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Re: Sauropod eating habits



> Date: Wed, 24 Dec 2003 16:35:06 +1100
> From: "Phil Hore" <comicsandheroes@hotmail.com>
> 
> One thing I've noticed throughout this thread is how many people
> claim a sauropod would strip the land bare. Do we have any honest
> estimates of sauropod consumption? They're are not mammals after all
> and would possibly (this is a guess) eat about as much as an
> elephant. Elepants are very harsh on the landscape, and can actualy
> terra-form it, but they do live in a very harsh envirmoment.

I hope there are more recent papers, and that others will supply the
refs, but the only one I know of that makes a serious attempt at
estimating sauropod feeding rates , Weaver 1989, is fourteen years
old.  The abstract follows:

        One testable hypothesis of the theory that dinosaurs were
        endothermic is the observation that sauropod dinosaurs were
        too large, their heads too small, and their food was too
        indigestible for them to be warm-blooded.  Calculations on the
        daily calorie requirements of the sauropod _Brachiosaurus_,
        adjusted for digestibility and the energetic cost of
        ``free-living,'' were compared with the caloric density of
        Late Jurassic food plants and the feeding rates of an elephant
        and a giraffe.  Using _Brachiosaurus_ as a model I concluded
        that endothermy in large sauropod (greater than 55 metric
        tons) was impossible.  Depending on assumptions about feeding
        rates and the cost of free-living, endothermy in smaller
        sauropods ranges from improbable to impossible.

The main problem with this paper is that its ideas about how quickly
_Brachiosaurus_ could get food into itself seems wrong-headed: "I
believe the giraffe is a more appropriate model.  The head of
_Brachiosaurus_ and of a giraffe are about the same size."  This is
not true -- see, for example Figure 6 on p193 of Paul 1998.  This
shows the both skulls (and some others) in right lateral view, showing
not only that the _Brachiosaurus_ head is twice as big, but that it's
nearly all food-gathering machinery, with a cropping width of about
0.5 as compared with the giraffe's 10cm or so.

No only that, of course, but the giraffe has to waste time chewing its
food -- not once, but twice, since it's a ruminant -- not something
that a _Brachiosaurus_ has to bother with.  So all in all it doesn't
seem unreasonable to assume that, contra Weaver, a _Brachiosaurus_
could ingest material at five to ten times the rate of a giraffe.

(BTW., one could in any case argue that, in the light of the growth
rates deduced from long-bone histology in Sander 2000, the notion of
ectothermic sauropods is less compelling than it's ever been.)

References.

Paul, G. S.  1998.  Terramegathermy and Cope's Rule in the land of
titans. Modern Geology 23:179-217.

Sander, P. Martin.  2000.  Longbone histology of the Tendaguru
sauropods: implications for growth and biology.  Paleobiology, 26(3),
2000, pp. 466-488.

Weaver, Jan.  1989.  The Improbable Endotherm - The
Energetics of Brachiosaurus.  Paleobiology 9(2):173-182.

Since it's Christmas, I guess I can supply copies of the Weaver and
Paul papers to those who wish to know more.  Let me know OFF-LIST if
you'd like to see any of these.

 _/|_    _______________________________________________________________
/o ) \/  Mike Taylor  <mike@indexdata.com>  http://www.miketaylor.org.uk
)_v__/\  "Yeah, and if a frog had wings, he wouldn't bump his ass
         when he hopped" -- Cassanda, _Wayne's World_.

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