Re: Carnivore Energetics: Why Are Lions Not As Big As Elephants? .. and why aren't antelopes?

[john bois <jbois@verizon.net>]

I think there is gee-whiz (not to say Freudian) bias that makes us think
that big is better.  I like the way you reframe the question: what "forced"
sauropods to grow bigger.  Yes, there has to be enabling too--insects could
not be as big as sauropods--but enabling merely _allows_ natural selection,
it doesn't fuel natural selection.  So what was gained by becoming bigger?
Two hypotheses: The most popular isn a combintion of protection from
predators (presumably a benefit enjoyed by mammals but not utilized to the
extent of dinosaurs), and a winning strategy in outcompeting other
herbivores, i.e., food processing and fewer calories needed per gram body
weight (also a benefit for mammals).  The second hypothesis is that fairly
large animals cannot hide their nests easily and are therefore susceptible
to nest predation--this sets up an arms race between dinosaurian
pred/prey--this is a protection advantage not needed by mammals (who can
simply run away with baby inside).  In this view, large size in dinosaurs is
more of an evil necessity than an unalloyed gee whiz perk of superior
dinosaurian metabolic potential.

----- Original Message ----- 
From: "Botterweg, Rrp" <ronald.botterweg@capgemini.com>
To: "DML" <dinosaur@usc.edu>
Sent: Friday, January 19, 2007 6:25 AM
Subject: RE: Carnivore Energetics: Why Are Lions Not As Big As Elephants? ..
and why aren't antelopes?



True, that is why I said "why aren't MODERN mammalian herbivores larger,
etc.". What limits their size? Probably food availability, although there
may be physiological/anatomical limits as well (endothermy and energy
requirements, among others). Or the other side of the same question: what
enabled ánd forced sauropods to grow so big? I am sure the latter question
has been discussed a lot before, which leaves the first one (about size
limit of modern mammalian herbivores).


-----Oorspronkelijk bericht-----
Van: David Marjanovic [mailto:david.marjanovic@gmx.at]
Verzonden: do 18-1-2007 13:22
Aan: DML
Onderwerp: Re: Carnivore Energetics: Why Are Lions Not As Big As Elephants?
.. and why aren't antelopes?

> So the question becomes: why aren't modern mammalian herbivores larger
> than they are?

We have had *Paraceratherium*...





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