physiology of sperm whale dive

From: Greg Early (gearly@neaq.org)
Date: Tue Feb 06 2001 - 15:56:00 EST


John,

No models that I am aware of.

Years ago the navy trained a dolphin to activate a camera at depth to get a
picture of what he looked like under pressure. The dolphin ("Tuffy") took
a bunch of pictures of himself, looking a bit "tucked up" (sort of like he
was sucking in his stomach) but otherwise not all that altered at depth.
Since then, the feeling has generally been that marine mammals are
anatomically efficient at compressing and collapsing air spaces such that
aft4er about three or four atmospheres (only about 120 feet or so) they are
no longer significantly compressed. This makes sense when you consider
that volume is directly related to pressure and the greatest incremental
changes occur as one descend through shallow water (one atmosphere is 33
feet of sea water, so half of all compression will occur there). Research
on gas exchange on smaller animals (seals) seems to bear this out, although
it is anybodies guess if this is the same for sperm whales.

There has been some interesting speculation about the effects of
temperature and pressure on the "melon" (the large fatty "forehead") of
sperm whales. Some have speculated that changes in density due to either
temperature or pressure change the density of fats in this organ and allow
the whale to control it buoyancy during dives. Again, no one has been able
to test such a notion, so far, but it tends to fit with some of the
peculiar properties of the fats in this tissue.

As for squids, scientists feel that quite a bit of the marine mammal
biomass is dependant on squids of one size or another. In the case of
sperm whales, most likely one type of very large squid. In general,
however the food resources are usually felt to be very patchy, with areas
of abundance surrounded by areas of low productivity. This is one of the
general selective pressures that has often been cited for why whales
developed large size and migratory lifestyles...

There have been some good general books about the deep ocean (and sperm
whales) written by Richard Ellis. That might be a good place to start.

ge

ps

not to slight sperm whales, but elephant seals have been known to dive to
2000 meters as well and hooded seals dive to over 1000 meters....

At 01:37 PM 2/1/01 -0800, you wrote:
>Hi. I'm curious about what happens to the shape of a whale's body as
>it dives. Sperm whales dive as deep as 2000 m -- has anyone created
>a model, image, or movie showing what a sperm whale looks like at
>that depth?
>
>How does the change in shape affect echolocation? How does the
>bouyant force change as the whale dives?
>
>Is there a paper or book I can read which gives information about the
>food chain at such depths? I've read that sperm whales eat squid;
>what do the squid eat? There must be a lot of food in the deep
>ocean, and I wonder what the energy source is.
>
>Thanks for taking the time to address my questions!
>
>John
>--
>John Gilbert
>Genesis Test and Training Engineer
>Jet Propulsion Laboratory
>voice: 818-393-3004 fax: 818-354-1392
>
>They all laughed when I said I wanted to be a comedian. Well,
>they're not laughing now!
>



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