Hopf cyclicity and global dynamics for a predator-prey system of Leslie type with simplified Holling type IV functional response.

This paper is concerned with a predator-prey model of Leslie type with simplified Holling type IV functional response, provided that it has either a unique non-degenerate positive equilibrium or three distinct positive equilibria. The type and stability of each equilibrium, Hopf cyclicity of each weak focus, and the number and distribution of limit cycles in the first quadrant are studied. It is shown that every equilibrium cannot be a center. If system has a unique positive equilibrium which is a weak focus, then its order is at most $2$ and it has Hopf cyclicity $2$. Moreover, some sufficient conditions for the global stability of the unique equilibrium are established by applying Dulac's criterion and constructing the Liapunov function. If system has three distinct positive equilibria, then one of them is a saddle and the others are both anti-saddles. For two anti-saddles, we prove that the Hopf cyclicity for positive equilibrium with smaller abscissa (resp. bigger abscissa) is $2$ (resp. $1$). Furthermore, if both anti-saddle positive equilibria are weak foci, then they are unstable multiple foci with multiplicity one. Moreover, one limit cycle can bifurcate from each of them simultaneously. Numerical simulations demonstrate that there is a big stable limit cycle enclosing these two small limit cycles.