Unpalatable prey resolves the paradox of enrichment

Enrichment is an increasingly serious trend in natural ecosystems. A theore tical model of a predator-prey system with a natural assumption of satiatio n in predation predicts that enrichment causes the populations to fluctuate to stochastic extinction. However, this 'paradox of enrichment' does not a lways occur in experimental and natural communities. Here we present a theo retical model that describes a novel mechanism for resolving the paradox in the case of a predator with optimal selective feeding. Specifically, a les s profitable but edible (thus 'unpalatable') prey species sharply reduces t he amplitude of population oscillations and firmly prevents the minimum abu ndances of species from falling below certain values. The presence of such an unpalatable prey thus guarantees the robustness of the system against en richment.