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Re: Theropod "migrations"



At 11:56 AM 4/26/99 -0500, Joe Daniel wrote:

>> That is the point of the comment "meat is meat": for most carnivores, it
>> doesn't matter if it feeds on the meat from a local animal or the meat of
>> animal from another part of the world.
>>
>
>This is not really true. Physiologically, sure. Behaviorally, no. Almost all
>predators have a "menu" of prey items that they will hunt. Animals that are not
>on that list are usually ignored. Sometimes if the predator is in extremis it
>may go after something that is not normally a prey item but this is the
>exception, not the rule. People are not safe from bears in the woods not
because
>the bear thinks of us as food, but as competitors. Tigers and lions don't
make a
>habit of attacking and eating people usually until they are old and unable to
>hunt their regular prey and even then it is rare. These are just as examples,
>not meant to be an exhaustive defense.

While it is true that many predator species have a certain range of
potential prey items (based often, but not exclusively, on size).
Furthermore, predators can establish themselves in new ecosystems where none
of their home "crop" is present quite easily if artificially introduced
there (as can, as previously noted, can at least some domesticated herbivores).

It would be interesting to find out to what extent the idea that "big
predators don't habitually hunt humans" is/was true in pre-village human
societies...

>So the point of this is that yes, predators do follow the ranges of their prey
>species. but, since they usually have more than one prey species, the
predators'
>ranges can be bigger than the prey species.

And again, sometimes *vastly* bigger, which was the point of this exchange.
_Panthera leo_'s old range included southern Europe, almost all of Africa,
and much of western Asia prior to the historic reduction in distribution.
How many bovid species have as big a range?

In any case, I hope we can try and shift the topic back towards dinosaurs
soon...

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661