Subject: Re: Whale anatomy, beaching, and social structure.

Rui Prieto (rprieto@dop.uac.pt)
Mon, 21 Sep 1998 19:44:00 -0000

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>Dear Scientist of the Week,
>        My name is Kristen Haskell.  I'm in tenth grade doing a report on
>whales for my biology course.  I would like to know more information about
the
>causes of whales beaching themselves.  I would also like some information
on
>their anatomy and their social structure such as the size of their groups
and
>leaders.  The report must be at least 20 pages long so please don't be
afraid
>to detailed in your answers.  If there are other websites you think I
should
>visit please include their addresses and other possible resources I could
use.
>If you know where I could get a grapic on a whale's anatomy I would
appreciate
>that as well.  Thank you for taking the time to answer my questions.
Please
>send all replies care of this e-mail address.
>
>Sincerely,
>
>Kristen Haskell
>

That's a big report you have on hands... I'll try to help as much as I can.

No one knows exactly why whales breach. There are several hypotheses to
explain that, but there is probably not a simple explanation. They may
breach to get rid of parasites and hitchhikers. Whales get   a lot of
external parasites, like some barnacles, whale-lice (which is a small crab
that feeds on whale skin) remoras (fishes that cling themselves with a kind
of suction cup and hitchhike this way) and more. It's possible that some of
these parasites cause some discomfort to the whales like itch and pain, and
they may try to get rid of some, by jumping into the air and falling in the
water with a big splash.
They may also breach as a mean of communication. The sound a breach makes
travels a long distance in the water, and may be used to send some kind of
message to other animals, like "danger!!" or "come closer".  But it's
possible that this be related to their social organization. A breach may be
used to show the strength of a given animal, or just to show that it is
annoyed or happy. Probably the true about breaching lies somewhere between
all these answers. As most animal behaviors, it is possible that the
breaches are used for several purposes, depending on the context. And maybe
that's why there are different kinds of breaches. To know more about some of
these and other behaviors, go to
http://www.aquaticadventures.com/sbbeh.html.

About the size and social structure of the groups, that varies with the
species and sometimes with the season of the year. Some cetaceans are highly
gregarious, which means that they live in groups. Some species of dolphins,
for instance, will sometimes form groups having thousands of animals. On the
other hand, other species are not gregarious spend most of the time in small
groups or even isolated. And even in the same species, there may be
differences between the size of the groups. Sperm whales, have a very
complex social organization, and the females and young animals form groups,
but big males are often found isolated, when out of the breeding season.
The social structure is also complicated and different between species,
areas, and seasons. A "classic" structure of a dolphin school when traveling
will have a leader on the head of the group and other adult males at the
borders. In the middle of the group will stay the females with the
youngsters. But even this formation can have several variances.

For the cetacean anatomy, its very difficult to describe it without the aid
of images, but I will touch the main characteristics. As you can see in any
photo of a whale or a dolphin, they are very different in external
appearance to the other mammals. That's because they had to adapt their
bodies to an aquatic existence. Therefore, they lost hairs to move
underwater with less effort. To substitute the hair, they evolved a thick
layer of insulating blubber. The hind limbs where lost and the external
sexual organs were concealed inside cavities in the body for the same
reason. The forelimbs acquired a paddle-like shape to help with steering and
the nasal passages migrated to the top of the head (the blowholes) to make
breathing easier. At the end of the tail a structure was developed to help
swimming (the flukes). But inside they are very similar to other mammals.
The kidneys look like they are made of grapes and are said to be lobulated.
This makes them more effective getting rid of the excess salt. The ribs are
more flexible and have more joints, to avoid breaking when under the great
pressures of deep diving. The toothed cetaceans have a fatty structure in
front of the skull, called melon, which is used in the transmission of high
frequency sounds related to the echolocation. And the baleen whales have
long, horny structures, called baleen, hanging from the mouth roof  that are
used to filter the water containing
the food.
For some images of cetaceans dissections, go to
http://edtech.clas.pdx.edu/CAB97/~miller ; http://www.alaska.net/~pratt/ ;
http://whale.wheelock.edu/whalenet-stuff/slide_shows/ .

There are a lot of links and information in Whale Net that you can use to
your report. Try the Whale Net Archives, where you will find answers to
questions made from other people, or go to Whale Net Search engine
(http://whale.wheelock.edu:2834/cgi-bin/search.cgi/x-catalog:/whale.wheelock
.edu:2834/WhaleNet) and type key words like "breaching" and "behavior". You
will find the results amusing. The link page
(http://whale.wheelock.edu/whalenet-stuff/interwhale.html) have suggestions
to other places in the Internet where you will find more info about whales
and the bibliographies page
(http://whale.wheelock.edu/whalenet-stuff/ed_resources.html#biblio) have
suggestion on books to read and other places to learn more about Cetaceans.
And look for more resouces in the WhaleNet. This place is wonderfull to
learn and explore...

Have a good work,

Rui   :-+);

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