Landscape ecology of house mouse outbreaks in southeastern Australia.
House mouse Mus domesticus outbreaks in the grain-growing areas of south-eastern Australia occur irregularly and may be local or widespread, covering thousands of square kilometres. All natural and agricultural habitats are occupied when house mouse numbers are high, and the question we addressed was whether we can distinguish source and sink habitats within these agricultural landscapes so that management practices can be better targeted. Live-trapping on replicated grids in 15 habitats, including eucalypt woodland, cypress pine woodland, areas of permanent water and crop habitats, was carried out from 1983 to 1988 at 9-week intervals. Agricultural cropland (including crops, fallow and pastures), farm buildings, seepage areas and natural woodland could be source habitats. Farm buildings, seepage areas and saltbush areas all had high mouse densities entering the 1983-84 outbreak and were refuge habitats for mice. Cropland habitats quickly became the source area in spring 1983, and woodlands were initially sinks that lagged 2-4 months behind the population growth shown in crops. Adult female mice in cropland habitats were more often in breeding condition compared with mice in natural woodland. Mice also had higher indices of residency in cropland than in natural woodland. Synthesis and applications. In non-irrigated cereal production areas of south-eastern Australia, house mice move from refuge habitats in seepage areas and farm buildings into crops, build up in numbers in cropland habitats, and then invade woodland habitats, which by themselves cannot generate outbreaks of this pest species. Monitoring for incipient outbreaks should concentrate on refuges in seepage areas and crops and their associated fence lines as source habitat indicators. Population control in these habitats in spring would reduce the likelihood of population outbreaks in autumn, leading to reduced rodenticide use and a concomitant reduction in environmental hazards.