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Re: copes law

At 04:53 PM 1/25/97 -0500, you wrote:
>       Seems to me that at least part of this might have something to do
>with the nature of mass extinction. Big animals were hit especially hard
>by the KT event. With all those niches open for big things, of course
>mammal lineages would tend to increase in size.  Whether a similar pattern
>is observed in other extinctions or local extinctions, I don't know. It
>might just be that big animals are more vulnerable to extinction. 

Al other things being equal, a larger species will generally be more
vulnerable to habitat loss or change than a smaller species because it
requires more resources (space, food) or sometimes more difficult ones to
come by (eg suitable shelter).   Top predators are particularly vulnerable
to decreases in their prey species (which are often larger too) and may be
the first to go.  The first species lost when habitat is reduced are
usually the larger ones.

Of course all things are NOT always equal - a large habitat generalist may
be better able to cope with change (the cause of all extinctions) than a
small specialist, for example, or certain taxa may be less able to cope
with (say)  temperature shifts regardless of size than others - so this
general observation may be difficult, if not impossible, to apply to the
fossil record.
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court                 
Mississauga, Ontario, Canada L5L 3W2          Internet: ornstn@inforamp.net