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Re: The duck that ruled the world




On Sun, 28 May 2000, dbensen wrote:

> According to Jared Diamond (Germs, Guns, and Steel),  Edward O. Wilson (The
> Diversity of Life), and me (I didn't write a book, though), these birds
(and not
> just birds, virtually all megafauna) died off because they didn't
instinctively
> recognize humans as predators.  

Not just humans, surely.  Imagine prey thinking, upon being approached by
a tiger: "It's OK.  It's not a human."


There is a definite correlation between decreasing
> diversity of megafauna and human spread all around the world EXCEPT in Africa.

Also, there's more space to hide and exist in Africa.  Places where humans
are not.  There is no doubt that African fauna is predator-resistant due
to arms races with their predators.  I love the statistic that more
zoo-keepers are injured by zebras than tigers, lions, and bears.  But even
in Kansas buffalo thrived in presence of humans--what does that tell
you?


> Why?  Because humans evolved in Africa and the megafauna there
recognized us as
> predators.

You quoted Wilson. He definitely recognizes other animals apart from Man,
as having the effect you claim.

>  When humans moved to New Zealand, it wasn't just the large birds that
> suffered, it was EVERYTHING bigger then a cat.  Of course, some large birds
> survived (cassowaries and rheas) and with them, the ability to hide or defend
> themselves or breed may have been factors in their survival (after all,
N. America
> still has bison, deer, moose, and antelope), but these animals are the
exception.

I'm sorry, I'm lost.  It sounds like you're agreeing with me.  I am
arguing that animals that can conceal their nests are the ones that
survive.

> >>The next question: Why didn't
> any moa-sized species (the biggest moa, anyway) evolve (anywhere
> else but islands) during the entire Cenozoic, when there was no Man?<<
> 
> What about those giant flightless birds in South America (can't
remember what they
> were called) and that duck thing (the one that ruled the world)?

None as big as the largest moa, I believe.  Don't have figures at
hand.  My argument is that there is some maximum size for
concealment in modern biomes and that recent predators are constantly
keeping this trim.  In places where this trimming effect is absent (where
there are no mammals), nesting birds may grow big.  Why, in Africa, are
there no moa-sized birds?  There are plenty of very large mammals.  Why
not birds?  Not because big birds are unafraid of predators, surely.  But
because big birds are more easily spotted by predators (including humans).