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RE: Herbivore protection



Predator satiation is not about keeping predators full for a day, or a
week.  It works fine even over a couple months.   

The key observation is that predators cannot adjust their population
numbers very quickly - say in less than a year.  

So, the total population of predators in an area depends on the leanest
time of year - i.e. a period of time longer than they can go without
eating.   This more or less sets the base number of predators.  

Wildebeest give birth the same time.  This saturates the base predator
population - not just on the first day, but over the course of the first
couple months.  A large proportion of juveniles are lost (50% or more in
the first year) as the local predator population eats itself full every
day.   After a few months the wildebeest young are old enough that they
become harder to catch.

The rate of food available to predators during the first few months
after the wildebeest give birth is enormous - it could easily support
many times the population density.

Dinosaurs had such a high fecundity rate that it is very likely that
they relied on predator satiation to some degree.  There is no reason to
have that many young otherwise.

Nathan

> -----Original Message-----
> From: John Bois [SMTP:jbois@umd5.umd.edu]
> Sent: Friday, May 30, 1997 2:16 PM
> To:   Stanley Friesen
> Cc:   brucet@mindspring.com; dinosaur@usc.edu
> Subject:      Re: Herbivore protection
> 
> 
> 
> On Thu, 29 May 1997, Stanley Friesen wrote:
> > This method (predator satiation) is a tried and true one, widespread
> in
> > living things today. It is used by sea turtles, grunion, sea gulls
> and
> > penguins(dinosaur descendents), many species of oak, and on and on.
> 
> These creatures are probably not analogous to dinosaurs in this
> respect.
> Sea turtle babies spend less than a day in the open air.  Before that
> they
> are hidden under much sand.  Lay and leave policies reduce predation.
> Maiasaurs probably tended their nest. 
> 
> Penguins usually take advantage of differential locational ability,
> i.e.,
> with their swimming ability and low-temperature tolerance they can
> group
> together in areas of low predator density, eg., hostile Antarctica,
> rugged
> off-shore islands etc.  Again, it hard to imagine any place that a
> dinosaur prey could reach that a dinosaur predator could not.
> Differential abilities no doubt existed but probably not on the
> gradients
> we see between, for example, penguins and many of the animals that
> would
> eat them.