzz.'

Most bat sounds are well above the range of human hearing, so we're not aware of the volume of their screams. Bats that hunt in the open, such as the big brown bat, generate amazingly high-volume sound: 110 decibels measured at 4 inches from the bat's mouth ? the loudness of a smoke detector 4 inches from your ears. Bats that forage in closer quarters, such as a forest, emit low-intensity sound: about 60 decibels, or the level of normal human conversation.

To read more about these amazing creatures, check out Terry Krautwurst's story, 'Fantastic Bats,' in the October/November 2005 issue of Mother Earth News.