Populations of predators and their prey usually follow predictable cycles. When the number of prey increases — perhaps as their food supply becomes more abundant — predator populations also grow. When the predator population becomes too large, however, the prey population often plummets, leaving too little food for the predators, whose population also then crashes. Co-evolutionary changes in species may reverse traditional predator-prey population cycles, creating the appearance that prey are eating the predators, according to a new study.