Can Changes in Social Behaviour Help to Explain House Mouse Plagues in Australia?

House mouse plagues in the grain-growing areas of eastern Australia are a graphic illustration of the failure of social mechanisms of population control that are postulated by the self-regulation hypothesis to prevent unlimited increase in numbers. Yet house mice are well known for the strength and variety of social interactions and are clearly capable of regulating their own numbers through social mortality. Most of the research on house mouse plagues has assumed that extrinsic agencies - predators, diseases, food supplies, and weather - determine when and where mouse plagues will occur. Some aspects of these plagues cannot, however, be explained that easily, among them the low phase, which may persist for 1-3 years. We focus here on the low phase of plagues and the trigger that flips a population from the low into the increase phase of a plague. Can social factors in house mouse populations explain the low phase, and is a change in social organization a necessary condition for generating a plague? Two possible models are presented to suggest predictions to be tested by further studies of social mechanisms of population limitation in feral house mice.