6 REASONS WHY FERAL HOUSE MOUSE-POPULATIONS MIGHT HAVE LOW RECAPTURE RATES

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 h ouse mice between September 1992 and May 1993 in agricultural fields o n the Darling Downs of south-eastern Queensland during a phase of popu lation increase. Low recapture rates during the breeding season were d ue to low trappability and during the non-breeding period to nomadic m ovements. During the breeding season radio-collared mice of both sexes survived well and moved mostly small distances (<11 m). Low trappabil ity has consequences for the precision of population indices that rely on catch per unit effort. Capture-recapture models robust to heteroge neity of trap responses should be used to census feral Mus populations .