Thursday, October 25, 2012

HEARING: It's Not What You Think It Is – Part 2

Howdy folks. It’s that time again and this time we are on to part 2 of amazing animal hearing.

In my last blog we discussed how the dolphin uses the bone of its jaw to pick up high frequencies and how the elephant can communicate up to thirty miles away with just its feet. So what’s next?
 Big-eared Bat - bats use sonar to "hear"

Well, I suppose we can’t talk about hearing without mentioning the bat.  Of course most people know that bats use ultrasonic echolocation to find their way (and their prey) in the dark.  As the bat is soaring through the air with the greatest of ease, it’s making very high-pitched noises that shoot out into the world, bounce off stuff and come back to the bat, basically telling the bat what’s out there.

What bats use is basically the same as what we humans use in submarines.  You know; like in the movies when the guy (or gal) is in the sub and you hear that BING… BING… BING… in the background.  That …BING… is the sonar, with the BING bouncing off what is around the sub and being “heard” with devices within the sub.  A bat’s sonar is super sensitive and helps them build a three dimensional map of the world.

The bat’s echolocation is so sensitive it can tell the bat the texture of the stuff around it and even how fast the bat is moving.  Some bats have the added ability to change the shape of their ears to help them pick up different types of sounds depending on the situation--if it is looking for its next meal, or just a place to hang for the night.

So, even though the range of a bat’s hearing (how far away they can hear noises) is fairly average, they rank high on my list for the sheer amount of information they get just from their ears.

While we are on the subject of nocturnal creatures, we might as well take some time to talk about the animal that started us down this path in the first place, the Barn Owl.
A Barn Owl's ears are not where you think they are.

Tyto alba…aka The Common Barn Owl…is quite possibly the most beautiful animal on Earth (in my humble opinion anyway).  Barn Owls are one very well distributed species.  Like bats, Barn Owls can be found all over the world, with the exception of Antarctica.  Also, like the bat, their hearing is remarkable.

If you have ever had the pleasure of seeing a Barn Owl in person, you know their most distinguished feature is their facial disk.  This is the ring of stiff feathers that gives their face that heart-shaped look.  Do any of you have satellite television?  Well this facial disk acts just like your satellite antenna, except that the Barn Owl’s “antenna” gathers sound.  All that noise is directed to their receivers, or ear openings.  Not only that, but their ears have flaps of skin covering them, and these flaps are not in a straight line on their heads.  On a Barn Owl the right ear flap is higher and further back on the head than the left ear.  This means that sound reaches each ear at a slightly different time.  The Barn Owl uses this difference in time to pinpoint exactly where the sound is located.  So when a mouse goes scurrying across a field way late at night, our Barn Owl friend can tell exactly where that mouse is without ever seeing it.

So our journey through naturally occurring sound receiving apparati continues.  Now we know, and knowledge is half the battle.  Our struggle for knowledge is not over yet.  Come back soon and we will continue our exploration of one of the most amazing senses--hearing.
WBS's Straw-colored Fruit Bats-- Batty & Scar

The next time you visit the World Bird Sanctuary take a stroll through our Nature Center where you’ll find our two Straw-colored Fruit Bats, Batty and Scar, just “hanging out” in their enclosure.

Be sure to check out our blog for the next installment on the wonderful sense of hearing….same bat time, same bat channel next month.

Submitted by Neal Cowan, World Bird Sanctuary Naturalist

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