Subject: Whale/dolphin/porpoise

Jennifer D. Philips (jphilips@soest.hawaii.edu)
Sun, 03 May 1998 12:04:44 -1000

>What is the definition of a whale?  How do the definitions of a dolphin
>and a porpoise differ from that of a whale?
>


That is a good question because there are not any universally accepted
definitions of either of these groups!  You would think there would be, but
centuries of common name useage has ended up with a system that tries to
make some sense, but has no sharp line or clear definitions.  What is
universally accepted is that there is a group of animals called the
Cetaceans, which includes all whales, dolphins, and porpoises.  Of the
Cetaceans, there are two accepted groups:  the Mysticetes, or the baleen
whales, and the Odontocetes, or the toothed whales.  Mysticetes include
humpbacks, blues, grays, minkes, seis, fins, bryde's, bowheads, rights, and
pygmy rights, and they have definite differences to their anatomy that make
them different that the rest.  They have baleen instead of teeth, they have
two external blowholes, and they are huge!  The problem comes in defining
the sub-groups of Odontocetes because some of these animals are called
whales, some are called dolphins, and some are called porpoises.  First,
'true' porpoises have some anatomical differences that sets them apart,
though the differences are minor:  they have spade-shaped teeth (whereas
most 'dolphins' have conical teeth), their skull is structured differently
so that they do not have a beak (aka rostrum), and they are all very small.
 They belong to a subgroup called the Phocoenidae.  The remaining members
of the 'toothed whale' group includes the large toothed whales such as the
huge sperm whale, the beluga, narwhal, all the many beaked whales, and the
members of the family Delphinidae.  The family Delphinidae, which is
commonly known as the 'dolphins', unfortunately ALSO has some members that
are commonly called 'whales', such as the killer whale, the melon headed
whale, etc.   Oh!  Its confusing!  So, after that long and probably
senseless explanation, all I can tell you is this:  Whales tend to be
bigger, porpoises smaller, dolphins in between, with much overlap across
the divisions.  Just understand that through the centuries, names for
animals that people interacted with in their environment differed across
regions even for the same animal.  Eventually common names emerged, and if
that meant the orca ended up being called the 'killer whale' instead of the
'killer dolphin', it was only because of chance.  As more genetical
analysis of family lineage become more common, we will most likely see that
what we though was a good way to classify the Cetaceans really was full of
errors.  

I hope this helps!  There is much room for research when it comes to
understanding this topic more...  good luck!

Aloha - 

Jen

      
__________________________________

Jennifer D. Philips		
jphilips@soest.hawaii.edu

Marine Mammal Research Program
HIMB, University of Hawaii at Manoa
PO Box 1106			
Kailua, HI  96734
voice:  (808) 247-5063
fax: (808) 247-5831
__________________________________