Many feral house mouse populations have low recapture rates (0-20%) in live-trapping studies carried out at 2-4-week intervals. We consider six hypotheses to explain low recapture rates. We radio-collared 155 house mice between September 1992 and May 1993 in agricultural fields on the Darling Downs of south-eastern Queensland during a phase of population increase. Low recapture rates during the breeding season were due to low trappability and during the non-breeding period to nomadic movements. During the breeding season radio-collared mice of both sexes survived well and moved mostly small distances (