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Re: Forty years of predation on Serengeti.



Although it is probably correct to assume that the
vulnerability  of juvenile large dinosaurs was greater
in a Mesozoic ecosystem (such as the Morrison
paleoecology of N. America)than those in a modern
mammalian ecosystem like the Serengeti, there
apparently were some similarities. In John R.
Forster's PALEOECOLOGICAL ANALYSIS OF THE VERTEBRATE
FAUNA OF THE MORRISON FORMATION (NMM, 2003, the study
concludes that in the Morrison there may have been a
lower abundance of vertebrate prey species in the
middle adult weight catagories (10-500 kg), due in
part from predation pressure by theropods in the
middle-large size ranges; this is similar to the
situation that Sinclair et al report in their
findings. Another is seasonal wet and dryness, which
would have limited megaherbivore forage and been a
strong impetus for migration.--Mark Hallett     
--- John Bois <jbois@umd5.umd.edu> wrote:
> Important paper with some relevance (perhaps) to
> dinosaurs: Sinclair,
> A.R.E., Simon Mduma and Justin S. Brashares 2003
> Patterns of predation in
> a diverse predator--prey system. _Nature_ Vol 425,
> pp.288-290.
> Concludes that smaller prey are target of diverse
> predators (many preying
> opportunistically) and are limited by predation. 
> Larger prey--at a
> threshold of around 150 kg (e.g., giraffes, rhinos,
> and elephants)--are
> somewhat immune and are instead limited by food
> availability.  Rhinos and
> elephants suffer almost no predation and even their
> juveniles are prey
> "only rarely".
> 
> This must be a huge contrast with dinosaurs--even
> very large
> dinosaurs--whose very small juveniles must have been
> fodder for diverse
> predators.  Because of this, Mesozoic ecosystems
> were entirely different;
> reproductive dynamics, pred/prey ratios, etc., etc.
> 
> Interesting that when, during time of heavy poaching
> predators were
> removed  from Serengeti system, numbers of small
> prey went up...but large
> animals remained limited by food supply!  How does
> this affect the vaunted
> advantage of large size: ability to process large
> quantities of food?
> I mean, who cares if one can process vast amounts of
> food, if vast amounts of food are unavailable?  One
> would have to argue
> there was more food in the Mesozoic.  Otherwise,
> like the elephants,
> predator-resistance seems its prime value.
> 
> Enough rumination.


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