Subject: Baleen vs. Toothed whale blowholes

Jennifer D. Philips (jphilips@soest.hawaii.edu)
Sat, 09 May 1998 19:02:05 -1000

>Ms. Philips,  
>
>my name is Dave kelley and my question is this...
>
>	I understand that the respiratory system of the baleen whale is
>uncomplicated and that they have NO secondary air sacs which in turn
>means that they must take in a large volume of air on each breath. 
>However, this doesn't explain the reason that baleen whales have a
>double or two part blowhole.  
>Hence my question, why do baleen whales have two blowholes were the
>toothed whales only have one??
>
>	i thank you for your input...
>
>--Dave
>


Dave - 

Good question, though I'm not sure if the two are related!  Actually, the
question of blowholes is one that others have been curious about as well.
The lack of 'secondary air sacs' in the baleen whales, as you mentioned,
would not be related to the number of blow holes, though it could be
related to breathing and respiration otherwise.  It is true that whales
replace 80 - 90 % of the volumn of their lungs each time they take a
breath, but they also have proportionatly small lungs compared to land
mammals, which means they do not take in huge volumns of air to compensate
for the lack of 'secondary air sacs'.  Actually, they take in a moderate
volumn of air, considering their small lung size, and compensate for this
by having finer and more capillaries reaching their lungs, and an unusually
high concentration of myoglobin (the substance that holds oxygen in the
muscle tissue) so that even after their lungs collapse from pressure, their
muscles remain oxygenated.  On the topic of the number of blowholes, I am
not sure if there is a good theory on WHY baleen whales have two holes and
toothed whales have one.  Toothed whales actually do have two nasal
passages, but they are joined just below the blowhole to form only one
passage.  Baleen whales, like the toothed whales, have two nasal passages,
but the passages are not joined before exit.  However, I do not know why
this is.  It is thought that baleen whales evolved from the toothed whales,
and if they did, its just possible that the single blowhole in the toothed
whales evolved after the baleen whales split off.

Thanks for your question.  I hope this info helps.  (and I am sorry about
the delay in responding!  Your message was lost in my email-box, I only
found it again today!)

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
__________________________________