Abstract:
The positive solutions are investigated for a predatorprey model with general functional response. A priori estimation to the positive solutions of the model is given, and the fixed point index theory is utilized for discussing the existence of the positive solutions. By calculating degW′(I-F,D),indexW′(F,(0,0)) and indexW′(F,(θ,0)), we obtain that predator and prey coexist if and only if predator′s death rate c is controlled between the lower limit -d2λ0 and the upper limit -λ1(d2,-efv(θ,0)), and prey′s inherent growth rate is lager than d1λ0.