Hi Nick,


Last things first.  Yes people can use echolocation without the aid of
things like sonar instruments.  Echolocation can be either passive or
active.  With passive echolocation, you would determine something about
your surroundings just by the ambient noise.  For example, if you walked
into your house in the dark, you could probably tell when you walked from
the hallway into a large room, by the way your footsteps sounded.  In
active sonar, specialized sounds are produced and received, and provide a
higher quality of information.  In people, the best example is the way
the blind use a cane.  The canes are used for both "feeling" , but can
also be tapped on the ground to send information to the blind person
about their surroundings.


In the case of dolphins it is a bit strange.  Most of the dolphins that
have well developed sonar, have lost the ability to move their heads a
great deal. Their neck vertebrae are small and fused together. (there are
exceptions...beluga for example, have very good sonar and very flexible
necks).  However, if you watch a dolphin using sonar, you often see them
move their head around while they are making sonar sounds.  I suspect it
is a little like squinting your eyes in order to see something better in
people.  


Dolphins do, in fact use their ears to hear, but their ears are highly
modified.  In addition, they probably do not use their external ears
(that little hole in our ear that the sound goes in), in the same way
that we do.  Dolphins probably receive sounds through their lower jaws,
rather than their external ears.


You can check WhaleNet (particularly the ASK archives) for some of this 
or...


http://nmml.afsc.noaa.gov/education/cetaceans/cetaceaechol.htm

http://207.87.7.160/killer_whale/commkw.html


good luck, sounds like an interesting project.


ge



At 04:40 AM 1/22/01 -0500, you wrote: 

>>>>

<excerpt>Hi. I'm Nick. I am a 5th grqder doing a science  project. I am
looking to see if humans have a sense of echolacation. I got the  idea
from bats and dolphins.
<fontfamily><param>Arial</param><color><param>0606,0000,0000</param> 
Here is the question : when dolphins or other  whales use echolocation,
<underline>do they move their heads back and forth </underline>to help 
them  better sense the direction of the sound returning? Or do they just 
swim straight into the sound. I guess the change in position related to
the  returning sound might help them, but I CAN'T FIND THIS INFORMATION.
Also, what  sense organ do they use?Is it like our ears?  Also, do you
know if anyone knows if humans have  the semse of echolocation?  Thanks. 

</color></fontfamily></excerpt><fontfamily><param>Arial</param><color><param>0606,0000,0000</param>


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