Periodic Solutions in Periodic Delayed Gause-Type Predator-Prey Systems

Reasonable sucient conditions are obtained for the existence of positive periodic solutions in periodic delayed Gause-type predator-prey systems. Our approach involves the application of coincidence degree theorem and estimations of uniform upper bounds on solutions. This method imposes minimum restrictions on the form and magnitude of time delays. Indeed, our results are applicable to discrete, distributed and statedependent delays. Our results indicate that seasonal eects on population models often lead to synchronous solutions. In addition, we may conclude that when both seasonality and time delay are present, the seasonality is often the generating force for the often observed fluctuations in population densities, including the inherently oscillatory predator-prey dynamics.