House mouse plagues in the grain-growing areas of eastern Australia ar
e a graphic illustration of the failure of social mechanisms of popula
tion control that are postulated by the self-regulation hypothesis to
prevent unlimited increase in numbers. Yet house mice are well known f
or the strength and variety of social interactions and are clearly cap
able of regulating their own numbers through social mortality. Most of
the research on house mouse plagues has assumed that extrinsic agenci
es - predators, diseases, food supplies, and weather - determine when
and where mouse plagues will occur. Some aspects of these plagues cann
ot, 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 expl
ain the low phase, and is a change in social organization a necessary
condition for generating a plague? Two possible models are presented t
o suggest predictions to be tested by further studies of social mechan
isms of population limitation in feral house mice.