Existence of positive periodic solutions for neutral delay Gause-type predator-prey system

By using a continuation theorem based on coincidence degree theory, we establish easily verifiable criteria for the existence of positive periodic solutions for neutral delay Gause-ype predator-prey system. {x'(t) = x(t)[r(t) - a(t)x(t - sigma(t)) - b(t)x'(t - sigma(t))] - phi(t, x(t))y(t - tau(1)(t)), y'(t) = y(t)[-d(t) + h(t, x(t - tau(2)(t)))]. In addition, our results are applicable to neutral delay predator-prey systems with different types of functional responses such as Holling-type II and Ivlev-type. (C) 2011 Elsevier Inc. All rights reserved.