POPULATION-DYNAMICS OF AN OUTBREAK POPULATION OF HOUSE MICE (MUS-DOMESTICUS) IN THE IRRIGATED RICE-GROWING AREA OF AUSTRALIA

Conditions appear ideal for annual plagues of house mice in irrigated rice-growing areas of Australia, yet plagues in these areas usually co incide with those in the dry farms. In an irrigated rice crop near Jer ilderie, New South Wales, we examined in detail the demography of an i ncipient plague population of Mus domesticus. Breeding occurred from w inter 1983 to autumn 1984 and the population increased from low levels to plague levels (2500 ha-1) by May. We found no evidence for a rigid territorial social organisation. Dispersal of tagged animals was low throughout the breeding season, yet between 60% and 76% of the trappab le population was new each trapping session. Testosterone levels incre ased when the average male body weight was low, suggesting that social suppression of reproduction was not occurring. We conclude that plagu es in these areas can develop within approximately 12 months from the onset of drought-breaking rains.