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predators and prey

There's a point that's been raised on this list that could use some
clarification.  Among extant large mammals, predators do not "control" prey
populations.  Lions, leopards, cheetahs and hyenas do not have a significant
impact on the vast herds in East Africa upon which they prey.  The idea that
large herbivores are held in check by predators is a fiction promoted by
armchair naturalists who, quite rightly, decry the mindless annihilation of
predators.  However, large predators are not population control specialists.
Large herbivore populations are not predator-limited, but resource-limited.
Deer in North America are so populous not because their predators have been
eliminated, because other than wolves they have not been eliminated, and the
number of deer killed by man certainly greatly exceeds that which would be
killed by wolves.  Rather, deer are so numerous because there is so much for
them to eat.  They are limited by their resources, not by  carnivores.
Large predators are generally marginal members of any ecosystem, and they
barely manage to scrape out a living.  Population-wise, the herbivores
barely notice.

Bill Altimari
Department of Herpetology
Arizona-Sonora Desert Museum