Saturday, July 21, 2012

Hearing...It's Not What You Think It Is

It’s that time again--time for another blog.  This time I wanted to share some interesting tidbits I discovered while researching hearing in the animal kingdom.
This Barn Owl's ears are not where you would expect them to be
Since spending so much time with a Barn Owl, I’ve become curious about the way they see the universe.  I already knew what little we go over in the time allowed during programs for the sanctuary (like how their ear flaps are situated so one is higher and further back on the side of the head than the other, or that their facial discs act like little satellite dishes and direct sound to their ears), but I was hungry for more.  And so, on to Google!

My first instinct was to search for the animal with the best ears and work my way down from there.  That, however, proved to be a mistake, as it turns out, an “ear” is not as static a concept as previously conceived.  There is more than one way to skin a cat, as it were.  Not all animals strictly use the ears on the sides of their heads for hearing, and many pick up vibrations through other parts of their bodies.

Sound is defined as a vibration through a medium.  In general, we here on Earth pick up the vibrations in the air around us.  Every time you have a conversation with a friend, attend a concert, or honk your horn at the jerk who just cut you off in traffic, your ears are picking up those vibrations in the air and sending them to our brains for interpretation.  Of course air is not the only thing that can carry vibrations, and in fact, air is actually one of the least reliable mediums in which to transmit sound.  So it should come as no surprise (though I have to admit it caught me off guard) that some of the best listeners in the animal world rely more on earth or water for transmission of vibrations.
 These African Elephants can hear with their feet!
Elephants come in towards the top of the list for the sheer range of hearing.  These giants of the African savannah can communicate for up to thirty miles over land.  You might not think this is too terribly unrealistic; they do have some impressive ears.  No, the impressive part is that they are not listening with their ears, but rather, with their feet.  Ultra-low frequencies are generated in the chest of the first elephant, perpetuated through the Earth, and received through the feet of other elephants.
This Bottlenose Dolphin "hears" through it's jaw
Dolphins find themselves on the other end of the spectrum.  They too have found a way to communicate over great distances, and like the elephant, have found the “ear” rather unnecessary.  Dolphins are able to pick up ultra-high frequencies through their jaws.

We have peered into Pandora’s Box.  Now we know.  Our search for the best auditors has only just begun, but Mother Nature is not going to give up her secrets without a fight.  We have found two animals occupying the extremes of the audible spectrum.  I’ve got some work to do.  Check out my next blog and we will continue our adventure.

Submitted by Neal Cowan, World Bird Sanctuary Naturalist

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