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Re: hibernation



>We've been discussing metabolism strategies (cold blooded, etc) and I thought
>there was a very interesting article in this months Discovery (dec96 p48)
>about some very different appraoches to this problem by some rather unknown
>species. I bring this up because it inforces the idea that there are many
>ways to skin this cat with a few good real and wild approaches. Try on the
>pygmy possum. It hibernates all winter at about 35 f and 1% of its awake
>metabolism. That compares to a bears 5 degree lowering and 33% of its awake
>matabolism. This guy really shuts down. Then there is a lemur (gray mouse
>lemur) that will drop 30F everyday to save calories. This ends up saving
>anout 40 to 50% on its daily diet. But they are not "cold blooded" because
>they can raise their internal temperature internally. So what were the
>dino's??? Probably a lot more variable than we might ever think.
>
>paul sparks

Yes, and golden mantle and 13-line ground squirrels have been documented
hibernating at body temps 1.5 to 3 degrees above freezing.  In laboratory
settings, it is possible to get extended body temperatures at 0.5deg C for
5 weeks with an ability to rewarm but it is unclear as to whether this
rewarming could occur in nature.  It certainly does in the lab, but the
stimulus was an external one.   Hummingbirds routinely drop their
metabolism into torpors as do many desert rodents.  There is no doubt in my
mind that dinosaurs had a variety of metabolic strategies.  Evidently,
modern ectotherms and endotherms do and these have evolutionary continuity
with their predecessors.

------------------------------------------------------------------------------
Richard Hengst
Biol. Sciences
Purdue Univ. / North Central
Westville, IN  46391
phone   219/785-5251
fax     219  785-5355
email   rhengst@purduenc.edu