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Re: Herbivore protection
John Bois wrote:
> However, I argue that satiating
> predators in a colony among a predator population greater than that of
> bese-level doesn't make sense. The only decent arguement for this is the
> possibility that colonizers are better able to synchronize incubation.
> But at an incubation time of at least one month (does anyone argue this)
> how critical can timing be? And aren't there easier ways of doing this.
> I mean day length or something.
An interesting thought occurs to me after reading the above: the notion
of population cycles among certain r-type animals. The best-known
example of this is long-term cicada species, the famous "thirteen-year"
and "seventeen-year" cicadas that fill summer nights with auditory
pollution in many parts of the US. Somewhere, I don't recall where, I
ran across a very logical-sounding argument about how cicadas run in 7,
11, 13, and 17-year cycles because it's impossible for a cicada-predator
to adapt to such a long-term odd-number cycle, so no predator species
can evolve that specializes in cicadas and the cicadas have a better
chance of survival. Several species of small mammals, like snowshoe
hares, follow similar though shorter-term patterns.
I've often wondered how and why hadrosaurs maintained such high
reproductive levels, eighteen eggs or more per female per breeding
season. Either they had monstrously high infant mortality, monstrously
high adult mortality, or they weren't reproducing as much as we think
they were. Maybe hadrosaurs also ran on a three- or five-year cycle, so
that the reproductive rate and the long-term losses to predation more or
less balanced out.
> Finally, large clutch herbivores have not prevailed over time. Most
> large herbivorous animals of today have very small clutches.
Beware of "post hoc ergo propter hoc." Modern large herbivores are all
mammals. I can't think of any herbivorous mammal larger than a warthog
that produces more than one or two young per year. I wonder if a large
viviparous animal *could* produce more than one or two young per year.
K-strategy may be a less-than-optimal strategy that was forced on large
mammals by other aspects of their physiology.