Components of the Bat's Echolocation System

Bats are truly remarkable animals. These flying mammals are incredible navigators that use a form of directional guidance called echolocation to find their way through night skies. With approximately 900 species of bats in existence, more than half use echolocation as their primary "GPS system" to seek out places to roost and food to hunt. Also known as biosonar, the ability to echolocate involves sound production, sound reception through the ear and the brain's interpretation of information.

  1. Echolocation: An Overview

    • Bats use their calls to create a "sonic map" of their surroundings.

      Bat Conservation International (BCI) says on its website that bats are not blind but just physiologically better adapted to use echolocation for navigational purposes. The Bat Conservation Trust's website explains that bats emit their call while flying, then listen for the echoes as they "build up a sonic map of their surroundings." This sonic map in turn provides valuable data concerning objects and their distance. BCI says that a bat's echolocation is so highly tuned it can detect obstacles as fine as a human hair.

    Sound Production

    • The way bats produce calls for echolocation is species-specific.

      In his 1998 article in "Scientific American" entitled "How Do Bats Echolocate and How Are They Adapted To This Activity?," Professor Alain Van Ryckegham says that a bat's ability to echolocate begins when it produces sound by either clicking its tongue or by making noises that start in the larynx and resonate through the nostrils. Since call production is species-specific, researchers can identify bats based on how they create their calls.

    The Ears

    • Van Ryckegham explains that bat calls are emitted as either constant frequencies, known as a "CF calls," or frequently modulated frequencies, known as "FM calls." These calls can be as low as 50 decibels or can reach as high as 120 decibels. Most bat calls are a combination of these two ultrasonic sounds. While most bat sounds are undetectable to the human ear, a bat can easily detect both emissions and returning echoes thanks to a complex series of muscle contractions in the ear.

    The Brain

    • Once the ears receive CF and FM calls the brain attempts to decipher the information. In their 1990 study "Specialized Subsystems for Processing Biologically Important Complex Sounds: Cross-correlation Analysis for Ranging in the Bat's Brain," researcher N. Suga and colleagues explain that the bat's brain processes the calls to create an environmental "map." This information allows bats to immediately recognize moving prey, open spaces, trees, obstacles or enclosed areas. BCI states that information gathered from echolocation may be passed from generation to generation.

    New Echolocation Research

    • New 3-D imaging helped biologists learn how bats produce sounds.

      In January 2010, "Science Daily" reported in its article "Bat Echolocation: 3-D Imaging Differentiates How Various Bats Generate Biosonar Signals," that 3-D scans created at The University of Western Ontario revealed distinct connections between a bat's larynx and the ear. This observation allowed researchers to understand how some bats use their larynx to produce sounds. According to lead biologist Brock Fenton, this discovery may alter the way bat fossil records are interpreted and encourage other biologists to use non-lethal methods to study other animals.