Re: cause of Gigantism in sauropods

["Habib, Michael" <MHabib@Chatham.edu>]

Very cool.  I've read about that previously.  I find it interesting that to 
some extent, if we considered felid predator:prey ratios to be an acceptable 
proxy for theropods (which I doubt, actually, more on that some other time), 
then the carnivora discussion speaks to some extent in favor of both models: 
many felids are capable of taking down prey a few times their mass, but very 
few do so regularly.  Bobcats apparently have more skill in this than other 
cats, or else they encounter wounded/injured animals more frequently.  I also 
note, again, that the inverse size effect seems to hold (though it's going out 
on a limb a bit): smaller felids, like bobcats, entertain greater maximum 
prey:predator size ratios than larger solitary cats.


On Feb 7, 2011, at 5:00 PM, Alaric Shapli wrote:

> I've heard that bobcats sometimes take down mule deer. A quick web search 
> turned up this:
> 
> http://www.carnivoraforum.com/index.cgi?board=video&action=display&thread=4601
> 
> 
> -----Original Message----- 
> From: Habib, Michael
> Sent: Monday, February 07, 2011 1:11 PM
> To: vultur-10@neo.tamu.edu
> Cc: dinosaur
> Subject: Re: cause of Gigantism in sauropods
> 
> 
> 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 their own mass, much less 6-8 times.
> 
> 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 
> 

Michael Habib
Assistant Professor of Biology
Chatham University
Woodland Road, Pittsburgh PA  15232
Buhl Hall, Room 226A
mhabib@chatham.edu
(443) 280-0181