[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Dinosaur Extinction (Again)



Andrew Robinson writes;

>I understand the _argument_ that animals at the top of the food
>chain should go extinct preferentially over animals lower in the
>food chain because the animals at the top are fewer in number and
>more dependent on those below than vice versa.  However I ask
>again, is there any evidence in the fossil record (KT or
>otherwise) or in ecological studies to support this argument?

This may not be exactly what you had in mind.

Remember the problems we had with DDT in the Sixties?  As the
pesticide got into the water, it was absorbed by the smaller fish.
These fish were subsequently eaten by much larger fish, and eventually
ended up in the bellies of the Bald Eagle.  Because of the dynamics of
the food chain, the effect of DDT was magnified in the eagles; this
resulted in the well-known problems of thinned eggshells, and the
like.  If we hadn't banned the use of DDT in this country, and
performed a massive rescue campaign, the eagles would probably be
extinct by now.

This example supports the idea that ecological problems intensify as
one goes to higher and higher trophic levels, and that problems that
are minor inconvienences to the prey species can easily become lethal
to the predator.  If the food for a prey species becomes scarcer, the
prey will die off to a level that can supported by the supply.  If
this new prey population is below the level that can support a
predator, then the predators will die off accordingly (and go extinct,
in the most extreme examples).

Rob Meyerson
Orphan Vertebrate Paleontologist

***
"If you're falling from a cliff, you might as well try to fly."
        -J.S.