Chaos to order: preliminary experiments with a population dynamics models of three trophic levels

Hastings and Powell [Ecology 72(3) (1991) 896] produced a new example of a chaotic population system in a simple tri-trophic food chain with Holling type II functional response. Toxin producing phytoplankton (TPP) reduces the grazing pressure of zooplankton. The present note modifies Hastings and Powell model by introducing an extra mortality term in zooplankton population. Our result suggests that chaotic behaviour less likely occurs in a real food chain dynamics.