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In a message dated 4/14/01 4:52:44 PM Eastern Daylight Time,
<< This does lead me to a side question: How do birds (especially large
active flyers like geese) dump excess heat? If I remember correctly, birds
don't sweat... and ... I think you might have missed my point. I'm saying
that with the heat trapped on the body, while it would allow for a warm
body, it could also
lead to heat stroke if not used carefully. Hence one reason why I wouldnt'
mind knowing how birds cool down as it might lead to an explanation on how
an ectothermic animal could cool down with a insulatory covering (besides
just being small enough to do it). >>
If the problem with endothermy is the possibility of heat stroke, an
alternate question is what is needed to prevent it. Gregory Paul, I think in
personal correspondence, indicated that the body of a camel (a long neck
mammal) can get warmer, 113 degrees if I remember. Cooling the key parts is
the essential. If that is the brain, then how can this occur. Again, in a
warm, body temperature environment, the only means of cooling is evaporative,
changing the physical state of water to gas to absorbs heat. An evaporative
cooler (moist surfaces, near or around the brain or blood vessels leeding to
it placed in the air intake passageway) cooling the head/brain only, while
letting the rest of the body heat up (and aiding growth or digestion?), makes
sense to me. Is there evidence for this in an Ostrich? I have seen some
diagrams where measured bird temperatures are different in the head and body.
These were small birds.
I like to think that a large brained or short necked body needs a more
constant body temperature as there is little opportunity for cooling the
blood before it gets to the brain. I have no evidence to offer to support
this. Does this mean a long necked animal is more likely to become gigantic?
(or one with good head cooling features)
As an aside, If an endothermic sauropod in a hot environment uses
evaporative cooling and lives in a relatively dry climate, obtaining water
would be important, especially in a draught. I picture digging for water
with the toe claws. In fact, I think this is the primary reason that a
sauropods foot does not look like that of an elephant but has a few outcurved
claws. I have not seen this written on in any illustration and do not know
if it is a new theory. If any of you artists out there ever want to make my
day..... I would appreciate it.
Mark "can not draw" Shelly