Subject: Migration

Phil Clapham (phillip.clapham@noaa.gov)
Tue, 19 Jan 1999 08:03:58 -0500

Hi:

Actually, we really don't know for sure why whales migrate.  This is
pretty amazing since it's one of the most basic facts about most
species, but there's still no certainty about why they do it.

Most of the large baleen whales migrate in various ways, though in some
it's only part of the population that makes the migration.  Of the
whales that do, most of them go from cold, productive feeding areas in
high latitudes to warmer water in the tropics or subtropics where they
calve and sometimes mate.  Many migrations are very long - in humpback
whales and gray whales individuals may travel as much as 10,000 miles
roundtrip between feeding and breeding grounds!

Unlike in many other species of animals, whales don't migrate for food. 
In fact, the baleen whales generally fast when they're on migration,
sometimes for weeks (they live off large reserves of fat during this
time, which is in the winter months).  So why migrate at all?  The basic
theories relate to the question of whether it's energetically better to
travel to warm water and not feed than stay in cold water where you're
losing heat (and therefore you have to use more energy to stay warm) in
winter.  Another version is that females about to give birth migrate so
that their calves are born in warm water; the idea is that the calves
don't  have enough blubbner to keep them warm in cold water in winter. 
But this doesn't make much sense, because much smaller animals (like
porpoises) are found in cold water and do fine.

Other ideas - such as migration being an evolutionary holdover that's no
longer useful - don't make much sense (at least not to me!)  But for a
whale to go so far and not eat for weeks or even months, there
presumably must be SOME good reason to do it!

Phil Clapham

Scott Kingsolver wrote:
> 
> I'm in Middle school and I'm writing a paper on Whale migration, could
> you give me some reasons asto hy they migrate?Your information would
> help me out a lot.
> 
> ______________________________________________________
> Get Your Private, Free Email at http://www.hotmail.com

-- 



Phillip J. Clapham, Ph.D.
Northeast Fisheries Science Center
166 Water Street
Woods Hole, MA 02543

tel (508) 495-2316
fax (508) 495-2066
Internet: phillip.clapham@noaa.gov