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Re: Theory of Non-Avian Dino Extinction



At 11:48 PM 3/18/97 -0500, Matt Fraser wrote:
> If there are
>no extant birds that hibernate, and we accept the Dino-Avian close 
>relationship, then it seems somewhat unlikely, although certainly
>not impossible, for Dinos to have been hibernators.

This depends on *why* few birds hibernate.

Since the poorwill does hibernate, this rules out any intrinsic metabolic
or physiological factor.

As I read this thread a possible reason occurred to me: perhaps birds do
not generally hibernate because they have a better alternative, that is
unavailable to most other tetrapods.  I am talking about truly long range
migration by flying.  No purely terrestrial tetrapod migrates even a
quarter the distance of some long-ranging birds.

The longest confirmed terrestrial migrations I know of are the Serengeti
ungulates.  (There are difficulties regarding the reports of longer range
migrations by American bison, so I do not count those as confirmed - but
even if confirmed this would still be a small distance compared to the
birds that fly from north temperate zone to the tropics each year).

> Perhaps if we found out why birds don't, it might give us some
>insight into whether Dinos did.

If my guess is right, the answer is that dinosaurs, as non-flyers, would be
more prone to hibernation than birds.

>... If they could hibernate, it might save them a lot
>of energy. ...

Well, hibernation also means greater susceptibility to predation, and less
time spent reproducing or preparing to reproduce.


Also, I am not sure that the long north-south migration developed from
drift-related elongation of routes, since the predominant directions of
continental movement since the Jurassic have been east-west, not
north-south.   That is, the Amazon basin was never all that much closer to
new Jersey than it is now.

--------------
May the peace of God be with you                sarima@ix.netcom.com
                                                      swf@elsegundoca.ncr.com