The Distribution of Rattus villosissimus (Waite) during Plague and Non-plague Years

Abstract

In September 1968 a questionnaire was sent to 1000 properties in Central Australia in an attempt to determine: (1) the distribution of R. villosissimus; (2) the dates and extent of past plagues of this species; (3) the direction and extent of mass movements of rats; (4) local factors which might account for the outbreak of plagues. In all, 289 replies were received. They confirmed the dates of past plagues and revealed a hitherto unrecorded plague in 1948. They showed that some plagues lasted for several years and that some were more widespread than others, and they suggested that there are 'refuge' areas on the Barkly Tableland of the Northern Territory, near Richmond and Julia Creek in Queensland and in the Lake Eyre Basin, where rats survive between plagues and build up into plague numbers during favourable conditions. The relationship between rainfall and the outbreak of rat plagues, and the role of predators during a plague, are discussed. It is suggested that the plaguing behaviour and mass movements of R. t;illosissimus ensure the survival of the species in a potentially lethal environment where the extinction of local populations is probably not uncommon.