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Tiger Moths and Bats
Tiger Moth is an insect prey which is able to hear their echo-location calls , makes a click of its own and can trick them !
Bats are familiar with moths because of the kind of echo they get from their wings flapping normally. But some moths like the Tiger Moth are sharper than this. They can produce similar clicks of their own , which are too high for us to hear. They emit these clicks from a pair of organs called “tymbals”. They can sense echo location calls of the bats and when they sense a bat nearby , they start producing clicks very very quickly ( equivalent to 4500 clicks per second of the bat ‘s call ) or else stop flapping their wings altogether for some time and just drop from the air ! Bat calls do not find the wings of the moth steady enough so as to reflect back and tell the bat about their presence. Our poor bat is not able to make as many clicks in a second and is not able to sense the moth at all ! Also so many clicks from the moth confuse the bat and he can’t make sense of his own echo in the noise of so many clicks .
But wait , there is more to come . A kind of bats known as “whispering bats” , produce very soft calls ( low intensity ; intensity means loudness ) so that these moths are not able to sense them in the first place . They even stop producing the calls as they near the moths so that they are not detected. Tiger Moths and Whispering Bats always live in this tension of who is smarter than whom!
What if there is too much noise around ? Doesn’t the sound they produce and its echo get disturbed by the environmental sounds ?
Not at all ! Their outer ears can hear and pass just those frequencies to the brain that are produced in the bat vocal chords . So , they can hear just the sound they have themselves produced and other sounds get filtered out .
You know that a cement floor reflects your ball with more speed than a mud/sand floor .
Sometimes , a hard or a very nearby object returns their echo so strongly that they sense a danger that the echo may deafen them. What do they do to protect themselves ?
They reduce the loudness of the call in the middle of producing them , so as to be safe. Only a few kinds of bats can change this loudness in the middle of their “click”.
Also the bat ear canal contains a special organ which can help in closing the canal to reduce the entrance of loud sounds.
These capabilities protect them from loud and unnecessary sounds.
Let us see if we can solve a puzzle about their hearing !
Click : Bat Hearing Puzzle