Subject: Re: WHALES and diving

Daniel K. Odell (odell@pegasus.cc.ucf.edu)
Thu, 30 Jan 1997 21:00:34 -0500 (EST)

Actually, the correct term is 'diving'.  

Part I
I believe that 'sounding' is a term that comes from the whaling
litterature to describe a situation when a harpooned whale dove towards
the bottom. 'Sounding' is a nautical term that refers to to an activity in
which sailors determine how deep the water is - originally by dropping a
weighted, marked line.  Sam Clemens too his pseudonym 'Mark Twain' from
sounding activities on Mississippi river boats (quarter twain, half twain,
mark twain - terms used to describe different depths).  Today this is done
with electronic depth finders.

Part II (let me know if this is too complicated)

The simple answer: Whales are nearly neutrally bouyant (they float low in
the water)but they still have a slight positive bouyancy (blubber floats).
So, they have to exert some effort to dive.  Exactly how much effort is
not known.  As they descend the air in the lungs compresses and they
become less positively bouyant.  The closer they are to neutral bouyancy,
the less energy they need to expend to dive and surface.  Remember - this
is somewhat speculative since it hasn't been measured on free-ranging
whales.
So, what about whales like sperm whales that dive to great depths?  The
deeper they go, the more negatively bouyant (they sink) they become
(within some limits) and the faster they sink.  If they are negatively
bouyant, it takes more energy to swim to the surface.  Some scientists
speculate that the sperm whale can control the overall density of its body
by changing the oil in its huge spermaceti organ (in its forehead) between
liquid and solid states by heating or cooling it.  To dive, the sperm
whale may decrease blood flow to the spermaceti and change it from liquid
to solid (increasing its density and making it easier to dive).  To
surface, the sperm whale increases blood flow to the spermaceti organ and
changes the oil from solid to liquid (decreased density, making it the
whale more positively bouyant and easier to surface).
Remember, this is speculation and hasn't been proven.

Dan Odell
Sea World
  

On Thu, 30 Jan 1997, Lamarche,J. Louise wrote:

> I understand the proper term for a whale diving underwater is "sounding". 
>  When a whale sounds, how does it remain underwater?  Does it have to put 
> an effort into remaining underwater or is it more difficult for the 
> whale to stay at surface-level?
>