Subject: Blue whale: food web, interactions/symbiosis

Phillip Colla (oceanlight@oceanlight.com)
Mon, 14 Jun 1999 08:42:40 -0700

>I am doing a project on the Blue Whale
>but i have a hard time finding its niche.  In this section,
>i have to include the species place withing the ecosystem, place
>in food web, interactions/symbiosis with other species.  I hope
>you can give me the answer soon.  Thank you.

I can give you my personal responses to your questions, which
should get your going in the right direction.  You can research
from that point on.

Blue whales occupy an interesting place in the "food web".  In
general, blue whales eat only tiny creatures (krill and similar
crustaceans).  Some people feel that they have evolved to filter
feed (with baleen) these small animals is because this is the
only type of animal that a) exists in great enough numbers to
sustain a blue whale population and b) can be caught by a blue
whale.  (Note: other baleen whales fit the same description).
An example of an animal that blue whales feed upon is:

  http://www.oceanlight.com/html/pelagic_tuna_crab.html

While these tuna crabs are NOT krill, they are known to be consumed
by blue whales and, like krill, they are tiny compared to a blue
whale.

Blue whales are, in general, eaten by creatures much smaller than
themselves.  Orca whales are known to at least occasionally kill
and partially devour blue whales.  But I believe that in most cases
blue whales die of disease, old age, or other "natural" cause, and
are then eaten by fishes, sharks, microscopic organisms and birds
as they decay.  (Note: on one occasion a fin whale, closely related
to the blue whale, was food for a pack of coyotes in Baja California,
after it washed ashore.  A similar demise has probably occured to a
blue whale at some time.)

Given that blue whales eat only tiny animals, and that blue whales
are usually eaten by tiny whales, it can be said that blue whales
are engaged in a very "short" food chain.

Your question about interactions is too broad for me to answer fully.  During
its lifetime, a blue whale probably encounters tens of thousands of
species of animals in the ocean, many of which it interacts with in
some way.  Blue whales have been seen in the company of many species
of dolphins and other whales, including orca.  I have personally seen
them near minke, fin and humpback whales, Risso's and bottlenose dolphins,
and probably some other animals I have forgotten.  I have also
photographed blue whales covered with some species of remora -- hundreds
of remora on a single blue whale:

   http://www.oceanlight.com/html/blue_whale_uw.html

as well as copepods trailing from a blue whale's fluke:

   http://www.oceanlight.com/assets/images/1909.jpg

Best regards,

Phillip Colla
Research Associate: http://www.hwrf.org
Photographer: http://www.oceanlight.com