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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.
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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