[CINC] Cetacean spouts

[WhaleBear at cs.com]

One of the more impressive aspects of the viewing of cetaceans is the 
spout, which occurs during exhalation.  Cetaceans have a truly gargantuan 
inspiration and exhalation that in blue whales can lead to a spout of over 9 
meters.  Humans exchange, on the average, 10-15% of their total lung capacity with 
each breath.(this is called tidal volume)  Maximal voluntary minute 
ventilation (or the maximum amount of air that can be moved in and out in a minute) 
is in the range of 125-170 liters per minute.  Cetaceans exchange 90-95% of 
their total lung capacity with each breath (which has obvious adaptive 
value for an animal that undertakes breathhold diving).  A mature fin whale has 
an approximately 3000 liter tidal volume.  Measurements are difficult to 
come by, but expiration/inspiration has been measured at anywhere from 0.8 to 4 
seconds.  This calculates to, if only one breath is taken in a minute, a 
maximum of 6000 liters per minute.  

While in the lungs, air is warmed to the animal's core temperature.  It is 
then expelled under tremendous pressure.  The rapid expulsion and rapid 
cooling as it contacts atmospheric temperature leads to condensation, which 
accounts for the spout.  There are a multitude of observations that less 
forceful exhalations lead to a lesser (or no) spout, and there are similar 
observations that spouts tend to be less prominent in the tropics (but not always, 
as there are multiple variables involved), where the air is warmer.  A second 
contribution to the spout comes from any water on top of the blowhole as 
the air is expelled..

Lungs also have a certain amount of moisture from transudation of plasma 
elements through the alveolar (air cell) wall.  This liquid contains 
surfactants, which are phospholipids secreted by alveolar epithelial cells (Type II) 
and which function to lower alveolar surface tension and keep the alveoli 
from collapsing at end exhalation.

Additionally, I don't think I've ever necropsied a cetacean that is 
completely free of at least small foci of pneumonia, which involves at least the 
microscopic collection of what is essentially pus.  The alveolar moisture, the 
surfactants, and any purulence all contribute to giving "whale breath" its 
rather pungent odor.  In the 1950s, two prominent British reseachers, Fraser 
and Purves, postulated the additional presence of a nitrogen-absorbing foam 
in the airways of cetaceans; this hypothesis has not held up.  Ketone 
bodies are not involved, as they have a characteristic "sickly sweet" odor that 
I've never smelled in my almost 45 years of working with Cetacea.  Although 
"whale breath" can smell rather fishy, the smell does not come from anything 
in the GI tract.  Unlike humans, cetaceans have respiratory and digestive 
tracts that are completely separated (this is accomplished by extremely 
elongated laryngeal (arytenoid) cartilages).

So the spout is composed of condensed air that is undergoing expulsion at 
pressure and rapid temperatire change, surfactant-containing moisture from 
the alveoli, and any purulence from small or large foci of pneumonia.  It is 
the latter two that give the exhalation its odor.

I will post on cetaceans and earthquakes (an earlier question) in the next 
few days.

Cheers,

Chuck Rennie
Azul Research Co-op</HTML>