Bats

Have been reading a slightly old book called The Blind Watchmaker by Richard Dawkins. Its yet another fabulous book by Dawkins. I wanted to share a section from it where Dawkins beautifully describes the wonderful sonar systems that bats use to navigate, technically called echolocation. In the second chapter Dawkins describes in details some of the sophistications of the sonar system of bats. It just blew my mind off. Take this:

• Due to the inverse square law property of the intensity of sound with respect to distance from source, the intensity of the echo falls of at the rate of the fourth power of the distance of the object from the bat. So, a very high pitched initial sound is needed. But, this could damage the bats ear drums. So, the bat has a mechanism by which it presses the ear drums with a muscle every time it sends out a sound and this prevents the ear drum from oscillating much and saves it.
• Echo from a farther object from an earlier made sound and the echo from a nearer object from a latter sound might come back at the same time. To differentiate between them, the bats continuously vary the carrier frequency. So, older echoes can be distinguished from earlier ones.
• In order to zero in on a moving target like a moth, bats exploit Doppler effect. Instead of simply exploiting the shift in pitch of the echoes coming from a moth, bats sometimes vary the pitch of their clicks so that the pitch of the echo from a rapidly flying moth remains fairly constant at around the maximum sensitivity region of their ears.
• Its an interesting question as to how in a cave full of bats of a similar species, how bats manage to retain their mental image of the cave given that they will hear the echoes of every bat. One suggestion is that bats do a sanity test. If an echo from another bat does not fit the mental image by not passing the sanity test, bats simply ignore the echo.

These are just some of the features of the echolocation system of bats. Of course, not all species of bats have all of these. But, the extraordinary skill of bats just blew me away. Apparently, besides bats, dolphins, whales and porpoises are some of the other animals that use echolocation. Check the following beautiful video.


Dawkins later on went to make a documentary based on the book. The book was primarily intended to debunk all the crazy ideas of creationists and advocates of intelligent design. You can find it here.