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Re: cause of Gigantism in sauropods

"> Living terrestrial vertebrate predators rarely take prey even three
> times their own mass, much less 6-8 times.?

Might there be a problem with scaling laws here?

I don't know of any arthropods that take prey larger than themselves without 
the use of poisons.

When an animal is approaching a physical size limit (just to be able to pump 
blood, support its own, weight, and maintain mobility), I'd think its ability 
to defend itself does not increase proportionately with an increase in size.

in other words, when on the scale of sauropods, perhaps there were diminishing 
returns for an increase in size.

I don't think they needed the bite force of a T rex to deliver a death blow to 
a sauropod that let a theropod get too close to its neck.

--- On Mon, 2/7/11, Habib, Michael <MHabib@Chatham.edu> wrote:

> From: Habib, Michael <MHabib@Chatham.edu>
> Subject: Re: cause of Gigantism in sauropods
> To: "vultur-10@neo.tamu.edu" <vultur-10@neo.tamu.edu>
> Cc: "dinosaur" <dinosaur@usc.edu>
> Date: Monday, February 7, 2011, 10:11 AM
> On Feb 7, 2011, at 12:45 AM, <vultur-10@neo.tamu.edu>
> wrote:
> >>> 
> > 
> > So in the Morrison, the sauropod-theropod size gap
> seems smaller than the elephant-lion one. I see little
> reason to believe that Saurophaganax or A. maximus could not
> take down even Giraffatitan or Supersaurus.
> Neat comparison with the body mass estimates (thanks for
> punching the numbers!) but I'm not sure I quite agree with
> your conclusion.  It seems reasonable that something
> like Saurophaganax could take down something like
> Giraffatitan under very rare, extreme circumstances, just as
> living terrestrial macro-predators (or groups of them) very
> rarely kill much larger animals than themselves. 
> However, I see no reason to expect that such events were
> common, or even occurred with a high enough frequency for us
> to seriously consider them as major factors in our 
> reconstructions of Mesozoic ecology.  Living
> terrestrial vertebrate predators rarely take prey even three
> times th
> The elephant-lion size ratio probably does not represent
> the ratio at which predation is regular or ecologically
> important; at best it is a ratio at which a very rare
> predation event is still barely feasible - and that is for a
> specific guild of predators and herbivorous mammals. 
> The more important size ratio is the maximum predator:prey
> mass ratio among *regular* predation events.  Phrased
> as a question: Of those large terrestrial animals that are
> predated as adults with a high enough frequency for its
> impact on total population mortality to be measurable, how
> large are their smallest predators (or total mass of packs,
> if they are predated by groups)?
> I don't know exactly what the answer to that question is,
> but qualitative observation suggests that the size gap is
> pretty small.  The vast majority of predators, even
> large ones, mostly take prey smaller than themselves. 
> Even animals like water buffalo, which are a fraction of the
> size of elephants, are large enough as adults to be predated
> upon rarely (albeit more often than elephants).  
> Cheers,
> --Mike
> Michael Habib
> Assistant Professor of Biology
> Chatham University
> Woodland Road, Pittsburgh PA  15232
> Buhl Hall, Room 226A
> mhabib@chatham.edu
> (443) 280-0181