Re: Warm Blooded vs. Cold Blooded

[head@lust.isem.smu.edu (Jason Head)]

At 12:43 PM 9/12/95, Jeffrey Martz wrote:
>> Actually, I've heard nearly the opposite for the largest sauropods.  They
>> had such large mass and large volume to surface area ratios that they may
>> have had problems getting rid of any excess heat.  They were large enought
>> to pass through the diurnal cycles with little change to core body
>>temperature.
>> I believe that the term "bulk homeotherm" has been used to describe their
>> possible metabolism.  I've even seen speculation that the juveniles might
>> have had a more active metabolism which changed as they became adults.
>
>     What about the other side of that: what does an animal that massive do
>to cool down?  It might be a little hard for Brachiosaurus to find
>shade.  The Morrison was supposed to be pretty dry, so they couldn't have
>submnerged themselves in water all the time to cool off.  Evaporative
>coolong out thier mouths like crocodilians wouldn't have worked to well for
>animals with such big bodies and little heads.  Is that one possible reason
>sauropods had such little heads, so thier brains could cool off easier?
>     What sort of possible comperable cooling mechanisms are used by
>modern animals?
>
>J.Martz

        Here's a hypothesis that ties much of the sauropod neck discussions
to metabolism:  "warm" or "cold" blooded, sauropods probably generated lots
of heat (mass + digestion of plants).   Two possible solutions to dealing
w/ body could be (1) maximize the surface area/volume ratio, allowing for
faster rates of heat loss, and (2) keeping the most temperature sensitive
areas {brain & genitals} as far away from the heat source as possible.  The
long neck and tail of sauropods would serve quite well as regions of heat
loss, as they would have high S.A./V. ratios.  The neck would also move the
brain farther away from the body core heat, thus keeping it from being
fried.  As for the genitals, who knows?  Can't even hazard a guess as to
how temperature was regulated there.  Due to their size, it would seem
unlikely that sauropods would go for evaportaive cooling as a form of heat
regulation.   How sauropods could handle water regulation is baffling (EG
how is dessication prevented when you've got 15 ft. of trachea +
esophagus?).  Retaining water must have been a chore.  Just a thought.






Jason J. Head
V.P. graduate student
Dept. of Geological Sciences
Southern Methodist University
Dallas, Tx. 75275