Positive periodic solutions for a neutral delay ratio-dependent predator–prey model with a Holling type II functional response

By using a continuation theorem based on coincidence degree theory, some new and interesting sufficient conditions are obtained for the existence of positive periodic solutions for a neutral delay ratio-dependent predator–prey model with the Holling type II functional response: {x′(t)=x(t)[a(t)−b(t)x(t−σ(t))−h(t)x′(t−σ(t))]−c(t)x(t)y(t)my(t)+x(t),y′(t)=y(t)[−d(t)+f(t)x(t−τ(t))my(t−τ(t))+x(t−τ(t))]. An example is presented to illustrate the feasibility of our main results.