Chaotic dynamics in the Volterra predator-prey model via linked twist   maps
  We prove the existence of infinitely many periodic solutions and complicated dynamics, due to the presence of a topological horseshoe, for the classical Volterra predator--prey model with a periodic harvesting. The proof relies on some recent results about chaotic planar maps combined with the study of geometric features which are typical of linked twist maps. 
Marina Pireddu, Fabio Zanolin