How do bats use echolocation?

One may think that bats move around at night by using their eyes, this is wrong. Bats are unique mammals as they use sound to navigate, a mechanism known as echolocation. This remarkable high frequency system is used for foraging at night. Bats have eyes and can see just like most of the animals.

How do they do it?
Most bats create echolocation sounds by contracting their larynx (voice box), though other species produce the echoes by clicking their tongues. Using their mouth or nose,bats send out sound waves. Echoes are produced immediately when the sound waves hit an object. This echo bounces off the object and goes back to the bats’ ears. Since they are keen listeners and have good ears, they listen to the echo. An echo tells a bat several things that help them figure out:

• The precise location of the object
• The distance between the bat and the object
• How big the object is
• The shape of the object

How is it beneficial
Bats make calls whenever they fly and listen to the returning reverberations to build up a sonic map of their environs. The bat echolocate and can tell how far away an object is by listening to how long it takes the echoes to return to them. By emitting loud ultrasounds then varying to low frequencies, bats can distinguish their prey and other objects in air. It also helps them avoid collisions in the dark.

Characteristics of the sound waves
Echolocation calls are typically ultrasonic- vary from20 to 200 kHz in terms of frequency. Human hearing peaks at 20 kHz although we can still hear echolocation clicks from a variety of bats. The calls are generally characterized by frequency; their duration; and their intensity level in decibels (dB). Low frequency sound travels further than high sounds, so the bats use the high frequency calls to give more precise information about range, size, direction, position, and speed of a prey.

Morphological and physiological adaptations of bats
The brain cells and the ears of a bat are tuned to sound frequencies they emit and the resultant echoes. The receptor cells in the ear make them extremely sensitive, so, for them to listen to their echoes, the middle ear muscle contracts and separate some special bones in the ear to reduce the hearing sensitivity in about 6ms.