Population dynamics and environemental changes during natural irruptions of Australian desert rodents.

Abstract

Populations of Pseudomys hermannsburgensis and Notomys alexis were studied during a 33-month period (January 1991 to September 1993) in a sand-dune habitat in south-western Queensland. Population numbers of both species fluctuated dramatically over time with an approximately 40-fold difference between periods of lowest and highest abundance. Increased numbers were due primarily to an influx of juveniles to the population. A high turnover of individuals in both populations resulted in low rates of recapture. Numbers of both species were correlated positively with an index of rainfall with a time-lag of four months. P. hermannsburgensis showed spatial and temporal correlations with seed availability, whereas N. alexis displayed a strong, but non-significant, temporal trend with seed availability. These data suggest strongly that natural irruptions of Australian desert rodents are triggered by rainfall and possibly rain-induced food availability.