Wednesday, August 7, 2013

#42 Bats and Echolocation

We are all somewhat familiar with bats. 

But when I took some time to research them more seriously, I was astonished by their abilities.

Some bats can reach a top speed of 60 miles per hour. They come in all different sizes and live almost everywhere. There are 1,240 species of bat identified which is about 20% of all mammals classified.

The most astounding feature of bats is that they can fly around in total darkness very quickly without ever hitting another bat, some tree branch, or a wall. In darkness, they can locate a mosquito or moth that is flying, then track it down, catch it, and eat it.

Scientists have discovered that bats have the ability to do this by using sound and what they call “Echolocation”. It means that they make a loud noise and then by listening for the echoes that come back they figure out all the landscape and other animals around them.

There are tremendous challenges that had to be overcome in order for this system to work.

1. The sounds they make have to be loud enough to echo back to their ears and be detected. Imagine how much sound is going to echo off a flying mosquito? Not much. As you may remember from science class, sound energy dissipates at the rate of the square of the distance from the source. Bouncing off a mosquito back toward the bat, it is again going to be dissipating as the square of the new distance. Some bats make noise as loud as 140 decibels. Luckily for us the sound waves are above our ability to hear them (ultrasonic). We experience pain at 125 decibels.

2. Their eardrums must be extremely sensitive to detect mosquito echoes, but how do they not blow out their own eardrums when they make a 140 dB noise. It seems they have muscles in their ears that act to muffle or disconnect the tiny little “hammer” and “stirrup.”

3. The sound cannot be continuous or else the echo also would be continuous and interfere with interpreting the “data” and causing confusion. They make a “clicking” sound at a rate of about 10 per second when they are cruising but reaching up to a maximum of 200 per second when chasing a prey. The sounds may also be varied like a whistle or changed depending on the prey they are chasing and the like.

4. The sound of each individual bat has to be unique. Bats might roost in a colony of 1000’s. How come their noises don’t interfere and cause confusion and collisions with other bats all making loud noises at the same time?

5. The bat brain has to make calculations which take into account the Doppler Effect. Sound waves change pitch if the source of the noise is moving away (lower) or coming closer (higher). You may have experienced a train whistle sounds lower after it has passed you by. Imagine the complicated computer programming that would be necessary to duplicate what a tiny bat’s brain can do when chasing a moving mosquito.

6. Sound waves used must be the shorter ones. Longer sound waves would not be useful for accurately identifying tiny little objects that are just millimeters in length.

7. Sound waves travel faster in warmer air than in colder air so they will travel out and back faster on warmer days. Bat brains have to take this into account.

8. Different surfaces reflect sound differently. Water, wood, metal, plants all must be echoing back sound waves that are slightly distorted based on their surface properties.

9. The bat brain has to be really fast. Think how fast that mosquito is moving and in all different directions. The bat brain has to get the information from the ears and calculate how fast to move and in which direction quickly enough to catch the mosquito.

10. The bat brain has to interpret all objects in its environment. The bat has to figure out the difference between a swarm of mosquitoes and a tree branch or another bat instantly.

11. Bats also have to be able to recognize the opposite sex in the dark. Otherwise they can’t find a mate and reproduce. Infants have to be able to locate their own mothers in order to get milk.

There are other things going on as well, but that should be enough to amaze anyone.

When my kids were young, they used to play a game in the swimming pool called “Marco Polo”. One person closed his eyes and tried to catch others who would shout out “Marco”. That was hard enough because they would move after they shouted out. But suppose they didn’t have to shout and the person with his eyes closed made all the noises and tried to locate the others by the echoes he heard.

Darwinian evolution requires gradual incremental steps of development over many generations. Bat echolocation is far beyond the design capabilities of human beings although we have some understanding though developing sonar. Echolocation is a capability that needs to be working almost instantly because you will never catch a mosquito gradually. If a bat is flying in the dark and his echolocation is not working, he’ll soon crash into something and seriously injure himself.

Flying is a phenomenal ability for a mammal. Flying in the dark is many times more amazing. Natural Selection would quickly kill off the bats that tried flying in the dark without echolocation. Bats with good eyes flying in the daytime would surely outlive bats with bad eyesight or trying to fly at night. Echolocation has no chance to develop over many generations. The odds of flying and echolocation developing simultaneously over many generations are astronomical.

Speaking of odds, scientists have also found echolocation used by whales and dolphins. These species and bats are totally unrelated. To have both accidentally "evolve" this phenomenal ability is beyond common sense. There must have been a cosmic designer that created both species using a common pattern.

There must be God.

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