Can Vertebrate Predators Regulate Their Prey?

Small rodent populations in our area in southern Sweden do not cycle as they do in the north, but stay fairly stable between years. The noncyclic pattern can be ascribed to a continuous high predation rate from some generalist predators, viz., common buzzard, red fox, and domestic cat. They subsisted mainly on other prey, rabbits, which were not regulated by predation but fluctuated stochastically (adverse winter weather and myxomatosis). These generalist predators showed numerical stability but changed their diet in response to changing prey densities. The generality of the observations was tested in a simulation model. The results of the simulations were in agreement with field data.