Subject: Dolphin echolocation in captivity

Jen Philips (jphilips@soest.hawaii.edu)
Mon, 8 Dec 1997 13:39:25 -1000 (HST)

On Sun, 7 Dec 1997, Glen T. Fisher wrote:

> Dear Jen, 
> 	I read on line that you're doing reaserch with dolphins on their 
> echolocation capabities.  A group of activists sent me a letter asking
> for money to suport their cause, most of the letter was propaganda, but
> they did say that captive dolphins do not use echolocation because the
> acustics in the tanks of oceanariums creat echos that give the dolphins
> headaches.  That seemed to make sense, except when I thought about all
> the expeaments done with ehcolocation in those same tanks. Was what I
> heard about bad acustics just more propaganda? Or is there something
> different about show tanks that reaserch tanks have improved on?
> 	Tamara Fisher, Mtl. Quebec
> 

Tamara - 

Good question.  The answer is that dolphins are echolocators, whereever
they are living.  Even in captivity, dolphins continue to use their
echolocation capabilities to navigate their pool, to find objects in the
pool, and to find fish during feeds, to give just a few examples.
Typically, they continuously are producing echolocation signals, mixed
with other sounds such as whisles.  So, I would say that the letter was
wrong in this aspect.  What they don't understand, and what is really
important when considering the echolocation of dolphins, is that they can
and do adjust the intensity, or loudness, of their clicks as they need to.
This has been demonstrated in a number of experiments.  Most early
research with dolphin echolocation was indeed conducted in tanks.  Later,
research began to be conducted in open ocean pens, areas of open water
enclosed by open wire mesh.  It was found that the clicks dolphins were
producing in these open pens were louder.  This was partly due to the fact
that the open environment was itself much louder, due to other organisms
such as 'snapping shrimp' , and in order to perform the task necessary,
the dolphins adapted by making their own signals louder.  But it was also
likely due to the non-echoic nature of the pens as compared to the tanks.
So captive dolphins in tanks do continue echolocating, especially because
captive dolphins tend to be well taken care of, healthy animals, by virtue
of the care they are given by their keepers.  To adapt, they produce
quieter clicks.  

Hope this answers your questions! 

Aloha!  Jen Philips 
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Jennifer D. Philips				jphilips@soest.hawaii.edu

Marine Mammal Research Program - HIMB		(808) 236-4001
University of Hawaii, Manoa          
Honolulu, HI  96822	      "First, there were some amoebas. Deviant
			       amoebas adapted better to the environment,
			       thus becoming monkeys..."       - S.Adams
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