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Re: [Crocodiles Outlasting the Dinosaurs]



owner-dinosaur@usc.edu wrote:
> I just received an Earthwatch press release (citing an interview posted on
> the Nova web site), which notes that crocodiles can survive for long
> periods without eating, and suggests that might explain how they survived
> the KT extinction while the dinosaurs did not. I include the most relevant
> part below; you can check the whole interview at the Nova site.
> >
> >This interview with a former PI (and former Earthwatch staffer) Perran Ross 
> >on
> >the NOVA site might be of interest.  Also interviews crocodile PI Alison
> >Leslie on Nile crocs in South Africa..
> >
> >http://www.pbs.org/wgbh/nova/crocs/dinosaurs/
> >--
> >
> >
> >               Outlasting the Dinosaurs
> > An Interview with Dr. James Perran Ross
> >
> >
> > NOVA: And crocs can go for long periods without eating, right?
> >
> > Ross: Yes, they have an awesome capacity to deal with starvation. There
> >are numerous examples of animals not feeding for an entire year. They
> >become desperately thin, but they're still active and are perfectly
> >capable of feeding when food appears. So again, if the demise of the
> >dinosaurs was caused by an asteroid-winter type of scenario, then
> >crocodiles may well have been able to survive that.
> >
> >  There is another element. Crocodiles, for all their ability to get their
> >body temperature up when they have sunlight, do very well at low body
> >temperature in the darkness. All their systems continue to work adequately
> >well. There is some speculation that at least all the big dinosaurs were
> >probably homoiothermic, or warm-blooded. That is, they had developed the
> >circulatory and metabolic changes that enable one to maintain a body
> >temperature independently of the surrounding temperature.
> >
> > If this was so, they constantly had to pay the great cost of becoming
> >warm-blooded, which as we know ourselves is you have to eat all the time.
> >The energetic cost of maintaining your body temperature burns up more than
> >80 percent of what you eat. So dinosaurs that had made the commitment to
> >becoming warm-blooded had given up their capacity to not eat for long
> >periods. At the time that was a very effective trade-off, but when crunch
> >time came with the asteroid or whatever it was, it was the crocodiles that
> >still retained the primitive ability to continue to function at low body
> >temperature and therefore not require as much to eat.
============================================================================================================================================
It's a nice thought at first, but it wouldn't explain how mammals and birds 
that were true endotherms, survived the blast. 

I think it had more to do with the fact that all the survivors of the impact 
were marsh and shoreline residents. It seemed that anything fully terrestrial 
or fully aquatic felt an extinction of some sort. 

Of course thats not to say that the crocodylatarsia didn't suffer extinction 
(Deinosuchus I hardly knew ye.) All the living versions are but a mere fraction 
of their prior diversity.

I saw that NOVA special. It was the best crocodile documentary I've ever 
watched. Instead of focusing on that same nile croc taking down that same 
wildebeest, they focused, almost entirely, on crocodilian social life.

In my opinion seeing a _Caiman crocodilus_ lead her young from one water hole 
to another is much more interesting than the typical croc vs. wildebeest 
battles.

By the way, was I the only one who saw hot air coming out of that male 
alligator when it was calling for a mate. Methinks more work should be done on 
crocodilian physiology. Then again I might be jumping to conclusions.

Stick a fork in me, I'm done.

Archosaur J


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