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Re: predators and prey



Bill Altimari (walti@AZStarNet.com) writes:

> Among extant large mammals, predators do not "control" prey
> populations.

I think Bill's trying to swing the pendulum too far the other way.
For instance:

Author(s):      KREBS CJ; BOUTIN S; BOONSTRA R; SINCLAIR ARE; SMITH JNM; DALE 
                  MRT; MARTIN K; TURKINGTON R 
Title:          IMPACT OF FOOD AND PREDATION ON THE SNOWSHOE HARE CYCLE
                    
Source:         SCIENCE V0269 N5227 AUG 25 1995 pp. 1112-1115. 
Abstract:       Snowshoe hare populations in the boreal forests of North 
                America go through 10-year cycles. Supplemental food and 
                mammalian predator abundance were manipulated in a factorial
                design on 1-square-kilometer areas for 8 years in the Yukon.
                Two blocks of forest were fertilized to test for nutrient 
                effects. Predator exclosure doubled and food addition
                tripled hare density during the cyclic peak and decline. 
                Predator exclosure combined with food addition increased 
                density 11-fold. Added nutrients increased plant growth but 
                not hare density. Food and predation together had a more 
                than additive effect, which suggests that a three-trophic-
                level interaction generates hare cycles. 

I also seem to recall reading an article about population dynamics on
a particular island -- as I recall, the conclusion of the paper was
that the predators (wolves, I think) actually were the primary
determinant of the density of prey on the island.  Unfortunately I
couldn't find that reference...  Anybody else remember seeing it?  It
would have been within the last year or two most likely also in
_Science_. 

-- 
Mickey Rowe     (rowe@lepomis.psych.upenn.edu)