Permanence in delayed ratio-dependent predator-prey models with monotonic functional responses

摘要

In this paper, sufficient conditions for permanence of the general delayed ratio-dependent predator-prey model [GRAPHICS] are obtained when functional response g is monotonic, where a(t), b(t), c(t), d(t) and e(t) are all positive periodic continuous functions with period omega > 0, tau is a positive constant. We find that the conditions on existence of a positive periodic solution imply the permanence of the above system. As applications, some examples are given. (c) 2006 Elsevier Ltd. All rights reserved.